wdiff draft-xu-idr-neighbor-autodiscovery-08.txt draft-xu-idr-neighbor-autodiscovery-09.txt

Network Working Group X. Xu
Internet-Draft Alibaba Inc
Intended status: Standards Track K. Bi Talaulikar
Expires: November 16, 2018 January 17, 2019 Cisco Systems
K. Bi
Huawei
J. Tantsura
Nuage Networks
N. Triantafillis
LinkedIn
K. Talaulikar
Cisco
May 15,
July 16, 2018

BGP Neighbor Autodiscovery
draft-xu-idr-neighbor-autodiscovery-08 Auto-Discovery
draft-xu-idr-neighbor-autodiscovery-09

Abstract

BGP has been is being used as the underlay routing protocol in many hyper-
scale some large-
scaled data centers. centers (DCs). Most popular design followed is to do
hop-by-hop external BGP (eBGP) session configurations between
neighboring routers on a per link basis. The provisioning of BGP
neighbors in routers across such a DC brings its own operational
complexity.

This document proposes introduces a BGP neighbor
autodiscovery discovery mechanism that
greatly simplifies BGP deployments.
This mechanism is very useful for those hyper-scale data centers
where operations in such DC and other networks by
automatic setup of BGP is used as the underlay routing protocol. sessions between neighbor routers using this
mechanism.

Requirements Language

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 RFC 2119 [RFC2119].

Status of This Memo

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

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.

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."

This Internet-Draft will expire on November 16, 2018. January 17, 2019.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 4
3. BGP Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. UDP Message Header . . . . . . . . . . . . . . . . . . . . . 5
5. Hello Message Format . . . . . . . . . . . . . . . . . . 3
4. . . 6
6. Hello Message Procedure TLVs . . . . . . . . . . . . . . . . . . . . . 8
6.1. Accepted ASN List TLV . . . . . . . . . . . . . . . . . . 8
6.2. Peering Address TLV . . . . . . . . . . . . . . . . . . . 9
6.3. Local Prefix TLV . . . . . . . . . . . . . . . . . . . . 10
5. Contributors
6.4. Link Attributes TLV . . . . . . . . . . . . . . . . . . . 12
6.5. Neighbor TLV . . . . . . . . . . . 11
6. Acknowledgements . . . . . . . . . . . 14
6.6. Cryptographic Authentication TLV . . . . . . . . . . . . 11 15
7. Neighbor Discovery Procedure . . . . . . . . . . . . . . . . 17
7.1. Interface State . . . . . . . . . . . . . . . . . . . . . 17
7.2. Adjacency State Machine . . . . . . . . . . . . . . . . . 18
7.3. Peering Route . . . . . . . . . . . . . . . . . . . . . . 19
8. Interactions with Base BGP Protocol . . . . . . . . . . . . . 20
9. Security Considerations . . . . . . . . . . . . . . . . . . . 21
10. Manageability Considerations . . . . . . . . . . . . . . . . 22
10.1. Operational Considerations . . . . . . . . . . . . . . . 22
10.2. Management Considerations . . . . . . . . . . . . . . . 23
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7.1. 23
11.1. BGP Hello Message . . . . . . . . . . . . . . . . . . . . 12
7.2. 24
11.2. TLVs of BGP Hello Message . . . . . . . . . . . . . . . 24
12. Acknowledgements . 12
8. Security Considerations . . . . . . . . . . . . . . . . . . . 12
9. . . 24
13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 24
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
9.1. 25
14.1. Normative References . . . . . . . . . . . . . . . . . . 13
9.2. 25
14.2. Informative References . . . . . . . . . . . . . . . . . 13 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 27

1. Introduction

BGP has been is being used as the underlay routing protocol instead of IGP link-
state routing protocols like IS-IS and OSPF in
many hyper-scale some large-scale data
centers [RFC7938]. Furthermore, there is an
ongoing effort to leverage BGP link-state distribution mechanism to
achieve BGP-SPF [I-D.keyupate-lsvr-bgp-spf]. However, (DCs). [RFC7938] describes the design, configuration and
operational aspects of using BGP is not
good as an IGP from in such networks. The most popular
design scheme involves the perspective setup of external BGP (eBGP) sessions over
individual links between directly connected routers using their
interface addresses. Such BGP neighbor provisioning requires
provisioning of deployment automation and
simplicity. For instance, the neighbor IP address and the Autonomous System (AS)
Number (ASN) of for each and every BGP neighbor have to be manually
configured on every link address.
As a DC fabric comprising of topology described in [RFC7938] grows
with addition of new leafs, spines and links between them, the BGP routers although these BGP peers are directly
connected. Furthermore, for those BGP routers
provisioning needs to be carefully setup. Unlike with the link-state
protocols, there is no automatic discovery of neighbors simply by
adding links and nodes in the fabric and route exchange over them
getting enabled seamlessly in the case of BGP.

In some DC designs with BGP, multiple physical links being connected, it's usually are added between a leaf
and spine to add additional bandwidth. Use of link-aggregation at
Layer 2 level may not ideal be desirable in such cases due to establish BGP the risk of
flow polarization on account of a mix of ECMP at Layer 2 and Layer 3
levels. In such cases, one option is for a eBGP sessions to be setup
between two BGP neighbors over their directly connected interface addresses because each of the links between them. In
such a case, the BGP session scale and the resultant increase in
update volume would be unnecessarily increased, meanwhile, it processing may not be suitable to configure those links as pose scalability challenges. A second option
is for a Link Aggregation
Group (LAG) due single eBGP session to some reasons. As a result, it's more common that be setup between the loopback interface IP
addresses between the neighbor and then configure some static routes
for it pointing over the underlying links as ECMP. In this option
there is an additional provisioning task introduced in the form of those directly connected BGP peers
are used
static routing.

