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[lisp] Later Monday morning diffs

From: Dino Farinacci <dino at cisco.com>
To: lisp at ietf.org
Date: Mon, 28 Sep 2009 11:40:27 -0700

While talking with the chairs, the changes for this rev are:

(1) Add nonce back to the Map-Register to avoid replay attacks perNoel and Sam's comment.

(2) Add text indicating that only Map-Requests and PIM Join/Prunemessages (for multicast) can be encapsulated in the new EncapsulatedControl Messsage per Sam and Margaret's comment.


Diffs and spec attached.

Thanks,
Dino/Dave/Darrel/Vince

Title: wdiff draft-ietf-lisp-04.txt draft-ietf-lisp-05.txt

Network Working Group D. Farinacci
Internet-Draft V. Fuller
Intended status: Experimental D. Meyer
Expires: March 20, April 1, 2010 D. Lewis
cisco Systems
September 16, 28, 2009

Locator/ID Separation Protocol (LISP)
draft-ietf-lisp-04.txt
(PROPOSED) draft-ietf-lisp-05.txt (NOT POSTED YET)

Status of this Memo

This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.

Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."

The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.

The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.

This Internet-Draft will expire on March 20, April 1, 2010.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents in effect on the date of
publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document.

Abstract

This draft describes a simple, incremental, network-based protocol to
implement separation of Internet addresses into Endpoint Identifiers
(EIDs) and Routing Locators (RLOCs). This mechanism requires no
changes to host stacks and no major changes to existing database
infrastructures. The proposed protocol can be implemented in a
relatively small number of routers.

This proposal was stimulated by the problem statement effort at the
Amsterdam IAB Routing and Addressing Workshop (RAWS), which took
place in October 2006.

Table of Contents

1. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 8
4. Basic Overview . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1. Packet Flow Sequence . . . . . . . . . . . . . . . . . . . 14
5. Tunneling Details . . . . . . . . . . . . . . . . . . . . . . 16
5.1. LISP IPv4-in-IPv4 Header Format . . . . . . . . . . . . . 17
5.2. LISP IPv6-in-IPv6 Header Format . . . . . . . . . . . . . 18
5.3. Tunnel Header Field Descriptions . . . . . . . . . . . . . 19
5.4. Dealing with Large Encapsulated Packets . . . . . . . . . 21
5.4.1. A Stateless Solution to MTU Handling . . . . . . . . . 22
5.4.2. A Stateful Solution to MTU Handling . . . . . . . . . 22
6. EID-to-RLOC Mapping . . . . . . . . . . . . . . . . . . . . . 24
6.1. LISP IPv4 and IPv6 Control Plane Packet Formats . . . . . 24
6.1.1. LISP Packet Type Allocations . . . . . . . . . . . . . 26
6.1.2. Map-Request Message Format . . . . . . . . . . . . . . 26
6.1.3. EID-to-RLOC UDP Map-Request Message . . . . . . . . . 28
6.1.4. Map-Reply Message Format . . . . . . . . . . . . . . . 29 30
6.1.5. EID-to-RLOC UDP Map-Reply Message . . . . . . . . . . 32 33
6.1.6. Map-Register Message Format . . . . . . . . . . . . . 33 34
6.1.7. Encapsualted Control Message Format . . . . . . . . . 36
6.2. Routing Locator Selection . . . . . . . . . . . . . . . . 36 38
6.3. Routing Locator Reachability . . . . . . . . . . . . . . . 37 39
6.3.1. Echo Nonce Algorithm . . . . . . . . . . . . . . . . . 39 42
6.3.2. RLOC Probing Algorithm . . . . . . . . . . . . . . . . 41 43
6.4. Routing Locator Hashing . . . . . . . . . . . . . . . . . 41 44
6.5. Changing the Contents of EID-to-RLOC Mappings . . . . . . 42 45
6.5.1. Clock Sweep . . . . . . . . . . . . . . . . . . . . . 43 45
6.5.2. Solicit-Map-Request (SMR) . . . . . . . . . . . . . . 44 46
7. Router Performance Considerations . . . . . . . . . . . . . . 46 48
8. Deployment Scenarios . . . . . . . . . . . . . . . . . . . . . 47 49
8.1. First-hop/Last-hop Tunnel Routers . . . . . . . . . . . . 48 50
8.2. Border/Edge Tunnel Routers . . . . . . . . . . . . . . . . 48 50
8.3. ISP Provider-Edge (PE) Tunnel Routers . . . . . . . . . . 49 51
9. Traceroute Considerations . . . . . . . . . . . . . . . . . . 50 52
9.1. IPv6 Traceroute . . . . . . . . . . . . . . . . . . . . . 51 53
9.2. IPv4 Traceroute . . . . . . . . . . . . . . . . . . . . . 51 53
9.3. Traceroute using Mixed Locators . . . . . . . . . . . . . 51 53
10. Mobility Considerations . . . . . . . . . . . . . . . . . . . 53 55
10.1. Site Mobility . . . . . . . . . . . . . . . . . . . . . . 53 55
10.2. Slow Endpoint Mobility . . . . . . . . . . . . . . . . . . 53 55
10.3. Fast Endpoint Mobility . . . . . . . . . . . . . . . . . . 53 55
10.4. Fast Network Mobility . . . . . . . . . . . . . . . . . . 55 57
10.5. LISP Mobile Node Mobility . . . . . . . . . . . . . . . . 55 57
11. Multicast Considerations . . . . . . . . . . . . . . . . . . . 57 59
12. Security Considerations . . . . . . . . . . . . . . . . . . . 58 60
13. Prototype Plans and Status . . . . . . . . . . . . . . . . . . 59 61
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 62 64
14.1. Normative References . . . . . . . . . . . . . . . . . . . 62 64
14.2. Informative References . . . . . . . . . . . . . . . . . . 63 65
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 66 68
Appendix B. Document Change Log . . . . . . . . . . . . . . . . . 69
B.1. Changes to draft-ietf-lisp-05.txt . . . . . . . . . . . . 69
B.2. Changes to draft-ietf-lisp-04.txt . . . . . . . . . . . . 69
B.3. Changes to draft-ietf-lisp-03.txt . . . . . . . . . . . . 71
B.4. Changes to draft-ietf-lisp-02.txt . . . . . . . . . . . . 71
B.5. Changes to draft-ietf-lisp-01.txt . . . . . . . . . . . . 72
B.6. Changes to draft-ietf-lisp-00.txt . . . . . . . . . . . . 72
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 67 73

1. Requirements Notation

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].

2. Introduction

Many years of discussion about the current IP routing and addressing
architecture have noted that its use of a single numbering space (the
"IP address") for both host transport session identification and
network routing creates scaling issues (see [CHIAPPA] and [RFC1498]).
A number of scaling benefits would be realized by separating the
current IP address into separate spaces for Endpoint Identifiers
(EIDs) and Routing Locators (RLOCs); among them are:

1. Reduction of routing table size in the "default-free zone" (DFZ).
Use of a separate numbering space for RLOCs will allow them to be
assigned topologically (in today's Internet, RLOCs would be
assigned by providers at client network attachment points),
greatly improving aggregation and reducing the number of
globally-visible, routable prefixes.

2. More cost-effective multihoming for sites that connect to
different service providers where they can control their own
policies for packet flow into the site without using extra
routing table resources of core routers.

3. Easing of renumbering burden when clients change providers.
Because host EIDs are numbered from a separate, non-provider-
assigned and non-topologically-bound space, they do not need to
be renumbered when a client site changes its attachment points to
the network.

4. Traffic engineering capabilities that can be performed by network
elements and do not depend on injecting additional state into the
routing system. This will fall out of the mechanism that is used
to implement the EID/RLOC split (see Section 4).

5. Mobility without address changing. Existing mobility mechanisms
will be able to work in a locator/ID separation scenario. It
will be possible for a host (or a collection of hosts) to move to
a different point in the network topology either retaining its
home-based address or acquiring a new address based on the new
network location. A new network location could be a physically
different point in the network topology or the same physical
point of the topology with a different provider.

This draft describes protocol mechanisms to achieve the desired
functional separation. For flexibility, the mechanism used for
forwarding packets is decoupled from that used to determine EID to
RLOC mappings. This document covers the former. For the later, see
[CONS], [ALT], [EMACS], [RPMD], and [NERD]. This work is in response
to and intended to address the problem statement that came out of the
RAWS effort [RFC4984].

The Routing and Addressing problem statement can be found in [RADIR].

This draft focuses on a router-based solution. Building the solution
into the network will facilitate incremental deployment of the
technology on the Internet. Note that while the detailed protocol
specification and examples in this document assume IP version 4
(IPv4), there is nothing in the design that precludes use of the same
techniques and mechanisms for IPv6. It should be possible for IPv4
packets to use IPv6 RLOCs and for IPv6 EIDs to be mapped to IPv4
RLOCs.

Related work on host-based solutions is described in Shim6 [SHIM6]
and HIP [RFC4423]. Related work on a router-based solution is
described in [GSE]. This draft attempts to not compete or overlap
with such solutions and the proposed protocol changes are expected to
complement a host-based mechanism when Traffic Engineering
functionality is desired.

Some of the design goals of this proposal include:

1. Require no hardware or software changes to end-systems (hosts).

2. Minimize required changes to Internet infrastructure.

3. Be incrementally deployable.

4. Require no router hardware changes.

5. Minimize the number of routers which have to be modified. In
particular, most customer site routers and no core routers
require changes.

6. Minimize router software changes in those routers which are
affected.

7. Avoid or minimize packet loss when EID-to-RLOC mappings need to
be performed.

There are 4 variants of LISP, which differ along a spectrum of strong
to weak dependence on the topological nature and possible need for
routability of EIDs. The variants are:

LISP 1: uses EIDs that are routable through the RLOC topology for
bootstrapping EID-to-RLOC mappings. [LISP1] This was intended as
a prototyping mechanism for early protocol implementation. It is
now deprecated and should not be deployed.

LISP 1.5: uses EIDs that are routable for bootstrapping EID-to-RLOC
mappings; such routing is via a separate topology.

LISP 2: uses EIDS that are not routable and EID-to-RLOC mappings are
implemented within the DNS. [LISP2]

LISP 3: uses non-routable EIDs that are used as lookup keys for a
new EID-to-RLOC mapping database. Use of Distributed Hash Tables
[DHTs] [LISPDHT] to implement such a database would be an area to
explore. Other examples of new mapping database services are
[CONS], [ALT], [RPMD], [NERD], and [APT].

This document on LISP 1.5, and LISP 3 variants, both of which rely on
a router-based distributed cache and database for EID-to-RLOC
mappings. The LISP 1.0 mechanism works but does not allow reduction
of routing information in the default-free-zone of the Internet. The
LISP 2 mechanisms are put on hold and may never come to fruition
since it is not architecturally pure to have routing depend on
directory and directory depend on routing. The LISP 3 mechanisms
will be documented elsewhere but may use the control-plane options
specified in this specification.

3. Definition of Terms

Provider Independent (PI) Addresses: an address block assigned from
a pool where blocks are not associated with any particular
location in the network (e.g. from a particular service provider),
and is therefore not topologically aggregatable in the routing
system.

Provider Assigned (PA) Addresses: a block of IP addresses that are
assigned to a site by each service provider to which a site
connects. Typically, each block is sub-block of a service
provider CIDR block and is aggregated into the larger block before
being advertised into the global Internet. Traditionally, IP
multihoming has been implemented by each multi-homed site
acquiring its own, globally-visible prefix. LISP uses only
topologically-assigned and aggregatable address blocks for RLOCs,
eliminating this demonstrably non-scalable practice.

Routing Locator (RLOC): the IPv4 or IPv6 address of an egress
tunnel router (ETR). It is the output of a EID-to-RLOC mapping
lookup. An EID maps to one or more RLOCs. Typically, RLOCs are
numbered from topologically-aggregatable blocks that are assigned
to a site at each point to which it attaches to the global
Internet; where the topology is defined by the connectivity of
provider networks, RLOCs can be thought of as PA addresses.
Multiple RLOCs can be assigned to the same ETR device or to
multiple ETR devices at a site.

Endpoint ID (EID): a 32-bit (for IPv4) or 128-bit (for IPv6) value
used in the source and destination address fields of the first
(most inner) LISP header of a packet. The host obtains a
destination EID the same way it obtains an destination address
today, for example through a DNS lookup or SIP exchange. The
source EID is obtained via existing mechanisms used to set a
host's "local" IP address. An EID is allocated to a host from an
EID-prefix block associated with the site where the host is
located. An EID can be used by a host to refer to other hosts.
EIDs MUST NOT be used as LISP RLOCs. Note that EID blocks may be
assigned in a hierarchical manner, independent of the network
topology, to facilitate scaling of the mapping database. In
addition, an EID block assigned to a site may have site-local
structure (subnetting) for routing within the site; this structure
is not visible to the global routing system. When used in
discussions with other Locator/ID separation proposals, a LISP EID
will be called a "LEID". Throughout this document, any references
to "EID" refers to an LEID.

EID-prefix: A power-of-2 block of EIDs which are allocated to a
site by an address allocation authority. EID-prefixes are
associated with a set of RLOC addresses which make up a "database
mapping". EID-prefix allocations can be broken up into smaller
blocks when an RLOC set is to be associated with the smaller EID-
prefix. A globally routed address block (whether PI or PA) is not
an EID-prefix. However, a globally routed address block may be
removed from global routing and reused as an EID-prefix. A site
that receives an explicitly allocated EID-prefix may not use that
EID-prefix as a globally routed prefix assigned to RLOCs.

End-system: is an IPv4 or IPv6 device that originates packets with
a single IPv4 or IPv6 header. The end-system supplies an EID
value for the destination address field of the IP header when
communicating globally (i.e. outside of its routing domain). An
end-system can be a host computer, a switch or router device, or
any network appliance.

Ingress Tunnel Router (ITR): a router which accepts an IP packet
with a single IP header (more precisely, an IP packet that does
not contain a LISP header). The router treats this "inner" IP
destination address as an EID and performs an EID-to-RLOC mapping
lookup. The router then prepends an "outer" IP header with one of
its globally-routable RLOCs in the source address field and the
result of the mapping lookup in the destination address field.
Note that this destination RLOC may be an intermediate, proxy
device that has better knowledge of the EID-to-RLOC mapping closer
to the destination EID. In general, an ITR receives IP packets
from site end-systems on one side and sends LISP-encapsulated IP
packets toward the Internet on the other side.

Specifically, when a service provider prepends a LISP header for
Traffic Engineering purposes, the router that does this is also
regarded as an ITR. The outer RLOC the ISP ITR uses can be based
on the outer destination address (the originating ITR's supplied
RLOC) or the inner destination address (the originating hosts
supplied EID).

TE-ITR: is an ITR that is deployed in a service provider network
that prepends an additional LISP header for Traffic Engineering
purposes.

Egress Tunnel Router (ETR): a router that accepts an IP packet
where the destination address in the "outer" IP header is one of
its own RLOCs. The router strips the "outer" header and forwards
the packet based on the next IP header found. In general, an ETR
receives LISP-encapsulated IP packets from the Internet on one
side and sends decapsulated IP packets to site end-systems on the
other side. ETR functionality does not have to be limited to a
router device. A server host can be the endpoint of a LISP tunnel
as well.

TE-ETR: is an ETR that is deployed in a service provider network
that strips an outer LISP header for Traffic Engineering purposes.

xTR: is a reference to an ITR or ETR when direction of data flow is
not part of the context description. xTR refers to the router that
is the tunnel endpoint. Used synonymously with the term "Tunnel
Router". For example, "An xTR can be located at the Customer Edge
(CE) router", meaning both ITR and ETR functionality is at the CE
router.

EID-to-RLOC Cache: a short-lived, on-demand table in an ITR that
stores, tracks, and is responsible for timing-out and otherwise
validating EID-to-RLOC mappings. This cache is distinct from the
full "database" of EID-to-RLOC mappings, it is dynamic, local to
the ITR(s), and relatively small while the database is
distributed, relatively static, and much more global in scope.

EID-to-RLOC Database: a global distributed database that contains
all known EID-prefix to RLOC mappings. Each potential ETR
typically contains a small piece of the database: the EID-to-RLOC
mappings for the EID prefixes "behind" the router. These map to
one of the router's own, globally-visible, IP addresses.

Recursive Tunneling: when a packet has more than one LISP IP
header. Additional layers of tunneling may be employed to
implement traffic engineering or other re-routing as needed. When
this is done, an additional "outer" LISP header is added and the
original RLOCs are preserved in the "inner" header. Any
references to tunnels in this specification refers to dynamic
encapsulating tunnels and never are they statically configured.

Reencapsulating Tunnels: when a packet has no more than one LISP IP
header (two IP headers total) and when it needs to be diverted to
new RLOC, an ETR can decapsulate the packet (remove the LISP
header) and prepends a new tunnel header, with new RLOC, on to the
packet. Doing this allows a packet to be re-routed by the re-
encapsulating router without adding the overhead of additional
tunnel headers. Any references to tunnels in this specification
refers to dynamic encapsulating tunnels and never are they
statically configured.

LISP Header: a term used in this document to refer to the outer
IPv4 or IPv6 header, a UDP header, and a LISP header, an ITR
prepends or an ETR strips.

Address Family Indicator (AFI): a term used to describe an address
encoding in a packet. An address family currently pertains to an
IPv4 or IPv6 address. See [AFI] for details.

Negative Mapping Entry: also known as a negative cache entry, is an
EID-to-RLOC entry where an EID-prefix is advertised or stored with
no RLOCs. That is, the locator-set for the EID-to-RLOC entry is
empty or has an encoded locator count of 0. This type of entry
could be used to describe a prefix from a non-LISP site, which is
explicitly not in the mapping database. There are a set of well
defined actions that are encoded in a Negative Map-Reply.

Data Probe: a LISP-encapsulated data packet where the inner header
destination address equals the outer header destination address
used to trigger a Map-Reply by a decapsulating ETR. In addition,
the original packet is decapsulated and delivered to the
destination host. A Data Probe is used in some of the mapping
database designs to "probe" or request a Map-Reply from an ETR; in
other cases, Map-Requests are used. See each mapping database
design for details.

4. Basic Overview

One key concept of LISP is that end-systems (hosts) operate the same
way they do today. The IP addresses that hosts use for tracking
sockets, connections, and for sending and receiving packets do not
change. In LISP terminology, these IP addresses are called Endpoint
Identifiers (EIDs).

Routers continue to forward packets based on IP destination
addresses. When a packet is LISP encapsulated, these addresses are
referred to as Routing Locators (RLOCs). Most routers along a path
between two hosts will not change; they continue to perform routing/
forwarding lookups on the destination addresses. For routers between
the source host and the ITR as well as routers from the ETR to the
destination host, the destination address is an EID. For the routers
between the ITR and the ETR, the destination address is an RLOC.

This design introduces "Tunnel Routers", which prepends LISP headers
on host-originated packets and strip them prior to final delivery to
their destination. The IP addresses in this "outer header" are
RLOCs. During end-to-end packet exchange between two Internet hosts,
an ITR prepends a new LISP header to each packet and an egress tunnel
router strips the new header. The ITR performs EID-to-RLOC lookups
to determine the routing path to the the ETR, which has the RLOC as
one of its IP addresses.

Some basic rules governing LISP are:

o End-systems (hosts) only send to addresses which are EIDs. They
don't know addresses are EIDs versus RLOCs but assume packets get
to LISP routers, which in turn, deliver packets to the destination
the end-system has specified.

o EIDs are always IP addresses assigned to hosts.

o LISP routers mostly deal with Routing Locator addresses. See
details later in Section 4.1 to clarify what is meant by "mostly".

o RLOCs are always IP addresses assigned to routers; preferably,
topologically-oriented addresses from provider CIDR blocks.

o When a router originates packets it may use as a source address
either an EID or RLOC. When acting as a host (e.g. when
terminating a transport session such as SSH, TELNET, or SNMP), it
may use an EID that is explicitly assigned for that purpose. An
EID that identifies the router as a host MUST NOT be used as an
RLOC; an EID is only routable within the scope of a site. A
typical BGP configuration might demonstrate this "hybrid" EID/RLOC
usage where a router could use its "host-like" EID to terminate
iBGP sessions to other routers in a site while at the same time
using RLOCs to terminate eBGP sessions to routers outside the
site.

o EIDs are not expected to be usable for global end-to-end
communication in the absence of an EID-to-RLOC mapping operation.
They are expected to be used locally for intra-site communication.

o EID prefixes are likely to be hierarchically assigned in a manner
which is optimized for administrative convenience and to
facilitate scaling of the EID-to-RLOC mapping database. The
hierarchy is based on a address allocation hierarchy which is not
dependent on the network topology.

o EIDs may also be structured (subnetted) in a manner suitable for
local routing within an autonomous system.

An additional LISP header may be prepended to packets by a transit
router (i.e. TE-ITR) when re-routing of the path for a packet is
desired. An obvious instance of this would be an ISP router that
needs to perform traffic engineering for packets in flow through its
network. In such a situation, termed Recursive Tunneling, an ISP
transit acts as an additional ingress tunnel router and the RLOC it
uses for the new prepended header would be either an TE-ETR within
the ISP (along intra-ISP traffic engineered path) or in an TE-ETR
within another ISP (an inter-ISP traffic engineered path, where an
agreement to build such a path exists).

This specification mandates that no more than two LISP headers get
prepended to a packet. This avoids excessive packet overhead as well
as possible encapsulation loops. It is believed two headers is
sufficient, where the first prepended header is used at a site for
Location/Identity separation and second prepended header is used
inside a service provider for Traffic Engineering purposes.

Tunnel Routers can be placed fairly flexibly in a multi-AS topology.
For example, the ITR for a particular end-to-end packet exchange
might be the first-hop or default router within a site for the source
host. Similarly, the egress tunnel router might be the last-hop
router directly-connected to the destination host. Another example,
perhaps for a VPN service out-sourced to an ISP by a site, the ITR
could be the site's border router at the service provider attachment
point. Mixing and matching of site-operated, ISP-operated, and other
tunnel routers is allowed for maximum flexibility. See Section 8 for
more details.

4.1. Packet Flow Sequence

This section provides an example of the unicast packet flow with the
following conditions:

o Source host "host1.abc.com" is sending a packet to
"host2.xyz.com", exactly what host1 would do if the site was not
using LISP.

o Each site is multi-homed, so each tunnel router has an address
(RLOC) assigned from the service provider address block for each
provider to which that particular tunnel router is attached.

o The ITR(s) and ETR(s) are directly connected to the source and
destination, respectively.

o Data Probes are used to solicit Map-Replies versus using Map-
Requests. And the Data Probes are sent on the underlying topology
(the LISP 1.0 variant) but could also be sent over an alternative
topology (the LISP 1.5 variant) as it would in [ALT].

Client host1.abc.com wants to communicate with server host2.xyz.com:

1. host1.abc.com wants to open a TCP connection to host2.xyz.com.
It does a DNS lookup on host2.xyz.com. An A/AAAA record is
returned. This address is used as the destination EID and the
locally-assigned address of host1.abc.com is used as the source
EID. An IPv4 or IPv6 packet is built using the EIDs in the IPv4
or IPv6 header and sent to the default router.

2. The default router is configured as an ITR. The ITR must be able
to map the EID destination to an RLOC of the ETR at the
destination site. The ITR prepends a LISP header to the packet,
with one of its RLOCs as the source IPv4 or IPv6 address. The
destination EID from the original packet header is used as the
destination IPv4 or IPv6 in the prepended LISP header.
Subsequent packets, where the outer destination address is the
destination EID will be sent until EID-to-RLOC mapping is
learned.

3. In LISP 1, the packet is routed through the Internet as it is
today. In LISP 1.5, the packet is routed on a different topology
which may have EID prefixes distributed and advertised in an
aggregatable fashion. In either case, the packet arrives at the
ETR. The router is configured to "punt" the packet to the
router's processor. See Section 7 for more details. For LISP
2.0 and 3.0, the behavior is not fully defined yet.

4. The LISP header is stripped so that the packet can be forwarded
by the router control plane. The router looks up the destination
EID in the router's EID-to-RLOC database (not the cache, but the
configured data structure of RLOCs). An EID-to-RLOC Map-Reply
message is originated by the ETR and is addressed to the source
RLOC in the LISP header of the original packet (this is the ITR).
The source RLOC of the Map-Reply is one of the ETR's RLOCs.

5. The ITR receives the Map-Reply message, parses the message (to
check for format validity) and stores the mapping information
from the packet. This information is put in the ITR's EID-to-
RLOC mapping cache (this is the on-demand cache, the cache where
entries time out due to inactivity).

6. Subsequent packets from host1.abc.com to host2.xyz.com will have
a LISP header prepended by the ITR using the appropriate RLOC as
the LISP header destination address learned from the ETR. Note,
the packet may be sent to a different ETR than the one which
returned the Map-Reply due to the source site's hashing policy or
the destination site's locator-set policy.

7. The ETR receives these packets directly (since the destination
address is one of its assigned IP addresses), strips the LISP
header and forwards the packets to the attached destination host.

In order to eliminate the need for a mapping lookup in the reverse
direction, an ETR MAY create a cache entry that maps the source EID
(inner header source IP address) to the source RLOC (outer header
source IP address) in a received LISP packet. Such a cache entry is
termed a "gleaned" mapping and only contains a single RLOC for the
EID in question. More complete information about additional RLOCs
SHOULD be verified by sending a LISP Map-Request for that EID. Both
ITR and the ETR may also influence the decision the other makes in
selecting an RLOC. See Section 6 for more details.

5. Tunneling Details

This section describes the LISP Data Message which defines the
tunneling header used to encapsulate IPv4 and IPv6 packets which
contain EID addresses. Even though the following formats illustrate
IPv4-in-IPv4 and IPv6-in-IPv6 encapsulations, the other 2
combinations are supported as well.

Since additional tunnel headers are prepended, the packet becomes
larger and in theory can exceed the MTU of any link traversed from
the ITR to the ETR. It is recommended, in IPv4 that packets do not
get fragmented as they are encapsulated by the ITR. Instead, the
packet is dropped and an ICMP Too Big message is returned to the
source.

Based on informal surveys of large ISP traffic patterns, it appears
that most transit paths can accommodate a path MTU of at least 4470
bytes. The exceptions, in terms of data rate, number of hosts
affected, or any other metric are expected to be vanishingly small.

To address MTU concerns, mainly raised on the RRG mailing list, the
LISP deployment process will include collecting data during its pilot
phase to either verify or refute the assumption about minimum
available MTU. If the assumption proves true and transit networks
with links limited to 1500 byte MTUs are corner cases, it would seem
more cost-effective to either upgrade or modify the equipment in
those transit networks to support larger MTUs or to use existing
mechanisms for accommodating packets that are too large.

For this reason, there is currently no plan for LISP to add any new
additional, complex mechanism for implementing fragmentation and
reassembly in the face of limited-MTU transit links. If analysis
during LISP pilot deployment reveals that the assumption of
essentially ubiquitous, 4470+ byte transit path MTUs, is incorrect,
then LISP can be modified prior to protocol standardization to add
support for one of the proposed fragmentation and reassembly schemes.
Note that two simple existing schemes are detailed in Section 5.4.

5.1. LISP IPv4-in-IPv4 Header Format

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ |Version| IHL |Type of Service| Total Length |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Identification |Flags| Fragment Offset |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
OH | Time to Live | Protocol = 17 | Header Checksum |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Source Routing Locator |
\ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | Destination Routing Locator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Source Port = xxxx | Dest Port = 4341 |
UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L |N|L|E| rflags | Nonce |
I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
S / | Locator Status Bits |
P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ |Version| IHL |Type of Service| Total Length |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Identification |Flags| Fragment Offset |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IH | Time to Live | Protocol | Header Checksum |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Source EID |
\ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | Destination EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

5.2. LISP IPv6-in-IPv6 Header Format

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ |Version| Traffic Class | Flow Label |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Payload Length | Next Header=17| Hop Limit |
v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
O + +
u | |
t + Source Routing Locator +
e | |
r + +
| |
H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
d | |
r + +
| |
^ + Destination Routing Locator +
| | |
\ + +
\ | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Source Port = xxxx | Dest Port = 4341 |
UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L |N|L|E| rflags | Nonce |
I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
S / | Locator Status Bits |
P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ |Version| Traffic Class | Flow Label |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Payload Length | Next Header | Hop Limit |
v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
I + +
n | |
n + Source EID +
e | |
r + +
| |
H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
d | |
r + +
| |
^ + Destination EID +
\ | |
\ + +
\ | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

5.3. Tunnel Header Field Descriptions

Inner Header: is the inner header, preserved from the datagram
received from the originating host. The source and destination IP
addresses are EIDs.

Outer Header: is the outer header prepended by an ITR. The address
fields contain RLOCs obtained from the ingress router's EID-to-
RLOC cache. The IP protocol number is "UDP (17)" from [RFC0768].
The DF bit of the Flags field is set to 0 when the method in
Section 5.4.1 is used and set to 1 when the method in
Section 5.4.2 is used.

UDP Header: contains a ITR selected source port when encapsulating a
packet. See Section 6.4 for details on the hash algorithm used
select a source port based on the 5-tuple of the inner header.
The destination port MUST be set to the well-known IANA assigned
port value 4341.

UDP Checksum: this field SHOULD be transmitted as zero by an ITR for
either IPv4 [RFC0768] or IPv6 encapsulation [UDP-TUNNELS]. When a
packet with a zero UDP checksum is received by an ETR, the ETR
MUST accept the packet for decapsulation. When an ITR transmits a
non-zero value for the UDP checksum, it MUST send a correctly
computed value in this field. When an ETR receives a packet with
a non-zero UDP checksum, it MAY choose to verify the checksum
value. If it chooses to perform such verification, and the
verification fails, the packet MUST be silently dropped. If the
ETR chooses not to perform the verification, or performs the
verification successfully, the packet MUST be accepted for
decapsulation. The handling of UDP checksums for all tunneling
protocols, including LISP, is under active discussion within the
IETF. When that discussion concludes, any necessary changes will
be made to align LISP with the outcome of the broader discussion.

UDP Length: for an IPv4 encapsulated packet, the inner header Total
Length plus the UDP and LISP header lengths are used. For an IPv6
encapsulated packet, the inner header Payload Length plus the size
of the IPv6 header (40 bytes) plus the size of the UDP and LISP
headers are used. The UDP header length is 8 bytes.

N: this is the nonce-present bit. When this bit is set to 1, the
low-order 24-bits of the first 32-bits of the LISP header contains
a Nonce. See section Section 6.3.1 for details.

L: this is the Locator-Status-Bits field enabled bit. When this bit
is set to 1, the Locator-Status-Bits in the second 32-bits of the
LISP header are in use.

E: this is the echo-nonce-request bit. When this bit is set to 1,
the N bit must be 1. This bit should be ignored and has no
meaning when the N bit is set to 0. See section Section 6.3.1 for
details.

rflags: this 4-bit field is reserved for future flag use. It is set
to 0 on transmit and ignored on receipt.

LISP Nonce: is a 24-bit value that is randomly generated by an ITR
when the N-bit is set to 1. The nonce is also used when the E-bit
is set to request the nonce value to be echoed by the other side
when packets are returned. When the E-bit is clear but the N-bit
is set, an ITR is either echoing a previously requested echo-nonce
or providing a random nonce. See section Section 6.3.1 for more
details.

LISP Locator Status Bits: in the LISP header are set by an ITR to
indicate to an ETR the up/down status of the Locators in the
source site. Each RLOC in a Map-Reply is assigned an ordinal
value from 0 to n-1 (when there are n RLOCs in a mapping entry).
The Locator Status Bits are numbered from 0 to n-1 from the least
significant bit of the 32-bit field. When a bit is set to 1, the
ITR is indicating to the ETR the RLOC associated with the bit
ordinal has up status. See Section 6.3 for details on how an ITR
can determine other ITRs at the site are reachable. When a site
has multiple EID-prefixes which result in multiple mappings (where
each could have a different locator-set), the Locator Status Bits
setting in an encapsulated packet MUST reflect the mapping for the
EID-prefix that the inner-header source EID address matches.

When doing Recursive Tunneling or ITR/PTR encapsulation:

o The outer header Time to Live field (or Hop Limit field, in case
of IPv6) SHOULD be copied from the inner header Time to Live
field.

o The outer header Type of Service field (or the Traffic Class
field, in the case of IPv6) SHOULD be copied from the inner header
Type of Service field (with one caveat, see below).

When doing Re-encapsulated Tunneling:

o The new outer header Time to Live field SHOULD be copied from the
stripped outer header Time to Live field.

o The new outer header Type of Service field SHOULD be copied from
the stripped OH header Type of Service field (with one caveat, see
below).

Copying the TTL serves two purposes: first, it preserves the distance
the host intended the packet to travel; second, and more importantly,
it provides for suppression of looping packets in the event there is
a loop of concatenated tunnels due to misconfiguration.

The ECN field occupies bits 6 and 7 of both the IPv4 Type of Service
field and the IPv6 Traffic Class field [RFC3168]. The ECN field
requires special treatment in order to avoid discarding indications
of congestion [RFC3168]. ITR encapsulation MUST copy the 2-bit ECN
field from the inner header to the outer header. Re-encapsulation
MUST copy the 2-bit ECN field from the stripped outer header to the
new outer header. If the ECN field contains a congestion indication
codepoint (the value is '11', the Congestion Experienced (CE)
codepoint), then ETR decapsulation MUST copy the 2-bit ECN field from
the stripped outer header to the surviving inner header that is used
to forward the packet beyond the ETR. These requirements preserve
Congestion Experienced (CE) indications when a packet that uses ECN
traverses a LISP tunnel and becomes marked with a CE indication due
to congestion between the tunnel endpoints.

5.4. Dealing with Large Encapsulated Packets

In the event that the MTU issues mentioned above prove to be more
serious than expected, this section proposes 2 simple mechanisms to
deal with large packets. One is stateless using IP fragmentation and
the other is stateful using Path MTU Discovery [RFC1191].

It is left to the implementor to decide if the stateless or stateful
mechanism should be implemented. Both or neither can be decided as
well since it is a local decision in the ITR regarding how to deal
with MTU issues. Sites can interoperate with differing mechanisms.