Furthermore, there is also a need for BGP session establishment purpose. To make those
loopback addresses of to be able to describe its
links and its neighbors on its directly connected BGP peers reachable from one
another, either static routes have links and export
this information via BGP-LS [RFC7752] to be configured or some kind provide a detail link-level
topology view using a standards based mechanism of
IGP has to be enabled. a data center
running only BGP. The former ability of BGP in discovering its neighbors
over its links, monitoring their liveliness and learning the link
attributes (such as addresses) is not good from required for the network
automation perspective while conveying the latter is not good from
link-state topology in a BGP network. This information can be
leveraged by the network
simplification perspective (i.e., running less BGP-SPF proposal [I-D.ietf-lsvr-bgp-spf] which
introduces link-state routing protocols). capabilities in BGP. This draft specifies information
can also be leveraged to convey the link-state topology in a network
running traditional BGP neighbor autodiscovery mechanism by
borrowing some ideas from routing using BGP-LS as described in
[I-D.ketant-idr-bgp-ls-bgp-only-fabric] and to enabled end to end
traffic engineering use-cases spanning across DCs and the Label Distribution Protocol (LDP)
[RFC5036] core/access
networks.

2. Terminology

This memo makes use of the terms defined in [RFC4271] and [RFC7938] . More specifically,

3. Overview

At a high level, this specification introduces the use of UDP based
BGP Hello messages to be exchanged between directly connected BGP
routers could
automatically for neighbor discovery.

1. Information is exchanged between BGP routers on a per link basis
leading to discovery of each others peering address and other through
information.

2. The TCP session establishment for the BGP protocol operation and
the BGP routing exchange of over these sessions can then follow
without any change/modification from the to-be-
defined existing BGP Hello messages. The protocol
operations as specified in [RFC4271].

3. As part of the neighbor information exchange the route to a
neighbor's peering address is also automatically setup pointing
over the links over which the neighbor is discovered.

4. This route is used for both the BGP TCP session establishment process as
defined in [RFC4271] could be triggered once directly connected
well as for resolution of the BGP
neighbors are discovered from one another. Note that next-hop (NH) for the routes
learnt via the neighbor instead of an underlying IGP or static
route.

Auto-discovery of BGP session
should neighbors and their liveness detection may be established over the discovered
performed via different mechanisms. This document prefers the peering address use of
an extension to BGP protocol since the deployments and use-cases
targeted (i.e. large-scale DCs) are already running BGP as their
routing protocol. Extending BGP with neighbor discovery capabilities
is operationally and implementation wise a simpler approach than
requiring a new or an additional protocol to be first extended to do
this functionality (to exchange BGP-specific parameters) and then
also integrated its operations with BGP protocol operations.

Following are the key objectives and goals of the BGP neighbor
discovery mechanism proposed in most cases this document:

o Existing BGP update processing is unchanged
o Minimal changes for integration of the peering address neighbor discovery state
machine with the existing BGP Peer state machine for auto-
discovered neighbors only

o Auto-discovery mechanism is a loopback
address. In addition, restricted to eliminate directly connected BGP
speakers only and uses link-local multicast addresses only for the need
hello messaging

o Liveness detection is used for monitoring the BGP adjacency status
for directly connected BGP routers over individual links and is
BGP specific. It is not intended to replace the functionality for
existing generic mechanisms like BFD and LLDP.

o Hello processing is separate from the core BGP protocol operations
such that BGP route processing scale and performance is not
impacted

The BGP neighbor discovery mechanism defined in this document borrows
ideas from the Label Distribution Protocol (LDP) [RFC5036]. However,
most importantly, only the concept of configuring static
routes or enabling IGP link-local signaling based
neighbor discovery is borrow while the discovery aspect for targeted
LDP sessions does not apply to this BGP neighbor discovery mechanism.

The further sections in this document first describe the loopback addresses, a certain type newly
introduced message formats and TLVs and then go on to describe the
procedures of
routes towards the BGP neighbor's loopback addresses as advertised neighbor discovery mechanism and its
integration with the base BGP protocol mechanism as
peering addresses are dynamically instantiated once specified in
[RFC4271].

The operational and management aspects of the BGP neighbor
has been discovered. discovery
mechanism are described in Section 10.

4. UDP Message Header

The administrative distance of such type BGP neighbor discovery mechanism will operate using UDP messages.
The UDP port of
routes MUST TBD (179 is the preferred port number to be smaller than their equivalents that are learnt by assigned
as specified in Section 11) is used which is same as the
regular TCP port 179
used by BGP. The BGP update messages . Otherwise, circular dependency would
occur once these loopback addresses are advertised via the regular UDP message common header format is specified
as follows:

2. Terminology Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 1: BGP UDP Message Header

Version: This memo makes use 1-octet unsigned integer indicates the protocol
version number of the terms defined message. The current BGP version number is
4.

Type: The type of BGP message

Message Length: This 2-octet unsigned integer specifies the length
in [RFC4271].

3. octets of the entire BGP UDP message including the header.

AS number: AS Number of the UDP message sender.

BGP Identifier: BGP Identifier of the UDP message sender.

BGP UDP messages can be sent using either IPv4 or IPv6 depending on
the address used for session establishment and provisioned on the
interfaces over which these messages are sent.

5. Hello Message Format

A BGP router uses UDP based Hello messages to automatically discover
directly connected BGP neighbors, a BGP
router periodically sends BGP HELLO neighbors and to check their liveliness. The
Hello messages out those interfaces on
which and the BGP neighbor autodiscovery are enabled. discovery mechanism operates only
on those interfaces where it is specifically enabled on. The BGP HELLO message
MUST sent as a UDP packet with a destination port of TBD (179
neighbor discovery mechanism is intend for link-local signaling
between directly connected BGP nodes and hence the
preferred port number value) BGP Hello messages
MUST be addressed for to the "all routers on this subnet" group multicast
address (i.e., 224.0.0.2 in the IPv4 case and FF02::2 in the IPv6 case).
case) and the TTL for the IP packets SHOULD be set to 1. The IP
source address is MUST be set to the address of the interface over which
the message is sent out. out which would be the primary interface address
or unnumbered address in the IPv4 case and the IPv6 link-local
address on the interface in the IPv6 case.

The HELLO Hello message contains the following fields: format is as follows:

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 | Type | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AS number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BGP Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Adjacency Hold Time | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLVs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 1: 2: BGP Hello Message

Version: This 1-octet unsigned integer indicates the protocol
version number of the message. The current BGP version number is
4.

Type: The type of BGP message (Hello - TBD value from BGP Message
Types Registry)

Message Length: This 2-octet unsigned integer specifies the length
in octets of the TLVs field.

AS number: AS Number of the Hello message sender.

BGP Identifier: BGP Identifier of the Hello message sender.

Adjacency Hold Time: Hello adjacency hold timer in seconds. Hello
Adjacency Hold Time specifies the time the receiving BGP peer will neighbor
router SHOULD maintain its record of Hellos
from the sending BGP peer neighbor adjacency state without
receipt of another Hello. The
RECOMMENDED default value is 15 seconds. A value of 0 means that the receiving
BGP peer should maintain its record until immediately mark that the link sender is UP. going down.

Reserved: SHOULD be set to 0 by sender and MUST be ignored by
receiver.

TLVs: This field contains one or more TLVs as described below.

BGP HELLO messages can be sent using either IPv4 or IPv6 addresses
depending on the addressing used for session establishment and
provisioned on the interfaces over which these messages are sent.
Either IPv4 or IPv6 address (but never both on the same link) are
used for the BGP Hello message exchange and the neighbor discovery
mechanism based on the local configuration policy.

In a BGP DC network that is using IPv6 only in the fabric underlay,
it is possible that no IPv6 global addresses are assigned to the
interfaces between the nodes and the IPv6 Global address(es) are
assigned only to the loopback interfaces of these nodes. Such a
design could ease introducing of nodes in the fabric and links
between them from a provisioning aspect. The BGP neighbor discovery
mechanism described in this document works on links between routers
having only IPv6 link-local addresses and setting up BGP sessions
between them using their loopback IPv6 Global addresses in an
automatic manner.

The neighbor discovery procedure using the Hello message is described
in Section 7 and its relation with the BGP Keepalives and Hold Timer
for the TCP session is described in Section 8.

6. Hello Message TLVs

The BGP Hello message carries TLVs as described in this section that
enable exchange of information on a per interface basis between
directly connected BGP neighbors. These messages enable the neighbor
discovery process.

6.1. Accepted ASN List TLV

The Accepted ASN List TLV is an optional TLV that is used to signal
the AS numbers from which the BGP router would accept BGP sessions.
When not signaled, it indicates that the router will accept BGP
peering from any ASN from its neighbors. Indicating the list of ASNs
from which a router will accept BGP sessions helps avoid the neighbor
discovery process getting stuck in a 1-way state where one side keeps
attempting to setup adjacency while the other does not accept it due
to incorrect ASN.

The operational and management aspects of this ASN based policy
control for BGP neighbor discovery are described further in
Section 10.

Only a single instance of this TLV is included and its format is
shown below.

Figure 2: 3: Accepted ASN List TLV

Type: TBD1

Length:Specifies the length of the Value field in octets. octets (in
multiple of 4)

Accepted ASN-List: This variable-length field contains one or more
accepted 4-octet ASNs.

6.2. Peering Address TLV

The Peering Address TLV is used to indicate to the neighbor the
address to which they should establish the BGP TCP session. For each
peering address, the router can specify its supported AFI/SAFI(s).
When the AFI/SAFI values are specified as 0/0, then it indicates that
the neighbor can attempt for negotiation of any AFI/SAFIs. The
indication of AFI/SAFI(s) in the Peering Address TLV is not intended
as an alternative for the MP capabilities negotiation mechanism.

The Peering Address TLV format mechanism done
as part of the BGP TCP session establishment.

This is shown below a mandatory TLV and at least one instance of this TLV MUST be
present. Multiple instances of this TLV MAY be present one for each
peering address (e.g. IPv4 and IPv6 or multiple IPv4 addresses for
different AFI/SAFI sessions).

The Peering Address TLV format is shown below.

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AFI | SAFI | ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-TLVs ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 3: 4: Peering Address TLV

Type: TBD2

Length:Specifies the length of the Value field in octets.

Flags : Current defined bits are as follows. All other bits
SHOULD be cleared by sender and MUST be ignored by receiver.

Bit 0x1 - address is IPv6 when set and IPv4 when clear

Number of AFI/SAFI: indicates the number of AFI/SAFI pairs that
the router supports on the given peering address.

Reserved: sender SHOULD set to 0 and receiver MUST ignore.

Address: This 4 or 16 octect octet field indicates the IPv4 or IPv6
address which is used for establishing BGP sessions.

AFI/SAFI : one or more pairs of these values that indicate the
supported capabilities on the peering address.

Sub-TLVs : currently none defined

6.3. Local Prefix TLV

When the Peering Address to be used for the BGP TCP session
establishment is not the directly connected interface address (e.g.
when it is a using loopback address) then local prefix(es) that cover the its
peering address(es) MUST be signaled by a BGP router to its neighbor
as part of the router. Hello message. This allows the neighbor to learn
these local prefix(es) and to program routes for them over the
directly connected interfaces over which they are being signalled. signaled.
The Local Prefixes Prefix TLV is this an optional TLV and it MUST be used to
only signal prefixes that are locally configured on the router and
its router. The
procedure for resolving the peering address signaled via the Peering
Address TLV over the local prefixes signaled is described in
Section 7.3.