Both stateless and stateful mechanisms also apply to Reencapsulating
and Recursive Tunneling. So any actions reference below to an ITR
also apply to an TE-ITR.

5.4.1. A Stateless Solution to MTU Handling

An ITR stateless solution to handle MTU issues is described as
follows:

1. Define an architectural constant S for the maximum size of a
packet, in bytes, an ITR would receive from a source inside of
its site.

2. Define L to be the maximum size, in bytes, a packet of size S
would be after the ITR prepends the LISP header, UDP header, and
outer network layer header of size H.

3. Calculate: S + H = L.

When an ITR receives a packet from a site-facing interface and adds H
bytes worth of encapsulation to yield a packet size of L bytes, it
resolves the MTU issue by first splitting the original packet into 2
equal-sized fragments. A LISP header is then prepended to each
fragment. This will ensure that the new, encapsulated packets are of
size (S/2 + H), which is always below the effective tunnel MTU.

When an ETR receives encapsulated fragments, it treats them as two
individually encapsulated packets. It strips the LISP headers then
forwards each fragment to the destination host of the destination
site. The two fragments are reassembled at the destination host into
the single IP datagram that was originated by the source host.

This behavior is performed by the ITR when the source host originates
a packet with the DF field of the IP header is set to 0. When the DF
field of the IP header is set to 1, or the packet is an IPv6 packet
originated by the source host, the ITR will drop the packet when the
size is greater than L, and sends an ICMP Too Big message to the
source with a value of S, where S is (L - H).

When the outer header encapsulation uses an IPv4 header the DF bit is
always set to 0.

This specification recommends that L be defined as 1500.

5.4.2. A Stateful Solution to MTU Handling

An ITR stateful solution to handle MTU issues is describe as follows
and was first introduced in [OPENLISP]:

1. The ITR will keep state of the effective MTU for each locator per
mapping cache entry. The effective MTU is what the core network
can deliver along the path between ITR and ETR.

2. When an IPv6 encapsulated packet or an IPv4 encapsulated packet
with DF bit set to 1, exceeds what the core network can deliver,
one of the intermediate routers on the path will send an ICMP Too
Big message to the ITR. The ITR will parse the ICMP message to
determine which locator is affected by the effective MTU change
and then record the new effective MTU value in the mapping cache
entry.

3. When a packet is received by the ITR from a source inside of the
site and the size of the packet is greater than the effective MTU
stored with the mapping cache entry associated with the
destination EID the packet is for, the ITR will send an ICMP Too
Big message back to the source. The packet size advertised by
the ITR in the ICMP Too Big message is the effective MTU minus
the LISP encapsulation length.

Even though this mechanism is stateful, it has advantages over the
stateless IP fragmentation mechanism, by not involving the
destination host with reassembly of ITR fragmented packets.

6. EID-to-RLOC Mapping

6.1. LISP IPv4 and IPv6 Control Plane Packet Formats

The following new UDP packet types are used to retrieve EID-to-RLOC
mappings:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Traffic Class | Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Length | Next Header=17| Hop Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Source Routing Locator +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Destination Routing Locator +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Source Port | Dest Port |
UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| LISP Message |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The LISP UDP-based messages are the Map-Request and Map-Reply
messages. When a UDP Map-Request is sent, the UDP source port is
chosen by the sender and the destination UDP port number is set to
4342. When a UDP Map-Reply is sent, the source UDP port number is
set to 4342 and the destination UDP port number is copied from the
source port of either the Map-Request or the invoking data packet.

The UDP Length field will reflect the length of the UDP header and
the LISP Message payload.

The UDP Checksum is computed and set to non-zero for Map-Request and
Map-Reply messages. It MUST be checked on receipt and if the
checksum fails, the packet MUST be dropped.

LISP-CONS [CONS] use TCP to send LISP control messages. The format
of control messages includes the UDP header so the checksum and
length fields can be used to protect and delimit message boundaries.

This main LISP specification is the authoritative source for message
format definitions for the Map-Request and Map-Reply messages.

6.1.1. LISP Packet Type Allocations

This section will be the authoritative source for allocating LISP
Type values. Current allocations are:

Reserved: 0 b'0000'
LISP Map-Request: 1 b'0001'
LISP Map-Reply: 2 b'0010'
LISP Map-Register: 3 b'0011'
LISP-CONS Open
LISP Encapsulated Control Message: 8 b'1000'
LISP-CONS Push-Add Message: 9 b'1001'
LISP-CONS Push-Delete Message: 10 b'1010'
LISP-CONS Unreachable Message 11 b'1011'

6.1.2. Map-Request Message Format

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type=1 |A|M|P|S| Reserved | Record Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . . . Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source-EID-AFI | ITR-AFI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source EID Address ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Originating ITR RLOC Address ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Reserved | EID mask-len | EID-prefix-AFI |
Rec +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | EID-prefix ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Map-Reply Record ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mapping Protocol Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Packet field descriptions:

Type: 1 (Map-Request)

A: This is an authoritative bit, which is set to 0 for UDP-based Map-
Requests sent by an ITR.

M: When set, it indicates a Map-Reply Record segment is included in
the Map-Request.

P: Indicates that a Map-Request should be treated as a "piggyback"
locator reachability probe. The receiver should respond with a
Map-Reply with the P bit set and the nonce copied from the Map-
Request. See section Section 6.3.2 for more details.

S: This is the SMR bit. See Section 6.5.2 for details.

Reserved: Set to 0 on transmission and ignored on receipt.

Record Count: The number of records in this Map-Request message. A
record is comprised of the portion of the packet that is labeled
'Rec' above and occurs the number of times equal to Record Count.
For this version of the protocol, a receiver MUST accept and
process Map-Requests that contain one or more records, but a
sender MUST only send Map-Requests containing one record. Support
for requesting multiple EIDs in a single Map-Request message will
be specified in a future version of the protocol.

Nonce: An 8-byte random value created by the sender of the Map-
Request. This nonce will be returned in the Map-Reply. The
security of the LISP mapping protocol depends critically on the
strength of the nonce in the Map-Request message. The nonce
SHOULD be generated by a properly seeded pseudo-random (or strong
random) source. See [RFC4086] for advice on generating security-
sensitive random data.

Source-EID-AFI: Address family of the "Source EID Address" field.

ITR-AFI: Address family of the "Originating ITR RLOC Address" field.

Source EID Address: This is the EID of the source host which
originated the packet which is invoking this Map-Request. When
Map-Requests are used for refreshing a map-cache entry or for
RLOC-probing, the value 0 is used.

Originating ITR RLOC Address: Used to give the ETR the option of
returning a Map-Reply in the address-family of this locator.

EID mask-len: Mask length for EID prefix.

EID-AFI: Address family of EID-prefix according to [RFC2434]

EID-prefix: 4 bytes if an IPv4 address-family, 16 bytes if an IPv6
address-family. When a Map-Request is sent by an ITR because a
data packet is received for a destination where there is no
mapping entry, the EID-prefix is set to the destination IP address
of the data packet. And the 'EID mask-len' is set to 32 or 128
for IPv4 or IPv6, respectively. When an xTR wants to query a site
about the status of a mapping it already has cached, the EID-
prefix used in the Map-Request has the same mask-length as the
EID-prefix returned from the site when it sent a Map-Reply
message.

Map-Reply Record: When the M bit is set, this field is the size of
the "Record" field in the Map-Reply format. This Map-Reply record
contains the EID-to-RLOC mapping entry associated with the Source
EID. This allows the ETR which will receive this Map-Request to
cache the data if it chooses to do so.

Mapping Protocol Data: See [CONS] or [ALT] for details. This field
is optional and present when the UDP length indicates there is
enough space in the packet to include it.

6.1.3. EID-to-RLOC UDP Map-Request Message

A Map-Request is sent from an ITR when it needs a mapping for an EID,
wants to test an RLOC for reachability, or wants to refresh a mapping
before TTL expiration. For the initial case, the destination IP
address used for the Map-Request is the destination-EID from the
packet which had a mapping cache lookup failure. For the later 2
cases, the destination IP address used for the Map-Request is one of
the RLOC addresses from the locator-set of the map cache entry. The
source address is either an IPv4 or IPv6 RLOC address depending if
the Map-Request is using an IPv4 versus IPv6 header, respectively.
In all cases, the UDP source port number for the Map-Request message
is a randomly allocated 16-bit value and the UDP destination port
number is set to the well-known destination port number 4342. A
successful Map-Reply updates the cached set of RLOCs associated with
the EID prefix range.

Map-Requests can also be LISP encapsulated using UDP destination port
4341
4342 with a LISP type value set to "Encapsulated Control Message",
when sent from an ITR to a Map-Resolver. Likewise, Map-Requests are
LISP encapsulated the same way from a Map-Server to an ETR. Details
on encapsulated Map-Requests and Map-Resolvers can be found in
[LISP-MS].

Map-Requests MUST be rate-limited. It is recommended that a Map-
Request for the same EID-prefix be sent no more than once per second.

An ITR that is configured with mapping database information (i.e. it
is also an ETR) may optionally include those mappings in a Map-
Request. When an ETR configured to accept and verify such
"piggybacked" mapping data receives such a Map-Request, it may
originate a "verifying Map-Request", addressed to the original ITR.
If the ETR has a map-cache entry that matches the "piggybacked" EID
and the RLOC is in the locator-set for the entry, then it may send
the "verifying Map-Request" to the original Map-Request source. If
not, then it MUST send it to the "piggybacked" EID. Doing this
forces the "verifying Map-Request" to go through the mapping database
system to reach the authoritative source of information about that
EID, guarding against RLOC-spoofing in in the "piggybacked" mapping
data.

6.1.4. Map-Reply Message Format

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type=2 |P|E| Reserved | Record Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . . . Nonce |
+-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Record TTL |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
R | Locator Count | EID mask-len | ACT |A| Reserved |
e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
c | Reserved | EID-AFI |
o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
r | EID-prefix |
d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| /| Priority | Weight | M Priority | M Weight |
| L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| o | Unused Flags |R| Loc-AFI |
| c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| \| Locator |
+-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mapping Protocol Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Packet field descriptions:

Type: 2 (Map-Reply)

P: Indicates that the Map-Reply is in response to a "piggyback"
locator reachability Map-Request. The nonce field should contain
a copy of the nonce value from the original Map-Request. See
section Section 6.3.2 for more details.

E: Indicates that the ETR which sends this Map-Reply message is
advertising that the site is enabled for the Echo-Nonce locator
reachability algorithm. See Section 6.3.1 for more details.

Reserved: Set to 0 on transmission and ignored on receipt.

Record Count: The number of records in this reply message. A record
is comprised of that portion of the packet labeled 'Record' above
and occurs the number of times equal to Record count.

Nonce: A 24-bit value set in a Data-Probe packet or a 64-bit value
from the Map-Request is echoed in this Nonce field of the Map-
Reply.

Record TTL: The time in minutes the recipient of the Map-Reply will
store the mapping. If the TTL is 0, the entry should be removed
from the cache immediately. If the value is 0xffffffff, the
recipient can decide locally how long to store the mapping.

Locator Count: The number of Locator entries. A locator entry
comprises what is labeled above as 'Loc'. The locator count can
be 0 indicating there are no locators for the EID-prefix.

EID mask-len: Mask length for EID prefix.

ACT: This 3-bit field describes negative Map-Reply actions. These
bits are used only when the 'Locator Count' field is set to 0.
The action bits are encoded only in Map-Reply messages. The
actions defined are used by an ITR or PTR when a destination EID
matches a negative mapping cache entry. Unassigned values should
cause a map-cache entry to be created and, when packets match this
negative cache entry, they will be dropped. The current assigned
values are:

(0) No action: No action Drop: The packet is being conveyed by the sender of the
Map-Reply message. dropped silently.

(1) Natively-Forward: The packet is not encapsulated or dropped
but natively forwarded.

(2) Drop: The packet is dropped silently.

(3) Send-Map-Request: The packet invokes sending a Map-Request.

A: The Authoritative bit, when sent by a UDP-based message is always
set by the ETR. See [CONS] for TCP-based Map-Replies.

EID-AFI: Address family of EID-prefix according to [RFC2434].

EID-prefix: 4 bytes if an IPv4 address-family, 16 bytes if an IPv6
address-family.

Priority: each RLOC is assigned a unicast priority. Lower values
are more preferable. When multiple RLOCs have the same priority,
they may be used in a load-split fashion. A value of 255 means
the RLOC MUST NOT be used for unicast forwarding.

Weight: when priorities are the same for multiple RLOCs, the weight
indicates how to balance unicast traffic between them. Weight is
encoded as a percentage of total unicast packets that match the
mapping entry. If a non-zero weight value is used for any RLOC,
then all RLOCs must use a non-zero weight value and then the sum
of all weight values MUST equal 100. If a zero value is used for
any RLOC weight, then all weights MUST be zero and the receiver of
the Map-Reply will decide how to load-split traffic. See
Section 6.4 for a suggested hash algorithm to distribute load
across locators with same priority and equal weight values. When
a single RLOC exists in a mapping entry, the weight value MUST be
set to 100 and ignored on receipt.

M Priority: each RLOC is assigned a multicast priority used by an
ETR in a receiver multicast site to select an ITR in a source
multicast site for building multicast distribution trees. A value
of 255 means the RLOC MUST NOT be used for joining a multicast
distribution tree.

M Weight: when priorities are the same for multiple RLOCs, the
weight indicates how to balance building multicast distribution
trees across multiple ITRs. The weight is encoded as a percentage
of total number of trees build to the source site identified by
the EID-prefix. If a non-zero weight value is used for any RLOC,
then all RLOCs must use a non-zero weight value and then the sum
of all weight values MUST equal 100. If a zero value is used for
any RLOC weight, then all weights MUST be zero and the receiver of
the Map-Reply will decide how to distribute multicast state across
ITRs.

Unused Flags: set to 0 when sending and ignored on receipt.

R: when this bit is set, the locator is known to be reachable from
the Map-Reply sender's perspective.

Locator: an IPv4 or IPv6 address (as encoded by the 'Loc-AFI' field)
assigned to an ETR or router acting as a proxy replier for the
EID-prefix. Note that the destination RLOC address MAY be an
anycast address. A source RLOC can be an anycast address as well.
The source or destination RLOC MUST NOT be the broadcast address
(255.255.255.255 or any subnet broadcast address known to the
router), and MUST NOT be a link-local multicast address. The
source RLOC MUST NOT be a multicast address. The destination RLOC
SHOULD be a multicast address if it is being mapped from a
multicast destination EID.

Mapping Protocol Data: See [CONS] or [ALT] for details. This field
is optional and present when the UDP length indicates there is
enough space in the packet to include it.

6.1.5. EID-to-RLOC UDP Map-Reply Message

When a Data Probe packet or a Map-Request triggers a Map-Reply to be
sent, the RLOCs associated with the EID-prefix matched by the EID in
the original packet destination IP address field will be returned.
The RLOCs in the Map-Reply are the globally-routable IP addresses of
the ETR but are not necessarily reachable; separate testing of
reachability is required.

Note that a Map-Reply may contain different EID-prefix granularity
(prefix + length) than the Map-Request which triggers it. This might
occur if a Map-Request were for a prefix that had been returned by an
earlier Map-Reply. In such a case, the requester updates its cache
with the new prefix information and granularity. For example, a
requester with two cached EID-prefixes that are covered by a Map-
Reply containing one, less-specific prefix, replaces the entry with
the less-specific EID-prefix. Note that the reverse, replacement of
one less-specific prefix with multiple more-specific prefixes, can
also occur but not by removing the less-specific prefix rather by
adding the more-specific prefixes which during a lookup will override
the less-specific prefix.

Replies SHOULD be sent for an EID-prefix no more often than once per
second to the same requesting router. For scalability, it is
expected that aggregation of EID addresses into EID-prefixes will
allow one Map-Reply to satisfy a mapping for the EID addresses in the
prefix range thereby reducing the number of Map-Request messages.

The addresses for a encapsulated data packets or Map-Request message
are swapped and used for sending the Map-Reply. The UDP source and
destination ports are swapped as well. That is, the source port in
the UDP header for the Map-Reply is set to the well-known UDP port
number 4342.

Map-Reply records can have an empty locator-set. This type of a Map-
Reply is called a Negative Map-Reply. Negative Map-Replies convey
special actions by the sender to the ITR or PTR which have solicited
the Map-Reply. There are two primary applications for Negative Map-
Replies. The first is for a Map-Resolver to instruct an ITR or PTR
when a destination is for a LISP site versus a non-LISP site. And
the other is to source quench Map-Requests which are sent for non-
allocated EIDs.

For each Map-Reply record, the list of locators in a locator-set MUST
appear in the same order for each ETR that originates a Map-Reply
message. The locator-set MUST be sorted in order of ascending IP
address where an IPv4 locator address is considered numerically 'less
than' an IPv6 locator address.

6.1.6. Map-Register Message Format

The usage details of the Map-Register message can be found in
specification [LISP-MS]. This section solely defines the message
format.

The message is sent in a UDP with a destination UDP port of 4342 and a
randomly selected UDP source port number. Before an IPv4 or IPv6 network
layer header is prepended, an AH header is prepended to carry
authentication information. The format conforms to the IPsec
specification [RFC4302]. The Map-Register message will use transport
mode by setting the IP protocol number field or the IPv6 next-header
field to 51.

The AH header from [RFC4302] is:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Payload Len | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Security Parameters Index (SPI) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number Field |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Authentication Data (variable) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The Next Header field is set to UDP. The SPI field is set to 0
(since no Security Association or Key Exchange protocol is being
used). The Sequence Number is a randomly chosen value by the sender.
The Authentication Data is 16 bytes and holds a SHA-1 or SHA-128
HMAC.

The Map-Register message format is:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type=3 |P| Reserved | Record Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| . . . Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key ID | Authentication Data Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Authentication Data ~
+-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Record TTL |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
R | Locator Count | EID mask-len | ACT |A| Reserved |
e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
c | Reserved | EID-AFI |
o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
r | EID-prefix |
d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| /| Priority | Weight | M Priority | M Weight |
| L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| o | Unused Flags |R| Loc-AFI |
| c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| \| Locator |
+-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Packet field descriptions:

Type: 3 (Map-Register)

P: Set to 1 by an ETR which sends a Map-Register message requesting
for the Map-Server to proxy Map-Reply. The Map-Server will send
non-authoritative Map-Replies on behalf of the ETR. Details on
this usage will be provided in a future version of this draft.

Reserved: Set to 0 on transmission and ignored on receipt.

Record Count: The number of records in this Map-Register message. A
record is comprised of that portion of the packet labeled 'Record'
above and occurs the number of times equal to Record count.

Nonce: This 8-byte Nonce field is set to 0 in Map-Register messages.

Key ID: A configured ID to find the configured Message
Authentication Code (MAC) algorithm and key value used for the
authentication function.

Authentication Data Length: The definition length in bytes of the rest
Authentication Data field that follows this field. The length of
the Map-Register can be found in the
Map-Reply section.

6.2. Routing Locator Selection

Both client-side and server-side may need control over the selection
of RLOCs for conversations between them. This control Authentication Data field is achieved by
manipulating dependent on the Priority and Weight fields in EID-to-RLOC Map-Reply
messages. Alternatively, RLOC information may be gleaned from
received tunneled packets or EID-to-RLOC Map-Request messages. Message
Authentication Code (MAC) algorithm used. The following enumerates different scenarios for choosing RLOCs and
the controls that are available:

o Server-side returns one RLOC. Client-side can only use one RLOC.
Server-side has complete control of the selection.

o Server-side returns a list of RLOC where length field allows
a subset of the list has
the same best priority. Client can only use device that doesn't know the subset list
according MAC algorithm to correctly parse
the weighting assigned by the server-side. In this
case, packet.

Authentication Data: The message digest used from the server-side controls both output of the subset list and load-
splitting across its members.
Message Authentication Code (MAC) algorithm. The client-side can use RLOCs
outside of entire Map-
Register payload is authenticated with this field preset to 0.
After the subset list if MAC is computed, it determines that the subset list is unreachable (unless RLOCs are set to a Priority of 255). Some
sharing placed in this field.
Implementations of control exists: the server-side determines the
destination RLOC list this specification MUST include support for
HMAC-SHA-1-96 [RFC2404] and load distribution while the client-side
has the option support for HMAC-SHA-128-256 [RFC4634]
is recommended.

The definition of using alternatives to this list if RLOCs in the
list are unreachable.

o Server-side sets weight rest of 0 for the RLOC subset list. In this
case, the client-side Map-Register can choose how the traffic load is spread
across be found in the subset list.
Map-Reply section.

6.1.7. Encapsualted Control Message Format

An Encapsulated Control Message is shared by the server-side
determining the list used to encapsulate control
packets sent between xTRs and the client determining load distribution.
Again, the client can use alternative RLOCs if the server-provided
list of RLOCs are unreachable.

o Either side (more likely on the server-side ETR) decides not to
send a Map-Request. For example, if the server-side ETR does not
send Map-Requests, it gleans RLOCs from the client-side ITR,
giving the client-side ITR responsibility for bidirectional mapping database system described
in [LISP-MS].

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | IPv4 or IPv6 Header |
OH | (uses RLOC
reachability and preferability. Server-side ETR gleaning of the
client-side ITR addresses) |
\ | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Source Port = xxxx | Dest Port = 4342 |
UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
LH |Type=8 | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | IPv4 or IPv6 Header |
IH | (uses RLOC is done by caching the inner header source or EID and the addresses) |
\ | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Source Port = xxxx | Dest Port = yyyy |
UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
LCM | LISP Control Message |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Packet header descriptions:

OH: The outer IPv4 or IPv6 header source which uses RLOC of received packets. The
client-side ITR controls how traffic is returned addresses in the
source and can alternate
using an destination header address fields.

UDP: The outer UDP header with destination port 4342. The source RLOC, which then can
port is randomly allocated. The checksum field MUST be added non-zero.

LH: Type 8 is defined to the
list the server-side ETR uses to return traffic. Since no
Priority be a "LISP Encapsulated Control Message"
and what follows is either an IPv4 or Weights are provided using this method, IPv6 header as encoded by
the server-
side ETR must assume each client-side ITR first 4 bits after the reserved field.

IH: The inner IPv4 or IPv6 header which can use either RLOC uses or EID
addresses in the same best
Priority with header address fields. When a Weight of zero. In addition, since EID-prefix
encoding cannot be conveyed Map-Request is
encapsulated in data packets, this packet format the EID-to-RLOC cache destination address in this
header is an EID.

UDP: The inner UDP header where the port assignments depends on tunnel routers can grow to be very large.

o A "gleaned" map-cache entry, one learned from the source RLOC of a
received encapsulated packet, is only stored and used for a few
seconds, pending verification. Verification
control packet being encapsulated. When the control packet is performed by
sending a
Map-Request to or Map-Register, the source EID (the inner header IP
source address) of port is randomly assigned
and the received encapsulated packet. A reply to
this "verifying Map-Request" destination port is used to fully populate 4342. When the map-
cache entry for control packet is a
Map-Reply, the "gleaned" EID and source port is stored 4342 and used for the
time indicated destination port is
assigned from the TTL field of a received Map-Reply. When a
verified map-cache entry is stored, data gleaning no longer occurs
for subsequent packets which have a source EID that matches the
EID-prefix port of the verified entry.

RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be
reachable when the R-bit for the locator record is set to 1. Neither
the information contained in a Map-Reply or that stored in the
mapping database system provide reachability information for RLOCs.
Such reachability needs invoking Map-Request. Port
number 4341 MUST NOT be assigned to either port. The checksum
field MUST be determined separately, using non-zero.

LCM: The format is one or
more of the Routing Locator Reachability Algorithms control message formats described in the
next
this section.

6.3. At this time, only Map-Request messages and PIM
Join-Prune messages [MLISP] are allowed to be encapsulated.
Encapsulating other types of LISP control messages are for further
study.

6.2. Routing Locator Reachability

Several mechanisms for determining RLOC reachability are currently
defined:

1. An ETR Selection

Both client-side and server-side may examine the Loc-Status-Bits in need control over the LISP header selection
of an
encapsulated data packet received from an ITR. If the ETR RLOCs for conversations between them. This control is
also acting as an ITR and has traffic to return to achieved by
manipulating the original
ITR site, it can use this status Priority and Weight fields in EID-to-RLOC Map-Reply
messages. Alternatively, RLOC information to help select an
RLOC.

2. An ITR may receive an ICMP Network be gleaned from
received tunneled packets or ICMP Host Unreachable
message EID-to-RLOC Map-Request messages.

The following enumerates different scenarios for an RLOC it is using. This indicates choosing RLOCs and
the controls that are available:

o Server-side returns one RLOC. Client-side can only use one RLOC.
Server-side has complete control of the selection.

o Server-side returns a list of RLOC is
likely down.

3. An ITR which participates in where a subset of the global routing system can
determine that an RLOC is down if no BGP RIB route exists that
matches list has
the RLOC IP address.

4. An ITR may receive an ICMP Port Unreachable message from a
destination host. This occurs if an ITR attempts to same best priority. Client can only use
interworking [INTERWORK] the subset list
according to the weighting assigned by the server-side. In this
case, the server-side controls both the subset list and LISP-encapsulated data load-
splitting across its members. The client-side can use RLOCs
outside of the subset list if it determines that the subset list
is sent to a
non-LISP-capable site.

5. An ITR may receive a Map-Reply from a ETR in response unreachable (unless RLOCs are set to a
previously sent Map-Request. The RLOC source Priority of 255). Some
sharing of control exists: the Map-Reply is
likely up since server-side determines the ETR was able to send
destination RLOC list and load distribution while the Map-Reply client-side
has the option of using alternatives to this list if RLOCs in the
ITR.

6. When an ETR receives an encapsulated packet from an ITR,
list are unreachable.

o Server-side sets weight of 0 for the
source RLOC from subset list. In this
case, the outer header of client-side can choose how the packet traffic load is likely up.

7. An ITR/ETR pair can use spread
across the Locator Reachability Algorithms
described in this section, namely Echo-Noncing or RLOC-Probing.

When determining Locator up/down reachability subset list. Control is shared by examining the Loc-
Status-Bits from server-side
determining the LISP encapsulated data packet, an ETR will
receive up to date status from an encapsulating ITR about
reachability for all ETRs at list and the site. CE-based ITRs at client determining load distribution.
Again, the source
site client can determine reachability relative to each other using the site
IGP as follows:

o Under normal circumstances, each ITR will advertise a default
route into the site IGP.

o If an ITR fails or use alternative RLOCs if the upstream link to its PE fails, its
default route will either time-out or be withdrawn.

Each ITR can thus observe the presence or lack server-provided
list of a default route
originated by the others to determine the Locator Status Bits it sets
for them. RLOCs listed in a Map-Reply are numbered with ordinals 0 unreachable.

o Either side (more likely on the server-side ETR) decides not to n-1. The
Loc-Status-Bits in
send a LISP encapsulated packet are numbered from 0 to
n-1 starting with the least significant bit. Map-Request. For example, if an RLOC
listed in the 3rd position of the Map-Reply goes down (ordinal value
2), then all ITRs at the site will clear the 3rd least significant
bit (xxxx x0xx) of the Loc-Status-Bits field for the packets they
encapsulate.

When an server-side ETR decapsulates a packet, does not
send Map-Requests, it will check for any change in
the Loc-Status-Bits field. When a bit goes gleans RLOCs from 1 to 0, the client-side ITR,
giving the client-side ITR responsibility for bidirectional RLOC
reachability and preferability. Server-side ETR will
refrain from encapsulating packets to an gleaning of the
client-side ITR RLOC that is indicated as
down. It will only resume using that RLOC if done by caching the corresponding Loc-
Status-Bit returns to a value inner header source
EID and the outer header source RLOC of 1. Loc-Status-Bits are associated
with a locator-set per EID-prefix. Therefore, when a locator becomes
unreachable, the Loc-Status-Bit that corresponds received packets. The
client-side ITR controls how traffic is returned and can alternate
using an outer header source RLOC, which then can be added to that locator's
position in the
list returned by the last Map-Reply will be set server-side ETR uses to
zero for that particular EID-prefix.

When ITRs at the site return traffic. Since no
Priority or Weights are not deployed provided using this method, the server-
side ETR must assume each client-side ITR RLOC uses the same best
Priority with a Weight of zero. In addition, since EID-prefix
encoding cannot be conveyed in CE routers, data packets, the IGP EID-to-RLOC cache
on tunnel routers can
still be used grow to determine be very large.

o A "gleaned" map-cache entry, one learned from the reachability source RLOC of Locators provided they
are injected into the IGP. This is typically done when a /32 address
received encapsulated packet, is configured on only stored and used for a loopback interface.

When ITRs receive ICMP Network or Host Unreachable messages as few
seconds, pending verification. Verification is performed by
sending a
method Map-Request to determine unreachability, they will refrain from using
Locators which are described in Locator lists the source EID (the inner header IP
source address) of Map-Replies.
However, using the received encapsulated packet. A reply to
this approach "verifying Map-Request" is unreliable because many network
operators turn off generation used to fully populate the map-
cache entry for the "gleaned" EID and is stored and used for the
time indicated from the TTL field of ICMP Unreachable messages.

If an ITR does receive an ICMP Network or Host Unreachable message,
it MAY originate its own ICMP Unreachable message destined for the
host that originated the data packet the ITR encapsulated.

Also, BGP-enabled ITRs can unilaterally examine the BGP RIB to see if
a locator address from a locator-set in received Map-Reply. When a mapping
verified map-cache entry matches a
prefix. If it does not find one and BGP is running in the Default
Free Zone (DFZ), it can decide to not use the locator even though the
Loc-Status-Bits indicate the locator is up. In this case, the path
from the ITR to the ETR stored, data gleaning no longer occurs
for subsequent packets which have a source EID that is assigned matches the locator is not
available. More details are in [LOC-ID-ARCH].

Optionally, an ITR can send a Map-Request to a Locator and if a Map-
Reply is returned, reachability
EID-prefix of the Locator has been determined.
Obviously, sending such probes increases the number of control verified entry.

RLOCs that appear in EID-to-RLOC Map-Reply messages originated by tunnel routers for active flows, so Locators are assumed to be
reachable when they are advertised.

This assumption does create a dependency: Locator unreachability is
detected by the receipt of ICMP Host Unreachable messages. When an
Locator has been determined to be unreachable, it is not used R-bit for
active traffic; this the locator record is set to 1. Neither
the same as if it were listed information contained in a Map-Reply
with priority 255.

The ITR can test or that stored in the
mapping database system provide reachability of the unreachable Locator by
sending periodic Requests. Both Requests and Replies MUST information for RLOCs.
Such reachability needs to be rate-
limited. determined separately, using one or
more of the Routing Locator reachability testing is never done with data
packets since that increases Reachability Algorithms described in the risk of packet loss
next section.

6.3. Routing Locator Reachability

Several mechanisms for end-to-end
sessions.

When an determining RLOC reachability are currently
defined:

1. An ETR decapsulates a packet, it knows that it is reachable from may examine the encapsulating ITR because that is how Loc-Status-Bits in the LISP header of an
encapsulated data packet arrived. In
most cases, received from an ITR. If the ETR can is
also reach the acting as an ITR but cannot assume this and has traffic to
be true due return to the possibility of path asymmetry. In the presence of
unidirectional traffic flow from an original
ITR site, it can use this status information to help select an ETR, the
RLOC.

2. An ITR should not
use the lack of return traffic as may receive an indication ICMP Network or ICMP Host Unreachable
message for an RLOC it is using. This indicates that the ETR is
unreachable. Instead, it must use an alternate mechanisms to
determine reachability.

6.3.1. Echo Nonce Algorithm

When there RLOC is bidirectional data flow between a pair of locators, a
simple mechanism called "nonce echoing"
likely down.

3. An ITR which participates in the global routing system can be used to
determine
reachability between that an RLOC is down if no BGP RIB route exists that
matches the RLOC IP address.

4. An ITR and ETR. When may receive an ICMP Port Unreachable message from a
destination host. This occurs if an ITR wants attempts to solicit a
nonce echo, it sets the N and E bits use
interworking [INTERWORK] and places LISP-encapsulated data is sent to a 24-bit nonce
non-LISP-capable site.

5. An ITR may receive a Map-Reply from a ETR in the
LISP header response to a
previously sent Map-Request. The RLOC source of the next encapsulated data packet.

When this packet Map-Reply is received by
likely up since the ETR, ETR was able to send the encapsulated packet is
forwarded as normal. When Map-Reply to the
ITR.

6. When an ETR next sends a data receives an encapsulated packet to the from an ITR, it includes the nonce received earlier with
source RLOC from the N bit set and E
bit cleared. The ITR sees outer header of the packet is likely up.

7. An ITR/ETR pair can use the Locator Reachability Algorithms
described in this "echoed nonce" and knows section, namely Echo-Noncing or RLOC-Probing.

When determining Locator up/down reachability by examining the path to
and Loc-
Status-Bits from the LISP encapsulated data packet, an ETR is up.

The ITR will set the E-bit and N-bit
receive up to date status from an encapsulating ITR about
reachability for every packet it sends while
in echo-nonce-request state. The time all ETRs at the ITR waits to process site. CE-based ITRs at the
echoed nonce before it determines source
site can determine reachability relative to each other using the path is unreachable is variable
and site
IGP as follows:

o Under normal circumstances, each ITR will advertise a choice left for default
route into the implementation. site IGP.

o If the an ITR is receiving packets from the ETR but does not see fails or if the
nonce echoed while being in echo-nonce-request state, then the path upstream link to the ETR is unreachable. This decision may its PE fails, its
default route will either time-out or be overridden by other
locator reachability algorithms. Once the withdrawn.

Each ITR determines can thus observe the path presence or lack of a default route
originated by the others to determine the ETR is down Locator Status Bits it can switch to another locator sets
for that EID-prefix.

Note that "ITR" and "ETR" them.

RLOCs listed in a Map-Reply are relative terms here. Both devices must
be implementing both ITR and ETR functionality for the echo nonce
mechanism numbered with ordinals 0 to operate.