The Local Prefix TLV format is as shown below.

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Mask | ...
+-+-+-+-+-+-+-+-+

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Mask | ...
+-+-+-+-+-+-+-+-+

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-TLVs ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 4: 5: Local Prefixes Prefix TLV

Type: TBD3

Length:Specifies

Length: Specifies the length of the Value field in octets

No. of IPv4 Prefixes : specifies the number of IPv4 prefixes.
When value is 0, then it indicates no IPv4 Prefixes are present.

No. of IPv6 Prefixes : specifies the number of IPv6 prefixes.
When value is 0, then it indicates no IPv6 Prefixes are present.

IPv4 Prefix Address & Prefix Mask: Zero or more pairs of IPv4
prefix address and their mask.

IPv6 Prefix Address & Prefix Mask: Zero or more pairs of IPv6
prefix address and their mask.

Sub-TLVs : currently none defined

6.4. Link Attributes TLV

The Link Attributes TLV is a mandatory TLV that signals to the
neighbor the link attributes of the interface on the local router. A
single instance of this TLV MUST be present in the message. This TLV
enables a BGP router to learn all its neighbors IP addresses on the
specific link as well as its link identifiers. All the IPv4
addresses configured on the interface are signaled to the neighbor.
When the interface has IPv4 unnumbered address then that is not
included in this TLV. Only the IPv6 global addresses configured on
the interface are signaled to the neighbor. In case of an interface
running dual stack, both IPv4 and IPv6 addresses are signaled in a
single TLV irrespective of which one is used for UDP message
exchange.

More sub-TLVs may be defined in the future to exchange other link
attributes between BGP neighbors.

The Link Attributes TLV format is as shown below.

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Local Interface Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Mask | ...
+-+-+-+-+-+-+-+-+

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Local Global Interface Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Mask | ...
+-+-+-+-+-+-+-+-+

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-TLVs ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 5: 6: Link Attributes TLV

Type: TBD4

Length:Specifies

Length: Specifies the length of the Value field in octets

Local Interface ID : the local interface ID of the interface (e.g.
the MIB-2 ifIndex) ifIndex). This helps uniquely identify the link even
when there are multiple links between two neighbors using IPv4
unnumbered address or only having IPv6 link-local addresses.

Flags : Currently defined bits are as follows. Other bits SHOULD
be cleared by sender and MUST be ignored by receiver.

Bit 0x1 - indicates link is enabled for IPv4

Bit 0x2 - indicates link is enabled for IPv6

Reserved: SHOULD be set to 0 by sender and MUST be ignored by
receiver.

No. of IPv4 Addresses : specifies the number of IPv4 local addresses on
the interface. When value is 0, then it indicates no IPv4
Prefixes are present or the interface is IP unnumbered. IPv4 unnumbered if it is
enabled for IPv4

No. of IPv6 Addresses : specifies the number of IPv6 Global global
addresses on the interface. When value is 0, then it indicates no
IPv6 Global Prefixes are present or and the interface is only
configured with IPv6 link-local addresses if it is enabled for
IPv6.

IPv4 Address & Mask: Zero or more pairs of IPv4 address and their
mask.

IPv6 Address & Mask: Zero or more pairs of IPv6 address and their
mask.

Sub-TLVs : currently none defined

6.5. Neighbor TLV

The Neighbor TLV is used by a BGP router to indicate the peering
address and information about the neighbors that have been discovered
by the router its hello
adjacency status with its neighboring router(s) on the specific link and their status. link.
The neighbor is identified by its Peering Address which has been
accepted. The BGP TCP session establishment process begins when both the
hello adjacency is formed between the two neighbors accept each
other over at least one underlying inter-connecting
directly connected link between them. Multiple instances of this TLV
MAY be present in a Hello message - one for each peering address of
each of its neighbor on that particular interface.

The Neighbor TLV format is as shown below.

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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Status | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Neighbor Peering Address (4-octet or 16-octet) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-TLVs ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 6: 7: Neighbor TLV

Type: TBD5

Length:Specifies
Length: Specifies the length of the Value field in octets

Flags : Currently defined 0x1 bit is clear when Peering Address is
IPv4 and set when IPv6. Other bits SHOULD be clear by sender and
MUST be ignored by receiver.

Status : Indicates the status code of the peering for the
particular session over this link. The following codes are
currently defined

0 - Indicates 1-way detection of the peer

1 - Indicates rejection of the peer due to local policy reasons
(i.e. local router would not be initiating or accepting session
to this neighbor) neighbor).

2 - Indicates 2-way detection of the peering by both neighbors

3 - Indicates that the BGP TCP peering session has been
established between the neighbors and that this link would be utilized for
forwarding to the peer BGP nexthop

Reserved: SHOULD be set to 0 by sender and MUST be ignored by
receiver.

Neighbor Peering Address: This 4 or 16 octect octet field indicates the
IPv4 or IPv6 peering address of the neighbor for which peering
status is being reported.