The ITR and ETR may both go into echo-nonce-request state at the same
time. n-1. The number of packets sent or the time during which echo nonce
requests are sent is an implementation specific setting. However,
when an ITR is
Loc-Status-Bits in echo-nonce-request state, it can echo a LISP encapsulated packet are numbered from 0 to
n-1 starting with the ETR's
nonce least significant bit. For example, if an RLOC
listed in the next set 3rd position of packets that it encapsulates and the Map-Reply goes down (ordinal value
2), then
subsequently, continue sending echo-nonce-request packets.

This mechanism does not completely solve all ITRs at the forward path
reachability problem as traffic may be unidirectional. That is, site will clear the 3rd least significant
bit (xxxx x0xx) of the Loc-Status-Bits field for the packets they
encapsulate.

When an ETR receiving traffic at decapsulates a site may not may not be packet, it will check for any change in
the same device as
an ITR which transmits traffic from that site or Loc-Status-Bits field. When a bit goes from 1 to 0, the site ETR will
refrain from encapsulating packets to site
traffic is unidirectional so there is no ITR returning traffic.

The echo-nonce algorithm an RLOC that is bilateral. That is, indicated as
down. It will only resume using that RLOC if one side sets the
E-bit and the other side is not enabled for echo-noncing, then the
echoing corresponding Loc-
Status-Bit returns to a value of the nonce does not occur and the requesting side may
regard the 1. Loc-Status-Bits are associated
with a locator-set per EID-prefix. Therefore, when a locator unreachable erroneously. An ITR should only set becomes
unreachable, the E-bit Loc-Status-Bit that corresponds to that locator's
position in a encapsulated data packet when it knows the ETR is
enabled for echo-noncing. This is conveyed list returned by the E-bit in the Map-
Reply message.

Note that other locator reachability mechanisms are being researched
and can last Map-Reply will be used set to compliment or even override the Echo Nonce
Algorithm. See next section
zero for an example of control-plane probing.

6.3.2. RLOC Probing Algorithm

RLOC Probing is a method that an ITR or PTR particular EID-prefix.

When ITRs at the site are not deployed in CE routers, the IGP can use
still be used to determine the reachability status of one or more locators that it has cached in a
map-cache entry. The P-bit (Probe Bit) of the Map-Request and Map-
Reply messages Locators provided they
are used for RLOC Probing.

RLOC probing injected into the IGP. This is typically done in the control-plane when a /32 address
is configured on a timer basis where an
ITR or PTR will originate loopback interface.

When ITRs receive ICMP Network or Host Unreachable messages as a Map-Request destined
method to a locator address determine unreachability, they will refrain from one of its own locator addresses. A Map-Request used as an
RLOC-probe is NOT encapsulated and NOT sent to a Map-Server or on the
ALT like one would when soliciting mapping data. The EID record
encoded using
Locators which are described in the Map-Request Locator lists of Map-Replies.
However, using this approach is the EID-prefix unreliable because many network
operators turn off generation of the map-cache entry
cached by the ITR or PTR. The ICMP Unreachable messages.

If an ITR does receive an ICMP Network or PTR may include a mapping data
record for Host Unreachable message,
it MAY originate its own database mapping information.

When an ETR receives a Map-Request ICMP Unreachable message with destined for the P-bit set, it
returns a Map-Reply with
host that originated the P-bit set. The source address of data packet the
Map-Reply is set from ITR encapsulated.

Also, BGP-enabled ITRs can unilaterally examine the destination BGP RIB to see if
a locator address of the Map-Request from a locator-set in a mapping entry matches a
prefix. If it does not find one and
the destination address of the Map-Reply BGP is set from running in the source
address of Default
Free Zone (DFZ), it can decide to not use the Map-Request. The Map-Reply should contain mapping
data for locator even though the EID-prefix contained in
Loc-Status-Bits indicate the Map-Request. This provides locator is up. In this case, the opportunity for path
from the ITR or PTR, which sent the RLOC-probe to get
mapping updates if there were changes to the ETR's database mapping
entries.

There are advantages and disadvantages of RLOC Probing. The greatest
benefit of RLOC Probing is ETR that it can handle many failure scenarios
allowing the ITR to determine when is assigned the path to a specific locator is
reachable or has become unreachable, thus providing not
available. More details are in [LOC-ID-ARCH].

Optionally, an ITR can send a robust
mechanism for switching Map-Request to using another locator from the cached
locator. RLOC Probing can also provide RTT estimates between a pair
of locators which can be useful for network management purposes as
well as for selecting low delay paths. The major disadvantage of
RLOC Probing Locator and if a Map-
Reply is in returned, reachability of the Locator has been determined.
Obviously, sending such probes increases the number of control
messages required and the
amount of bandwidth used to obtain those benefits, especially if the
requirement originated by tunnel routers for failure detection times active flows, so Locators
are very small.

Continued research and testing will attempt assumed to characterize be reachable when they are advertised.

This assumption does create a dependency: Locator unreachability is
detected by the
tradeoffs receipt of failure detection times versus message overhead.

6.4. Routing Locator Hashing ICMP Host Unreachable messages. When an ETR provides an EID-to-RLOC mapping in a Map-Reply message
Locator has been determined to
a requesting ITR, the locator-set be unreachable, it is not used for
active traffic; this is the EID-prefix may contain
different priority values for each locator address. When more than
one best same as if it were listed in a Map-Reply
with priority locator exists, the 255.

The ITR can decide how to load
share traffic against test the corresponding locators.

The following hash algorithm may be used by an ITR to select a
locator for a packet destined to an EID for reachability of the EID-to-RLOC mapping:

1. Either a source unreachable Locator by
sending periodic Requests. Both Requests and destination address hash can Replies MUST be used or the
traditional 5-tuple hash which includes the source and
destination addresses, source and destination TCP, UDP, or SCTP
port numbers and rate-
limited. Locator reachability testing is never done with data
packets since that increases the IP protocol number field or IPv6 next-
protocol fields risk of a packet a host originates from within a LISP
site. loss for end-to-end
sessions.

When an ETR decapsulates a packet is not a TCP, UDP, or SCTP packet, the
source and destination addresses only it knows that it is reachable from
the header are used to
compute the hash.

2. Take the hash value and divide it by encapsulating ITR because that is how the number of locators
stored in packet arrived. In
most cases, the locator-set for ETR can also reach the EID-to-RLOC mapping.

3. The remainder will ITR but cannot assume this to
be yield a value of 0 true due to "number the possibility of locators
minus 1". Use path asymmetry. In the remainder presence of
unidirectional traffic flow from an ITR to select an ETR, the locator in ITR should not
use the
locator-set.

Note lack of return traffic as an indication that when a packet is LISP encapsulated, the source port number
in the outer UDP header needs ETR is
unreachable. Instead, it must use an alternate mechanisms to be set. Selecting a random value
allows core routers which are attached
determine reachability.

6.3.1. Echo Nonce Algorithm

When there is bidirectional data flow between a pair of locators, a
simple mechanism called "nonce echoing" can be used to Link Aggregation Groups
(LAGs) determine
reachability between an ITR and ETR. When an ITR wants to load-split the encapsulated packets across member links of
such LAGs. Otherwise, core routers would see solicit a single flow, since
packets have
nonce echo, it sets the N and E bits and places a source address 24-bit nonce in the
LISP header of the ITR, for packets which are
originated next encapsulated data packet.

When this packet is received by different EIDs at the source site. A suggested setting
for ETR, the source port number computed by an ITR encapsulated packet is a 5-tuple hash
function on the inner header,
forwarded as described above.

Many core router implementations use normal. When the ETR next sends a 5-tuple hash to decide how to
balance data packet load across members of a LAG. The 5-tuple hash to the
ITR, it includes the source and destination addresses of nonce received earlier with the packet N bit set and E
bit cleared. The ITR sees this "echoed nonce" and knows the
source path to
and destination ports when from the protocol number in ETR is up.

The ITR will set the E-bit and N-bit for every packet it sends while
in echo-nonce-request state. The time the ITR waits to process the
echoed nonce before it determines the path is TCP or UDP. For this reason, UDP encoding unreachable is used variable
and a choice left for LISP
encapsulation.

6.5. Changing the Contents of EID-to-RLOC Mappings

Since the LISP architecture uses a caching scheme to retrieve and
store EID-to-RLOC mappings, implementation.

If the only way an ITR can get a more up-to-
date mapping is to re-request the mapping. However, receiving packets from the ITRs do ETR but does not
know when see the mappings change and
nonce echoed while being in echo-nonce-request state, then the ETRs do not keep track of who
requested its mappings. For scalability reasons, we want to maintain
this approach but need path
to provide a way for ETRs change their
mappings and inform the sites that are currently communicating with the ETR site using such mappings.

When a locator record is added unreachable. This decision may be overridden by other
locator reachability algorithms. Once the ITR determines the path to
the end of a locator-set, it ETR is
easy down it can switch to update mappings. We assume new mappings will maintain the
same another locator ordering as for that EID-prefix.

Note that "ITR" and "ETR" are relative terms here. Both devices must
be implementing both ITR and ETR functionality for the old mapping but just have new locators
appended echo nonce
mechanism to operate.

The ITR and ETR may both go into echo-nonce-request state at the end same
time. The number of packets sent or the list. So some ITRs can have a new mapping
while other ITRs have only an old mapping that is used until they time out. When during which echo nonce
requests are sent is an ITR has only implementation specific setting. However,
when an old mapping but detects bits set ITR is in the loc-status-bits that correspond to locators beyond the list echo-nonce-request state, it
has cached, it simply ignores them.

When a locator record is removed from a locator-set, ITRs that have
the mapping cached will not use the removed locator because the xTRs
will set the loc-status-bit to 0. So even if can echo the locator is ETR's
nonce in the
list, next set of packets that it will encapsulates and then
subsequently, continue sending echo-nonce-request packets.

This mechanism does not completely solve the forward path
reachability problem as traffic may be used. For new mapping requests, unidirectional. That is, the xTRs can
set
ETR receiving traffic at a site may not may not be the locator address to 0 as well same device as setting the corresponding
loc-status-bit to 0. This forces ITRs with old
an ITR which transmits traffic from that site or new mappings to
avoid using the removed locator.

If many changes occur site to a mapping over a long period of time, site
traffic is unidirectional so there is no ITR returning traffic.

The echo-nonce algorithm is bilateral. That is, if one
will find empty record slots in side sets the middle
E-bit and the other side is not enabled for echo-noncing, then the
echoing of the locator-set nonce does not occur and new
records appended to the locator-set. At some point, it would be
useful to compact requesting side may
regard the locator-set so locator unreachable erroneously. An ITR should only set
the loc-status-bit settings can
be efficiently packed.

We propose here two approaches E-bit in a encapsulated data packet when it knows the ETR is
enabled for locator-set compaction, one
operational and echo-noncing. This is conveyed by the E-bit in the Map-
Reply message.

Note that other a protocol mechanism. The operational
approach uses a clock sweep method. The protocol approach uses the
concept of Solicit-Map-Requests.

6.5.1. Clock Sweep

The clock sweep approach uses planning in advance locator reachability mechanisms are being researched
and can be used to compliment or even override the use Echo Nonce
Algorithm. See next section for an example of
count-down TTLs control-plane probing.

6.3.2. RLOC Probing Algorithm

RLOC Probing is a method that an ITR or PTR can use to time out mappings determine the
reachability status of one or more locators that have already been cached. it has cached in a
map-cache entry. The default setting P-bit (Probe Bit) of the Map-Request and Map-
Reply messages are used for an EID-to-RLOC mapping TTL is 24 hours. So
there RLOC Probing.

RLOC probing is done in the control-plane on a 24 hour window timer basis where an
ITR or PTR will originate a Map-Request destined to time out old mappings. The following
clock sweep procedure is used:

1. 24 hours before a mapping change locator address
from one of its own locator addresses. A Map-Request used as an
RLOC-probe is NOT encapsulated and NOT sent to take effect, a network
administrator configures Map-Server or on the ETRs at a site to start
ALT like one would when soliciting mapping data. The EID record
encoded in the clock
sweep window.

2. During Map-Request is the clock sweep window, ETRs continue to send Map-Reply
messages with EID-prefix of the current (unchanged) mapping records. map-cache entry
cached by the ITR or PTR. The TTL ITR or PTR may include a mapping data
record for these mappings is set to 1 hour.

3. 24 hours later, all previous cache entries will have timed out,
and any active cache entries will time out within 1 hour. During
this 1 hour window its own database mapping information.

When an ETR receives a Map-Request message with the ETRs continue to send P-bit set, it
returns a Map-Reply messages with the current (unchanged) mapping records with P-bit set. The source address of the TTL
Map-Reply is set to
1 minute.

4. At from the end destination address of the 1 hour window, Map-Request and
the destination address of the ETRs will send Map-Reply
messages with is set from the new (changed) mapping records. So any active
caches can get source
address of the new Map-Request. The Map-Reply should contain mapping contents right away if not cached,
or
data for the EID-prefix contained in 1 minute if they had the mapping cached.

6.5.2. Solicit-Map-Request (SMR)

Soliciting a Map-Request is a selective way Map-Request. This provides
the opportunity for xTRs, at the site
where mappings change, to control ITR or PTR, which sent the rate they receive requests for
Map-Reply messages. SMRs are also used RLOC-probe to tell remote ITRs get
mapping updates if there were changes to update
the mappings they have cached.

Since the xTRs don't keep track of remote ITRs that have cached their
mappings, they can not tell exactly who needs the new ETR's database mapping
entries. So an xTR will solicit Map-Requests from sites it is
currently sending encapsulated data to,

There are advantages and only from those sites. disadvantages of RLOC Probing. The xTRs greatest
benefit of RLOC Probing is that it can locally decide the algorithm for how often and to how handle many sites it sends SMR messages.

An SMR message is simply a bit set in a Map-Request message. An failure scenarios
allowing the ITR
or PTR will send a Map-Request to determine when they receive an SMR message.
Both the SMR sender and the Map-Request responder must rate-limited
these messages.

The following procedure shows how a SMR exchange occurs when path to a site specific locator is doing locator-set compaction
reachable or has become unreachable, thus providing a robust
mechanism for an EID-to-RLOC mapping:

1. When switching to using another locator from the database mappings cached
locator. RLOC Probing can also provide RTT estimates between a pair
of locators which can be useful for network management purposes as
well as for selecting low delay paths. The major disadvantage of
RLOC Probing is in an ETR change, the ETRs at number of control messages required and the site
begin
amount of bandwidth used to send Map-Requests with obtain those benefits, especially if the SMR bit set
requirement for each locator
in each map-cache entry the ETR caches.

2. A remote xTR which receives failure detection times are very small.

Continued research and testing will attempt to characterize the SMR
tradeoffs of failure detection times versus message will schedule sending overhead.

6.4. Routing Locator Hashing

When an ETR provides an EID-to-RLOC mapping in a Map-Request Map-Reply message to
a requesting ITR, the source locator address of the SMR
message. A newly allocated random nonce is selected and the EID-
prefix uses is locator-set for the EID-prefix may contain
different priority values for each locator address. When more than
one copied from best priority locator exists, the SMR message.

3. The remote xTR retransmits the Map-Request slowly until it gets a
Map-Reply while continuing ITR can decide how to use load
share traffic against the cached mapping.

4. corresponding locators.

The ETRs at the site with the changed mapping will reply following hash algorithm may be used by an ITR to select a
locator for a packet destined to an EID for the
Map-Request with EID-to-RLOC mapping:

1. Either a Map-Reply message provided source and destination address hash can be used or the Map-Request
nonce matches
traditional 5-tuple hash which includes the nonce from source and
destination addresses, source and destination TCP, UDP, or SCTP
port numbers and the SMR. The Map-Reply messages
SHOULD be rate limited. This IP protocol number field or IPv6 next-
protocol fields of a packet a host originates from within a LISP
site. When a packet is important to avoid Map-Reply
implosion.

5. The ETRs, at the site with not a TCP, UDP, or SCTP packet, the changed mapping, records
source and destination addresses only from the fact
that header are used to
compute the site that sent hash.

2. Take the Map-Request has received hash value and divide it by the new
mapping data number of locators
stored in the mapping cache entry locator-set for the remote site so
the loc-status-bits are reflective EID-to-RLOC mapping.

3. The remainder will be yield a value of 0 to "number of locators
minus 1". Use the new mapping for packets
going remainder to select the remote site. The ETR then stops sending SMR
messages.

For security reasons an ITR MUST NOT process unsolicited Map-Replies.
The nonce MUST be carried from SMR packet, into locator in the resultant Map-
Request, and then into Map-Reply
locator-set.

Note that when a packet is LISP encapsulated, the source port number
in the outer UDP header needs to reduce spoofing attacks.

To avoid map-cache entry corruption by be set. Selecting a third-party, random value
allows core routers which are attached to Link Aggregation Groups
(LAGs) to load-split the encapsulated packets across member links of
such LAGs. Otherwise, core routers would see a sender single flow, since
packets have a source address of an
SMR-based Map-Request must be verified. If the ITR, for packets which are
originated by different EIDs at the source site. A suggested setting
for the source port number computed by an ITR receives an SMR-
based Map-Request is a 5-tuple hash
function on the inner header, as described above.

Many core router implementations use a 5-tuple hash to decide how to
balance packet load across members of a LAG. The 5-tuple hash
includes the source and destination addresses of the packet and the
source is not and destination ports when the protocol number in the locator-set packet
is TCP or UDP. For this reason, UDP encoding is used for LISP
encapsulation.

6.5. Changing the
stored map-cache entry, then Contents of EID-to-RLOC Mappings

Since the responding Map-Request MUST be sent
with an EID destination LISP architecture uses a caching scheme to retrieve and
store EID-to-RLOC mappings, the only way an ITR can get a more up-to-
date mapping database system. Since the
mapping database system is more secure to reach an authoritative ETR,
it will deliver re-request the Map-Request to mapping. However, the authoritative source of ITRs do not
know when the
mapping data.

7. Router Performance Considerations

LISP is designed to be very hardware-based forwarding friendly. By
doing tunnel header prepending [RFC1955] mappings change and stripping instead the ETRs do not keep track of re-
writing addresses, existing hardware can support who
requested its mappings. For scalability reasons, we want to maintain
this approach but need to provide a way for ETRs change their
mappings and inform the forwarding model
with little or no modification. Where modifications sites that are required,
they should be limited currently communicating with
the ETR site using such mappings.

When a locator record is added to re-programming existing hardware rather
than requiring expensive design changes the end of a locator-set, it is
easy to hard-coded algorithms in
silicon.

A few implementation techniques update mappings. We assume new mappings will maintain the
same locator ordering as the old mapping but just have new locators
appended to the end of the list. So some ITRs can be have a new mapping
while other ITRs have only an old mapping that is used until they
time out. When an ITR has only an old mapping but detects bits set
in the loc-status-bits that correspond to incrementally
implement LISP:

o locators beyond the list it
has cached, it simply ignores them.

When a tunnel encapsulated packet locator record is received by an ETR, removed from a locator-set, ITRs that have
the outer
destination address may mapping cached will not be use the address of removed locator because the router. This
makes it challenging for xTRs
will set the control plane loc-status-bit to get packets from 0. So even if the
hardware. This may be mitigated by creating special FIB entries
for locator is in the EID-prefixes of EIDs served by the ETR (those for which
the router provides an RLOC translation). These FIB entries are
marked with a flag indicating that control plane processing should
be performed. The forwarding logic of testing for particular IP
protocol number value is
list, it will not necessary. No changes to existing,
deployed hardware should be needed to support this.

o On an ITR, prepending a used. For new IP header is as simple as adding more
bytes to a MAC rewrite string and prepending mapping requests, the string xTRs can
set the locator address to 0 as part of well as setting the outgoing encapsulation procedure. Many routers that support
GRE tunneling [RFC2784] corresponding
loc-status-bit to 0. This forces ITRs with old or 6to4 tunneling [RFC3056] can already
support this action.

o When a received packet's outer destination address contains an EID
which is not intended new mappings to be forwarded on
avoid using the routable topology
(i.e. LISP 1.5), removed locator.

If many changes occur to a mapping over a long period of time, one
will find empty record slots in the source address middle of a data packet or the
router interface with which locator-set and new
records appended to the source is associated (the
interface from which locator-set. At some point, it was received) can be associated with a VRF
(Virtual Routing/Forwarding), in which a different (i.e. non-
congruent) topology can would be used
useful to find EID-to-RLOC mappings.

8. Deployment Scenarios

This section will explore how and where ITRs and ETRs compact the locator-set so the loc-status-bit settings can
be deployed
and will discuss the pros and cons of each deployment scenario.
There are efficiently packed.

We propose here two basic deployment trade-offs to consider: centralized
versus distributed caches approaches for locator-set compaction, one
operational and flat, recursive, or re-encapsulating
tunneling.

When deciding on centralized versus distributed caching, the
following issues should be considered:

o Are the tunnel routers spread out so that the caches are spread
across all other a protocol mechanism. The operational
approach uses a clock sweep method. The protocol approach uses the memories
concept of each router?

o Should management "touch points" be minimized by choosing few
tunnel routers, just enough for redundancy?

o In general, using more ITRs doesn't increase management load,
since caches are built Solicit-Map-Requests.

6.5.1. Clock Sweep

The clock sweep approach uses planning in advance and stored dynamically. On the other hand,
more ETRs does require more management since EID-prefix-to-RLOC use of
count-down TTLs to time out mappings need that have already been cached.
The default setting for an EID-to-RLOC mapping TTL is 24 hours. So
there is a 24 hour window to be explicitly configured.

When deciding on flat, recursive, or re-encapsulation tunneling, the time out old mappings. The following issues should be considered:

o Flat tunneling implements a single tunnel between source site and
destination site. This generally offers better paths between
sources and destinations with a single tunnel path.

o Recursive tunneling
clock sweep procedure is when tunneled traffic used:

1. 24 hours before a mapping change is again further
encapsulated in another tunnel, either to implement VPNs or to
perform Traffic Engineering. When doing VPN-based tunneling, take effect, a network
administrator configures the ETRs at a site has some control since the site is prepending a new tunnel
header. In the case of TE-based tunneling, the site may have
control if it is prepending a new tunnel header, but if the site's
ISP is doing the TE, then to start the site has no control. Recursive
tunneling generally will result in suboptimal paths but at clock
sweep window.

2. During the
benefit of steering traffic clock sweep window, ETRs continue to resource available parts of send Map-Reply
messages with the
network.

o current (unchanged) mapping records. The technique of re-encapsulation ensures that packets only
require one tunnel header. So if a packet needs to be rerouted,
it TTL
for these mappings is first decapsulated by the ETR set to 1 hour.

3. 24 hours later, all previous cache entries will have timed out,
and then re-encapsulated with
a new tunnel header using a new RLOC.

The next sub-sections any active cache entries will describe where tunnel routers can reside
in time out within 1 hour. During
this 1 hour window the network.

8.1. First-hop/Last-hop Tunnel Routers

By locating tunnel routers close ETRs continue to hosts, send Map-Reply messages
with the EID-prefix current (unchanged) mapping records with the TTL set is at to
1 minute.

4. At the granularity end of an IP subnet. So at the expense of more EID-
prefix-to-RLOC sets for 1 hour window, the site, ETRs will send Map-Reply
messages with the new (changed) mapping records. So any active
caches in each tunnel router can remain relatively small. But caches always depend on get the number
of non-aggregated EID destination flows active through these tunnel
routers.

With more tunnel routers doing encapsulation, the increase new mapping contents right away if not cached,
or in control
traffic grows as well: since 1 minute if they had the EID-granularity mapping cached.

6.5.2. Solicit-Map-Request (SMR)

Soliciting a Map-Request is greater, more
Map-Requests and Map-Replies a selective way for xTRs, at the site
where mappings change, to control the rate they receive requests for
Map-Reply messages. SMRs are traveling between more routers.

The advantage of placing also used to tell remote ITRs to update
the caches and databases at these stub
routers is that mappings they have cached.

Since the products deployed in this part xTRs don't keep track of the network remote ITRs that have better price-memory ratios then cached their core router counterparts.
Memory
mappings, they can not tell exactly who needs the new mapping
entries. So an xTR will solicit Map-Requests from sites it is typically less expensive in these devices and fewer routes
are stored (only IGP routes). These devices tend to have excess
capacity, both for forwarding
currently sending encapsulated data to, and routing state.

LISP functionality only from those sites.
The xTRs can also be deployed in edge switches. These
devices generally have layer-2 ports facing hosts and layer-3 ports
facing locally decide the Internet. Spare capacity is also often available in these
devices as well.

8.2. Border/Edge Tunnel Routers

Using customer-edge (CE) routers algorithm for tunnel endpoints allows the EID
space associated with a site how often and to be reachable via how
many sites it sends SMR messages.

An SMR message is simply a small bit set of RLOCs
assigned to the CE routers for that site.

This offers the opposite benefit of the first-hop/last-hop tunnel
router scenario: in a Map-Request message. An ITR
or PTR will send a Map-Request when they receive an SMR message.
Both the number of mapping entries SMR sender and network management
touch points are reduced, allowing better scaling.

One disadvantage the Map-Request responder must rate-limited
these messages.

The following procedure shows how a SMR exchange occurs when a site
is that less of doing locator-set compaction for an EID-to-RLOC mapping:

1. When the network's resources are used to
reach host endpoints thereby centralizing database mappings in an ETR change, the point-of-failure domain
and creating network choke points ETRs at the CE router.

Note that more than one CE router at a site can be configured
begin to send Map-Requests with the same IP address. In this case an RLOC is an anycast address.
This allows resilience between SMR bit set for each locator
in each map-cache entry the CE routers. That is, if ETR caches.

2. A remote xTR which receives the SMR message will schedule sending
a CE
router fails, traffic Map-Request message to the source locator address of the SMR
message. A newly allocated random nonce is automatically routed selected and the EID-
prefix uses is the one copied from the SMR message.

3. The remote xTR retransmits the Map-Request slowly until it gets a
Map-Reply while continuing to use the other routers
using cached mapping.

4. The ETRs at the same anycast address. However, this comes site with the
disadvantage where changed mapping will reply to the site cannot control
Map-Request with a Map-Reply message provided the entrance point when Map-Request
nonce matches the anycast route is advertised out nonce from all border routers.

8.3. ISP Provider-Edge (PE) Tunnel Routers

Use of ISP PE routers as tunnel endpoint routers gives an ISP control
over the location of SMR. The Map-Reply messages
SHOULD be rate limited. This is important to avoid Map-Reply
implosion.

5. The ETRs, at the egress tunnel endpoints. That is, site with the ISP
can decide if changed mapping, records the tunnel endpoints are in fact
that the destination site (in
either CE routers or last-hop routers within a site) or at other PE
edges. The advantage of this case is that two or more tunnel headers
can be avoided. By having the PE be sent the first router on Map-Request has received the path to
encapsulate, it can choose a TE path first, and new
mapping data in the ETR can
decapsulate and re-encapsulate mapping cache entry for a tunnel to the destination end
site.

An obvious disadvantage is that the end remote site has no control over
where its packets flow or so
the RLOCs used.

As mentioned in earlier sections a combination loc-status-bits are reflective of these scenarios is
possible at the expense of extra packet header overhead, if both site
and provider want control, then recursive or re-encapsulating tunnels
are used.

9. Traceroute Considerations

When a source host in a LISP site initiates a traceroute to a
destination host in another LISP site, it is highly desirable new mapping for it
to see the entire path. Since packets are encapsulated from ITR
going to
ETR, the hop across the tunnel could be viewed as a single hop.
However, LISP traceroute will provide the entire path so the user can
see 3 distinct segments of the path remote site. The ETR then stops sending SMR
messages.

For security reasons an ITR MUST NOT process unsolicited Map-Replies.
The nonce MUST be carried from a source LISP host SMR packet, into the resultant Map-
Request, and then into Map-Reply to reduce spoofing attacks.

To avoid map-cache entry corruption by a
destination LISP host:

Segment 1 (in source LISP site based on EIDs):

source-host ---> first-hop ... next-hop ---> ITR

Segment 2 (in the core network based on RLOCs): third-party, a sender of an
SMR-based Map-Request must be verified. If an ITR ---> next-hop ... next-hop ---> ETR

Segment 3 (in the destination LISP site receives an SMR-
based on EIDs):

ETR ---> next-hop ... last-hop ---> destination-host

For segment 1 of Map-Request and the path, ICMP Time Exceeded messages are returned source is not in the normal matter as they are today. The ITR performs a TTL
decrement and test locator-set for 0 before encapsulating. So the ITR hop is
seen by
stored map-cache entry, then the traceroute source has responding Map-Request MUST be sent
with an EID address (the address of
site-facing interface).

For segment 2 of the path, ICMP Time Exceeded messages are returned destination to the ITR because mapping database system. Since the TTL decrement to 0
mapping database system is done on the outer
header, so the destination of the ICMP messages are more secure to reach an authoritative ETR,
it will deliver the ITR RLOC
address, Map-Request to the authoritative source source RLOC address of the encapsulated
traceroute packet. The ITR looks inside of the ICMP payload to
inspect the traceroute source so it can return the ICMP message
mapping data.

7. Router Performance Considerations

LISP is designed to
the address be very hardware-based forwarding friendly. By
doing tunnel header prepending [RFC1955] and stripping instead of the traceroute client as well as retaining the core
router IP address in the ICMP message. This is so the traceroute
client re-
writing addresses, existing hardware can display the core router address (the RLOC address) in support the
traceroute output. The ETR returns its RLOC address and responds forwarding model
with little or no modification. Where modifications are required,
they should be limited to
the TTL decrement re-programming existing hardware rather
than requiring expensive design changes to 0 like the previous core routers did.

For segment 3, the next-hop router downstream from the ETR will hard-coded algorithms in
silicon.

A few implementation techniques can be
decrementing the TTL for the used to incrementally
implement LISP:

o When a tunnel encapsulated packet that was encapsulated, sent into
the core, decapsulated is received by the an ETR, and forwarded because it isn't the
final destination. If the TTL is decremented to 0, any router on the
path to the outer
destination address may not be the address of the traceroute, including router. This
makes it challenging for the next-hop
router or destination, will send an ICMP Time Exceeded message control plane to get packets from the
source EID of the traceroute client. The ICMP message will
hardware. This may be
encapsulated mitigated by creating special FIB entries
for the local ITR and sent back to EID-prefixes of EIDs served by the ETR in the
originated traceroute source site, where the packet will be delivered
to (those for which
the host.

9.1. IPv6 Traceroute

IPv6 traceroute follows the procedure described above since the
entire traceroute data packet router provides an RLOC translation). These FIB entries are
marked with a flag indicating that control plane processing should
be performed. The forwarding logic of testing for particular IP
protocol number value is included in ICMP Time Exceeded
message payload. Therefore, only the ITR needs not necessary. No changes to pay special
attention for forwarding ICMP messages back existing,
deployed hardware should be needed to the traceroute source.

9.2. IPv4 Traceroute

For IPv4 traceroute, we cannot follow the above procedure since IPv4
ICMP Time Exceeded messages only include the invoking support this.

o On an ITR, prepending a new IP header and 8 is as simple as adding more
bytes that follow the IP header. Therefore, when a core router sends
an IPv4 Time Exceeded message to an ITR, all the ITR has in the ICMP
payload is the encapsulated header it prepended followed by a UDP
header. The original invoking IP header, MAC rewrite string and therefore prepending the identity string as part of
the traceroute source is lost.

The solution we propose to solve outgoing encapsulation procedure. Many routers that support
GRE tunneling [RFC2784] or 6to4 tunneling [RFC3056] can already
support this problem action.

o When a received packet's outer destination address contains an EID
which is not intended to cache traceroute
IPv4 headers in be forwarded on the ITR and to match them up with corresponding IPv4
Time Exceeded messages received from core routers and routable topology
(i.e. LISP 1.5), the ETR. The
ITR will use source address of a circular buffer for caching data packet or the IPv4 and UDP headers
of traceroute packets. It will select
router interface with which the source is associated (the
interface from which it was received) can be associated with a 16-bit number as VRF
(Virtual Routing/Forwarding), in which a key different (i.e. non-
congruent) topology can be used to find them later when EID-to-RLOC mappings.

8. Deployment Scenarios

This section will explore how and where ITRs and ETRs can be deployed
and will discuss the IPv4 Time Exceeded messages pros and cons of each deployment scenario.
There are received. two basic deployment trade-offs to consider: centralized
versus distributed caches and flat, recursive, or re-encapsulating
tunneling.

When an ITR encapsulates an IPv4 traceroute packet, it will use the
16-bit number as the UDP source port in deciding on centralized versus distributed caching, the encapsulating header.
When
following issues should be considered:

o Are the ICMP Time Exceeded message is returned to tunnel routers spread out so that the ITR, caches are spread
across all the UDP
header memories of the encapsulating header is present in the ICMP payload
thereby allowing the ITR to find the cached headers each router?

o Should management "touch points" be minimized by choosing few
tunnel routers, just enough for the
traceroute source. The ITR puts the cached headers in the payload redundancy?

o In general, using more ITRs doesn't increase management load,
since caches are built and sends stored dynamically. On the ICMP Time Exceeded message other hand,
more ETRs does require more management since EID-prefix-to-RLOC
mappings need to be explicitly configured.

When deciding on flat, recursive, or re-encapsulation tunneling, the traceroute source
retaining the source address of the original ICMP Time Exceeded
message (a core router
following issues should be considered:

o Flat tunneling implements a single tunnel between source site and
destination site. This generally offers better paths between
sources and destinations with a single tunnel path.

o Recursive tunneling is when tunneled traffic is again further
encapsulated in another tunnel, either to implement VPNs or to
perform Traffic Engineering. When doing VPN-based tunneling, the ETR of
site has some control since the site is prepending a new tunnel
header. In the case of TE-based tunneling, the traceroute
destination).

9.3. Traceroute using Mixed Locators

When either an IPv4 traceroute or IPv6 traceroute site may have
control if it is originated and prepending a new tunnel header, but if the ITR encapsulates it site's
ISP is doing the TE, then the site has no control. Recursive
tunneling generally will result in suboptimal paths but at the other address family header, you
cannot get all 3 segments
benefit of steering traffic to resource available parts of the traceroute. Segment 2
network.

o The technique of re-encapsulation ensures that packets only
require one tunnel header. So if a packet needs to be rerouted,
it is first decapsulated by the
traceroute ETR and then re-encapsulated with
a new tunnel header using a new RLOC.