Sub-TLVs : currently none defined

4. Hello Message Procedure

6.6. Cryptographic Authentication TLV

The Cryptographic Authentication TLV is an optional TLV that is used
to introduce an authentication mechanism for BGP peer receiving Hellos from another peer maintains Hello message by
securing against spoofing attacks. It also introduces a
cryptographic sequence number carried in the Hello
adjacency messages that can
be used to protect against replay attacks. Using this Cryptographic
Authentication TLV, one or more secret keys (with corresponding
Security Association (SA) IDs) are configured on each BGP router.
For each BGP Hello message, the key is used to generate and verify an
HMAC Hash that is stored in the Hellos. BGP Hello message. For the
cryptographic hash function, this document proposes to use SHA-1,
SHA-256, SHA-384, and SHA-512 defined in US NIST Secure Hash Standard
(SHS) [FIPS-180-4]. The peer maintains a hold
timer with HMAC authentication mode defined in
[RFC2104] is used. Of the above, implementations MUST include
support for at least HMAC-SHA-256, SHOULD include support for HMAC-
SHA-1, and MAY include support for HMAC-SHA-384 and HMAC-SHA-512.

Further details for ensuring the security of the BGP Hello adjacency, which it restarts whenever it
receives a UDP
messages are described in Section 9.

The Cryptographic Authentication TLV format is as shown below.

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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Security Association ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cryptographic Sequence Number (High-Order 32 Bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cryptographic Sequence Number (Low-Order 32 Bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Authentication Data (Variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 8: Cryptographic Authentication TLV

Type: TBD6

Length: Specifies the length of the Value field in octets

Security Association ID: The 32-bit field that maps to the
authentication algorithm and the secret key used to create the
message digest carried in Hello message payload.

Cryptographic Sequence Number: The 64-bit, strictly increasing
sequence number that matches is used to guard against replay attacks. The
64-bit sequence number MUST be incremented for every BGP Hello
message sent by the BGP router. Upon reception, the sequence
number MUST be greater than the sequence number in the last BGP
Hello adjacency. If message accepted from the hold timer
for sending BGP neighbor. Otherwise,
the BGP hello message is considered a Hello adjacency expires replayed packet and is
dropped. The Cryptographic Sequence Number is a single space per
BGP router.

Authentication Data: This field carries the peer discards digest computed by the
Cryptographic Authentication algorithm in use. The length of the
Authentication Data varies based on the cryptographic algorithm in
use, which is shown below:

HMAC-SHA1 20 bytes

HMAC-SHA-256 32 bytes

HMAC-SHA-384 48 bytes

HMAC-SHA-512 64 bytes

7. Neighbor Discovery Procedure

The neighbor discovery mechanism in BGP is implemented with the
introduction of an Interface state in BGP and an Adjacency Finite
State Machine (FSM). This section describes the states, FSM and
procedures involved.

7.1. Interface State

In order to perform neighbor discovery over its connected interfaces,
BGP needs to maintain state for all its connected interfaces over
which neighbor discovery is enabled. Once the neighbor discovery is
enabled and the link is UP, then BGP starts sending its Hello adjacency.

We recommend that
messages with the interval between TLVs listed in Section 6. The Neighbor TLV
described in Section 6.5 is, however, not included until after a
neighbor is learnt as part of the discovery process described in
further sections.

These Hello transmissions be messages are originated periodically at most an interval which
is less than or equal to one third of the Hello hold time. Adjacency Hold Time
specified in the message. The RECOMMENDED default value for the
Adjacency Hold Time is 45 seconds and this makes the hello message
interval to be 15 seconds. A Hello message SHOULD also be generated
in a triggered manner during the neighbor discovery process as a
change in the router's own or neighbor's Hello message is detected
which results in change in adjacency state or parameters.

When a router does not receive a Hello message from its neighbor for
a period equal to Adjacency Hold Time, then it MUST clean up its
adjacency to this neighbor. The relationship of the Adjacency Hold
Timer with the BGP Hold Timer at the TCP session with a peer has one level is described
further in Section 8.

Before the interface is shut or more the neighbor discovery is disabled on
it, the router SHOULD attempt to send out triggered Hello adjacencies. messages
with Adjacency Hold Time set to 0 and without including any Neighbor
TLV in it to indicate that the neighbor discovery is being turned OFF
on that router's interface. A router receiving a Hello message with
Adjacency Hold Time set to 0 MUST clean up its adjacency to the
originating router.

7.2. Adjacency State Machine

On a per interface basis, BGP session needs to maintain an adjacency state
for each neighbor that it discovers. The adjacency state is
maintained as a FSM and it has multiple Hello adjacencies the following states:

1. Init : This is the initial state that is setup when the router
detects a hello message from a new neighbor that it has not seen
previously. This is also the state to which the adjacency
transitions to when the router no longer sees itself in a
Neighbor TLV in the hello message from a pair neighbor.

2. 1-way : This is the state immediately after the Init when the
router sends its Hello message with inclusion of BGP peers the neighbor's
Peering Address in a Neighbor TLV with the status set to 1-way.

3. Reject : This is connected by multiple links the state (generally after Init) when the router
detects that have the same connection address
(e.g., multiple point-to-point links between neighbor cannot be accepted due to subnet
mismatch on the addresses on either end of the link or a pair
discrepancy in its Accepted ASN List TLV or due to some other
local policy. The router then sends its Hello message with
inclusion of routers). In this situation, neighbor's Peering Address in a Neighbor TLV
with the status set to rejection.

4. 2-way : This is the state after 1-way when the Hellos router detects its
own Peering Address in a BGP peer Neighbor TLV in the neighbor's hello
message with the status set to 1-way or 2-way. It then updates
the neighbor's status to 2-way in the Neighbor TLV in its own
Hello message and sends on it out. At this stage, both neighbors
have accepted each such link carry other. On transition to this state, the
router also installs peering route(s) in its own routing table
corresponding to the prefix(es) received from the neighbor in its
Local Prefix TLV so that reachability is established for the TCP
session formation. Next the TCP session formation can be
initialized via the BGP Peer FSM. If there is already a peering
route to the same address on another interfaces, then this new
interface is added as an ECMP path to it. If the BGP TCP session
is already initialized (established or connection in progress)
towards the same peering address then no further action is
required on this BGP Peer FSM.