The next sub-sections will describe where tunnel routers can not be conveyed reside
in the network.

8.1. First-hop/Last-hop Tunnel Routers

By locating tunnel routers close to hosts, the traceroute source since it EID-prefix set is
expecting addresses from intermediate hops in at
the same address format
for granularity of an IP subnet. So at the type expense of traceroute it originated. Therefore, in this case,
segment 2 will make more EID-
prefix-to-RLOC sets for the tunnel look like one hop. All site, the ITR has to
do to make this work is to not copy caches in each tunnel router
can remain relatively small. But caches always depend on the inner TTL to number
of non-aggregated EID destination flows active through these tunnel
routers.

With more tunnel routers doing encapsulation, the outer,
encapsulating header's TTL when a traceroute packet is encapsulated
using an RLOC from a different address family. This will cause no
TTL decrement to 0 to occur increase in core routers between control
traffic grows as well: since the ITR EID-granularity is greater, more
Map-Requests and ETR.

10. Mobility Considerations

There Map-Replies are several kinds of mobility of which only some might be traveling between more routers.

The advantage of
concern to LISP. Essentially they are as follows.

10.1. Site Mobility

A site wishes to change its attachment points to placing the Internet, caches and
its LISP Tunnel Routers will have new RLOCs when it changes upstream
providers. Changes databases at these stub
routers is that the products deployed in EID-RLOC mappings for sites are expected to be
handled by configuration, outside this part of the LISP protocol.

10.2. Slow Endpoint Mobility

An individual endpoint wishes to move, but is not concerned about
maintaining session continuity. Renumbering network
have better price-memory ratios then their core router counterparts.
Memory is involved. typically less expensive in these devices and fewer routes
are stored (only IGP routes). These devices tend to have excess
capacity, both for forwarding and routing state.

LISP functionality can
help with also be deployed in edge switches. These
devices generally have layer-2 ports facing hosts and layer-3 ports
facing the issues surrounding renumbering [RFC4192] [LISA96] by
decoupling Internet. Spare capacity is also often available in these
devices as well.

8.2. Border/Edge Tunnel Routers

Using customer-edge (CE) routers for tunnel endpoints allows the address EID
space used by associated with a site from the address spaces
used by its ISPs. [RFC4984]

10.3. Fast Endpoint Mobility

Fast endpoint mobility occurs when an endpoint moves relatively
rapidly, changing its IP layer network attachment point. Maintenance
of session continuity is to be reachable via a goal. small set of RLOCs
assigned to the CE routers for that site.

This is where offers the Mobile IPv4
[RFC3344bis] opposite benefit of the first-hop/last-hop tunnel
router scenario: the number of mapping entries and Mobile IPv6 [RFC3775] [RFC4866] mechanisms network management
touch points are used,
and primarily where interactions with LISP need to be explored.

The problem reduced, allowing better scaling.

One disadvantage is that as an endpoint moves, it may require changes less of the network's resources are used to
reach host endpoints thereby centralizing the mapping between its EID point-of-failure domain
and a set of RLOCs for its new creating network
location. When this is added to choke points at the overhead of mobile IP binding
updates, some packets might CE router.

Note that more than one CE router at a site can be delayed or dropped. configured with
the same IP address. In IPv4 mobility, when this case an endpoint RLOC is away from home, packets to it
are encapsulated and forwarded via a home agent which resides in the
home area the endpoint's address belongs to. The home agent will
encapsulate and forward packets either directly to an anycast address.
This allows resilience between the endpoint or to CE routers. That is, if a foreign agent which resides CE
router fails, traffic is automatically routed to the other routers
using the same anycast address. However, this comes with the
disadvantage where the endpoint has moved to.
Packets from site cannot control the entrance point when
the anycast route is advertised out from all border routers.

8.3. ISP Provider-Edge (PE) Tunnel Routers

Use of ISP PE routers as tunnel endpoint may be sent directly to routers gives an ISP control
over the correspondent
node, may be sent via location of the foreign agent, egress tunnel endpoints. That is, the ISP
can decide if the tunnel endpoints are in the destination site (in
either CE routers or may last-hop routers within a site) or at other PE
edges. The advantage of this case is that two or more tunnel headers
can be reverse-tunneled
back avoided. By having the PE be the first router on the path to
encapsulate, it can choose a TE path first, and the home agent ETR can
decapsulate and re-encapsulate for delivery a tunnel to the mobile node. As destination end
site.

An obvious disadvantage is that the
mobile node's EID end site has no control over
where its packets flow or available RLOC changes, LISP EID-to-RLOC
mappings are required for communication between the mobile node and the home agent, whether via foreign agent or not. RLOCs used.

As mentioned in earlier sections a mobile
endpoint changes networks, up to three LISP mapping changes may be
required:

o The mobile node moves from an old location to a new visited
network location and notifies its home agent that it has done so.
The Mobile IPv4 control packets the mobile node sends pass through
one combination of these scenarios is
possible at the new visited network's ITRs, which needs a EID-RLOC
mapping for the home agent.

o The home agent might not have the EID-RLOC mappings for the mobile
node's "care-of" address expense of extra packet header overhead, if both site
and provider want control, then recursive or its foreign agent re-encapsulating tunnels
are used.

9. Traceroute Considerations

When a source host in the new visited
network, a LISP site initiates a traceroute to a
destination host in which case another LISP site, it is highly desirable for it will need
to acquire them.

o When see the entire path. Since packets are sent directly to the correspondent node, it may
be that no traffic has been sent encapsulated from the new visited network ITR to
ETR, the correspondent node's network, and hop across the new visited network's
ITR tunnel could be viewed as a single hop.
However, LISP traceroute will need to obtain an EID-RLOC mapping for provide the correspondent
node's site.

In addition, if entire path so the IPv4 endpoint is sending packets from user can
see 3 distinct segments of the new
visited network using its original EID, then path from a source LISP will need host to
perform a route-returnability check
destination LISP host:

Segment 1 (in source LISP site based on EIDs):

source-host ---> first-hop ... next-hop ---> ITR

Segment 2 (in the new EID-RLOC mapping for
that EID.

In IPv6 mobility, packets can flow directly between core network based on RLOCs):

ITR ---> next-hop ... next-hop ---> ETR

Segment 3 (in the mobile node
and destination LISP site based on EIDs):

ETR ---> next-hop ... last-hop ---> destination-host

For segment 1 of the correspondent node path, ICMP Time Exceeded messages are returned
in either direction. The mobile node uses
its "care-of" address (EID). In this case, the route-returnability
check would not be needed but one more LISP mapping lookup may be
required instead:

o As above, three mapping changes may be needed normal matter as they are today. The ITR performs a TTL
decrement and test for 0 before encapsulating. So the mobile node
to communicate with its home agent and ITR hop is
seen by the traceroute source has an EID address (the address of
site-facing interface).

For segment 2 of the path, ICMP Time Exceeded messages are returned
to send packets the ITR because the TTL decrement to 0 is done on the
correspondent node.

o In addition, another mapping will be needed in outer
header, so the correspondent
node's ITR, in order for destination of the correspondent node to send packets ICMP messages are to the mobile node's "care-of" address (EID) at ITR RLOC
address, the new network
location.

When both endpoints are mobile source source RLOC address of the number encapsulated
traceroute packet. The ITR looks inside of potential mapping
lookups increases accordingly.

As a mobile node moves there are not only mobility state changes in the mobile node, correspondent node, and home agent, but also state
changes in ICMP payload to
inspect the ITRs and ETRs for at least some EID-prefixes.

The goal is to support rapid adaptation, with little delay or packet
loss for the entire system. Heuristics traceroute source so it can be added to LISP return the ICMP message to
reduce
the number address of mapping changes required and to reduce the delay
per mapping change. Also traceroute client as well as retaining the core
router IP mobility address in the ICMP message. This is so the traceroute
client can be modified to require
fewer mapping changes. In order to increase overall system
performance, there may be a need to reduce display the optimization of one
area core router address (the RLOC address) in order the
traceroute output. The ETR returns its RLOC address and responds to place fewer demands on another.

In LISP, one possibility is
the TTL decrement to "glean" information. When a packet
arrives, 0 like the previous core routers did.

For segment 3, the next-hop router downstream from the ETR could examine will be
decrementing the EID-RLOC mapping and use that
mapping TTL for all outgoing traffic to that EID. It can do this after
performing a route-returnability check, to ensure that the new
network location does have a internal route to packet that endpoint.
However, this does not cover was encapsulated, sent into
the case where an ITR (the node assigned core, decapsulated by the RLOC) at ETR, and forwarded because it isn't the mobile-node location has been compromised.

Mobile IP packet exchange is designed for an environment in which all
routing information
final destination. If the TTL is disseminated before packets can be forwarded.
In order decremented to allow 0, any router on the Internet to grow
path to support expected future
use, we are moving to an environment where some information may have
to be obtained after packets are in flight. Modifications to IP
mobility should be considered in order to optimize the behavior destination of the overall system. Anything which decreases traceroute, including the number of new EID-
RLOC mappings needed when a node moves, next-hop
router or maintains the validity of destination, will send an EID-RLOC mapping for a longer time, is useful.

10.4. Fast Network Mobility

In addition ICMP Time Exceeded message to endpoints, a network can be mobile, possibly changing
xTRs. A "network" can the
source EID of the traceroute client. The ICMP message will be as small as a single router and as large as
a whole site. This is different from site mobility in that it is
fast
encapsulated by the local ITR and possibly short-lived, but different from endpoint mobility sent back to the ETR in that a whole prefix is changing RLOCs. However, the mechanisms
are
originated traceroute source site, where the same and there is no new overhead in LISP. A map request for
any endpoint packet will return a binding for the entire mobile prefix.

If mobile networks become a more common occurrence, it may be useful delivered
to revisit the design of host.

9.1. IPv6 Traceroute

IPv6 traceroute follows the mapping service and allow for dynamic
updates of procedure described above since the database.

The issue of interactions between mobility and LISP
entire traceroute data packet is included in ICMP Time Exceeded
message payload. Therefore, only the ITR needs to be
explored further. Specific improvements pay special
attention for forwarding ICMP messages back to the entire system will
depend on the details of mapping mechanisms. Mapping mechanisms
should be evaluated on how well they support session continuity for
mobile nodes.

10.5. LISP Mobile Node Mobility

An mobile device can use traceroute source.

9.2. IPv4 Traceroute

For IPv4 traceroute, we cannot follow the LISP infrastructure to achieve mobility
by implementing above procedure since IPv4
ICMP Time Exceeded messages only include the LISP encapsulation and decapsulation functions
and acting as a simple ITR/ETR. By doing this, such a "LISP mobile
node" can use topologically-independent EID invoking IP addresses that are not
advertised into and do not impose a cost on the global routing
system. These EIDs are maintained at the edges of the mapping system
(in LISP Map-Servers and Map-Resolvers) header and are provided on demand to
only the correspondents of 8
bytes that follow the LISP mobile node.

Refer IP header. Therefore, when a core router sends
an IPv4 Time Exceeded message to an ITR, all the LISP Mobility Architecture specification [LISP-MN] for
more details.

11. Multicast Considerations

A multicast group address, as defined ITR has in the original Internet
architecture ICMP
payload is an identifier of the encapsulated header it prepended followed by a grouping of topologically
independent receiver host locations. UDP
header. The address encoding itself
does not determine original invoking IP header, and therefore the location identity
of the receiver(s). traceroute source is lost.

The multicast
routing protocol, and solution we propose to solve this problem is to cache traceroute
IPv4 headers in the network-based state ITR and to match them up with corresponding IPv4
Time Exceeded messages received from core routers and the protocol creates,
determines where the receivers are located.

In ETR. The
ITR will use a circular buffer for caching the context IPv4 and UDP headers
of LISP, traceroute packets. It will select a multicast group address is both an EID and 16-bit number as a Routing Locator. Therefore, no specific semantic or action needs key to be taken for a destination address, as it would appear in
find them later when the IPv4 Time Exceeded messages are received.
When an IP
header. Therefore, a group address that appears in ITR encapsulates an inner IP
header built by a source host will be used as the destination EID.
The outer IP header (the destination Routing Locator address),
prepended by a LISP router, IPv4 traceroute packet, it will use the same group address
16-bit number as the
destination Routing Locator.

Having said that, only the source EID and UDP source Routing Locator
needs port in the encapsulating header.
When the ICMP Time Exceeded message is returned to be dealt with. Therefore, an the ITR, the UDP
header of the encapsulating header is present in the ICMP payload
thereby allowing the ITR merely needs to put its
own IP address find the cached headers for the
traceroute source. The ITR puts the cached headers in the payload
and sends the ICMP Time Exceeded message to the traceroute source Routing Locator field when prepending
retaining the outer IP header. This source Routing Locator address, like any
other Routing Locator address MUST be globally routable.

Therefore, of the original ICMP Time Exceeded
message (a core router or the ETR of the site of the traceroute
destination).

9.3. Traceroute using Mixed Locators

When either an EID-to-RLOC mapping does not need to be performed by an
ITR when a received data packet is a multicast data packet or when
processing a source-specific Join (either by IGMPv3 IPv4 traceroute or PIM). But the
source Routing Locator IPv6 traceroute is decided by originated and
the multicast routing protocol ITR encapsulates it in a receiver site. That is, an EID to Routing Locator translation
is done at control-time.

Another approach is to have the ITR not encapsulate a multicast
packet and allow other address family header, you
cannot get all 3 segments of the traceroute. Segment 2 of the host built packet
traceroute can not be conveyed to flow into the core even
if the traceroute source address since it is allocated out of
expecting addresses from intermediate hops in the EID namespace. If same address format
for the
RPF-Vector TLV [RPFV] is used by PIM type of traceroute it originated. Therefore, in this case,
segment 2 will make the core, then core routers
can RPF to tunnel look like one hop. All the ITR (the Locator address which is injected into core
routing) rather than the host source address (the EID address which has to
do to make this work is to not injected into core routing).

To avoid any EID-based multicast state in copy the network core, inner TTL to the first
approach is chosen for LISP-Multicast. Details for LISP-Multicast
and Interworking with non-LISP sites outer,
encapsulating header's TTL when a traceroute packet is described encapsulated
using an RLOC from a different address family. This will cause no
TTL decrement to 0 to occur in specification
[MLISP].

12. Security Considerations

It is believed that most of core routers between the security mechanisms will ITR and ETR.

10. Mobility Considerations

There are several kinds of mobility of which only some might be part of
concern to LISP. Essentially they are as follows.

10.1. Site Mobility

A site wishes to change its attachment points to the mapping database service Internet, and
its LISP Tunnel Routers will have new RLOCs when using control plane procedures for
obtaining EID-to-RLOC mappings. For data plane triggered mappings,
as described it changes upstream
providers. Changes in this specification, protection is provided against
ETR spoofing by using Return- Routability mechanisms evidenced EID-RLOC mappings for sites are expected to be
handled by the
use configuration, outside of a 24-bit Nonce field in the LISP encapsulation header and a
64-bit Nonce field in the protocol.

10.2. Slow Endpoint Mobility

An individual endpoint wishes to move, but is not concerned about
maintaining session continuity. Renumbering is involved. LISP control message. The nonce, coupled can
help with the ITR accepting only solicited Map-Replies goes a long way
toward providing decent authentication.

LISP does not rely on a PKI infrastructure or issues surrounding renumbering [RFC4192] [LISA96] by
decoupling the address space used by a more heavy weight
authentication system. These systems challenge site from the scalability address spaces
used by its ISPs. [RFC4984]

10.3. Fast Endpoint Mobility

Fast endpoint mobility occurs when an endpoint moves relatively
rapidly, changing its IP layer network attachment point. Maintenance
of
LISP which was session continuity is a primary design goal.

DoS attack prevention will depend on implementations rate-limiting
Map-Requests and Map-Replies to the control plane as well as rate-
limiting This is where the number of data-triggered Map-Replies.

To deal with map-cache exhaustion attempts in an ITR/PTR, the
implementation should consider putting a maximum cap on the number of
entries stored with a reserve list for special or frequently accessed
sites. This should be a configuration policy control set by the
network administrator who manages ITRs Mobile IPv4
[RFC3344bis] and PTRs.

13. Prototype Plans Mobile IPv6 [RFC3775] [RFC4866] mechanisms are used,
and Status primarily where interactions with LISP need to be explored.

The operator community has requested problem is that the IETF take a practical
approach as an endpoint moves, it may require changes to solving
the scaling problems associated with global
routing state growth. This document offers mapping between its EID and a simple solution which
is intended set of RLOCs for use in a pilot program to gain experience in working
on this problem.

The authors hope that publishing its new network
location. When this specification will allow is added to the
rapid implementation overhead of multiple vendor prototypes mobile IP binding
updates, some packets might be delayed or dropped.

In IPv4 mobility, when an endpoint is away from home, packets to it
are encapsulated and deployment on forwarded via a small scale. Doing this home agent which resides in the
home area the endpoint's address belongs to. The home agent will help
encapsulate and forward packets either directly to the community:

o Decide whether a new EID-to-RLOC mapping database infrastructure
is needed endpoint or if to
a simple, UDP-based, data-triggered approach is
flexible and robust enough.

o Experiment with provider-independent assignment of EIDs while at foreign agent which resides where the same time decreasing endpoint has moved to.
Packets from the size of DFZ routing tables through
the use of topologically-aligned, provider-based RLOCs.

o Determine whether multiple levels of tunneling can endpoint may be used by ISPs sent directly to achieve their Traffic Engineering goals while simultaneously
removing the more specific routes currently injected into correspondent
node, may be sent via the
global routing system for this purpose.

o Experiment with mobility to determine if both acceptable
convergence and session continuity properties can foreign agent, or may be scalably
implemented reverse-tunneled
back to support both individual device roaming and site
service provider changes.

Here is a rough set of milestones:

1. Interoperable implementations have been available since the
beginning of 2009. We are trying home agent for delivery to converge on a packet format
so implementations can converge on the -04 and later drafts.

2. Continue pilot deployment using LISP-ALT as mobile node. As the database mapping
mechanism.

3. Continue prototyping and studying other database lookup schemes,
be it DNS, DHTs, CONS, ALT, NERD,
mobile node's EID or other mechanisms.

4. Implement the available RLOC changes, LISP Multicast draft [MLISP].

5. Implement EID-to-RLOC
mappings are required for communication between the LISP Mobile Node draft [LISP-MN].

6. Research more on how policy affects what gets returned in mobile node and
the home agent, whether via foreign agent or not. As a Map-
Reply mobile
endpoint changes networks, up to three LISP mapping changes may be
required:

o The mobile node moves from an ETR.

7. Continue to experiment with mixed locator-sets old location to understand how
LISP can help the a new visited
network location and notifies its home agent that it has done so.
The Mobile IPv4 to IPv6 transition.

8. Add more robustness to locator reachability between LISP sites.

As control packets the mobile node sends pass through
one of this writing the following accomplishments have been achieved:

1. A unit- and system-tested software switching implementation has
been completed on cisco NX-OS new visited network's ITRs, which needs a EID-RLOC
mapping for this draft the home agent.

o The home agent might not have the EID-RLOC mappings for both IPv4 and
IPv6 EIDs using a mixed locator-set of IPv4 and IPv6 locators.

2. A unit- and system-tested software switching implementation on
cisco NX-OS the mobile
node's "care-of" address or its foreign agent in the new visited
network, in which case it will need to acquire them.

o When packets are sent directly to the correspondent node, it may
be that no traffic has been completed for draft [ALT].

3. A unit- sent from the new visited network to
the correspondent node's network, and system-tested software switching implementation on
cisco NX-OS has been completed for draft [INTERWORK]. Support the new visited network's
ITR will need to obtain an EID-RLOC mapping for the correspondent
node's site.

In addition, if the IPv4 translation endpoint is provided and PTR support sending packets from the new
visited network using its original EID, then LISP will need to
perform a route-returnability check on the new EID-RLOC mapping for IPv4 and
that EID.

In IPv6 is provided.

4. The cisco NX-OS implementation supports an experimental
mechanism for slow mobility.

5. Dave Meyer, Vince Fuller, Darrel Lewis, Greg Shepherd, and
Andrew Partan continue to test all mobility, packets can flow directly between the features described above
on a dual-stack infrastructure.

6. Darrel Lewis and Dave Meyer have deployed both LISP translation mobile node
and LISP PTR support the correspondent node in either direction. The mobile node uses
its "care-of" address (EID). In this case, the pilot network. Point your browser route-returnability
check would not be needed but one more LISP mapping lookup may be
required instead:

o As above, three mapping changes may be needed for the mobile node
to http://www.lisp4.net communicate with its home agent and to see translation happening in action
so your non-LISP site can access a web server in a LISP site.

7. Soon http://www.lisp6.net will work where your IPv6 LISP site
can talk send packets to a IPv6 web server the
correspondent node.

o In addition, another mapping will be needed in a LISP site by using mixed
address-family based locators.

8. An public domain implementation of LISP is underway. See
[OPENLISP] the correspondent
node's ITR, in order for details.

9. We have deployed Map-Resolvers and Map-Servers on the LISP pilot
network correspondent node to send packets to gather experience with [LISP-MS]. The first layer of
the architecture mobile node's "care-of" address (EID) at the new network
location.

When both endpoints are mobile the xTRs which use Map-Servers for EID-
prefix registration and Map-Resolvers for EID-to-RLOC number of potential mapping
resolution. The second layer
lookups increases accordingly.

As a mobile node moves there are not only mobility state changes in
the Map-Resolvers mobile node, correspondent node, and Map-
Servers which connect to the ALT BGP peering infrastructure.
And home agent, but also state
changes in the third layer are ALT-routers which aggregate EID-prefixes
and forward Map-Requests.

10. A cisco IOS implementation is underway which currently supports
IPv4 encapsulation ITRs and decapsulation features.

11. A LISP router based LIG implementation ETRs for at least some EID-prefixes.

The goal is supported, deployed,
and used daily to debug and test support rapid adaptation, with little delay or packet
loss for the entire system. Heuristics can be added to LISP pilot network. See
[LIG] for details.

12. A Linux implementation to
reduce the number of LIG has been made available mapping changes required and
supported by Dave Meyer. It to reduce the delay
per mapping change. Also IP mobility can be run on any Linux modified to require
fewer mapping changes. In order to increase overall system
which resides
performance, there may be a need to reduce the optimization of one
area in either order to place fewer demands on another.

In LISP, one possibility is to "glean" information. When a LISP site or non-LISP site. See [LIG] packet
arrives, the ETR could examine the EID-RLOC mapping and use that
mapping for details. Public domain code all outgoing traffic to that EID. It can be downloaded from
http://github.com/davidmeyer/lig/tree/master.

13. An experimental implementation do this after
performing a route-returnability check, to ensure that the new
network location does have a internal route to that endpoint.
However, this does not cover the case where an ITR (the node assigned
the RLOC) at the mobile-node location has been written compromised.

Mobile IP packet exchange is designed for three
locator reachability algorithms. Two are the Echo-Noncing and
RLOC-Probing algorithms which are documented an environment in this
specification. The third is called TCP-counts which will be
documented in all
routing information is disseminated before packets can be forwarded.
In order to allow the Internet to grow to support expected future drafts.

14. The LISP pilot network has been converted from using MD5 HMAC
authentication
use, we are moving to an environment where some information may have
to be obtained after packets are in flight. Modifications to IP
mobility should be considered in order to optimize the behavior of
the overall system. Anything which decreases the number of new EID-
RLOC mappings needed when a node moves, or maintains the validity of
an EID-RLOC mapping for Map-Register messages a longer time, is useful.

10.4. Fast Network Mobility

In addition to SHA-1 HMAC
authentication. ETRs send with SHA-1 but Map-Servers endpoints, a network can
received be mobile, possibly changing
xTRs. A "network" can be as small as a single router and as large as
a whole site. This is different from either for compatibility purposes.

If interested site mobility in writing that it is
fast and possibly short-lived, but different from endpoint mobility
in that a LISP implementation, testing whole prefix is changing RLOCs. However, the mechanisms
are the same and there is no new overhead in LISP. A map request for
any endpoint will return a binding for the entire mobile prefix.

If mobile networks become a more common occurrence, it may be useful
to revisit the design of the mapping service and allow for dynamic
updates of the database.

The issue of interactions between mobility and LISP implementations, or want needs to be part of
explored further. Specific improvements to the LISP pilot program,
please contact lisp at ietf.org.

14. References

14.1. Normative References

[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.

[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
November 1990.

[RFC1498] Saltzer, J., "On entire system will
depend on the Naming and Binding details of Network
Destinations", RFC 1498, August 1993.

[RFC1955] Hinden, R., "New Scheme for Internet Routing and
Addressing (ENCAPS) for IPNG", RFC 1955, June 1996.

[RFC2119] Bradner, S., "Key words mapping mechanisms. Mapping mechanisms
should be evaluated on how well they support session continuity for
mobile nodes.

10.5. LISP Mobile Node Mobility

An mobile device can use in RFCs the LISP infrastructure to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC2434] Narten, T. achieve mobility
by implementing the LISP encapsulation and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.

[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., decapsulation functions
and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
March 2000.

[RFC3056] Carpenter, B. acting as a simple ITR/ETR. By doing this, such a "LISP mobile
node" can use topologically-independent EID IP addresses that are not
advertised into and K. Moore, "Connection do not impose a cost on the global routing
system. These EIDs are maintained at the edges of IPv6 Domains
via IPv4 Clouds", RFC 3056, February 2001.

[RFC3168] Ramakrishnan, K., Floyd, S., the mapping system
(in LISP Map-Servers and D. Black, "The Addition Map-Resolvers) and are provided on demand to
only the correspondents of Explicit Congestion Notification (ECN) the LISP mobile node.

Refer to IP",
RFC 3168, September 2001.

[RFC3775] Johnson, the LISP Mobility Architecture specification [LISP-MN] for
more details.

11. Multicast Considerations

A multicast group address, as defined in the original Internet
architecture is an identifier of a grouping of topologically
independent receiver host locations. The address encoding itself
does not determine the location of the receiver(s). The multicast
routing protocol, and the network-based state the protocol creates,
determines where the receivers are located.

In the context of LISP, a multicast group address is both an EID and
a Routing Locator. Therefore, no specific semantic or action needs
to be taken for a destination address, as it would appear in an IP
header. Therefore, a group address that appears in an inner IP
header built by a source host will be used as the destination EID.
The outer IP header (the destination Routing Locator address),
prepended by a LISP router, will use the same group address as the
destination Routing Locator.

Having said that, only the source EID and source Routing Locator
needs to be dealt with. Therefore, an ITR merely needs to put its
own IP address in the source Routing Locator field when prepending
the outer IP header. This source Routing Locator address, like any
other Routing Locator address MUST be globally routable.

Therefore, an EID-to-RLOC mapping does not need to be performed by an
ITR when a received data packet is a multicast data packet or when
processing a source-specific Join (either by IGMPv3 or PIM). But the
source Routing Locator is decided by the multicast routing protocol
in a receiver site. That is, an EID to Routing Locator translation
is done at control-time.

Another approach is to have the ITR not encapsulate a multicast
packet and allow the the host built packet to flow into the core even
if the source address is allocated out of the EID namespace. If the
RPF-Vector TLV [RPFV] is used by PIM in the core, then core routers
can RPF to the ITR (the Locator address which is injected into core
routing) rather than the host source address (the EID address which
is not injected into core routing).

To avoid any EID-based multicast state in the network core, the first
approach is chosen for LISP-Multicast. Details for LISP-Multicast
and Interworking with non-LISP sites is described in specification
[MLISP].

12. Security Considerations

It is believed that most of the security mechanisms will be part of
the mapping database service when using control plane procedures for
obtaining EID-to-RLOC mappings. For data plane triggered mappings,
as described in this specification, protection is provided against
ETR spoofing by using Return- Routability mechanisms evidenced by the
use of a 24-bit Nonce field in the LISP encapsulation header and a
64-bit Nonce field in the LISP control message. The nonce, coupled
with the ITR accepting only solicited Map-Replies goes a long way
toward providing decent authentication.

LISP does not rely on a PKI infrastructure or a more heavy weight
authentication system. These systems challenge the scalability of
LISP which was a primary design goal.

DoS attack prevention will depend on implementations rate-limiting
Map-Requests and Map-Replies to the control plane as well as rate-
limiting the number of data-triggered Map-Replies.

13. Prototype Plans and Status

The operator community has requested that the IETF take a practical
approach to solving the scaling problems associated with global
routing state growth. This document offers a simple solution which
is intended for use in a pilot program to gain experience in working
on this problem.

The authors hope that publishing this specification will allow the
rapid implementation of multiple vendor prototypes and deployment on
a small scale. Doing this will help the community:

o Decide whether a new EID-to-RLOC mapping database infrastructure
is needed or if a simple, UDP-based, data-triggered approach is
flexible and robust enough.

o Experiment with provider-independent assignment of EIDs while at
the same time decreasing the size of DFZ routing tables through
the use of topologically-aligned, provider-based RLOCs.

o Determine whether multiple levels of tunneling can be used by ISPs
to achieve their Traffic Engineering goals while simultaneously
removing the more specific routes currently injected into the
global routing system for this purpose.

o Experiment with mobility to determine if both acceptable
convergence and session continuity properties can be scalably
implemented to support both individual device roaming and site
service provider changes.

Here is a rough set of milestones:

1. Interoperable implementations have been available since the
beginning of 2009. We are trying to converge on a packet format
so implementations can converge on the -04 and later drafts.

2. Continue pilot deployment using LISP-ALT as the database mapping
mechanism.

3. Continue prototyping and studying other database lookup schemes,
be it DNS, DHTs, CONS, ALT, NERD, or other mechanisms.

4. Implement the LISP Multicast draft [MLISP].

5. Implement the LISP Mobile Node draft [LISP-MN].

6. Research more on how policy affects what gets returned in a Map-
Reply from an ETR.

7. Continue to experiment with mixed locator-sets to understand how
LISP can help the IPv4 to IPv6 transition.

8. Add more robustness to locator reachability between LISP sites.

As of this writing the following accomplishments have been achieved:

1. A unit- and system-tested software switching implementation has
been completed on cisco NX-OS for this draft for both IPv4 and
IPv6 EIDs using a mixed locator-set of IPv4 and IPv6 locators.

2. A unit- and system-tested software switching implementation on
cisco NX-OS has been completed for draft [ALT].

3. A unit- and system-tested software switching implementation on
cisco NX-OS has been completed for draft [INTERWORK]. Support
for IPv4 translation is provided and PTR support for IPv4 and
IPv6 is provided.

4. The cisco NX-OS implementation supports an experimental
mechanism for slow mobility.

5. Dave Meyer, Vince Fuller, Darrel Lewis, Greg Shepherd, and
Andrew Partan continue to test all the features described above
on a dual-stack infrastructure.

6. Darrel Lewis and Dave Meyer have deployed both LISP translation
and LISP PTR support in the pilot network. Point your browser
to http://www.lisp4.net to see translation happening in action
so your non-LISP site can access a web server in a LISP site.

7. Soon http://www.lisp6.net will work where your IPv6 LISP site
can talk to a IPv6 web server in a LISP site by using mixed
address-family based locators.

8. An public domain implementation of LISP is underway. See
[OPENLISP] for details.

9. We have deployed Map-Resolvers and Map-Servers on the LISP pilot
network to gather experience with [LISP-MS]. The first layer of
the architecture are the xTRs which use Map-Servers for EID-
prefix registration and Map-Resolvers for EID-to-RLOC mapping
resolution. The second layer are the Map-Resolvers and Map-
Servers which connect to the ALT BGP peering infrastructure.
And the third layer are ALT-routers which aggregate EID-prefixes
and forward Map-Requests.

10. A cisco IOS implementation is underway which currently supports
IPv4 encapsulation and decapsulation features.

11. A LISP router based LIG implementation is supported, deployed,
and used daily to debug and test the LISP pilot network. See
[LIG] for details.

12. A Linux implementation of LIG has been made available and
supported by Dave Meyer. It can be run on any Linux system
which resides in either a LISP site or non-LISP site. See [LIG]
for details. Public domain code can be downloaded from
http://github.com/davidmeyer/lig/tree/master.

13. An experimental implementation has been written for three
locator reachability algorithms. Two are the Echo-Noncing and
RLOC-Probing algorithms which are documented in this
specification. The third is called TCP-counts which will be
documented in future drafts.

14. The LISP pilot network has been converted from using MD5 HMAC
authentication for Map-Register messages to SHA-1 HMAC
authentication. ETRs send with SHA-1 but Map-Servers can
received from either for compatibility purposes.

If interested in writing a LISP implementation, testing any of the
LISP implementations, or want to be part of the LISP pilot program,
please contact lisp at ietf.org.

14. References

14.1. Normative References

[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.

[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
November 1990.

[RFC1498] Saltzer, J., "On the Naming and Binding of Network
Destinations", RFC 1498, August 1993.

[RFC1955] Hinden, R., "New Scheme for Internet Routing and
Addressing (ENCAPS) for IPNG", RFC 1955, June 1996.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within
ESP and AH", RFC 2404, November 1998.

[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.

[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
March 2000.

[RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains
via IPv4 Clouds", RFC 3056, February 2001.

[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP",
RFC 3168, September 2001.

[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in IPv6", RFC 3775, June 2004.

[RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness
Requirements for Security", BCP 106, RFC 4086, June 2005.

[RFC4302] Kent, S., "IP Authentication Header", RFC 4302,
December 2005.

[RFC4423] Moskowitz, R. and P. Nikander, "Host Identity Protocol
(HIP) Architecture", RFC 4423, May 2006.

[RFC4634] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and HMAC-SHA)", RFC 4634, July 2006.

[RFC4866] Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route
Optimization for Mobile IPv6", RFC 4866, May 2007.

[RFC4984] Meyer, D., Zhang, L., and K. Fall, "Report from the IAB
Workshop on Routing and Addressing", RFC 4984,
September 2007.

[UDP-TUNNELS]
Eubanks, M. and P. Chimento, "UDP Checksums for Tunneled
Packets"", draft-eubanks-chimento-6man-00.txt P. Chimento, "UDP Checksums for Tunneled
Packets"", draft-eubanks-chimento-6man-00.txt (work in
progress), February 2009.

14.2. Informative References

[AFI] IANA, "Address Family Indicators (AFIs)", ADDRESS FAMILY
NUMBERS http://www.iana.org/numbers.html, Febuary 2007.

[ALT] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "LISP
Alternative Topology (LISP-ALT)",
draft-ietf-lisp-alt-01.txt (work in progress), May 2009.

[APT] Jen, D., Meisel, M., Massey, D., Wang, L., Zhang, B., and
L. Zhang, "APT: A Practical Transit Mapping Service",
draft-jen-apt-01.txt (work in progress), November 2007.

[CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed
Enhancement to the Internet Architecture", Internet-
Draft http://www.chiappa.net/~jnc/tech/endpoints.txt,
1999.

[CONS] Farinacci, D., Fuller, V., and D. Meyer, "LISP-CONS: A
Content distribution Overlay Network Service for LISP",
draft-meyer-lisp-cons-03.txt (work in progress),
November 2007.

[DHTs] Ratnasamy, S., Shenker, S., and I. Stoica, "Routing
Algorithms for DHTs: Some Open Questions", PDF
file http://www.cs.rice.edu/Conferences/IPTPS02/174.pdf.

[EMACS] Brim, S., Farinacci, D., Meyer, D., and J. Curran, "EID
Mappings Multicast Across Cooperating Systems for LISP",
draft-curran-lisp-emacs-00.txt (work in progress),
November 2007.

[GSE] "GSE - An Alternate Addressing Architecture for IPv6",
draft-ietf-ipngwg-gseaddr-00.txt (work in progress), 1997.

[INTERWORK]
Lewis, D., Meyer, D., Farinacci, D., and V. Fuller,
"Interworking LISP with IPv4 and IPv6",
draft-ietf-lisp-interworking-00.txt (work in progress),
January 2009.

[LIG] Farinacci, D. and D. Meyer, "LISP Internet Groper (LIG)",
draft-farinacci-lisp-lig-01.txt (work in progress), February
May 2009.

14.2. Informative References

[AFI] IANA, "Address Family Indicators (AFIs)", ADDRESS FAMILY
NUMBERS http://www.iana.org/numbers.html, Febuary 2007.

[ALT]

[LISA96] Lear, E., Katinsky, J., Coffin, J., and D. Tharp,
"Renumbering: Threat or Menace?", Usenix , September 1996.

[LISP-MAIN]
Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "LISP
Alternative Topology (LISP-ALT)",
draft-ietf-lisp-alt-01.txt
"Locator/ID Separation Protocol (LISP)",
draft-farinacci-lisp-12.txt (work in progress), May
March 2009.

[APT] Jen,

[LISP-MN] Farinacci, D., Meisel, M., Massey, Fuller, V., Lewis, D., Wang, L., Zhang, B., and
L. Zhang, "APT: A Practical Transit Mapping Service",
draft-jen-apt-01.txt D. Meyer, "LISP
Mobility Architecture", draft-meyer-lisp-mn-00.txt (work
in progress), November 2007.

[CHIAPPA] Chiappa, J., "Endpoints July 2009.

[LISP-MS] Farinacci, D. and Endpoint names: A Proposed
Enhancement to the Internet Architecture", Internet-
Draft http://www.chiappa.net/~jnc/tech/endpoints.txt,
1999.

[CONS] V. Fuller, "LISP Map Server",
draft-ietf-lisp-ms-02.txt (work in progress),
September 2009.

[LISP1] Farinacci, D., Oran, D., Fuller, V., and J. Schiller,
"Locator/ID Separation Protocol (LISP1) [Routable ID
Version]",
Slide-set http://www.dinof.net/~dino/ietf/lisp1.ppt,
October 2006.

[LISP2] Farinacci, D., Oran, D., Fuller, V., and J. Schiller,
"Locator/ID Separation Protocol (LISP2) [DNS-based
Version]",
Slide-set http://www.dinof.net/~dino/ietf/lisp2.ppt,
November 2006.

[LISPDHT] Mathy, L., Iannone, L., and O. Bonaventure, "LISP-DHT:
Towards a DHT to map identifiers onto locators",
draft-mathy-lisp-dht-00.txt (work in progress),
February 2008.

[LOC-ID-ARCH]
Meyer, D. and D. Lewis, "Architectural Implications of
Locator/ID Separation",
draft-meyer-loc-id-implications-01.txt (work in progress),
Januaryr 2009.

[MLISP] Farinacci, D., Meyer, "LISP-CONS: A
Content distribution Overlay Network Service D., Zwiebel, J., and S. Venaas,
"LISP for LISP",
draft-meyer-lisp-cons-03.txt Multicast Environments",
draft-ietf-lisp-multicast-02.txt (work in progress),
October 2009.

[NERD] Lear, E., "NERD: A Not-so-novel EID to RLOC Database",
draft-lear-lisp-nerd-04.txt (work in progress),
April 2008.

[OPENLISP]
Iannone, L. and O. Bonaventure, "OpenLISP Implementation
Report", draft-iannone-openlisp-implementation-01.txt
(work in progress),
November 2007.

[DHTs] Ratnasamy, S., Shenker, S., and I. Stoica, July 2008.

[RADIR] Narten, T., "Routing
Algorithms for DHTs: Some Open Questions", PDF
file http://www.cs.rice.edu/Conferences/IPTPS02/174.pdf.

[EMACS] Brim, S., Farinacci, D., Meyer, D., and J. Curran, "EID
Mappings Multicast Across Cooperating Systems for LISP",
draft-curran-lisp-emacs-00.txt Addressing Problem Statement",
draft-narten-radir-problem-statement-00.txt (work in
progress),
November July 2007.

[GSE] "GSE - An Alternate Addressing Architecture

[RFC3344bis]
Perkins, C., "IP Mobility Support for IPv6",
draft-ietf-ipngwg-gseaddr-00.txt IPv4, revised",
draft-ietf-mip4-rfc3344bis-05 (work in progress), 1997.

[INTERWORK]
Lewis, D., Meyer, D., Farinacci, D.,
July 2007.

[RFC4192] Baker, F., Lear, E., and V. Fuller,
"Interworking LISP with IPv4 R. Droms, "Procedures for
Renumbering an IPv6 Network without a Flag Day", RFC 4192,
September 2005.

[RPFV] Wijnands, IJ., Boers, A., and IPv6",
draft-ietf-lisp-interworking-00.txt E. Rosen, "The RPF Vector
TLV", draft-ietf-pim-rpf-vector-08.txt (work in progress),
January 2009.

[LIG] Farinacci, D.

[RPMD] Handley, M., Huici, F., and D. Meyer, "LISP Internet Groper (LIG)",
draft-farinacci-lisp-lig-01.txt A. Greenhalgh, "RPMD: Protocol
for Routing Protocol Meta-data Dissemination",
draft-handley-p2ppush-unpublished-2007726.txt (work in
progress),
May 2009.

[LISA96] Lear, E., Katinsky, J., Coffin, J., and D. Tharp,
"Renumbering: Threat or Menace?", Usenix , September 1996.

[LISP-MAIN]
Farinacci, D., Fuller, V., Meyer, D., July 2007.

[SHIM6] Nordmark, E. and D. Lewis,
"Locator/ID Separation Protocol (LISP)",
draft-farinacci-lisp-12.txt M. Bagnulo, "Level 3 multihoming shim
protocol", draft-ietf-shim6-proto-06.txt (work in
progress),
March 2009.

[LISP-MN] Farinacci, D., Fuller, V., Lewis, D., October 2006.

Appendix A. Acknowledgments

An initial thank you goes to Dave Oran for planting the seeds for the
initial ideas for LISP. His consultation continues to provide value
to the LISP authors.

A special and appreciative thank you goes to Noel Chiappa for
providing architectural impetus over the past decades on separation
of location and D. Meyer, "LISP
Mobility Architecture", draft-meyer-lisp-mn-00.txt (work
in progress), July 2009.

[LISP-MS] Farinacci, D. identity, as well as detailed review of the LISP
architecture and V. Fuller, "LISP Map Server",
draft-ietf-lisp-ms-02.txt (work in progress),
September 2009.

[LISP1] Farinacci, D., Oran, D., Fuller, V., documents, coupled with enthusiasm for making LISP a
practical and J. Schiller,
"Locator/ID Separation Protocol (LISP1) [Routable ID
Version]",
Slide-set http://www.dinof.net/~dino/ietf/lisp1.ppt,
October 2006.

[LISP2] Farinacci, D., Oran, D., Fuller, V., incremental transition for the Internet.

The authors would like to gratefully acknowledge many people who have
contributed discussion and J. ideas to the making of this proposal.
They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller,
"Locator/ID Separation Protocol (LISP2) [DNS-based
Version]",
Slide-set http://www.dinof.net/~dino/ietf/lisp2.ppt,
November 2006.

[LISPDHT] Mathy, L.,
Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston,
David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley,
Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler,
Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi
Iannone, L., Robin Whittle, Brian Carpenter, Joel Halpern, Roger
Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van Beijnum, Roland
Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien Saucez, Damian
Lezama, Attilla De Groot, Parantap Lahiri, David Black, Roque
Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, Margaret
Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, and O. Bonaventure, "LISP-DHT:
Towards a DHT Jari
Arkko.

In particular, we would like to thank Dave Meyer for his clever
suggestion for the name "LISP". ;-)

This work originated in the Routing Research Group (RRG) of the IRTF.
The individual submission [LISP-MAIN] was converted into this IETF
LISP working group draft.

Appendix B. Document Change Log

B.1. Changes to map identifiers onto locators",
draft-mathy-lisp-dht-00.txt (work draft-ietf-lisp-05.txt

o Posted October 2009.

o Added this Document Change Log appendix.

o Added section indicating that encapsulated Map-Requests must use
destination UDP port 4342.

o Don't use AH in progress),
February 2008.

[LOC-ID-ARCH]
Meyer, D. Map-Registers. Put key-id, auth-length, and D. Lewis, "Architectural Implications of
Locator/ID Separation",
draft-meyer-loc-id-implications-01.txt (work auth-
data in progress),
Januaryr 2009.

[MLISP] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas,
"LISP Map-Register payload.

o Added Jari to acknowledgment section.

o State the source-EID is set to 0 when using Map-Requests to
refresh or RLOC-probe.

o Make more clear what source-RLOC should be for Multicast Environments",
draft-ietf-lisp-multicast-01.txt (work in progress),
May 2009.

[NERD] Lear, E., "NERD: A Not-so-novel EID a Map-Request.

o The LISP-CONS authors thought that the Type definitions for CONS
should be removed from this specification.

o Removed nonce from Map-Register message, it wasn't used so no need
for it.

o Clarify what to RLOC Database",
draft-lear-lisp-nerd-04.txt (work in progress),
April 2008.

[OPENLISP]
Iannone, L. do for unspecified Action bits for negative Map-
Replies. Since No Action is a drop, make value 0 Drop.

B.2. Changes to draft-ietf-lisp-04.txt

o Posted September 2009.

o How do deal with record count greater than 1 for a Map-Request.
Damien and O. Bonaventure, "OpenLISP Implementation
Report", draft-iannone-openlisp-implementation-01.txt
(work in progress), July 2008.

[RADIR] Narten, T., "Routing Joel comment. Joel suggests: 1) Specify that senders
compliant with the current document will always set the count to
1, and Addressing Problem Statement",
draft-narten-radir-problem-statement-00.txt (work in
progress), July 2007.

[RFC3344bis]
Perkins, C., "IP Mobility Support note that the count is included for IPv4, revised",
draft-ietf-mip4-rfc3344bis-05 (work future extensibility.
2) Specify what a receiver compliant with the draft should do if
it receives a request with a count greater than 1. Presumably, it
should send some error back?

o Add Fred Templin in progress),
July 2007.

[RFC4192] Baker, F., Lear, E., ack section.

o Add Margaret and R. Droms, "Procedures Sam to the ack section for
Renumbering their great comments.

o Say more about LAGs in the UDP section per Sam Hartman's comment.

o Sam wants to use MAY instead of SHOULD for ignoring checksums on
ETR. From the mailing list: "You'd need to word it as an IPv6 Network without ITR MAY
send a Flag Day", RFC 4192,
September 2005.

[RPFV] Wijnands, IJ., Boers, A., zero checksum, an ETR MUST accept a 0 checksum and E. Rosen, "The RPF Vector
TLV", draft-ietf-pim-rpf-vector-08.txt (work MAY
ignore the checksum completely. And of course we'd need to
confirm that can actually be implemented. In particular, hardware
that verifies UDP checksums on receive needs to be checked to make
sure it permits 0 checksums."

o Margaret wants a reference to
http://www.ietf.org/id/draft-eubanks-chimento-6man-00.txt.

o Fix description in progress),
January 2009.

[RPMD] Handley, M., Huici, F., and A. Greenhalgh, "RPMD: Protocol Map-Request section. Where we describe Map-
Reply Record, change "R-bit" to "M-bit".

o Add the mobility bit to Map-Replies. So PTRs don't probe so often
for Routing Protocol Meta-data Dissemination",
draft-handley-p2ppush-unpublished-2007726.txt (work in
progress), July 2007.

[SHIM6] Nordmark, E. and M. Bagnulo, "Level 3 multihoming shim
protocol", draft-ietf-shim6-proto-06.txt (work in
progress), October 2006.

Appendix A. Acknowledgments

An initial thank you goes MNs but often enough to Dave Oran get mapping updates.

o Indicate SHA1 can be used as well for planting Map-Registers.

o More Fred comments on MTU handling.

o Isidor comment about specing better periodic Map-Registers. Will
be fixed in draft-ietf-lisp-ms-02.txt.

o Margaret's comment on gleaning: "The current specification does
not make it clear how long gleaned map entries should be retained
in the seeds cache, nor does it make it clear how/ when they will be
validated. The LISP spec should, at the very least, include a
(short) default lifetime for gleaned entries, require that they be
validated within a short period of time, and state that a new
gleaned entry should never overwrite an entry that was obtained
from the
initial ideas for LISP. His consultation continues mapping system. The security implications of storing
"gleaned" entries should also be explored in detail."

o Add section on RLOC-probing per working group feedback.

o Change "loc-reach-bits" to provide value "loc-status-bits" per comment from
Noel.

o Remove SMR-bit from data-plane. Dino prefers to have it in the
control plane only.

o Change LISP authors.

A special and appreciative thank you goes header to Noel Chiappa for
providing architectural impetus over allow a "Research Bit" so the past decades on separation
of location Nonce and identity, as well as detailed review of the LISP
architecture LSB
fields can be turned off and documents, coupled with enthusiasm used for making LISP another future purpose. For
Luigi et al versioning convergence.

o Add a
practical and incremental transition for the Internet.

The authors would like to gratefully acknowledge many people who have
contributed discussion and ideas N-bit to the making of this proposal.
They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller,
Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston,
David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley,
Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler,
Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi
Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Roger
Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van Beijnum, Roland
Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien Saucez, Damian
Lezama, Attilla De Groot, Parantap Lahiri, David Black, Roque
Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, Margaret
Wasserman, data header suggested by Noel. Then the nonce
field could be used when N is not 1.

o Clarify that when E-bit is 0, the nonce field can be an echoed
nonce or a random nonce. Comment from Jesper.

o Indicate when doing data-gleaning that a verifying Map-Request is
sent to the source-EID of the gleaned data packet so we can avoid
map-cache corruption by a 3rd party. Comment from Pedro.

o Indicate that a verifying Map-Request, for accepting mapping data,
should be sent over the the ALT (or to the EID).

o Reference IPsec RFC 4302. Comment from Sam Hartman, Michael Hofling, and Brian Weis.

o Put E-bit in Map-Reply to tell ITRs that the ETR supports echo-
noncing. Comment by Pedro Marques.

In particular, we would like and Dino.

o Jesper made a comment to thank Dave Meyer for his clever
suggestion for loosen the name "LISP". ;-)

This language about requiring the
copy of inner TTL to outer TTL since the text to get mixed-AF
traceroute to work originated would violate the "MUST" clause. Changed from
MUST to SHOULD in section 5.3.

B.3. Changes to draft-ietf-lisp-03.txt

o Posted July 2009.

o Removed loc-reach-bits longword from control packets per Damien
comment.

o Clarifications in MTU text from Roque.

o Added text to indicate that the Routing Research Group (RRG) locator-set be sorted by locator
address from Isidor.

o Clarification text from JohnZ in Echo-Nonce section.

B.4. Changes to draft-ietf-lisp-02.txt

o Posted July 2009.

o Encapsulation packet format change to add E-bit and make loc-
reach-bits 32-bits in length.

o Added Echo-Nonce Algorithm section.

o Clarification how ECN bits are copied.

o Moved S-bit in Map-Request.

o Added P-bit in Map-Request and Map-Reply messages to anticipate
RLOC-Probe Algorithm.

o Added to Mobility section to reference draft-meyer-lisp-mn-00.txt.

B.5. Changes to draft-ietf-lisp-01.txt

o Posted 2 days after draft-ietf-lisp-00.txt in May 2009.

o Defined LEID to be a "LISP EID".

o Indicate encapsulation use IPv4 DF=0.

o Added negative Map-Reply messages with drop, native-forward, and
send-map-request actions.

o Added Proxy-Map-Reply bit to Map-Register.

B.6. Changes to draft-ietf-lisp-00.txt

o Posted May 2009.

o Rename of the IRTF.
The individual submission [LISP-MAIN] was converted into this IETF
LISP working group draft. draft-farinacci-lisp-12.txt.

o Acknowledgment to RRG.

Authors' Addresses

Dino Farinacci
cisco Systems
Tasman Drive
San Jose, CA 95134
USA

Email: dino at cisco.com

Vince Fuller
cisco Systems
Tasman Drive
San Jose, CA 95134
USA

Email: vaf at cisco.com

Dave Meyer
cisco Systems
170 Tasman Drive
San Jose, CA
USA

Email: dmm at cisco.com

Darrel Lewis
cisco Systems
170 Tasman Drive
San Jose, CA
USA

Email: darlewis at cisco.com



Network Working Group                                       D. Farinacci
Internet-Draft                                                 V. Fuller
Intended status: Experimental                                   D. Meyer
Expires: April 1, 2010                                          D. Lewis
                                                           cisco Systems
                                                      September 28, 2009


                 Locator/ID Separation Protocol (LISP)
           (PROPOSED) draft-ietf-lisp-05.txt (NOT POSTED YET)

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on April 1, 2010.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.







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Abstract

   This draft describes a simple, incremental, network-based protocol to
   implement separation of Internet addresses into Endpoint Identifiers
   (EIDs) and Routing Locators (RLOCs).  This mechanism requires no
   changes to host stacks and no major changes to existing database
   infrastructures.  The proposed protocol can be implemented in a
   relatively small number of routers.

   This proposal was stimulated by the problem statement effort at the
   Amsterdam IAB Routing and Addressing Workshop (RAWS), which took
   place in October 2006.


Table of Contents

   1.  Requirements Notation  . . . . . . . . . . . . . . . . . . . .  4
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Definition of Terms  . . . . . . . . . . . . . . . . . . . . .  8
   4.  Basic Overview . . . . . . . . . . . . . . . . . . . . . . . . 12
     4.1.  Packet Flow Sequence . . . . . . . . . . . . . . . . . . . 14
   5.  Tunneling Details  . . . . . . . . . . . . . . . . . . . . . . 16
     5.1.  LISP IPv4-in-IPv4 Header Format  . . . . . . . . . . . . . 17
     5.2.  LISP IPv6-in-IPv6 Header Format  . . . . . . . . . . . . . 18
     5.3.  Tunnel Header Field Descriptions . . . . . . . . . . . . . 19
     5.4.  Dealing with Large Encapsulated Packets  . . . . . . . . . 21
       5.4.1.  A Stateless Solution to MTU Handling . . . . . . . . . 22
       5.4.2.  A Stateful Solution to MTU Handling  . . . . . . . . . 22
   6.  EID-to-RLOC Mapping  . . . . . . . . . . . . . . . . . . . . . 24
     6.1.  LISP IPv4 and IPv6 Control Plane Packet Formats  . . . . . 24
       6.1.1.  LISP Packet Type Allocations . . . . . . . . . . . . . 26
       6.1.2.  Map-Request Message Format . . . . . . . . . . . . . . 26
       6.1.3.  EID-to-RLOC UDP Map-Request Message  . . . . . . . . . 28
       6.1.4.  Map-Reply Message Format . . . . . . . . . . . . . . . 30
       6.1.5.  EID-to-RLOC UDP Map-Reply Message  . . . . . . . . . . 33
       6.1.6.  Map-Register Message Format  . . . . . . . . . . . . . 34
       6.1.7.  Encapsualted Control Message Format  . . . . . . . . . 36
     6.2.  Routing Locator Selection  . . . . . . . . . . . . . . . . 38
     6.3.  Routing Locator Reachability . . . . . . . . . . . . . . . 39
       6.3.1.  Echo Nonce Algorithm . . . . . . . . . . . . . . . . . 42
       6.3.2.  RLOC Probing Algorithm . . . . . . . . . . . . . . . . 43
     6.4.  Routing Locator Hashing  . . . . . . . . . . . . . . . . . 44
     6.5.  Changing the Contents of EID-to-RLOC Mappings  . . . . . . 45
       6.5.1.  Clock Sweep  . . . . . . . . . . . . . . . . . . . . . 45
       6.5.2.  Solicit-Map-Request (SMR)  . . . . . . . . . . . . . . 46
   7.  Router Performance Considerations  . . . . . . . . . . . . . . 48
   8.  Deployment Scenarios . . . . . . . . . . . . . . . . . . . . . 49
     8.1.  First-hop/Last-hop Tunnel Routers  . . . . . . . . . . . . 50



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     8.2.  Border/Edge Tunnel Routers . . . . . . . . . . . . . . . . 50
     8.3.  ISP Provider-Edge (PE) Tunnel Routers  . . . . . . . . . . 51
   9.  Traceroute Considerations  . . . . . . . . . . . . . . . . . . 52
     9.1.  IPv6 Traceroute  . . . . . . . . . . . . . . . . . . . . . 53
     9.2.  IPv4 Traceroute  . . . . . . . . . . . . . . . . . . . . . 53
     9.3.  Traceroute using Mixed Locators  . . . . . . . . . . . . . 53
   10. Mobility Considerations  . . . . . . . . . . . . . . . . . . . 55
     10.1. Site Mobility  . . . . . . . . . . . . . . . . . . . . . . 55
     10.2. Slow Endpoint Mobility . . . . . . . . . . . . . . . . . . 55
     10.3. Fast Endpoint Mobility . . . . . . . . . . . . . . . . . . 55
     10.4. Fast Network Mobility  . . . . . . . . . . . . . . . . . . 57
     10.5. LISP Mobile Node Mobility  . . . . . . . . . . . . . . . . 57
   11. Multicast Considerations . . . . . . . . . . . . . . . . . . . 59
   12. Security Considerations  . . . . . . . . . . . . . . . . . . . 60
   13. Prototype Plans and Status . . . . . . . . . . . . . . . . . . 61
   14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 64
     14.1. Normative References . . . . . . . . . . . . . . . . . . . 64
     14.2. Informative References . . . . . . . . . . . . . . . . . . 65
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 68
   Appendix B.  Document Change Log . . . . . . . . . . . . . . . . . 69
     B.1.  Changes to draft-ietf-lisp-05.txt  . . . . . . . . . . . . 69
     B.2.  Changes to draft-ietf-lisp-04.txt  . . . . . . . . . . . . 69
     B.3.  Changes to draft-ietf-lisp-03.txt  . . . . . . . . . . . . 71
     B.4.  Changes to draft-ietf-lisp-02.txt  . . . . . . . . . . . . 71
     B.5.  Changes to draft-ietf-lisp-01.txt  . . . . . . . . . . . . 72
     B.6.  Changes to draft-ietf-lisp-00.txt  . . . . . . . . . . . . 72
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 73
























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1.  Requirements Notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].














































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2.  Introduction

   Many years of discussion about the current IP routing and addressing
   architecture have noted that its use of a single numbering space (the
   "IP address") for both host transport session identification and
   network routing creates scaling issues (see [CHIAPPA] and [RFC1498]).
   A number of scaling benefits would be realized by separating the
   current IP address into separate spaces for Endpoint Identifiers
   (EIDs) and Routing Locators (RLOCs); among them are:

   1.  Reduction of routing table size in the "default-free zone" (DFZ).
       Use of a separate numbering space for RLOCs will allow them to be
       assigned topologically (in today's Internet, RLOCs would be
       assigned by providers at client network attachment points),
       greatly improving aggregation and reducing the number of
       globally-visible, routable prefixes.

   2.  More cost-effective multihoming for sites that connect to
       different service providers where they can control their own
       policies for packet flow into the site without using extra
       routing table resources of core routers.

   3.  Easing of renumbering burden when clients change providers.
       Because host EIDs are numbered from a separate, non-provider-
       assigned and non-topologically-bound space, they do not need to
       be renumbered when a client site changes its attachment points to
       the network.

   4.  Traffic engineering capabilities that can be performed by network
       elements and do not depend on injecting additional state into the
       routing system.  This will fall out of the mechanism that is used
       to implement the EID/RLOC split (see Section 4).

   5.  Mobility without address changing.  Existing mobility mechanisms
       will be able to work in a locator/ID separation scenario.  It
       will be possible for a host (or a collection of hosts) to move to
       a different point in the network topology either retaining its
       home-based address or acquiring a new address based on the new
       network location.  A new network location could be a physically
       different point in the network topology or the same physical
       point of the topology with a different provider.

   This draft describes protocol mechanisms to achieve the desired
   functional separation.  For flexibility, the mechanism used for
   forwarding packets is decoupled from that used to determine EID to
   RLOC mappings.  This document covers the former.  For the later, see
   [CONS], [ALT], [EMACS], [RPMD], and [NERD].  This work is in response
   to and intended to address the problem statement that came out of the



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   RAWS effort [RFC4984].

   The Routing and Addressing problem statement can be found in [RADIR].

   This draft focuses on a router-based solution.  Building the solution
   into the network will facilitate incremental deployment of the
   technology on the Internet.  Note that while the detailed protocol
   specification and examples in this document assume IP version 4
   (IPv4), there is nothing in the design that precludes use of the same
   techniques and mechanisms for IPv6.  It should be possible for IPv4
   packets to use IPv6 RLOCs and for IPv6 EIDs to be mapped to IPv4
   RLOCs.

   Related work on host-based solutions is described in Shim6 [SHIM6]
   and HIP [RFC4423].  Related work on a router-based solution is
   described in [GSE].  This draft attempts to not compete or overlap
   with such solutions and the proposed protocol changes are expected to
   complement a host-based mechanism when Traffic Engineering
   functionality is desired.

   Some of the design goals of this proposal include:

   1.  Require no hardware or software changes to end-systems (hosts).

   2.  Minimize required changes to Internet infrastructure.

   3.  Be incrementally deployable.

   4.  Require no router hardware changes.

   5.  Minimize the number of routers which have to be modified.  In
       particular, most customer site routers and no core routers
       require changes.

   6.  Minimize router software changes in those routers which are
       affected.

   7.  Avoid or minimize packet loss when EID-to-RLOC mappings need to
       be performed.

   There are 4 variants of LISP, which differ along a spectrum of strong
   to weak dependence on the topological nature and possible need for
   routability of EIDs.  The variants are:








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   LISP 1:  uses EIDs that are routable through the RLOC topology for
      bootstrapping EID-to-RLOC mappings.  [LISP1] This was intended as
      a prototyping mechanism for early protocol implementation.  It is
      now deprecated and should not be deployed.

   LISP 1.5:  uses EIDs that are routable for bootstrapping EID-to-RLOC
      mappings; such routing is via a separate topology.

   LISP 2:  uses EIDS that are not routable and EID-to-RLOC mappings are
      implemented within the DNS.  [LISP2]

   LISP 3:  uses non-routable EIDs that are used as lookup keys for a
      new EID-to-RLOC mapping database.  Use of Distributed Hash Tables
      [DHTs] [LISPDHT] to implement such a database would be an area to
      explore.  Other examples of new mapping database services are
      [CONS], [ALT], [RPMD], [NERD], and [APT].

   This document on LISP 1.5, and LISP 3 variants, both of which rely on
   a router-based distributed cache and database for EID-to-RLOC
   mappings.  The LISP 1.0 mechanism works but does not allow reduction
   of routing information in the default-free-zone of the Internet.  The
   LISP 2 mechanisms are put on hold and may never come to fruition
   since it is not architecturally pure to have routing depend on
   directory and directory depend on routing.  The LISP 3 mechanisms
   will be documented elsewhere but may use the control-plane options
   specified in this specification.

























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3.  Definition of Terms

   Provider Independent (PI) Addresses:   an address block assigned from
      a pool where blocks are not associated with any particular
      location in the network (e.g. from a particular service provider),
      and is therefore not topologically aggregatable in the routing
      system.

   Provider Assigned (PA) Addresses:   a block of IP addresses that are
      assigned to a site by each service provider to which a site
      connects.  Typically, each block is sub-block of a service
      provider CIDR block and is aggregated into the larger block before
      being advertised into the global Internet.  Traditionally, IP
      multihoming has been implemented by each multi-homed site
      acquiring its own, globally-visible prefix.  LISP uses only
      topologically-assigned and aggregatable address blocks for RLOCs,
      eliminating this demonstrably non-scalable practice.

   Routing Locator (RLOC):   the IPv4 or IPv6 address of an egress
      tunnel router (ETR).  It is the output of a EID-to-RLOC mapping
      lookup.  An EID maps to one or more RLOCs.  Typically, RLOCs are
      numbered from topologically-aggregatable blocks that are assigned
      to a site at each point to which it attaches to the global
      Internet; where the topology is defined by the connectivity of
      provider networks, RLOCs can be thought of as PA addresses.
      Multiple RLOCs can be assigned to the same ETR device or to
      multiple ETR devices at a site.

   Endpoint ID (EID):   a 32-bit (for IPv4) or 128-bit (for IPv6) value
      used in the source and destination address fields of the first
      (most inner) LISP header of a packet.  The host obtains a
      destination EID the same way it obtains an destination address
      today, for example through a DNS lookup or SIP exchange.  The
      source EID is obtained via existing mechanisms used to set a
      host's "local" IP address.  An EID is allocated to a host from an
      EID-prefix block associated with the site where the host is
      located.  An EID can be used by a host to refer to other hosts.
      EIDs MUST NOT be used as LISP RLOCs.  Note that EID blocks may be
      assigned in a hierarchical manner, independent of the network
      topology, to facilitate scaling of the mapping database.  In
      addition, an EID block assigned to a site may have site-local
      structure (subnetting) for routing within the site; this structure
      is not visible to the global routing system.  When used in
      discussions with other Locator/ID separation proposals, a LISP EID
      will be called a "LEID".  Throughout this document, any references
      to "EID" refers to an LEID.





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   EID-prefix:   A power-of-2 block of EIDs which are allocated to a
      site by an address allocation authority.  EID-prefixes are
      associated with a set of RLOC addresses which make up a "database
      mapping".  EID-prefix allocations can be broken up into smaller
      blocks when an RLOC set is to be associated with the smaller EID-
      prefix.  A globally routed address block (whether PI or PA) is not
      an EID-prefix.  However, a globally routed address block may be
      removed from global routing and reused as an EID-prefix.  A site
      that receives an explicitly allocated EID-prefix may not use that
      EID-prefix as a globally routed prefix assigned to RLOCs.

   End-system:   is an IPv4 or IPv6 device that originates packets with
      a single IPv4 or IPv6 header.  The end-system supplies an EID
      value for the destination address field of the IP header when
      communicating globally (i.e. outside of its routing domain).  An
      end-system can be a host computer, a switch or router device, or
      any network appliance.

   Ingress Tunnel Router (ITR):   a router which accepts an IP packet
      with a single IP header (more precisely, an IP packet that does
      not contain a LISP header).  The router treats this "inner" IP
      destination address as an EID and performs an EID-to-RLOC mapping
      lookup.  The router then prepends an "outer" IP header with one of
      its globally-routable RLOCs in the source address field and the
      result of the mapping lookup in the destination address field.
      Note that this destination RLOC may be an intermediate, proxy
      device that has better knowledge of the EID-to-RLOC mapping closer
      to the destination EID.  In general, an ITR receives IP packets
      from site end-systems on one side and sends LISP-encapsulated IP
      packets toward the Internet on the other side.

      Specifically, when a service provider prepends a LISP header for
      Traffic Engineering purposes, the router that does this is also
      regarded as an ITR.  The outer RLOC the ISP ITR uses can be based
      on the outer destination address (the originating ITR's supplied
      RLOC) or the inner destination address (the originating hosts
      supplied EID).

   TE-ITR:   is an ITR that is deployed in a service provider network
      that prepends an additional LISP header for Traffic Engineering
      purposes.

   Egress Tunnel Router (ETR):   a router that accepts an IP packet
      where the destination address in the "outer" IP header is one of
      its own RLOCs.  The router strips the "outer" header and forwards
      the packet based on the next IP header found.  In general, an ETR
      receives LISP-encapsulated IP packets from the Internet on one
      side and sends decapsulated IP packets to site end-systems on the



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      other side.  ETR functionality does not have to be limited to a
      router device.  A server host can be the endpoint of a LISP tunnel
      as well.

   TE-ETR:   is an ETR that is deployed in a service provider network
      that strips an outer LISP header for Traffic Engineering purposes.

   xTR:   is a reference to an ITR or ETR when direction of data flow is
      not part of the context description. xTR refers to the router that
      is the tunnel endpoint.  Used synonymously with the term "Tunnel
      Router".  For example, "An xTR can be located at the Customer Edge
      (CE) router", meaning both ITR and ETR functionality is at the CE
      router.