5. Established : This is the state after 2-way when the router has
successfully setup its BGP TCP session with the neighbor's
Peering Address. In addition, It then updates the neighbor's status to eliminate
established in the need of
configuring static routes Neighbor TLV in its own Hello message and
sends it out.

Any downward transition from Established or enabling IGP 2-way state to a lower
state results in removal of that interface from the peering route(s)
for advertising that neighbor and the
loopback addresses, a certain type deletion of the route itself when the last
path is deleted. The deletion of routes towards the route may bring down the BGP
neighbor's
TCP session.

A BGP TCP session with an auto-discovered neighbor may have one or
more Hello adjacencies corresponding to it - one over each
interconnecting link between them.

7.3. Peering Route

BGP auto-discovered neighbors MAY setup their BGP TCP session over a
loopback addresses (i.e. carried in address instead of using the directly connected interface
address between them. When this is desired, the neighbors also
advertise the loopback address host prefix (or optionally a prefix
which covers more than a single loopback address when multiple are
used for different peering sessions) in their Local Prefixes
TLV) could Prefix TLV.
Before the TCP session can be dynamically created once established, the BGP reachability needs to
be setup in both direction by each neighbor has been
discovered. The administrative distance by programming their
local prefixes in their forwarding plane. These routes that are
programmed by BGP automatically using the prefixes advertised via the
Local Prefix TLV are called Peering Routes.

Peering Routes serve two purposes. First, they enable reachability
between the Peering Addresses (generally loopbacks) of such type the two
neighbors so that the BGP TCP session may come up between them.
Second, for the BGP routes learnt over the TCP session, where the
next-hop is the neighbor, they also provide the BGP NH resolution.

Unlike other BGP routes, these are not recursive routes as in they
point to the neighbor's interface and IP address. These routes that
are setup as part of the neighbor discovery procedure are hence
different from the regular iBGP and eBGP routes. These routes also
MUST have a better administrative distance as compared to the iBGP
and eBGP routes to ensure that they do not get displaced from the
forwarding by BGP routes learnt over the same session that was
established over these peering routes.

When there are multiple interconnecting links between two BGP
neighbors, a single BGP TCP session may be smaller than their equivalents setup between them over
which routes are then exchanged. However, in the forwarding, the
peering route will have multiple paths - one for each of these
interconnecting links. So the BGP routes learnt via over the session
actually end up getting resolved over the peering route and in turn
get the normal ECMP load balancing even with a single BGP
update messages. Otherwise, circular dependency problem would occur
once these loopback session.

8. Interactions with Base BGP Protocol

The BGP Finite State Machine (FSM) as specified in [RFC4271] is
unchanged and the BGP TCP session establishment, route updates and
processing continues to follow the BGP protocol specifications.

BGP peering addresses along with their respective ASNs have
traditionally been explicitly provisioned on both the BGP neighbors.
The difference that neighbor discovery mechanism brings about is in
elimination of this configuration as these parameters are advertised learnt via
the normal neighbor discovery procedure. Once BGP
update messages router learns its
neighbor's peering address and ASN and has accepted it for peering
based on its local policy configuration, then its initializes the BGP
Peer FSM for this neighbor in the Idle State - just as well. if this
neighbor was configured. From thereon, the BGP uses Peer FSM actions
follows.

The BGP Keepalives and Hold Timer for the regular receipt session over TCP apply
unchanged and they govern the operations of the BGP TCP session and
when it is brought down. While the BGP Keepalive works at the TCP
session level, the BGP Adjacency Hold Timer monitors the liveliness
on one or more underlying interconnecting link between the neighbors.
The reachability for the BGP TCP session may be over more than one
adjacency. The loss of BGP Hello messages on the UDP transport or
some link failure can result in the expiry of the Adjacency Hold
Timer. However, this does not result in bringing down of the BGP Hellos TCP
session for an auto-discovered BGP neighbor by default. An
implementation MAY provide an option to indicate bring a peer's
intent to keep BGP TCP session identified by down
when the Adjacency Hold Timer expiry brings down the last adjacency
between neighbors very similar to how BFD down brings the session
down.

When the Hello. A BGP peer
maintains a hold timer with each Hello Peer FSM for an auto-discovered neighbor (i.e. one that
is not provisioned explicitly), is in the Idle or Connect state then
the adjacency state for that it restarts neighbor needs to be monitored to check
if its BGP TCP session context needs to be cleaned-up. When there is
no adjacency state for an auto-discovered neighbor in 2-way or
Established state, then the BGP TCP session FSM state for such a
neighbor MUST be cleaned-up when it receives in Idle or Connect state. This is
similar to when the configuration for a Hello provisioned BGP neighbor is
deleted from a BGP router.

Since the BGP neighbor discovery mechanism runs over a UDP socket, it
is isolated from the core BGP protocol working which is TCP based.
Implementations SHOULD ensure that matches the adjacency. If hello processing does not
affect the timer
expires without receipt of base BGP operations and scalability. One option may be to
run the BGP neighbor discovery mechanism in a matching Hello separate thread from
the peer, rest of BGP
concludes processing. These implementation details, however,
are outside the scope of this document.

It is not generally expected that BGP sessions are explicitly
provisioned along with the peer no longer wishes neighbor discovery mechanism. However, in
such an event, the neighbor discovery mechanism MUST NOT affect or
result in any changes to keep provisioned BGP session neighbors and their
operations. Specifically, BGP peering to auto-discovered neighbors
MUST NOT be instantiated using the procedures described in this
document when the same BGP neighbor is already provisioned. The
configured BGP neighbor parameters take precedence and the auto-
discovered values and parameters are not used for such configured BGP
sessions.