   EID-to-RLOC Cache:   a short-lived, on-demand table in an ITR that
      stores, tracks, and is responsible for timing-out and otherwise
      validating EID-to-RLOC mappings.  This cache is distinct from the
      full "database" of EID-to-RLOC mappings, it is dynamic, local to
      the ITR(s), and relatively small while the database is
      distributed, relatively static, and much more global in scope.

   EID-to-RLOC Database:   a global distributed database that contains
      all known EID-prefix to RLOC mappings.  Each potential ETR
      typically contains a small piece of the database: the EID-to-RLOC
      mappings for the EID prefixes "behind" the router.  These map to
      one of the router's own, globally-visible, IP addresses.

   Recursive Tunneling:   when a packet has more than one LISP IP
      header.  Additional layers of tunneling may be employed to
      implement traffic engineering or other re-routing as needed.  When
      this is done, an additional "outer" LISP header is added and the
      original RLOCs are preserved in the "inner" header.  Any
      references to tunnels in this specification refers to dynamic
      encapsulating tunnels and never are they statically configured.

   Reencapsulating Tunnels:   when a packet has no more than one LISP IP
      header (two IP headers total) and when it needs to be diverted to
      new RLOC, an ETR can decapsulate the packet (remove the LISP
      header) and prepends a new tunnel header, with new RLOC, on to the
      packet.  Doing this allows a packet to be re-routed by the re-
      encapsulating router without adding the overhead of additional
      tunnel headers.  Any references to tunnels in this specification
      refers to dynamic encapsulating tunnels and never are they
      statically configured.







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   LISP Header:   a term used in this document to refer to the outer
      IPv4 or IPv6 header, a UDP header, and a LISP header, an ITR
      prepends or an ETR strips.

   Address Family Indicator (AFI):   a term used to describe an address
      encoding in a packet.  An address family currently pertains to an
      IPv4 or IPv6 address.  See [AFI] for details.

   Negative Mapping Entry:   also known as a negative cache entry, is an
      EID-to-RLOC entry where an EID-prefix is advertised or stored with
      no RLOCs.  That is, the locator-set for the EID-to-RLOC entry is
      empty or has an encoded locator count of 0.  This type of entry
      could be used to describe a prefix from a non-LISP site, which is
      explicitly not in the mapping database.  There are a set of well
      defined actions that are encoded in a Negative Map-Reply.

   Data Probe:   a LISP-encapsulated data packet where the inner header
      destination address equals the outer header destination address
      used to trigger a Map-Reply by a decapsulating ETR.  In addition,
      the original packet is decapsulated and delivered to the
      destination host.  A Data Probe is used in some of the mapping
      database designs to "probe" or request a Map-Reply from an ETR; in
      other cases, Map-Requests are used.  See each mapping database
      design for details.



























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4.  Basic Overview

   One key concept of LISP is that end-systems (hosts) operate the same
   way they do today.  The IP addresses that hosts use for tracking
   sockets, connections, and for sending and receiving packets do not
   change.  In LISP terminology, these IP addresses are called Endpoint
   Identifiers (EIDs).

   Routers continue to forward packets based on IP destination
   addresses.  When a packet is LISP encapsulated, these addresses are
   referred to as Routing Locators (RLOCs).  Most routers along a path
   between two hosts will not change; they continue to perform routing/
   forwarding lookups on the destination addresses.  For routers between
   the source host and the ITR as well as routers from the ETR to the
   destination host, the destination address is an EID.  For the routers
   between the ITR and the ETR, the destination address is an RLOC.

   This design introduces "Tunnel Routers", which prepends LISP headers
   on host-originated packets and strip them prior to final delivery to
   their destination.  The IP addresses in this "outer header" are
   RLOCs.  During end-to-end packet exchange between two Internet hosts,
   an ITR prepends a new LISP header to each packet and an egress tunnel
   router strips the new header.  The ITR performs EID-to-RLOC lookups
   to determine the routing path to the the ETR, which has the RLOC as
   one of its IP addresses.

   Some basic rules governing LISP are:

   o  End-systems (hosts) only send to addresses which are EIDs.  They
      don't know addresses are EIDs versus RLOCs but assume packets get
      to LISP routers, which in turn, deliver packets to the destination
      the end-system has specified.

   o  EIDs are always IP addresses assigned to hosts.

   o  LISP routers mostly deal with Routing Locator addresses.  See
      details later in Section 4.1 to clarify what is meant by "mostly".

   o  RLOCs are always IP addresses assigned to routers; preferably,
      topologically-oriented addresses from provider CIDR blocks.

   o  When a router originates packets it may use as a source address
      either an EID or RLOC.  When acting as a host (e.g. when
      terminating a transport session such as SSH, TELNET, or SNMP), it
      may use an EID that is explicitly assigned for that purpose.  An
      EID that identifies the router as a host MUST NOT be used as an
      RLOC; an EID is only routable within the scope of a site.  A
      typical BGP configuration might demonstrate this "hybrid" EID/RLOC



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      usage where a router could use its "host-like" EID to terminate
      iBGP sessions to other routers in a site while at the same time
      using RLOCs to terminate eBGP sessions to routers outside the
      site.

   o  EIDs are not expected to be usable for global end-to-end
      communication in the absence of an EID-to-RLOC mapping operation.
      They are expected to be used locally for intra-site communication.

   o  EID prefixes are likely to be hierarchically assigned in a manner
      which is optimized for administrative convenience and to
      facilitate scaling of the EID-to-RLOC mapping database.  The
      hierarchy is based on a address allocation hierarchy which is not
      dependent on the network topology.

   o  EIDs may also be structured (subnetted) in a manner suitable for
      local routing within an autonomous system.

   An additional LISP header may be prepended to packets by a transit
   router (i.e.  TE-ITR) when re-routing of the path for a packet is
   desired.  An obvious instance of this would be an ISP router that
   needs to perform traffic engineering for packets in flow through its
   network.  In such a situation, termed Recursive Tunneling, an ISP
   transit acts as an additional ingress tunnel router and the RLOC it
   uses for the new prepended header would be either an TE-ETR within
   the ISP (along intra-ISP traffic engineered path) or in an TE-ETR
   within another ISP (an inter-ISP traffic engineered path, where an
   agreement to build such a path exists).

   This specification mandates that no more than two LISP headers get
   prepended to a packet.  This avoids excessive packet overhead as well
   as possible encapsulation loops.  It is believed two headers is
   sufficient, where the first prepended header is used at a site for
   Location/Identity separation and second prepended header is used
   inside a service provider for Traffic Engineering purposes.

   Tunnel Routers can be placed fairly flexibly in a multi-AS topology.
   For example, the ITR for a particular end-to-end packet exchange
   might be the first-hop or default router within a site for the source
   host.  Similarly, the egress tunnel router might be the last-hop
   router directly-connected to the destination host.  Another example,
   perhaps for a VPN service out-sourced to an ISP by a site, the ITR
   could be the site's border router at the service provider attachment
   point.  Mixing and matching of site-operated, ISP-operated, and other
   tunnel routers is allowed for maximum flexibility.  See Section 8 for
   more details.





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4.1.  Packet Flow Sequence

   This section provides an example of the unicast packet flow with the
   following conditions:

   o  Source host "host1.abc.com" is sending a packet to
      "host2.xyz.com", exactly what host1 would do if the site was not
      using LISP.

   o  Each site is multi-homed, so each tunnel router has an address
      (RLOC) assigned from the service provider address block for each
      provider to which that particular tunnel router is attached.

   o  The ITR(s) and ETR(s) are directly connected to the source and
      destination, respectively.

   o  Data Probes are used to solicit Map-Replies versus using Map-
      Requests.  And the Data Probes are sent on the underlying topology
      (the LISP 1.0 variant) but could also be sent over an alternative
      topology (the LISP 1.5 variant) as it would in [ALT].

   Client host1.abc.com wants to communicate with server host2.xyz.com:

   1.  host1.abc.com wants to open a TCP connection to host2.xyz.com.
       It does a DNS lookup on host2.xyz.com.  An A/AAAA record is
       returned.  This address is used as the destination EID and the
       locally-assigned address of host1.abc.com is used as the source
       EID.  An IPv4 or IPv6 packet is built using the EIDs in the IPv4
       or IPv6 header and sent to the default router.

   2.  The default router is configured as an ITR.  The ITR must be able
       to map the EID destination to an RLOC of the ETR at the
       destination site.  The ITR prepends a LISP header to the packet,
       with one of its RLOCs as the source IPv4 or IPv6 address.  The
       destination EID from the original packet header is used as the
       destination IPv4 or IPv6 in the prepended LISP header.
       Subsequent packets, where the outer destination address is the
       destination EID will be sent until EID-to-RLOC mapping is
       learned.

   3.  In LISP 1, the packet is routed through the Internet as it is
       today.  In LISP 1.5, the packet is routed on a different topology
       which may have EID prefixes distributed and advertised in an
       aggregatable fashion.  In either case, the packet arrives at the
       ETR.  The router is configured to "punt" the packet to the
       router's processor.  See Section 7 for more details.  For LISP
       2.0 and 3.0, the behavior is not fully defined yet.




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   4.  The LISP header is stripped so that the packet can be forwarded
       by the router control plane.  The router looks up the destination
       EID in the router's EID-to-RLOC database (not the cache, but the
       configured data structure of RLOCs).  An EID-to-RLOC Map-Reply
       message is originated by the ETR and is addressed to the source
       RLOC in the LISP header of the original packet (this is the ITR).
       The source RLOC of the Map-Reply is one of the ETR's RLOCs.

   5.  The ITR receives the Map-Reply message, parses the message (to
       check for format validity) and stores the mapping information
       from the packet.  This information is put in the ITR's EID-to-
       RLOC mapping cache (this is the on-demand cache, the cache where
       entries time out due to inactivity).

   6.  Subsequent packets from host1.abc.com to host2.xyz.com will have
       a LISP header prepended by the ITR using the appropriate RLOC as
       the LISP header destination address learned from the ETR.  Note,
       the packet may be sent to a different ETR than the one which
       returned the Map-Reply due to the source site's hashing policy or
       the destination site's locator-set policy.

   7.  The ETR receives these packets directly (since the destination
       address is one of its assigned IP addresses), strips the LISP
       header and forwards the packets to the attached destination host.

   In order to eliminate the need for a mapping lookup in the reverse
   direction, an ETR MAY create a cache entry that maps the source EID
   (inner header source IP address) to the source RLOC (outer header
   source IP address) in a received LISP packet.  Such a cache entry is
   termed a "gleaned" mapping and only contains a single RLOC for the
   EID in question.  More complete information about additional RLOCs
   SHOULD be verified by sending a LISP Map-Request for that EID.  Both
   ITR and the ETR may also influence the decision the other makes in
   selecting an RLOC.  See Section 6 for more details.

















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5.  Tunneling Details

   This section describes the LISP Data Message which defines the
   tunneling header used to encapsulate IPv4 and IPv6 packets which
   contain EID addresses.  Even though the following formats illustrate
   IPv4-in-IPv4 and IPv6-in-IPv6 encapsulations, the other 2
   combinations are supported as well.

   Since additional tunnel headers are prepended, the packet becomes
   larger and in theory can exceed the MTU of any link traversed from
   the ITR to the ETR.  It is recommended, in IPv4 that packets do not
   get fragmented as they are encapsulated by the ITR.  Instead, the
   packet is dropped and an ICMP Too Big message is returned to the
   source.

   Based on informal surveys of large ISP traffic patterns, it appears
   that most transit paths can accommodate a path MTU of at least 4470
   bytes.  The exceptions, in terms of data rate, number of hosts
   affected, or any other metric are expected to be vanishingly small.

   To address MTU concerns, mainly raised on the RRG mailing list, the
   LISP deployment process will include collecting data during its pilot
   phase to either verify or refute the assumption about minimum
   available MTU.  If the assumption proves true and transit networks
   with links limited to 1500 byte MTUs are corner cases, it would seem
   more cost-effective to either upgrade or modify the equipment in
   those transit networks to support larger MTUs or to use existing
   mechanisms for accommodating packets that are too large.

   For this reason, there is currently no plan for LISP to add any new
   additional, complex mechanism for implementing fragmentation and
   reassembly in the face of limited-MTU transit links.  If analysis
   during LISP pilot deployment reveals that the assumption of
   essentially ubiquitous, 4470+ byte transit path MTUs, is incorrect,
   then LISP can be modified prior to protocol standardization to add
   support for one of the proposed fragmentation and reassembly schemes.
   Note that two simple existing schemes are detailed in Section 5.4.














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5.1.  LISP IPv4-in-IPv4 Header Format



        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     / |Version|  IHL  |Type of Service|          Total Length         |
    /  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   |         Identification        |Flags|      Fragment Offset    |
   |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   OH  |  Time to Live | Protocol = 17 |         Header Checksum       |
   |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   |                    Source Routing Locator                     |
    \  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     \ |                 Destination Routing Locator                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     / |       Source Port = xxxx      |       Dest Port = 4341        |
   UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     \ |           UDP Length          |        UDP Checksum           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   L   |N|L|E|  rflags |                 Nonce                         |
   I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   S / |                       Locator Status Bits                     |
   P   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     / |Version|  IHL  |Type of Service|          Total Length         |
    /  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   |         Identification        |Flags|      Fragment Offset    |
   |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   IH  |  Time to Live |    Protocol   |         Header Checksum       |
   |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   |                           Source EID                          |
    \  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     \ |                         Destination EID                       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
















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5.2.  LISP IPv6-in-IPv6 Header Format



        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     / |Version| Traffic Class |           Flow Label                  |
    /  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   |         Payload Length        | Next Header=17|   Hop Limit   |
   v   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
   O   +                                                               +
   u   |                                                               |
   t   +                     Source Routing Locator                    +
   e   |                                                               |
   r   +                                                               +
       |                                                               |
   H   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   d   |                                                               |
   r   +                                                               +
       |                                                               |
   ^   +                  Destination Routing Locator                  +
   |   |                                                               |
    \  +                                                               +
     \ |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     / |       Source Port = xxxx      |       Dest Port = 4341        |
   UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     \ |           UDP Length          |        UDP Checksum           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   L   |N|L|E|  rflags |                 Nonce                         |
   I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   S / |                       Locator Status Bits                     |
   P   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     / |Version| Traffic Class |           Flow Label                  |
    /  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   /   |         Payload Length        |  Next Header  |   Hop Limit   |
   v   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
   I   +                                                               +
   n   |                                                               |
   n   +                          Source EID                           +
   e   |                                                               |
   r   +                                                               +
       |                                                               |
   H   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   d   |                                                               |



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   r   +                                                               +
       |                                                               |
   ^   +                        Destination EID                        +
   \   |                                                               |
    \  +                                                               +
     \ |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


5.3.  Tunnel Header Field Descriptions

   Inner Header:  is the inner header, preserved from the datagram
      received from the originating host.  The source and destination IP
      addresses are EIDs.

   Outer Header:  is the outer header prepended by an ITR.  The address
      fields contain RLOCs obtained from the ingress router's EID-to-
      RLOC cache.  The IP protocol number is "UDP (17)" from [RFC0768].
      The DF bit of the Flags field is set to 0 when the method in
      Section 5.4.1 is used and set to 1 when the method in
      Section 5.4.2 is used.

   UDP Header:  contains a ITR selected source port when encapsulating a
      packet.  See Section 6.4 for details on the hash algorithm used
      select a source port based on the 5-tuple of the inner header.
      The destination port MUST be set to the well-known IANA assigned
      port value 4341.

   UDP Checksum:  this field SHOULD be transmitted as zero by an ITR for
      either IPv4 [RFC0768] or IPv6 encapsulation [UDP-TUNNELS].  When a
      packet with a zero UDP checksum is received by an ETR, the ETR
      MUST accept the packet for decapsulation.  When an ITR transmits a
      non-zero value for the UDP checksum, it MUST send a correctly
      computed value in this field.  When an ETR receives a packet with
      a non-zero UDP checksum, it MAY choose to verify the checksum
      value.  If it chooses to perform such verification, and the
      verification fails, the packet MUST be silently dropped.  If the
      ETR chooses not to perform the verification, or performs the
      verification successfully, the packet MUST be accepted for
      decapsulation.  The handling of UDP checksums for all tunneling
      protocols, including LISP, is under active discussion within the
      IETF.  When that discussion concludes, any necessary changes will
      be made to align LISP with the outcome of the broader discussion.

   UDP Length:  for an IPv4 encapsulated packet, the inner header Total
      Length plus the UDP and LISP header lengths are used.  For an IPv6
      encapsulated packet, the inner header Payload Length plus the size
      of the IPv6 header (40 bytes) plus the size of the UDP and LISP



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      headers are used.  The UDP header length is 8 bytes.

   N: this is the nonce-present bit.  When this bit is set to 1, the
      low-order 24-bits of the first 32-bits of the LISP header contains
      a Nonce.  See section Section 6.3.1 for details.

   L: this is the Locator-Status-Bits field enabled bit.  When this bit
      is set to 1, the Locator-Status-Bits in the second 32-bits of the
      LISP header are in use.

   E: this is the echo-nonce-request bit.  When this bit is set to 1,
      the N bit must be 1.  This bit should be ignored and has no
      meaning when the N bit is set to 0.  See section Section 6.3.1 for
      details.

   rflags:  this 4-bit field is reserved for future flag use.  It is set
      to 0 on transmit and ignored on receipt.

   LISP Nonce:  is a 24-bit value that is randomly generated by an ITR
      when the N-bit is set to 1.  The nonce is also used when the E-bit
      is set to request the nonce value to be echoed by the other side
      when packets are returned.  When the E-bit is clear but the N-bit
      is set, an ITR is either echoing a previously requested echo-nonce
      or providing a random nonce.  See section Section 6.3.1 for more
      details.

   LISP Locator Status Bits:  in the LISP header are set by an ITR to
      indicate to an ETR the up/down status of the Locators in the
      source site.  Each RLOC in a Map-Reply is assigned an ordinal
      value from 0 to n-1 (when there are n RLOCs in a mapping entry).
      The Locator Status Bits are numbered from 0 to n-1 from the least
      significant bit of the 32-bit field.  When a bit is set to 1, the
      ITR is indicating to the ETR the RLOC associated with the bit
      ordinal has up status.  See Section 6.3 for details on how an ITR
      can determine other ITRs at the site are reachable.  When a site
      has multiple EID-prefixes which result in multiple mappings (where
      each could have a different locator-set), the Locator Status Bits
      setting in an encapsulated packet MUST reflect the mapping for the
      EID-prefix that the inner-header source EID address matches.

   When doing Recursive Tunneling or ITR/PTR encapsulation:

   o  The outer header Time to Live field (or Hop Limit field, in case
      of IPv6) SHOULD be copied from the inner header Time to Live
      field.

   o  The outer header Type of Service field (or the Traffic Class
      field, in the case of IPv6) SHOULD be copied from the inner header



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      Type of Service field (with one caveat, see below).

   When doing Re-encapsulated Tunneling:

   o  The new outer header Time to Live field SHOULD be copied from the
      stripped outer header Time to Live field.

   o  The new outer header Type of Service field SHOULD be copied from
      the stripped OH header Type of Service field (with one caveat, see
      below).

   Copying the TTL serves two purposes: first, it preserves the distance
   the host intended the packet to travel; second, and more importantly,
   it provides for suppression of looping packets in the event there is
   a loop of concatenated tunnels due to misconfiguration.

   The ECN field occupies bits 6 and 7 of both the IPv4 Type of Service
   field and the IPv6 Traffic Class field [RFC3168].  The ECN field
   requires special treatment in order to avoid discarding indications
   of congestion [RFC3168].  ITR encapsulation MUST copy the 2-bit ECN
   field from the inner header to the outer header.  Re-encapsulation
   MUST copy the 2-bit ECN field from the stripped outer header to the
   new outer header.  If the ECN field contains a congestion indication
   codepoint (the value is '11', the Congestion Experienced (CE)
   codepoint), then ETR decapsulation MUST copy the 2-bit ECN field from
   the stripped outer header to the surviving inner header that is used
   to forward the packet beyond the ETR.  These requirements preserve
   Congestion Experienced (CE) indications when a packet that uses ECN
   traverses a LISP tunnel and becomes marked with a CE indication due
   to congestion between the tunnel endpoints.

5.4.  Dealing with Large Encapsulated Packets

   In the event that the MTU issues mentioned above prove to be more
   serious than expected, this section proposes 2 simple mechanisms to
   deal with large packets.  One is stateless using IP fragmentation and
   the other is stateful using Path MTU Discovery [RFC1191].

   It is left to the implementor to decide if the stateless or stateful
   mechanism should be implemented.  Both or neither can be decided as
   well since it is a local decision in the ITR regarding how to deal
   with MTU issues.  Sites can interoperate with differing mechanisms.

   Both stateless and stateful mechanisms also apply to Reencapsulating
   and Recursive Tunneling.  So any actions reference below to an ITR
   also apply to an TE-ITR.





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5.4.1.  A Stateless Solution to MTU Handling

   An ITR stateless solution to handle MTU issues is described as
   follows:

   1.  Define an architectural constant S for the maximum size of a
       packet, in bytes, an ITR would receive from a source inside of
       its site.

   2.  Define L to be the maximum size, in bytes, a packet of size S
       would be after the ITR prepends the LISP header, UDP header, and
       outer network layer header of size H.

   3.  Calculate: S + H = L.

   When an ITR receives a packet from a site-facing interface and adds H
   bytes worth of encapsulation to yield a packet size of L bytes, it
   resolves the MTU issue by first splitting the original packet into 2
   equal-sized fragments.  A LISP header is then prepended to each
   fragment.  This will ensure that the new, encapsulated packets are of
   size (S/2 + H), which is always below the effective tunnel MTU.

   When an ETR receives encapsulated fragments, it treats them as two
   individually encapsulated packets.  It strips the LISP headers then
   forwards each fragment to the destination host of the destination
   site.  The two fragments are reassembled at the destination host into
   the single IP datagram that was originated by the source host.

   This behavior is performed by the ITR when the source host originates
   a packet with the DF field of the IP header is set to 0.  When the DF
   field of the IP header is set to 1, or the packet is an IPv6 packet
   originated by the source host, the ITR will drop the packet when the
   size is greater than L, and sends an ICMP Too Big message to the
   source with a value of S, where S is (L - H).

   When the outer header encapsulation uses an IPv4 header the DF bit is
   always set to 0.

   This specification recommends that L be defined as 1500.

5.4.2.  A Stateful Solution to MTU Handling

   An ITR stateful solution to handle MTU issues is describe as follows
   and was first introduced in [OPENLISP]:

   1.  The ITR will keep state of the effective MTU for each locator per
       mapping cache entry.  The effective MTU is what the core network
       can deliver along the path between ITR and ETR.



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   2.  When an IPv6 encapsulated packet or an IPv4 encapsulated packet
       with DF bit set to 1, exceeds what the core network can deliver,
       one of the intermediate routers on the path will send an ICMP Too
       Big message to the ITR.  The ITR will parse the ICMP message to
       determine which locator is affected by the effective MTU change
       and then record the new effective MTU value in the mapping cache
       entry.

   3.  When a packet is received by the ITR from a source inside of the
       site and the size of the packet is greater than the effective MTU
       stored with the mapping cache entry associated with the
       destination EID the packet is for, the ITR will send an ICMP Too
       Big message back to the source.  The packet size advertised by
       the ITR in the ICMP Too Big message is the effective MTU minus
       the LISP encapsulation length.

   Even though this mechanism is stateful, it has advantages over the
   stateless IP fragmentation mechanism, by not involving the
   destination host with reassembly of ITR fragmented packets.
































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6.  EID-to-RLOC Mapping

6.1.  LISP IPv4 and IPv6 Control Plane Packet Formats

   The following new UDP packet types are used to retrieve EID-to-RLOC
   mappings:


       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Version|  IHL  |Type of Service|          Total Length         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |         Identification        |Flags|      Fragment Offset    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Time to Live | Protocol = 17 |         Header Checksum       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                    Source Routing Locator                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                 Destination Routing Locator                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     / |           Source Port         |         Dest Port             |
   UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     \ |           UDP Length          |        UDP Checksum           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       |                         LISP Message                          |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Version| Traffic Class |           Flow Label                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |         Payload Length        | Next Header=17|   Hop Limit   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       +                                                               +
       |                                                               |
       +                     Source Routing Locator                    +
       |                                                               |
       +                                                               +
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       +                                                               +



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       |                                                               |
       +                  Destination Routing Locator                  +
       |                                                               |
       +                                                               +
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     / |           Source Port         |         Dest Port             |
   UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     \ |           UDP Length          |        UDP Checksum           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       |                         LISP Message                          |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The LISP UDP-based messages are the Map-Request and Map-Reply
   messages.  When a UDP Map-Request is sent, the UDP source port is
   chosen by the sender and the destination UDP port number is set to
   4342.  When a UDP Map-Reply is sent, the source UDP port number is
   set to 4342 and the destination UDP port number is copied from the
   source port of either the Map-Request or the invoking data packet.

   The UDP Length field will reflect the length of the UDP header and
   the LISP Message payload.

   The UDP Checksum is computed and set to non-zero for Map-Request and
   Map-Reply messages.  It MUST be checked on receipt and if the
   checksum fails, the packet MUST be dropped.

   LISP-CONS [CONS] use TCP to send LISP control messages.  The format
   of control messages includes the UDP header so the checksum and
   length fields can be used to protect and delimit message boundaries.

   This main LISP specification is the authoritative source for message
   format definitions for the Map-Request and Map-Reply messages.















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6.1.1.  LISP Packet Type Allocations

   This section will be the authoritative source for allocating LISP
   Type values.  Current allocations are:


       Reserved:                          0    b'0000'
       LISP Map-Request:                  1    b'0001'
       LISP Map-Reply:                    2    b'0010'
       LISP Map-Register:                 3    b'0011'
       LISP Encapsulated Control Message: 8    b'1000'


6.1.2.  Map-Request Message Format



        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Type=1 |A|M|P|S|           Reserved            | Record Count  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Nonce . . .                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         . . . Nonce                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |         Source-EID-AFI        |            ITR-AFI            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                   Source EID Address  ...                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                Originating ITR RLOC Address ...               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     / |   Reserved    | EID mask-len  |        EID-prefix-AFI         |
   Rec +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     \ |                       EID-prefix  ...                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                   Map-Reply Record  ...                       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                     Mapping Protocol Data                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Packet field descriptions:








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   Type:   1 (Map-Request)

   A: This is an authoritative bit, which is set to 0 for UDP-based Map-
      Requests sent by an ITR.

   M: When set, it indicates a Map-Reply Record segment is included in
      the Map-Request.

   P: Indicates that a Map-Request should be treated as a "piggyback"
      locator reachability probe.  The receiver should respond with a
      Map-Reply with the P bit set and the nonce copied from the Map-
      Request.  See section Section 6.3.2 for more details.

   S: This is the SMR bit.  See Section 6.5.2 for details.

   Reserved:  Set to 0 on transmission and ignored on receipt.

   Record Count:  The number of records in this Map-Request message.  A
      record is comprised of the portion of the packet that is labeled
      'Rec' above and occurs the number of times equal to Record Count.
      For this version of the protocol, a receiver MUST accept and
      process Map-Requests that contain one or more records, but a
      sender MUST only send Map-Requests containing one record.  Support
      for requesting multiple EIDs in a single Map-Request message will
      be specified in a future version of the protocol.

   Nonce:  An 8-byte random value created by the sender of the Map-
      Request.  This nonce will be returned in the Map-Reply.  The
      security of the LISP mapping protocol depends critically on the
      strength of the nonce in the Map-Request message.  The nonce
      SHOULD be generated by a properly seeded pseudo-random (or strong
      random) source.  See [RFC4086] for advice on generating security-
      sensitive random data.

   Source-EID-AFI:  Address family of the "Source EID Address" field.

   ITR-AFI:  Address family of the "Originating ITR RLOC Address" field.

   Source EID Address:  This is the EID of the source host which
      originated the packet which is invoking this Map-Request.  When
      Map-Requests are used for refreshing a map-cache entry or for
      RLOC-probing, the value 0 is used.

   Originating ITR RLOC Address:  Used to give the ETR the option of
      returning a Map-Reply in the address-family of this locator.






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   EID mask-len:  Mask length for EID prefix.

   EID-AFI:  Address family of EID-prefix according to [RFC2434]

   EID-prefix:  4 bytes if an IPv4 address-family, 16 bytes if an IPv6
      address-family.  When a Map-Request is sent by an ITR because a
      data packet is received for a destination where there is no
      mapping entry, the EID-prefix is set to the destination IP address
      of the data packet.  And the 'EID mask-len' is set to 32 or 128
      for IPv4 or IPv6, respectively.  When an xTR wants to query a site
      about the status of a mapping it already has cached, the EID-
      prefix used in the Map-Request has the same mask-length as the
      EID-prefix returned from the site when it sent a Map-Reply
      message.

   Map-Reply Record:  When the M bit is set, this field is the size of
      the "Record" field in the Map-Reply format.  This Map-Reply record
      contains the EID-to-RLOC mapping entry associated with the Source
      EID.  This allows the ETR which will receive this Map-Request to
      cache the data if it chooses to do so.

   Mapping Protocol Data:  See [CONS] or [ALT] for details.  This field
      is optional and present when the UDP length indicates there is
      enough space in the packet to include it.

6.1.3.  EID-to-RLOC UDP Map-Request Message

   A Map-Request is sent from an ITR when it needs a mapping for an EID,
   wants to test an RLOC for reachability, or wants to refresh a mapping
   before TTL expiration.  For the initial case, the destination IP
   address used for the Map-Request is the destination-EID from the
   packet which had a mapping cache lookup failure.  For the later 2
   cases, the destination IP address used for the Map-Request is one of
   the RLOC addresses from the locator-set of the map cache entry.  The
   source address is either an IPv4 or IPv6 RLOC address depending if
   the Map-Request is using an IPv4 versus IPv6 header, respectively.
   In all cases, the UDP source port number for the Map-Request message
   is a randomly allocated 16-bit value and the UDP destination port
   number is set to the well-known destination port number 4342.  A
   successful Map-Reply updates the cached set of RLOCs associated with
   the EID prefix range.

   Map-Requests can also be LISP encapsulated using UDP destination port
   4342 with a LISP type value set to "Encapsulated Control Message",
   when sent from an ITR to a Map-Resolver.  Likewise, Map-Requests are
   LISP encapsulated the same way from a Map-Server to an ETR.  Details
   on encapsulated Map-Requests and Map-Resolvers can be found in
   [LISP-MS].



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   Map-Requests MUST be rate-limited.  It is recommended that a Map-
   Request for the same EID-prefix be sent no more than once per second.

   An ITR that is configured with mapping database information (i.e. it
   is also an ETR) may optionally include those mappings in a Map-
   Request.  When an ETR configured to accept and verify such
   "piggybacked" mapping data receives such a Map-Request, it may
   originate a "verifying Map-Request", addressed to the original ITR.
   If the ETR has a map-cache entry that matches the "piggybacked" EID
   and the RLOC is in the locator-set for the entry, then it may send
   the "verifying Map-Request" to the original Map-Request source.  If
   not, then it MUST send it to the "piggybacked" EID.  Doing this
   forces the "verifying Map-Request" to go through the mapping database
   system to reach the authoritative source of information about that
   EID, guarding against RLOC-spoofing in in the "piggybacked" mapping
   data.



































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6.1.4.  Map-Reply Message Format



        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Type=2 |P|E|            Reserved               | Record Count  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Nonce . . .                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         . . . Nonce                           |
   +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   |                          Record  TTL                          |
   |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   R   | Locator Count | EID mask-len  | ACT |A|      Reserved         |
   e   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   c   |           Reserved            |            EID-AFI            |
   o   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   r   |                          EID-prefix                           |
   d   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  /|    Priority   |    Weight     |  M Priority   |   M Weight    |
   | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | o |           Unused Flags      |R|           Loc-AFI             |
   | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  \|                             Locator                           |
   +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                     Mapping Protocol Data                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Packet field descriptions:

   Type:   2 (Map-Reply)

   P: Indicates that the Map-Reply is in response to a "piggyback"
      locator reachability Map-Request.  The nonce field should contain
      a copy of the nonce value from the original Map-Request.  See
      section Section 6.3.2 for more details.

   E: Indicates that the ETR which sends this Map-Reply message is
      advertising that the site is enabled for the Echo-Nonce locator
      reachability algorithm.  See Section 6.3.1 for more details.

   Reserved:  Set to 0 on transmission and ignored on receipt.






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   Record Count:  The number of records in this reply message.  A record
      is comprised of that portion of the packet labeled 'Record' above
      and occurs the number of times equal to Record count.

   Nonce:  A 24-bit value set in a Data-Probe packet or a 64-bit value
      from the Map-Request is echoed in this Nonce field of the Map-
      Reply.

   Record TTL:  The time in minutes the recipient of the Map-Reply will
      store the mapping.  If the TTL is 0, the entry should be removed
      from the cache immediately.  If the value is 0xffffffff, the
      recipient can decide locally how long to store the mapping.

   Locator Count:  The number of Locator entries.  A locator entry
      comprises what is labeled above as 'Loc'.  The locator count can
      be 0 indicating there are no locators for the EID-prefix.

   EID mask-len:  Mask length for EID prefix.

   ACT:  This 3-bit field describes negative Map-Reply actions.  These
      bits are used only when the 'Locator Count' field is set to 0.
      The action bits are encoded only in Map-Reply messages.  The
      actions defined are used by an ITR or PTR when a destination EID
      matches a negative mapping cache entry.  Unassigned values should
      cause a map-cache entry to be created and, when packets match this
      negative cache entry, they will be dropped.  The current assigned
      values are:



      (0) Drop:  The packet is dropped silently.

      (1) Natively-Forward:  The packet is not encapsulated or dropped
         but natively forwarded.

      (2) Send-Map-Request:  The packet invokes sending a Map-Request.

   A: The Authoritative bit, when sent by a UDP-based message is always
      set by the ETR.  See [CONS] for TCP-based Map-Replies.

   EID-AFI:  Address family of EID-prefix according to [RFC2434].