Mechanisms like BFD monitoring and Fast External Failover that
link are
currently used for eBGP sessions may still continue to be used where
necessary and are not affected by the neighbor discovery mechanism.

9. Security Considerations

BGP routers accept TCP connection attempts to port 179 only from the
provisioned BGP neighbors or, in some implementations, those from
within a configured address range. With the BGP neighbor auto-
discovery mechanism, it is now possible for BGP to automatically
learn neighbors and initiate/receive TCP connections from them. This
introduces the need for specific considerations to be taken care of
to ensure security of the BGP protocol operations.

This document introduces UDP messages in BGP for the neighbor
discovery mechanism using the BGP Hello messages. For security
purposes, implementations MUST exchange the Hello messages only on
interfaces specifically enabled for neighbor discovery. Hello
messages MUST NOT be accepted on other than the 224.0.0.2 or FF02::2
addresses. Optionally, implementations MAY set TTL to 255 when
originating the Hello messages and receivers check specifically for
the TLV to be 254 and discard the packet when this is not the case.
This ensures that the peer has failed. Hello packets signaling happens between
directly connected BGP routers only.

The BGP peer neighbor discovery mechanism is expected to be run typically
in DCs and between physically connected routers that are trustworthy.
The Cryptographic Authentication TLV (as described in Section 6.6)
SHOULD be used in deployments where this assumption of
trustworthiness is not valid. This mechanism is similar to one
defined for LDP Hello messages that are also UDP based as specified
in [RFC7349]. An updated future version of this document will
describe similar procedures for BGP hello in more details.

Once the BGP hello messages and the neighbor discovery mechanism is
secured, then deletes the
Hello adjacency. security considerations for BGP protocol operations
apply for the auto-discovered neighbor sessions. Specifically, for
the BGP TCP sessions with the automatically discovered directly
connected neighbors, the TTL of the BGP TCP messages (dest port=179)
MUST be set to 255. Any received BGP TCP message with TTL being less
than 254 MUST be dropped according to [RFC5082].

10. Manageability Considerations

This section is structured as recommended in [RFC5706].

10.1. Operational Considerations

The route BGP neighbor discovery mechanism introduced by this document is
not applicable to general BGP deployments and is specifically meant
for DC networks where BGP is used as a hop-by-hop routing protocol as
described in [RFC7938]. The neighbor discovery mechanism hence
SHOULD NOT be enabled by default in BGP.

Implementations SHOULD provide configuration methods that allow
enablement of BGP neighbor discovery on specific local interfaces.
In a DC network, it is expected that the operator selects the
appropriate links on which to enable this e.g. on a Tier 2 node it is
enabled on all links towards the Tier 1 and Tier 3 nodes while on a
Tier 3 node, it may be only enabled on the links towards the Tier 2
node. The details of this enablement are outside the scope of this
document since it varies based on the DC design and may be
implementation specific.

Implementations SHOULD provide configuration methods that enable the
setup of BGP neighbor's loopback neighbor templates that enables operator to setup BGP
neighbor discovery parameters on the BGP router. Some of the aspects
to be considered in such a template are:

o Local address to be used for the BGP TCP session peering along
with the local ASN and the AFI/SAFI enabled for the auto-
discovered sessions

o BGP policies to be enabled for the auto-discovered sessions

o Optionally specify the list of ASNs with which auto-discovered
sessions should be brought up. This is to ensure that had been dynamically created when links
between different Tier nodes are not used by BGP when they get
connected wrongly due to accidents (e.g. say a Tier 3 node is
connected to a Tier 1 node).

o Authentication methods that BGP Hello
adjacency SHOULD are need to be deleted accordingly. When enabled in an
environment which is not secure

o Local interfaces over which the last Hello
adjacency specific template needs to be
applied for an BGP session is deleted, neighbor discovery

o Other parameters like the Adjacency Hold Timer value to be used or
other optional features

This mechanism does not impose any restrictions on the way ASNs or
addresses are assigned to the nodes. Various automatic provisioning,
auto-configuration or zero-touch-provisioning mechanisms may be used.

Implementations SHOULD report the state of the BGP peer terminates operations over
each link enabled for neighbor discovery including the status of all
adjacencies learnt over it. Implementations SHOULD also report the
operations of the auto-discovered BGP TCP peering sessions similar to
the provisioned BGP neighbors.

Implementations SHOULD support logging of events like discovery of an
adjacency using neighbor discovery including peering route updates
and events like triggering of BGP TCP session establishment for them.
Errors and alarms related to loss of adjacencies and closing tear down of BGP
TCP peering sessions SHOULD also be generated so they could be
monitored.

10.2. Management Considerations

This document introduces UDP based messaging in BGP protocol and
therefore the transport connection.

5. Contributors

Satya Mohanty
Cisco
Email: satyamoh@cisco.com

Shunwan Zhuang
Huawei
Email: zhuangshunwan@huawei.com

Chao Huang
Alibaba Inc
Email: jingtan.hc@alibaba-inc.com

Guixin Bao
Alibaba Inc
Email: guixin.bgx@alibaba-inc.com

Jinghui Liu
Ruijie Networks
Email: liujh@ruijie.com.cn

Zhichun Jiang
Tecent
Email: zcjiang@tencent.com

6. Acknowledgements

The authors would like necessary fault management mechanisms are required to thank Enke Chen
be implemented for his valuable comments the same. Implementations MUST discard
unsupported message types or version types other than 4 received over
a UDP session. Such messages MUST NOT affect the neighbor discovery
mechanism in operation using the Hello messages. Unknown TLVs
received via the Hello messages MUST be ignored and the rest of the
Hello message MUST be processed. Implementations SHOULD discard
Hello messages with malformed TLVs and suggestions on this document.