   EID-prefix:  4 bytes if an IPv4 address-family, 16 bytes if an IPv6
      address-family.







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   Priority:  each RLOC is assigned a unicast priority.  Lower values
      are more preferable.  When multiple RLOCs have the same priority,
      they may be used in a load-split fashion.  A value of 255 means
      the RLOC MUST NOT be used for unicast forwarding.

   Weight:  when priorities are the same for multiple RLOCs, the weight
      indicates how to balance unicast traffic between them.  Weight is
      encoded as a percentage of total unicast packets that match the
      mapping entry.  If a non-zero weight value is used for any RLOC,
      then all RLOCs must use a non-zero weight value and then the sum
      of all weight values MUST equal 100.  If a zero value is used for
      any RLOC weight, then all weights MUST be zero and the receiver of
      the Map-Reply will decide how to load-split traffic.  See
      Section 6.4 for a suggested hash algorithm to distribute load
      across locators with same priority and equal weight values.  When
      a single RLOC exists in a mapping entry, the weight value MUST be
      set to 100 and ignored on receipt.

   M Priority:  each RLOC is assigned a multicast priority used by an
      ETR in a receiver multicast site to select an ITR in a source
      multicast site for building multicast distribution trees.  A value
      of 255 means the RLOC MUST NOT be used for joining a multicast
      distribution tree.

   M Weight:  when priorities are the same for multiple RLOCs, the
      weight indicates how to balance building multicast distribution
      trees across multiple ITRs.  The weight is encoded as a percentage
      of total number of trees build to the source site identified by
      the EID-prefix.  If a non-zero weight value is used for any RLOC,
      then all RLOCs must use a non-zero weight value and then the sum
      of all weight values MUST equal 100.  If a zero value is used for
      any RLOC weight, then all weights MUST be zero and the receiver of
      the Map-Reply will decide how to distribute multicast state across
      ITRs.

   Unused Flags:  set to 0 when sending and ignored on receipt.

   R: when this bit is set, the locator is known to be reachable from
      the Map-Reply sender's perspective.

   Locator:  an IPv4 or IPv6 address (as encoded by the 'Loc-AFI' field)
      assigned to an ETR or router acting as a proxy replier for the
      EID-prefix.  Note that the destination RLOC address MAY be an
      anycast address.  A source RLOC can be an anycast address as well.
      The source or destination RLOC MUST NOT be the broadcast address
      (255.255.255.255 or any subnet broadcast address known to the
      router), and MUST NOT be a link-local multicast address.  The
      source RLOC MUST NOT be a multicast address.  The destination RLOC



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      SHOULD be a multicast address if it is being mapped from a
      multicast destination EID.

   Mapping Protocol Data:  See [CONS] or [ALT] for details.  This field
      is optional and present when the UDP length indicates there is
      enough space in the packet to include it.

6.1.5.  EID-to-RLOC UDP Map-Reply Message

   When a Data Probe packet or a Map-Request triggers a Map-Reply to be
   sent, the RLOCs associated with the EID-prefix matched by the EID in
   the original packet destination IP address field will be returned.
   The RLOCs in the Map-Reply are the globally-routable IP addresses of
   the ETR but are not necessarily reachable; separate testing of
   reachability is required.

   Note that a Map-Reply may contain different EID-prefix granularity
   (prefix + length) than the Map-Request which triggers it.  This might
   occur if a Map-Request were for a prefix that had been returned by an
   earlier Map-Reply.  In such a case, the requester updates its cache
   with the new prefix information and granularity.  For example, a
   requester with two cached EID-prefixes that are covered by a Map-
   Reply containing one, less-specific prefix, replaces the entry with
   the less-specific EID-prefix.  Note that the reverse, replacement of
   one less-specific prefix with multiple more-specific prefixes, can
   also occur but not by removing the less-specific prefix rather by
   adding the more-specific prefixes which during a lookup will override
   the less-specific prefix.

   Replies SHOULD be sent for an EID-prefix no more often than once per
   second to the same requesting router.  For scalability, it is
   expected that aggregation of EID addresses into EID-prefixes will
   allow one Map-Reply to satisfy a mapping for the EID addresses in the
   prefix range thereby reducing the number of Map-Request messages.

   The addresses for a encapsulated data packets or Map-Request message
   are swapped and used for sending the Map-Reply.  The UDP source and
   destination ports are swapped as well.  That is, the source port in
   the UDP header for the Map-Reply is set to the well-known UDP port
   number 4342.

   Map-Reply records can have an empty locator-set.  This type of a Map-
   Reply is called a Negative Map-Reply.  Negative Map-Replies convey
   special actions by the sender to the ITR or PTR which have solicited
   the Map-Reply.  There are two primary applications for Negative Map-
   Replies.  The first is for a Map-Resolver to instruct an ITR or PTR
   when a destination is for a LISP site versus a non-LISP site.  And
   the other is to source quench Map-Requests which are sent for non-



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   allocated EIDs.

   For each Map-Reply record, the list of locators in a locator-set MUST
   appear in the same order for each ETR that originates a Map-Reply
   message.  The locator-set MUST be sorted in order of ascending IP
   address where an IPv4 locator address is considered numerically 'less
   than' an IPv6 locator address.

6.1.6.  Map-Register Message Format

   The usage details of the Map-Register message can be found in
   specification [LISP-MS].  This section solely defines the message
   format.

   The message is sent in UDP with a destination UDP port of 4342 and a
   randomly selected UDP source port number.

   The Map-Register message format is:

































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        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Type=3 |P|            Reserved                 | Record Count  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Nonce . . .                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         . . . Nonce                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |            Key ID             |  Authentication Data Length   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                     Authentication Data                       ~
   +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   |                          Record  TTL                          |
   |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   R   | Locator Count | EID mask-len  | ACT |A|      Reserved         |
   e   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   c   |           Reserved            |            EID-AFI            |
   o   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   r   |                          EID-prefix                           |
   d   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  /|    Priority   |    Weight     |  M Priority   |   M Weight    |
   | L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | o |           Unused Flags      |R|           Loc-AFI             |
   | c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  \|                             Locator                           |
   +-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Packet field descriptions:

   Type:   3 (Map-Register)

   P: Set to 1 by an ETR which sends a Map-Register message requesting
      for the Map-Server to proxy Map-Reply.  The Map-Server will send
      non-authoritative Map-Replies on behalf of the ETR.  Details on
      this usage will be provided in a future version of this draft.

   Reserved:  Set to 0 on transmission and ignored on receipt.

   Record Count:  The number of records in this Map-Register message.  A
      record is comprised of that portion of the packet labeled 'Record'
      above and occurs the number of times equal to Record count.

   Nonce:  This 8-byte Nonce field is set to 0 in Map-Register messages.






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   Key ID:  A configured ID to find the configured Message
      Authentication Code (MAC) algorithm and key value used for the
      authentication function.

   Authentication Data Length:  The length in bytes of the
      Authentication Data field that follows this field.  The length of
      the the Authentication Data field is dependent on the Message
      Authentication Code (MAC) algorithm used.  The length field allows
      a device that doesn't know the MAC algorithm to correctly parse
      the packet.

   Authentication Data:  The message digest used from the output of the
      Message Authentication Code (MAC) algorithm.  The entire Map-
      Register payload is authenticated with this field preset to 0.
      After the MAC is computed, it is placed in this field.
      Implementations of this specification MUST include support for
      HMAC-SHA-1-96 [RFC2404] and support for HMAC-SHA-128-256 [RFC4634]
      is recommended.

   The definition of the rest of the Map-Register can be found in the
   Map-Reply section.

6.1.7.  Encapsualted Control Message Format

   An Encapsulated Control Message is used to encapsulate control
   packets sent between xTRs and the mapping database system described
   in [LISP-MS].
























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        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     / |                       IPv4 or IPv6 Header                     |
   OH  |                      (uses RLOC addresses)                    |
     \ |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     / |       Source Port = xxxx      |       Dest Port = 4342        |
   UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     \ |           UDP Length          |        UDP Checksum           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   LH  |Type=8 |                   Reserved                            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     / |                       IPv4 or IPv6 Header                     |
   IH  |                  (uses RLOC or EID addresses)                 |
     \ |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     / |       Source Port = xxxx      |       Dest Port = yyyy        |
   UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     \ |           UDP Length          |        UDP Checksum           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   LCM |                      LISP Control Message                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Packet header descriptions:

   OH:   The outer IPv4 or IPv6 header which uses RLOC addresses in the
      source and destination header address fields.

   UDP:   The outer UDP header with destination port 4342.  The source
      port is randomly allocated.  The checksum field MUST be non-zero.

   LH:   Type 8 is defined to be a "LISP Encapsulated Control Message"
      and what follows is either an IPv4 or IPv6 header as encoded by
      the first 4 bits after the reserved field.

   IH:   The inner IPv4 or IPv6 header which can use either RLOC or EID
      addresses in the header address fields.  When a Map-Request is
      encapsulated in this packet format the destination address in this
      header is an EID.

   UDP:   The inner UDP header where the port assignments depends on the
      control packet being encapsulated.  When the control packet is a
      Map-Request or Map-Register, the source port is randomly assigned
      and the destination port is 4342.  When the control packet is a
      Map-Reply, the source port is 4342 and the destination port is
      assigned from the source port of the invoking Map-Request.  Port
      number 4341 MUST NOT be assigned to either port.  The checksum



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      field MUST be non-zero.

   LCM:   The format is one of the control message formats described in
      this section.  At this time, only Map-Request messages and PIM
      Join-Prune messages [MLISP] are allowed to be encapsulated.
      Encapsulating other types of LISP control messages are for further
      study.

6.2.  Routing Locator Selection

   Both client-side and server-side may need control over the selection
   of RLOCs for conversations between them.  This control is achieved by
   manipulating the Priority and Weight fields in EID-to-RLOC Map-Reply
   messages.  Alternatively, RLOC information may be gleaned from
   received tunneled packets or EID-to-RLOC Map-Request messages.

   The following enumerates different scenarios for choosing RLOCs and
   the controls that are available:

   o  Server-side returns one RLOC.  Client-side can only use one RLOC.
      Server-side has complete control of the selection.

   o  Server-side returns a list of RLOC where a subset of the list has
      the same best priority.  Client can only use the subset list
      according to the weighting assigned by the server-side.  In this
      case, the server-side controls both the subset list and load-
      splitting across its members.  The client-side can use RLOCs
      outside of the subset list if it determines that the subset list
      is unreachable (unless RLOCs are set to a Priority of 255).  Some
      sharing of control exists: the server-side determines the
      destination RLOC list and load distribution while the client-side
      has the option of using alternatives to this list if RLOCs in the
      list are unreachable.

   o  Server-side sets weight of 0 for the RLOC subset list.  In this
      case, the client-side can choose how the traffic load is spread
      across the subset list.  Control is shared by the server-side
      determining the list and the client determining load distribution.
      Again, the client can use alternative RLOCs if the server-provided
      list of RLOCs are unreachable.

   o  Either side (more likely on the server-side ETR) decides not to
      send a Map-Request.  For example, if the server-side ETR does not
      send Map-Requests, it gleans RLOCs from the client-side ITR,
      giving the client-side ITR responsibility for bidirectional RLOC
      reachability and preferability.  Server-side ETR gleaning of the
      client-side ITR RLOC is done by caching the inner header source
      EID and the outer header source RLOC of received packets.  The



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      client-side ITR controls how traffic is returned and can alternate
      using an outer header source RLOC, which then can be added to the
      list the server-side ETR uses to return traffic.  Since no
      Priority or Weights are provided using this method, the server-
      side ETR must assume each client-side ITR RLOC uses the same best
      Priority with a Weight of zero.  In addition, since EID-prefix
      encoding cannot be conveyed in data packets, the EID-to-RLOC cache
      on tunnel routers can grow to be very large.

   o  A "gleaned" map-cache entry, one learned from the source RLOC of a
      received encapsulated packet, is only stored and used for a few
      seconds, pending verification.  Verification is performed by
      sending a Map-Request to the source EID (the inner header IP
      source address) of the received encapsulated packet.  A reply to
      this "verifying Map-Request" is used to fully populate the map-
      cache entry for the "gleaned" EID and is stored and used for the
      time indicated from the TTL field of a received Map-Reply.  When a
      verified map-cache entry is stored, data gleaning no longer occurs
      for subsequent packets which have a source EID that matches the
      EID-prefix of the verified entry.

   RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be
   reachable when the R-bit for the locator record is set to 1.  Neither
   the information contained in a Map-Reply or that stored in the
   mapping database system provide reachability information for RLOCs.
   Such reachability needs to be determined separately, using one or
   more of the Routing Locator Reachability Algorithms described in the
   next section.

6.3.  Routing Locator Reachability

   Several mechanisms for determining RLOC reachability are currently
   defined:

   1.  An ETR may examine the Loc-Status-Bits in the LISP header of an
       encapsulated data packet received from an ITR.  If the ETR is
       also acting as an ITR and has traffic to return to the original
       ITR site, it can use this status information to help select an
       RLOC.

   2.  An ITR may receive an ICMP Network or ICMP Host Unreachable
       message for an RLOC it is using.  This indicates that the RLOC is
       likely down.

   3.  An ITR which participates in the global routing system can
       determine that an RLOC is down if no BGP RIB route exists that
       matches the RLOC IP address.




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   4.  An ITR may receive an ICMP Port Unreachable message from a
       destination host.  This occurs if an ITR attempts to use
       interworking [INTERWORK] and LISP-encapsulated data is sent to a
       non-LISP-capable site.

   5.  An ITR may receive a Map-Reply from a ETR in response to a
       previously sent Map-Request.  The RLOC source of the Map-Reply is
       likely up since the ETR was able to send the Map-Reply to the
       ITR.

   6.  When an ETR receives an encapsulated packet from an ITR, the
       source RLOC from the outer header of the packet is likely up.

   7.  An ITR/ETR pair can use the Locator Reachability Algorithms
       described in this section, namely Echo-Noncing or RLOC-Probing.

   When determining Locator up/down reachability by examining the Loc-
   Status-Bits from the LISP encapsulated data packet, an ETR will
   receive up to date status from an encapsulating ITR about
   reachability for all ETRs at the site.  CE-based ITRs at the source
   site can determine reachability relative to each other using the site
   IGP as follows:

   o  Under normal circumstances, each ITR will advertise a default
      route into the site IGP.

   o  If an ITR fails or if the upstream link to its PE fails, its
      default route will either time-out or be withdrawn.

   Each ITR can thus observe the presence or lack of a default route
   originated by the others to determine the Locator Status Bits it sets
   for them.

   RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1.  The
   Loc-Status-Bits in a LISP encapsulated packet are numbered from 0 to
   n-1 starting with the least significant bit.  For example, if an RLOC
   listed in the 3rd position of the Map-Reply goes down (ordinal value
   2), then all ITRs at the site will clear the 3rd least significant
   bit (xxxx x0xx) of the Loc-Status-Bits field for the packets they
   encapsulate.

   When an ETR decapsulates a packet, it will check for any change in
   the Loc-Status-Bits field.  When a bit goes from 1 to 0, the ETR will
   refrain from encapsulating packets to an RLOC that is indicated as
   down.  It will only resume using that RLOC if the corresponding Loc-
   Status-Bit returns to a value of 1.  Loc-Status-Bits are associated
   with a locator-set per EID-prefix.  Therefore, when a locator becomes
   unreachable, the Loc-Status-Bit that corresponds to that locator's



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   position in the list returned by the last Map-Reply will be set to
   zero for that particular EID-prefix.

   When ITRs at the site are not deployed in CE routers, the IGP can
   still be used to determine the reachability of Locators provided they
   are injected into the IGP.  This is typically done when a /32 address
   is configured on a loopback interface.

   When ITRs receive ICMP Network or Host Unreachable messages as a
   method to determine unreachability, they will refrain from using
   Locators which are described in Locator lists of Map-Replies.
   However, using this approach is unreliable because many network
   operators turn off generation of ICMP Unreachable messages.

   If an ITR does receive an ICMP Network or Host Unreachable message,
   it MAY originate its own ICMP Unreachable message destined for the
   host that originated the data packet the ITR encapsulated.

   Also, BGP-enabled ITRs can unilaterally examine the BGP RIB to see if
   a locator address from a locator-set in a mapping entry matches a
   prefix.  If it does not find one and BGP is running in the Default
   Free Zone (DFZ), it can decide to not use the locator even though the
   Loc-Status-Bits indicate the locator is up.  In this case, the path
   from the ITR to the ETR that is assigned the locator is not
   available.  More details are in [LOC-ID-ARCH].

   Optionally, an ITR can send a Map-Request to a Locator and if a Map-
   Reply is returned, reachability of the Locator has been determined.
   Obviously, sending such probes increases the number of control
   messages originated by tunnel routers for active flows, so Locators
   are assumed to be reachable when they are advertised.

   This assumption does create a dependency: Locator unreachability is
   detected by the receipt of ICMP Host Unreachable messages.  When an
   Locator has been determined to be unreachable, it is not used for
   active traffic; this is the same as if it were listed in a Map-Reply
   with priority 255.

   The ITR can test the reachability of the unreachable Locator by
   sending periodic Requests.  Both Requests and Replies MUST be rate-
   limited.  Locator reachability testing is never done with data
   packets since that increases the risk of packet loss for end-to-end
   sessions.

   When an ETR decapsulates a packet, it knows that it is reachable from
   the encapsulating ITR because that is how the packet arrived.  In
   most cases, the ETR can also reach the ITR but cannot assume this to
   be true due to the possibility of path asymmetry.  In the presence of



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   unidirectional traffic flow from an ITR to an ETR, the ITR should not
   use the lack of return traffic as an indication that the ETR is
   unreachable.  Instead, it must use an alternate mechanisms to
   determine reachability.

6.3.1.  Echo Nonce Algorithm

   When there is bidirectional data flow between a pair of locators, a
   simple mechanism called "nonce echoing" can be used to determine
   reachability between an ITR and ETR.  When an ITR wants to solicit a
   nonce echo, it sets the N and E bits and places a 24-bit nonce in the
   LISP header of the next encapsulated data packet.

   When this packet is received by the ETR, the encapsulated packet is
   forwarded as normal.  When the ETR next sends a data packet to the
   ITR, it includes the nonce received earlier with the N bit set and E
   bit cleared.  The ITR sees this "echoed nonce" and knows the path to
   and from the ETR is up.

   The ITR will set the E-bit and N-bit for every packet it sends while
   in echo-nonce-request state.  The time the ITR waits to process the
   echoed nonce before it determines the path is unreachable is variable
   and a choice left for the implementation.

   If the ITR is receiving packets from the ETR but does not see the
   nonce echoed while being in echo-nonce-request state, then the path
   to the ETR is unreachable.  This decision may be overridden by other
   locator reachability algorithms.  Once the ITR determines the path to
   the ETR is down it can switch to another locator for that EID-prefix.

   Note that "ITR" and "ETR" are relative terms here.  Both devices must
   be implementing both ITR and ETR functionality for the echo nonce
   mechanism to operate.

   The ITR and ETR may both go into echo-nonce-request state at the same
   time.  The number of packets sent or the time during which echo nonce
   requests are sent is an implementation specific setting.  However,
   when an ITR is in echo-nonce-request state, it can echo the ETR's
   nonce in the next set of packets that it encapsulates and then
   subsequently, continue sending echo-nonce-request packets.

   This mechanism does not completely solve the forward path
   reachability problem as traffic may be unidirectional.  That is, the
   ETR receiving traffic at a site may not may not be the same device as
   an ITR which transmits traffic from that site or the site to site
   traffic is unidirectional so there is no ITR returning traffic.

   The echo-nonce algorithm is bilateral.  That is, if one side sets the



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   E-bit and the other side is not enabled for echo-noncing, then the
   echoing of the nonce does not occur and the requesting side may
   regard the locator unreachable erroneously.  An ITR should only set
   the E-bit in a encapsulated data packet when it knows the ETR is
   enabled for echo-noncing.  This is conveyed by the E-bit in the Map-
   Reply message.

   Note that other locator reachability mechanisms are being researched
   and can be used to compliment or even override the Echo Nonce
   Algorithm.  See next section for an example of control-plane probing.

6.3.2.  RLOC Probing Algorithm

   RLOC Probing is a method that an ITR or PTR can use to determine the
   reachability status of one or more locators that it has cached in a
   map-cache entry.  The P-bit (Probe Bit) of the Map-Request and Map-
   Reply messages are used for RLOC Probing.

   RLOC probing is done in the control-plane on a timer basis where an
   ITR or PTR will originate a Map-Request destined to a locator address
   from one of its own locator addresses.  A Map-Request used as an
   RLOC-probe is NOT encapsulated and NOT sent to a Map-Server or on the
   ALT like one would when soliciting mapping data.  The EID record
   encoded in the Map-Request is the EID-prefix of the map-cache entry
   cached by the ITR or PTR.  The ITR or PTR may include a mapping data
   record for its own database mapping information.

   When an ETR receives a Map-Request message with the P-bit set, it
   returns a Map-Reply with the P-bit set.  The source address of the
   Map-Reply is set from the destination address of the Map-Request and
   the destination address of the Map-Reply is set from the source
   address of the Map-Request.  The Map-Reply should contain mapping
   data for the EID-prefix contained in the Map-Request.  This provides
   the opportunity for the ITR or PTR, which sent the RLOC-probe to get
   mapping updates if there were changes to the ETR's database mapping
   entries.

   There are advantages and disadvantages of RLOC Probing.  The greatest
   benefit of RLOC Probing is that it can handle many failure scenarios
   allowing the ITR to determine when the path to a specific locator is
   reachable or has become unreachable, thus providing a robust
   mechanism for switching to using another locator from the cached
   locator.  RLOC Probing can also provide RTT estimates between a pair
   of locators which can be useful for network management purposes as
   well as for selecting low delay paths.  The major disadvantage of
   RLOC Probing is in the number of control messages required and the
   amount of bandwidth used to obtain those benefits, especially if the
   requirement for failure detection times are very small.



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   Continued research and testing will attempt to characterize the
   tradeoffs of failure detection times versus message overhead.

6.4.  Routing Locator Hashing

   When an ETR provides an EID-to-RLOC mapping in a Map-Reply message to
   a requesting ITR, the locator-set for the EID-prefix may contain
   different priority values for each locator address.  When more than
   one best priority locator exists, the ITR can decide how to load
   share traffic against the corresponding locators.

   The following hash algorithm may be used by an ITR to select a
   locator for a packet destined to an EID for the EID-to-RLOC mapping:

   1.  Either a source and destination address hash can be used or the
       traditional 5-tuple hash which includes the source and
       destination addresses, source and destination TCP, UDP, or SCTP
       port numbers and the IP protocol number field or IPv6 next-
       protocol fields of a packet a host originates from within a LISP
       site.  When a packet is not a TCP, UDP, or SCTP packet, the
       source and destination addresses only from the header are used to
       compute the hash.

   2.  Take the hash value and divide it by the number of locators
       stored in the locator-set for the EID-to-RLOC mapping.

   3.  The remainder will be yield a value of 0 to "number of locators
       minus 1".  Use the remainder to select the locator in the
       locator-set.

   Note that when a packet is LISP encapsulated, the source port number
   in the outer UDP header needs to be set.  Selecting a random value
   allows core routers which are attached to Link Aggregation Groups
   (LAGs) to load-split the encapsulated packets across member links of
   such LAGs.  Otherwise, core routers would see a single flow, since
   packets have a source address of the ITR, for packets which are
   originated by different EIDs at the source site.  A suggested setting
   for the source port number computed by an ITR is a 5-tuple hash
   function on the inner header, as described above.

   Many core router implementations use a 5-tuple hash to decide how to
   balance packet load across members of a LAG.  The 5-tuple hash
   includes the source and destination addresses of the packet and the
   source and destination ports when the protocol number in the packet
   is TCP or UDP.  For this reason, UDP encoding is used for LISP
   encapsulation.





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6.5.  Changing the Contents of EID-to-RLOC Mappings

   Since the LISP architecture uses a caching scheme to retrieve and
   store EID-to-RLOC mappings, the only way an ITR can get a more up-to-
   date mapping is to re-request the mapping.  However, the ITRs do not
   know when the mappings change and the ETRs do not keep track of who
   requested its mappings.  For scalability reasons, we want to maintain
   this approach but need to provide a way for ETRs change their
   mappings and inform the sites that are currently communicating with
   the ETR site using such mappings.

   When a locator record is added to the end of a locator-set, it is
   easy to update mappings.  We assume new mappings will maintain the
   same locator ordering as the old mapping but just have new locators
   appended to the end of the list.  So some ITRs can have a new mapping
   while other ITRs have only an old mapping that is used until they
   time out.  When an ITR has only an old mapping but detects bits set
   in the loc-status-bits that correspond to locators beyond the list it
   has cached, it simply ignores them.

   When a locator record is removed from a locator-set, ITRs that have
   the mapping cached will not use the removed locator because the xTRs
   will set the loc-status-bit to 0.  So even if the locator is in the
   list, it will not be used.  For new mapping requests, the xTRs can
   set the locator address to 0 as well as setting the corresponding
   loc-status-bit to 0.  This forces ITRs with old or new mappings to
   avoid using the removed locator.

   If many changes occur to a mapping over a long period of time, one
   will find empty record slots in the middle of the locator-set and new
   records appended to the locator-set.  At some point, it would be
   useful to compact the locator-set so the loc-status-bit settings can
   be efficiently packed.

   We propose here two approaches for locator-set compaction, one
   operational and the other a protocol mechanism.  The operational
   approach uses a clock sweep method.  The protocol approach uses the
   concept of Solicit-Map-Requests.

6.5.1.  Clock Sweep

   The clock sweep approach uses planning in advance and the use of
   count-down TTLs to time out mappings that have already been cached.
   The default setting for an EID-to-RLOC mapping TTL is 24 hours.  So
   there is a 24 hour window to time out old mappings.  The following
   clock sweep procedure is used:





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   1.  24 hours before a mapping change is to take effect, a network
       administrator configures the ETRs at a site to start the clock
       sweep window.

   2.  During the clock sweep window, ETRs continue to send Map-Reply
       messages with the current (unchanged) mapping records.  The TTL
       for these mappings is set to 1 hour.

   3.  24 hours later, all previous cache entries will have timed out,
       and any active cache entries will time out within 1 hour.  During
       this 1 hour window the ETRs continue to send Map-Reply messages
       with the current (unchanged) mapping records with the TTL set to
       1 minute.

   4.  At the end of the 1 hour window, the ETRs will send Map-Reply
       messages with the new (changed) mapping records.  So any active
       caches can get the new mapping contents right away if not cached,
       or in 1 minute if they had the mapping cached.

6.5.2.  Solicit-Map-Request (SMR)

   Soliciting a Map-Request is a selective way for xTRs, at the site
   where mappings change, to control the rate they receive requests for
   Map-Reply messages.  SMRs are also used to tell remote ITRs to update
   the mappings they have cached.

   Since the xTRs don't keep track of remote ITRs that have cached their
   mappings, they can not tell exactly who needs the new mapping
   entries.  So an xTR will solicit Map-Requests from sites it is
   currently sending encapsulated data to, and only from those sites.
   The xTRs can locally decide the algorithm for how often and to how
   many sites it sends SMR messages.

   An SMR message is simply a bit set in a Map-Request message.  An ITR
   or PTR will send a Map-Request when they receive an SMR message.
   Both the SMR sender and the Map-Request responder must rate-limited
   these messages.

   The following procedure shows how a SMR exchange occurs when a site
   is doing locator-set compaction for an EID-to-RLOC mapping:

   1.  When the database mappings in an ETR change, the ETRs at the site
       begin to send Map-Requests with the SMR bit set for each locator
       in each map-cache entry the ETR caches.

   2.  A remote xTR which receives the SMR message will schedule sending
       a Map-Request message to the source locator address of the SMR
       message.  A newly allocated random nonce is selected and the EID-



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       prefix uses is the one copied from the SMR message.

   3.  The remote xTR retransmits the Map-Request slowly until it gets a
       Map-Reply while continuing to use the cached mapping.

   4.  The ETRs at the site with the changed mapping will reply to the
       Map-Request with a Map-Reply message provided the Map-Request
       nonce matches the nonce from the SMR.  The Map-Reply messages
       SHOULD be rate limited.  This is important to avoid Map-Reply
       implosion.

   5.  The ETRs, at the site with the changed mapping, records the fact
       that the site that sent the Map-Request has received the new
       mapping data in the mapping cache entry for the remote site so
       the loc-status-bits are reflective of the new mapping for packets
       going to the remote site.  The ETR then stops sending SMR
       messages.

   For security reasons an ITR MUST NOT process unsolicited Map-Replies.
   The nonce MUST be carried from SMR packet, into the resultant Map-
   Request, and then into Map-Reply to reduce spoofing attacks.

   To avoid map-cache entry corruption by a third-party, a sender of an
   SMR-based Map-Request must be verified.  If an ITR receives an SMR-
   based Map-Request and the source is not in the locator-set for the
   stored map-cache entry, then the responding Map-Request MUST be sent
   with an EID destination to the mapping database system.  Since the
   mapping database system is more secure to reach an authoritative ETR,
   it will deliver the Map-Request to the authoritative source of the
   mapping data.





















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7.  Router Performance Considerations

   LISP is designed to be very hardware-based forwarding friendly.  By
   doing tunnel header prepending [RFC1955] and stripping instead of re-
   writing addresses, existing hardware can support the forwarding model
   with little or no modification.  Where modifications are required,
   they should be limited to re-programming existing hardware rather
   than requiring expensive design changes to hard-coded algorithms in
   silicon.

   A few implementation techniques can be used to incrementally
   implement LISP:

   o  When a tunnel encapsulated packet is received by an ETR, the outer
      destination address may not be the address of the router.  This
      makes it challenging for the control plane to get packets from the
      hardware.  This may be mitigated by creating special FIB entries
      for the EID-prefixes of EIDs served by the ETR (those for which
      the router provides an RLOC translation).  These FIB entries are
      marked with a flag indicating that control plane processing should
      be performed.  The forwarding logic of testing for particular IP
      protocol number value is not necessary.  No changes to existing,
      deployed hardware should be needed to support this.

   o  On an ITR, prepending a new IP header is as simple as adding more
      bytes to a MAC rewrite string and prepending the string as part of
      the outgoing encapsulation procedure.  Many routers that support
      GRE tunneling [RFC2784] or 6to4 tunneling [RFC3056] can already
      support this action.

   o  When a received packet's outer destination address contains an EID
      which is not intended to be forwarded on the routable topology
      (i.e.  LISP 1.5), the source address of a data packet or the
      router interface with which the source is associated (the
      interface from which it was received) can be associated with a VRF
      (Virtual Routing/Forwarding), in which a different (i.e. non-
      congruent) topology can be used to find EID-to-RLOC mappings.














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8.  Deployment Scenarios

   This section will explore how and where ITRs and ETRs can be deployed
   and will discuss the pros and cons of each deployment scenario.
   There are two basic deployment trade-offs to consider: centralized
   versus distributed caches and flat, recursive, or re-encapsulating
   tunneling.

   When deciding on centralized versus distributed caching, the
   following issues should be considered:

   o  Are the tunnel routers spread out so that the caches are spread
      across all the memories of each router?

   o  Should management "touch points" be minimized by choosing few
      tunnel routers, just enough for redundancy?

   o  In general, using more ITRs doesn't increase management load,
      since caches are built and stored dynamically.  On the other hand,
      more ETRs does require more management since EID-prefix-to-RLOC
      mappings need to be explicitly configured.

   When deciding on flat, recursive, or re-encapsulation tunneling, the
   following issues should be considered:

   o  Flat tunneling implements a single tunnel between source site and
      destination site.  This generally offers better paths between
      sources and destinations with a single tunnel path.

   o  Recursive tunneling is when tunneled traffic is again further
      encapsulated in another tunnel, either to implement VPNs or to
      perform Traffic Engineering.  When doing VPN-based tunneling, the
      site has some control since the site is prepending a new tunnel
      header.  In the case of TE-based tunneling, the site may have
      control if it is prepending a new tunnel header, but if the site's
      ISP is doing the TE, then the site has no control.  Recursive
      tunneling generally will result in suboptimal paths but at the
      benefit of steering traffic to resource available parts of the
      network.

   o  The technique of re-encapsulation ensures that packets only
      require one tunnel header.  So if a packet needs to be rerouted,
      it is first decapsulated by the ETR and then re-encapsulated with
      a new tunnel header using a new RLOC.

   The next sub-sections will describe where tunnel routers can reside
   in the network.




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8.1.  First-hop/Last-hop Tunnel Routers

   By locating tunnel routers close to hosts, the EID-prefix set is at
   the granularity of an IP subnet.  So at the expense of more EID-
   prefix-to-RLOC sets for the site, the caches in each tunnel router
   can remain relatively small.  But caches always depend on the number
   of non-aggregated EID destination flows active through these tunnel
   routers.

   With more tunnel routers doing encapsulation, the increase in control
   traffic grows as well: since the EID-granularity is greater, more
   Map-Requests and Map-Replies are traveling between more routers.

   The advantage of placing the caches and databases at these stub
   routers is that the products deployed in this part of the network
   have better price-memory ratios then their core router counterparts.
   Memory is typically less expensive in these devices and fewer routes
   are stored (only IGP routes).  These devices tend to have excess
   capacity, both for forwarding and routing state.

   LISP functionality can also be deployed in edge switches.  These
   devices generally have layer-2 ports facing hosts and layer-3 ports
   facing the Internet.  Spare capacity is also often available in these
   devices as well.

8.2.  Border/Edge Tunnel Routers

   Using customer-edge (CE) routers for tunnel endpoints allows the EID
   space associated with a site to be reachable via a small set of RLOCs
   assigned to the CE routers for that site.

   This offers the opposite benefit of the first-hop/last-hop tunnel
   router scenario: the number of mapping entries and network management
   touch points are reduced, allowing better scaling.

   One disadvantage is that less of the network's resources are used to
   reach host endpoints thereby centralizing the point-of-failure domain
   and creating network choke points at the CE router.