7. should be logged as an
error.

11. IANA Considerations

7.1.

This documents requests IANA for updates to the BGP Parameters
registry as described in this section.

11.1. BGP Hello Message

This document requests IANA to allocate a new UDP port (179 is the
preferred number ) and a BGP message type code for BGP Hello message.

Value TLV Name Reference
----- ------------------------------------ -------------
Service Name: BGP-HELLO
Transport Protocol(s): UDP
Assignee: IESG <iesg@ietf.org>
Contact: IETF Chair <chair@ietf.org>.
Description: BGP Hello Message.
Reference: This document -- draft-xu-idr-neighbor-autodiscovery.
Port Number: TBD1 (179 is the preferred 179 (preferred value) -- To be assigned by IANA.

7.2.

11.2. TLVs of BGP Hello Message

This document requests IANA to create a new registry "TLVs of BGP
Hello Message" with the following registration procedure:

Registry Name: TLVs of BGP Hello Message.

Value TLV Name Reference
------- ------------------------------------------ ---------------------------------- -------------
0 Reserved This document
1 Accepted ASN List This document
2 Peering Address This document
3 Local Prefixes Prefix This document
4 Link Attributes This document
5 Neighbor This document
6-65500
6 Cryptographic Authentication This document
7-65500 Unassigned
65501-65534 Experimental This document
65535 Reserved This document

8. Security Considerations

For security purposes, BGP speakers usually only accept TCP
connection attempts to port 179 from the specified BGP peers or those
within the configured address range. With the BGP neighbor auto-
discovery mechanism, it's configurable

12. Acknowledgements

The authors would like to enable or disable sending/
receiving BGP hello messages on the per-interface basis and BGP hello
messages are only exchanged between physically connected peers that
are trustworthy. Therefore, the BGP neighbor auto-discovery
mechanism doesn't introduce additional security risks associated with
BGP.

In addition, thank Enke Chen for the BGP sessions with the automatically discovered
peers via the BGP hello messages, the TTL of the TCP/BGP messages
(dest port=179) MUST be set to 255. Any received TCP/BGP message
with TTL being less than 254 MUST be dropped according to [RFC5082].

9. his valuable comments
and suggestions on this document.

13. Contributors
Satya Mohanty
Cisco
Email: satyamoh@cisco.com

Shunwan Zhuang
Huawei
Email: zhuangshunwan@huawei.com

Chao Huang
Alibaba Inc
Email: jingtan.hc@alibaba-inc.com

Guixin Bao
Alibaba Inc
Email: guixin.bgx@alibaba-inc.com

Jinghui Liu
Ruijie Networks
Email: liujh@ruijie.com.cn

Zhichun Jiang
Tencent
Email: zcjiang@tencent.com

Shaowen Ma
Juniper Networks
mashaowen@gmail.com

14. References

9.1.

14.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.

[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.

[RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
"LDP Specification", RFC 5036, DOI 10.17487/RFC5036,
October 2007, <https://www.rfc-editor.org/info/rfc5036>.

[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C.
Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007,
<https://www.rfc-editor.org/info/rfc5082>.

[RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
Explicit Replication (BIER)", RFC 8279,
DOI 10.17487/RFC8279, November 2017,
<https://www.rfc-editor.org/info/rfc8279>.

9.2.

14.2. Informative References

[I-D.keyupate-lsvr-bgp-spf]

[FIPS-180-4]
"Secure Hash Standard (SHS), FIPS PUB 180-4", March 2012.

[I-D.ietf-lsvr-bgp-spf]
Patel, K., Lindem, A., Zandi, S., and W. Henderickx,
"Shortest Path Routing Extensions for BGP Protocol",
draft-keyupate-lsvr-bgp-spf-00
draft-ietf-lsvr-bgp-spf-01 (work in progress), May 2018.

[I-D.ketant-idr-bgp-ls-bgp-only-fabric]
Talaulikar, K., Filsfils, C., ananthamurthy, k., and S.
Zandi, "BGP Link-State Extensions for BGP-only Fabric",
draft-ketant-idr-bgp-ls-bgp-only-fabric-00 (work in
progress), March 2018.

[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104,
DOI 10.17487/RFC2104, February 1997,
<https://www.rfc-editor.org/info/rfc2104>.

[RFC5706] Harrington, D., "Guidelines for Considering Operations and
Management of New Protocols and Protocol Extensions",
RFC 5706, DOI 10.17487/RFC5706, November 2009,
<https://www.rfc-editor.org/info/rfc5706>.

[RFC7349] Zheng, L., Chen, M., and M. Bhatia, "LDP Hello
Cryptographic Authentication", RFC 7349,
DOI 10.17487/RFC7349, August 2014,
<https://www.rfc-editor.org/info/rfc7349>.

[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>.

[RFC7938] Lapukhov, P., Premji, A., and J. Mitchell, Ed., "Use of
BGP for Routing in Large-Scale Data Centers", RFC 7938,
DOI 10.17487/RFC7938, August 2016,
<https://www.rfc-editor.org/info/rfc7938>.

Authors' Addresses

Xiaohu Xu
Alibaba Inc

Email: xiaohu.xxh@alibaba-inc.com

Ketan Talaulikar
Cisco Systems

Email: ketant@cisco.com

Kunyang Bi
Huawei

Email: bikunyang@huawei.com

Jeff Tantsura
Nuage Networks

Email: jefftant.ietf@gmail.com

Nikos Triantafillis
LinkedIn

Email: nikos@linkedin.com

Ketan Talaulikar
Cisco

Email: ketant@cisco.com ntriantafillis@gmail.com