   Note that more than one CE router at a site can be configured with
   the same IP address.  In this case an RLOC is an anycast address.
   This allows resilience between the CE routers.  That is, if a CE
   router fails, traffic is automatically routed to the other routers
   using the same anycast address.  However, this comes with the
   disadvantage where the site cannot control the entrance point when
   the anycast route is advertised out from all border routers.





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8.3.  ISP Provider-Edge (PE) Tunnel Routers

   Use of ISP PE routers as tunnel endpoint routers gives an ISP control
   over the location of the egress tunnel endpoints.  That is, the ISP
   can decide if the tunnel endpoints are in the destination site (in
   either CE routers or last-hop routers within a site) or at other PE
   edges.  The advantage of this case is that two or more tunnel headers
   can be avoided.  By having the PE be the first router on the path to
   encapsulate, it can choose a TE path first, and the ETR can
   decapsulate and re-encapsulate for a tunnel to the destination end
   site.

   An obvious disadvantage is that the end site has no control over
   where its packets flow or the RLOCs used.

   As mentioned in earlier sections a combination of these scenarios is
   possible at the expense of extra packet header overhead, if both site
   and provider want control, then recursive or re-encapsulating tunnels
   are used.
































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9.  Traceroute Considerations

   When a source host in a LISP site initiates a traceroute to a
   destination host in another LISP site, it is highly desirable for it
   to see the entire path.  Since packets are encapsulated from ITR to
   ETR, the hop across the tunnel could be viewed as a single hop.
   However, LISP traceroute will provide the entire path so the user can
   see 3 distinct segments of the path from a source LISP host to a
   destination LISP host:


      Segment 1 (in source LISP site based on EIDs):

          source-host ---> first-hop ... next-hop ---> ITR

      Segment 2 (in the core network based on RLOCs):

          ITR ---> next-hop ... next-hop ---> ETR

      Segment 3 (in the destination LISP site based on EIDs):

          ETR ---> next-hop ... last-hop ---> destination-host

   For segment 1 of the path, ICMP Time Exceeded messages are returned
   in the normal matter as they are today.  The ITR performs a TTL
   decrement and test for 0 before encapsulating.  So the ITR hop is
   seen by the traceroute source has an EID address (the address of
   site-facing interface).

   For segment 2 of the path, ICMP Time Exceeded messages are returned
   to the ITR because the TTL decrement to 0 is done on the outer
   header, so the destination of the ICMP messages are to the ITR RLOC
   address, the source source RLOC address of the encapsulated
   traceroute packet.  The ITR looks inside of the ICMP payload to
   inspect the traceroute source so it can return the ICMP message to
   the address of the traceroute client as well as retaining the core
   router IP address in the ICMP message.  This is so the traceroute
   client can display the core router address (the RLOC address) in the
   traceroute output.  The ETR returns its RLOC address and responds to
   the TTL decrement to 0 like the previous core routers did.

   For segment 3, the next-hop router downstream from the ETR will be
   decrementing the TTL for the packet that was encapsulated, sent into
   the core, decapsulated by the ETR, and forwarded because it isn't the
   final destination.  If the TTL is decremented to 0, any router on the
   path to the destination of the traceroute, including the next-hop
   router or destination, will send an ICMP Time Exceeded message to the
   source EID of the traceroute client.  The ICMP message will be



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   encapsulated by the local ITR and sent back to the ETR in the
   originated traceroute source site, where the packet will be delivered
   to the host.

9.1.  IPv6 Traceroute

   IPv6 traceroute follows the procedure described above since the
   entire traceroute data packet is included in ICMP Time Exceeded
   message payload.  Therefore, only the ITR needs to pay special
   attention for forwarding ICMP messages back to the traceroute source.

9.2.  IPv4 Traceroute

   For IPv4 traceroute, we cannot follow the above procedure since IPv4
   ICMP Time Exceeded messages only include the invoking IP header and 8
   bytes that follow the IP header.  Therefore, when a core router sends
   an IPv4 Time Exceeded message to an ITR, all the ITR has in the ICMP
   payload is the encapsulated header it prepended followed by a UDP
   header.  The original invoking IP header, and therefore the identity
   of the traceroute source is lost.

   The solution we propose to solve this problem is to cache traceroute
   IPv4 headers in the ITR and to match them up with corresponding IPv4
   Time Exceeded messages received from core routers and the ETR.  The
   ITR will use a circular buffer for caching the IPv4 and UDP headers
   of traceroute packets.  It will select a 16-bit number as a key to
   find them later when the IPv4 Time Exceeded messages are received.
   When an ITR encapsulates an IPv4 traceroute packet, it will use the
   16-bit number as the UDP source port in the encapsulating header.
   When the ICMP Time Exceeded message is returned to the ITR, the UDP
   header of the encapsulating header is present in the ICMP payload
   thereby allowing the ITR to find the cached headers for the
   traceroute source.  The ITR puts the cached headers in the payload
   and sends the ICMP Time Exceeded message to the traceroute source
   retaining the source address of the original ICMP Time Exceeded
   message (a core router or the ETR of the site of the traceroute
   destination).

9.3.  Traceroute using Mixed Locators

   When either an IPv4 traceroute or IPv6 traceroute is originated and
   the ITR encapsulates it in the other address family header, you
   cannot get all 3 segments of the traceroute.  Segment 2 of the
   traceroute can not be conveyed to the traceroute source since it is
   expecting addresses from intermediate hops in the same address format
   for the type of traceroute it originated.  Therefore, in this case,
   segment 2 will make the tunnel look like one hop.  All the ITR has to
   do to make this work is to not copy the inner TTL to the outer,



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   encapsulating header's TTL when a traceroute packet is encapsulated
   using an RLOC from a different address family.  This will cause no
   TTL decrement to 0 to occur in core routers between the ITR and ETR.
















































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10.  Mobility Considerations

   There are several kinds of mobility of which only some might be of
   concern to LISP.  Essentially they are as follows.

10.1.  Site Mobility

   A site wishes to change its attachment points to the Internet, and
   its LISP Tunnel Routers will have new RLOCs when it changes upstream
   providers.  Changes in EID-RLOC mappings for sites are expected to be
   handled by configuration, outside of the LISP protocol.

10.2.  Slow Endpoint Mobility

   An individual endpoint wishes to move, but is not concerned about
   maintaining session continuity.  Renumbering is involved.  LISP can
   help with the issues surrounding renumbering [RFC4192] [LISA96] by
   decoupling the address space used by a site from the address spaces
   used by its ISPs.  [RFC4984]

10.3.  Fast Endpoint Mobility

   Fast endpoint mobility occurs when an endpoint moves relatively
   rapidly, changing its IP layer network attachment point.  Maintenance
   of session continuity is a goal.  This is where the Mobile IPv4
   [RFC3344bis] and Mobile IPv6 [RFC3775] [RFC4866] mechanisms are used,
   and primarily where interactions with LISP need to be explored.

   The problem is that as an endpoint moves, it may require changes to
   the mapping between its EID and a set of RLOCs for its new network
   location.  When this is added to the overhead of mobile IP binding
   updates, some packets might be delayed or dropped.

   In IPv4 mobility, when an endpoint is away from home, packets to it
   are encapsulated and forwarded via a home agent which resides in the
   home area the endpoint's address belongs to.  The home agent will
   encapsulate and forward packets either directly to the endpoint or to
   a foreign agent which resides where the endpoint has moved to.
   Packets from the endpoint may be sent directly to the correspondent
   node, may be sent via the foreign agent, or may be reverse-tunneled
   back to the home agent for delivery to the mobile node.  As the
   mobile node's EID or available RLOC changes, LISP EID-to-RLOC
   mappings are required for communication between the mobile node and
   the home agent, whether via foreign agent or not.  As a mobile
   endpoint changes networks, up to three LISP mapping changes may be
   required:





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   o  The mobile node moves from an old location to a new visited
      network location and notifies its home agent that it has done so.
      The Mobile IPv4 control packets the mobile node sends pass through
      one of the new visited network's ITRs, which needs a EID-RLOC
      mapping for the home agent.

   o  The home agent might not have the EID-RLOC mappings for the mobile
      node's "care-of" address or its foreign agent in the new visited
      network, in which case it will need to acquire them.

   o  When packets are sent directly to the correspondent node, it may
      be that no traffic has been sent from the new visited network to
      the correspondent node's network, and the new visited network's
      ITR will need to obtain an EID-RLOC mapping for the correspondent
      node's site.

   In addition, if the IPv4 endpoint is sending packets from the new
   visited network using its original EID, then LISP will need to
   perform a route-returnability check on the new EID-RLOC mapping for
   that EID.

   In IPv6 mobility, packets can flow directly between the mobile node
   and the correspondent node in either direction.  The mobile node uses
   its "care-of" address (EID).  In this case, the route-returnability
   check would not be needed but one more LISP mapping lookup may be
   required instead:

   o  As above, three mapping changes may be needed for the mobile node
      to communicate with its home agent and to send packets to the
      correspondent node.

   o  In addition, another mapping will be needed in the correspondent
      node's ITR, in order for the correspondent node to send packets to
      the mobile node's "care-of" address (EID) at the new network
      location.

   When both endpoints are mobile the number of potential mapping
   lookups increases accordingly.

   As a mobile node moves there are not only mobility state changes in
   the mobile node, correspondent node, and home agent, but also state
   changes in the ITRs and ETRs for at least some EID-prefixes.

   The goal is to support rapid adaptation, with little delay or packet
   loss for the entire system.  Heuristics can be added to LISP to
   reduce the number of mapping changes required and to reduce the delay
   per mapping change.  Also IP mobility can be modified to require
   fewer mapping changes.  In order to increase overall system



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   performance, there may be a need to reduce the optimization of one
   area in order to place fewer demands on another.

   In LISP, one possibility is to "glean" information.  When a packet
   arrives, the ETR could examine the EID-RLOC mapping and use that
   mapping for all outgoing traffic to that EID.  It can do this after
   performing a route-returnability check, to ensure that the new
   network location does have a internal route to that endpoint.
   However, this does not cover the case where an ITR (the node assigned
   the RLOC) at the mobile-node location has been compromised.

   Mobile IP packet exchange is designed for an environment in which all
   routing information is disseminated before packets can be forwarded.
   In order to allow the Internet to grow to support expected future
   use, we are moving to an environment where some information may have
   to be obtained after packets are in flight.  Modifications to IP
   mobility should be considered in order to optimize the behavior of
   the overall system.  Anything which decreases the number of new EID-
   RLOC mappings needed when a node moves, or maintains the validity of
   an EID-RLOC mapping for a longer time, is useful.

10.4.  Fast Network Mobility

   In addition to endpoints, a network can be mobile, possibly changing
   xTRs.  A "network" can be as small as a single router and as large as
   a whole site.  This is different from site mobility in that it is
   fast and possibly short-lived, but different from endpoint mobility
   in that a whole prefix is changing RLOCs.  However, the mechanisms
   are the same and there is no new overhead in LISP.  A map request for
   any endpoint will return a binding for the entire mobile prefix.

   If mobile networks become a more common occurrence, it may be useful
   to revisit the design of the mapping service and allow for dynamic
   updates of the database.

   The issue of interactions between mobility and LISP needs to be
   explored further.  Specific improvements to the entire system will
   depend on the details of mapping mechanisms.  Mapping mechanisms
   should be evaluated on how well they support session continuity for
   mobile nodes.

10.5.  LISP Mobile Node Mobility

   An mobile device can use the LISP infrastructure to achieve mobility
   by implementing the LISP encapsulation and decapsulation functions
   and acting as a simple ITR/ETR.  By doing this, such a "LISP mobile
   node" can use topologically-independent EID IP addresses that are not
   advertised into and do not impose a cost on the global routing



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   system.  These EIDs are maintained at the edges of the mapping system
   (in LISP Map-Servers and Map-Resolvers) and are provided on demand to
   only the correspondents of the LISP mobile node.

   Refer to the LISP Mobility Architecture specification [LISP-MN] for
   more details.













































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11.  Multicast Considerations

   A multicast group address, as defined in the original Internet
   architecture is an identifier of a grouping of topologically
   independent receiver host locations.  The address encoding itself
   does not determine the location of the receiver(s).  The multicast
   routing protocol, and the network-based state the protocol creates,
   determines where the receivers are located.

   In the context of LISP, a multicast group address is both an EID and
   a Routing Locator.  Therefore, no specific semantic or action needs
   to be taken for a destination address, as it would appear in an IP
   header.  Therefore, a group address that appears in an inner IP
   header built by a source host will be used as the destination EID.
   The outer IP header (the destination Routing Locator address),
   prepended by a LISP router, will use the same group address as the
   destination Routing Locator.

   Having said that, only the source EID and source Routing Locator
   needs to be dealt with.  Therefore, an ITR merely needs to put its
   own IP address in the source Routing Locator field when prepending
   the outer IP header.  This source Routing Locator address, like any
   other Routing Locator address MUST be globally routable.

   Therefore, an EID-to-RLOC mapping does not need to be performed by an
   ITR when a received data packet is a multicast data packet or when
   processing a source-specific Join (either by IGMPv3 or PIM).  But the
   source Routing Locator is decided by the multicast routing protocol
   in a receiver site.  That is, an EID to Routing Locator translation
   is done at control-time.

   Another approach is to have the ITR not encapsulate a multicast
   packet and allow the the host built packet to flow into the core even
   if the source address is allocated out of the EID namespace.  If the
   RPF-Vector TLV [RPFV] is used by PIM in the core, then core routers
   can RPF to the ITR (the Locator address which is injected into core
   routing) rather than the host source address (the EID address which
   is not injected into core routing).

   To avoid any EID-based multicast state in the network core, the first
   approach is chosen for LISP-Multicast.  Details for LISP-Multicast
   and Interworking with non-LISP sites is described in specification
   [MLISP].








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12.  Security Considerations

   It is believed that most of the security mechanisms will be part of
   the mapping database service when using control plane procedures for
   obtaining EID-to-RLOC mappings.  For data plane triggered mappings,
   as described in this specification, protection is provided against
   ETR spoofing by using Return- Routability mechanisms evidenced by the
   use of a 24-bit Nonce field in the LISP encapsulation header and a
   64-bit Nonce field in the LISP control message.  The nonce, coupled
   with the ITR accepting only solicited Map-Replies goes a long way
   toward providing decent authentication.

   LISP does not rely on a PKI infrastructure or a more heavy weight
   authentication system.  These systems challenge the scalability of
   LISP which was a primary design goal.

   DoS attack prevention will depend on implementations rate-limiting
   Map-Requests and Map-Replies to the control plane as well as rate-
   limiting the number of data-triggered Map-Replies.

   To deal with map-cache exhaustion attempts in an ITR/PTR, the
   implementation should consider putting a maximum cap on the number of
   entries stored with a reserve list for special or frequently accessed
   sites.  This should be a configuration policy control set by the
   network administrator who manages ITRs and PTRs.


























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13.  Prototype Plans and Status

   The operator community has requested that the IETF take a practical
   approach to solving the scaling problems associated with global
   routing state growth.  This document offers a simple solution which
   is intended for use in a pilot program to gain experience in working
   on this problem.

   The authors hope that publishing this specification will allow the
   rapid implementation of multiple vendor prototypes and deployment on
   a small scale.  Doing this will help the community:

   o  Decide whether a new EID-to-RLOC mapping database infrastructure
      is needed or if a simple, UDP-based, data-triggered approach is
      flexible and robust enough.

   o  Experiment with provider-independent assignment of EIDs while at
      the same time decreasing the size of DFZ routing tables through
      the use of topologically-aligned, provider-based RLOCs.

   o  Determine whether multiple levels of tunneling can be used by ISPs
      to achieve their Traffic Engineering goals while simultaneously
      removing the more specific routes currently injected into the
      global routing system for this purpose.

   o  Experiment with mobility to determine if both acceptable
      convergence and session continuity properties can be scalably
      implemented to support both individual device roaming and site
      service provider changes.

   Here is a rough set of milestones:

   1.  Interoperable implementations have been available since the
       beginning of 2009.  We are trying to converge on a packet format
       so implementations can converge on the -04 and later drafts.

   2.  Continue pilot deployment using LISP-ALT as the database mapping
       mechanism.

   3.  Continue prototyping and studying other database lookup schemes,
       be it DNS, DHTs, CONS, ALT, NERD, or other mechanisms.

   4.  Implement the LISP Multicast draft [MLISP].

   5.  Implement the LISP Mobile Node draft [LISP-MN].

   6.  Research more on how policy affects what gets returned in a Map-
       Reply from an ETR.



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   7.  Continue to experiment with mixed locator-sets to understand how
       LISP can help the IPv4 to IPv6 transition.

   8.  Add more robustness to locator reachability between LISP sites.

   As of this writing the following accomplishments have been achieved:

   1.   A unit- and system-tested software switching implementation has
        been completed on cisco NX-OS for this draft for both IPv4 and
        IPv6 EIDs using a mixed locator-set of IPv4 and IPv6 locators.

   2.   A unit- and system-tested software switching implementation on
        cisco NX-OS has been completed for draft [ALT].

   3.   A unit- and system-tested software switching implementation on
        cisco NX-OS has been completed for draft [INTERWORK].  Support
        for IPv4 translation is provided and PTR support for IPv4 and
        IPv6 is provided.

   4.   The cisco NX-OS implementation supports an experimental
        mechanism for slow mobility.

   5.   Dave Meyer, Vince Fuller, Darrel Lewis, Greg Shepherd, and
        Andrew Partan continue to test all the features described above
        on a dual-stack infrastructure.

   6.   Darrel Lewis and Dave Meyer have deployed both LISP translation
        and LISP PTR support in the pilot network.  Point your browser
        to http://www.lisp4.net to see translation happening in action
        so your non-LISP site can access a web server in a LISP site.

   7.   Soon http://www.lisp6.net will work where your IPv6 LISP site
        can talk to a IPv6 web server in a LISP site by using mixed
        address-family based locators.

   8.   An public domain implementation of LISP is underway.  See
        [OPENLISP] for details.

   9.   We have deployed Map-Resolvers and Map-Servers on the LISP pilot
        network to gather experience with [LISP-MS].  The first layer of
        the architecture are the xTRs which use Map-Servers for EID-
        prefix registration and Map-Resolvers for EID-to-RLOC mapping
        resolution.  The second layer are the Map-Resolvers and Map-
        Servers which connect to the ALT BGP peering infrastructure.
        And the third layer are ALT-routers which aggregate EID-prefixes
        and forward Map-Requests.





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   10.  A cisco IOS implementation is underway which currently supports
        IPv4 encapsulation and decapsulation features.

   11.  A LISP router based LIG implementation is supported, deployed,
        and used daily to debug and test the LISP pilot network.  See
        [LIG] for details.

   12.  A Linux implementation of LIG has been made available and
        supported by Dave Meyer.  It can be run on any Linux system
        which resides in either a LISP site or non-LISP site.  See [LIG]
        for details.  Public domain code can be downloaded from
        http://github.com/davidmeyer/lig/tree/master.

   13.  An experimental implementation has been written for three
        locator reachability algorithms.  Two are the Echo-Noncing and
        RLOC-Probing algorithms which are documented in this
        specification.  The third is called TCP-counts which will be
        documented in future drafts.

   14.  The LISP pilot network has been converted from using MD5 HMAC
        authentication for Map-Register messages to SHA-1 HMAC
        authentication.  ETRs send with SHA-1 but Map-Servers can
        received from either for compatibility purposes.

   If interested in writing a LISP implementation, testing any of the
   LISP implementations, or want to be part of the LISP pilot program,
   please contact lisp at ietf.org.
























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14.  References

14.1.  Normative References

   [RFC0768]  Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              August 1980.

   [RFC1191]  Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
              November 1990.

   [RFC1498]  Saltzer, J., "On the Naming and Binding of Network
              Destinations", RFC 1498, August 1993.

   [RFC1955]  Hinden, R., "New Scheme for Internet Routing and
              Addressing (ENCAPS) for IPNG", RFC 1955, June 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2404]  Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within
              ESP and AH", RFC 2404, November 1998.

   [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 2434,
              October 1998.

   [RFC2784]  Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
              Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
              March 2000.

   [RFC3056]  Carpenter, B. and K. Moore, "Connection of IPv6 Domains
              via IPv4 Clouds", RFC 3056, February 2001.

   [RFC3168]  Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
              of Explicit Congestion Notification (ECN) to IP",
              RFC 3168, September 2001.

   [RFC3775]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
              in IPv6", RFC 3775, June 2004.

   [RFC4086]  Eastlake, D., Schiller, J., and S. Crocker, "Randomness
              Requirements for Security", BCP 106, RFC 4086, June 2005.

   [RFC4423]  Moskowitz, R. and P. Nikander, "Host Identity Protocol
              (HIP) Architecture", RFC 4423, May 2006.

   [RFC4634]  Eastlake, D. and T. Hansen, "US Secure Hash Algorithms
              (SHA and HMAC-SHA)", RFC 4634, July 2006.



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   [RFC4866]  Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route
              Optimization for Mobile IPv6", RFC 4866, May 2007.

   [RFC4984]  Meyer, D., Zhang, L., and K. Fall, "Report from the IAB
              Workshop on Routing and Addressing", RFC 4984,
              September 2007.

   [UDP-TUNNELS]
              Eubanks, M. and P. Chimento, "UDP Checksums for Tunneled
              Packets"", draft-eubanks-chimento-6man-00.txt (work in
              progress), February 2009.

14.2.  Informative References

   [AFI]      IANA, "Address Family Indicators (AFIs)", ADDRESS FAMILY
              NUMBERS http://www.iana.org/numbers.html, Febuary 2007.

   [ALT]      Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "LISP
              Alternative Topology (LISP-ALT)",
              draft-ietf-lisp-alt-01.txt (work in progress), May 2009.

   [APT]      Jen, D., Meisel, M., Massey, D., Wang, L., Zhang, B., and
              L. Zhang, "APT: A Practical Transit Mapping Service",
              draft-jen-apt-01.txt (work in progress), November 2007.

   [CHIAPPA]  Chiappa, J., "Endpoints and Endpoint names: A Proposed
              Enhancement to the Internet Architecture", Internet-
              Draft http://www.chiappa.net/~jnc/tech/endpoints.txt,
              1999.

   [CONS]     Farinacci, D., Fuller, V., and D. Meyer, "LISP-CONS: A
              Content distribution Overlay Network  Service for LISP",
              draft-meyer-lisp-cons-03.txt (work in progress),
              November 2007.

   [DHTs]     Ratnasamy, S., Shenker, S., and I. Stoica, "Routing
              Algorithms for DHTs: Some Open Questions", PDF
              file http://www.cs.rice.edu/Conferences/IPTPS02/174.pdf.

   [EMACS]    Brim, S., Farinacci, D., Meyer, D., and J. Curran, "EID
              Mappings Multicast Across Cooperating Systems for LISP",
              draft-curran-lisp-emacs-00.txt (work in progress),
              November 2007.

   [GSE]      "GSE - An Alternate Addressing Architecture for  IPv6",
              draft-ietf-ipngwg-gseaddr-00.txt (work in progress), 1997.

   [INTERWORK]



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              Lewis, D., Meyer, D., Farinacci, D., and V. Fuller,
              "Interworking LISP with IPv4 and IPv6",
              draft-ietf-lisp-interworking-00.txt (work in progress),
              January 2009.

   [LIG]      Farinacci, D. and D. Meyer, "LISP Internet Groper (LIG)",
              draft-farinacci-lisp-lig-01.txt (work in progress),
              May 2009.

   [LISA96]   Lear, E., Katinsky, J., Coffin, J., and D. Tharp,
              "Renumbering: Threat or Menace?", Usenix , September 1996.

   [LISP-MAIN]
              Farinacci, D., Fuller, V., Meyer, D., and D. Lewis,
              "Locator/ID Separation Protocol (LISP)",
              draft-farinacci-lisp-12.txt (work in progress),
              March 2009.

   [LISP-MN]  Farinacci, D., Fuller, V., Lewis, D., and D. Meyer, "LISP
              Mobility Architecture", draft-meyer-lisp-mn-00.txt (work
              in progress), July 2009.

   [LISP-MS]  Farinacci, D. and V. Fuller, "LISP Map Server",
              draft-ietf-lisp-ms-02.txt (work in progress),
              September 2009.

   [LISP1]    Farinacci, D., Oran, D., Fuller, V., and J. Schiller,
              "Locator/ID Separation Protocol (LISP1) [Routable  ID
              Version]",
              Slide-set http://www.dinof.net/~dino/ietf/lisp1.ppt,
              October 2006.

   [LISP2]    Farinacci, D., Oran, D., Fuller, V., and J. Schiller,
              "Locator/ID Separation Protocol (LISP2) [DNS-based
              Version]",
              Slide-set http://www.dinof.net/~dino/ietf/lisp2.ppt,
              November 2006.

   [LISPDHT]  Mathy, L., Iannone, L., and O. Bonaventure, "LISP-DHT:
              Towards a DHT to map identifiers onto locators",
              draft-mathy-lisp-dht-00.txt (work in progress),
              February 2008.

   [LOC-ID-ARCH]
              Meyer, D. and D. Lewis, "Architectural Implications of
              Locator/ID  Separation",
              draft-meyer-loc-id-implications-01.txt (work in progress),
              Januaryr 2009.



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   [MLISP]    Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas,
              "LISP for Multicast Environments",
              draft-ietf-lisp-multicast-02.txt (work in progress),
              October 2009.

   [NERD]     Lear, E., "NERD: A Not-so-novel EID to RLOC Database",
              draft-lear-lisp-nerd-04.txt (work in progress),
              April 2008.

   [OPENLISP]
              Iannone, L. and O. Bonaventure, "OpenLISP Implementation
              Report", draft-iannone-openlisp-implementation-01.txt
              (work in progress), July 2008.

   [RADIR]    Narten, T., "Routing and Addressing Problem Statement",
              draft-narten-radir-problem-statement-00.txt (work in
              progress), July 2007.

   [RFC3344bis]
              Perkins, C., "IP Mobility Support for IPv4, revised",
              draft-ietf-mip4-rfc3344bis-05 (work in progress),
              July 2007.

   [RFC4192]  Baker, F., Lear, E., and R. Droms, "Procedures for
              Renumbering an IPv6 Network without a Flag Day", RFC 4192,
              September 2005.

   [RPFV]     Wijnands, IJ., Boers, A., and E. Rosen, "The RPF Vector
              TLV", draft-ietf-pim-rpf-vector-08.txt (work in progress),
              January 2009.

   [RPMD]     Handley, M., Huici, F., and A. Greenhalgh, "RPMD: Protocol
              for Routing Protocol Meta-data  Dissemination",
              draft-handley-p2ppush-unpublished-2007726.txt (work in
              progress), July 2007.

   [SHIM6]    Nordmark, E. and M. Bagnulo, "Level 3 multihoming shim
              protocol", draft-ietf-shim6-proto-06.txt (work in
              progress), October 2006.












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Appendix A.  Acknowledgments

   An initial thank you goes to Dave Oran for planting the seeds for the
   initial ideas for LISP.  His consultation continues to provide value
   to the LISP authors.

   A special and appreciative thank you goes to Noel Chiappa for
   providing architectural impetus over the past decades on separation
   of location and identity, as well as detailed review of the LISP
   architecture and documents, coupled with enthusiasm for making LISP a
   practical and incremental transition for the Internet.

   The authors would like to gratefully acknowledge many people who have
   contributed discussion and ideas to the making of this proposal.
   They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller,
   Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston,
   David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley,
   Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler,
   Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi
   Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Roger
   Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van Beijnum, Roland
   Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien Saucez, Damian
   Lezama, Attilla De Groot, Parantap Lahiri, David Black, Roque
   Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, Margaret
   Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, and Jari
   Arkko.

   In particular, we would like to thank Dave Meyer for his clever
   suggestion for the name "LISP". ;-)

   This work originated in the Routing Research Group (RRG) of the IRTF.
   The individual submission [LISP-MAIN] was converted into this IETF
   LISP working group draft.


















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Appendix B.  Document Change Log

B.1.  Changes to draft-ietf-lisp-05.txt

   o  Posted October 2009.

   o  Added this Document Change Log appendix.

   o  Added section indicating that encapsulated Map-Requests must use
      destination UDP port 4342.

   o  Don't use AH in Map-Registers.  Put key-id, auth-length, and auth-
      data in Map-Register payload.

   o  Added Jari to acknowledgment section.

   o  State the source-EID is set to 0 when using Map-Requests to
      refresh or RLOC-probe.

   o  Make more clear what source-RLOC should be for a Map-Request.

   o  The LISP-CONS authors thought that the Type definitions for CONS
      should be removed from this specification.

   o  Removed nonce from Map-Register message, it wasn't used so no need
      for it.

   o  Clarify what to do for unspecified Action bits for negative Map-
      Replies.  Since No Action is a drop, make value 0 Drop.

B.2.  Changes to draft-ietf-lisp-04.txt

   o  Posted September 2009.

   o  How do deal with record count greater than 1 for a Map-Request.
      Damien and Joel comment.  Joel suggests: 1) Specify that senders
      compliant with the current document will always set the count to
      1, and note that the count is included for future extensibility.
      2) Specify what a receiver compliant with the draft should do if
      it receives a request with a count greater than 1.  Presumably, it
      should send some error back?

   o  Add Fred Templin in ack section.

   o  Add Margaret and Sam to the ack section for their great comments.

   o  Say more about LAGs in the UDP section per Sam Hartman's comment.




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   o  Sam wants to use MAY instead of SHOULD for ignoring checksums on
      ETR.  From the mailing list: "You'd need to word it as an ITR MAY
      send a zero checksum, an ETR MUST accept a 0 checksum and MAY
      ignore the checksum completely.  And of course we'd need to
      confirm that can actually be implemented.  In particular, hardware
      that verifies UDP checksums on receive needs to be checked to make
      sure it permits 0 checksums."

   o  Margaret wants a reference to
      http://www.ietf.org/id/draft-eubanks-chimento-6man-00.txt.

   o  Fix description in Map-Request section.  Where we describe Map-
      Reply Record, change "R-bit" to "M-bit".

   o  Add the mobility bit to Map-Replies.  So PTRs don't probe so often
      for MNs but often enough to get mapping updates.

   o  Indicate SHA1 can be used as well for Map-Registers.

   o  More Fred comments on MTU handling.

   o  Isidor comment about specing better periodic Map-Registers.  Will
      be fixed in draft-ietf-lisp-ms-02.txt.

   o  Margaret's comment on gleaning: "The current specification does
      not make it clear how long gleaned map entries should be retained
      in the cache, nor does it make it clear how/ when they will be
      validated.  The LISP spec should, at the very least, include a
      (short) default lifetime for gleaned entries, require that they be
      validated within a short period of time, and state that a new
      gleaned entry should never overwrite an entry that was obtained
      from the mapping system.  The security implications of storing
      "gleaned" entries should also be explored in detail."

   o  Add section on RLOC-probing per working group feedback.

   o  Change "loc-reach-bits" to "loc-status-bits" per comment from
      Noel.

   o  Remove SMR-bit from data-plane.  Dino prefers to have it in the
      control plane only.

   o  Change LISP header to allow a "Research Bit" so the Nonce and LSB
      fields can be turned off and used for another future purpose.  For
      Luigi et al versioning convergence.

   o  Add a N-bit to the data header suggested by Noel.  Then the nonce
      field could be used when N is not 1.



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   o  Clarify that when E-bit is 0, the nonce field can be an echoed
      nonce or a random nonce.  Comment from Jesper.

   o  Indicate when doing data-gleaning that a verifying Map-Request is
      sent to the source-EID of the gleaned data packet so we can avoid
      map-cache corruption by a 3rd party.  Comment from Pedro.

   o  Indicate that a verifying Map-Request, for accepting mapping data,
      should be sent over the the ALT (or to the EID).

   o  Reference IPsec RFC 4302.  Comment from Sam and Brian Weis.

   o  Put E-bit in Map-Reply to tell ITRs that the ETR supports echo-
      noncing.  Comment by Pedro and Dino.

   o  Jesper made a comment to loosen the language about requiring the
      copy of inner TTL to outer TTL since the text to get mixed-AF
      traceroute to work would violate the "MUST" clause.  Changed from
      MUST to SHOULD in section 5.3.

B.3.  Changes to draft-ietf-lisp-03.txt

   o  Posted July 2009.

   o  Removed loc-reach-bits longword from control packets per Damien
      comment.

   o  Clarifications in MTU text from Roque.

   o  Added text to indicate that the locator-set be sorted by locator
      address from Isidor.

   o  Clarification text from JohnZ in Echo-Nonce section.

B.4.  Changes to draft-ietf-lisp-02.txt

   o  Posted July 2009.

   o  Encapsulation packet format change to add E-bit and make loc-
      reach-bits 32-bits in length.

   o  Added Echo-Nonce Algorithm section.

   o  Clarification how ECN bits are copied.

   o  Moved S-bit in Map-Request.





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   o  Added P-bit in Map-Request and Map-Reply messages to anticipate
      RLOC-Probe Algorithm.

   o  Added to Mobility section to reference draft-meyer-lisp-mn-00.txt.

B.5.  Changes to draft-ietf-lisp-01.txt

   o  Posted 2 days after draft-ietf-lisp-00.txt in May 2009.

   o  Defined LEID to be a "LISP EID".

   o  Indicate encapsulation use IPv4 DF=0.

   o  Added negative Map-Reply messages with drop, native-forward, and
      send-map-request actions.

   o  Added Proxy-Map-Reply bit to Map-Register.

B.6.  Changes to draft-ietf-lisp-00.txt

   o  Posted May 2009.

   o  Rename of draft-farinacci-lisp-12.txt.

   o  Acknowledgment to RRG.


























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Authors' Addresses

   Dino Farinacci
   cisco Systems
   Tasman Drive
   San Jose, CA  95134
   USA

   Email: dino at cisco.com


   Vince Fuller
   cisco Systems
   Tasman Drive
   San Jose, CA  95134
   USA

   Email: vaf at cisco.com


   Dave Meyer
   cisco Systems
   170 Tasman Drive
   San Jose, CA
   USA

   Email: dmm at cisco.com


   Darrel Lewis
   cisco Systems
   170 Tasman Drive
   San Jose, CA
   USA

   Email: darlewis at cisco.com















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