wdiff draft-chakrabarti-nordmark-6man-efficient-nd-04.txt draft-chakrabarti-nordmark-6man-efficient-nd-05.txt

6man WG S. Chakrabarti
Internet-Draft Ericsson
Updates: 4861 (if approved) E. Nordmark
Intended status: Standards Track Arista Networks
Expires: April 25, August 18, 2014 P. Thubert
Cisco Systems
M. Wasserman
Painless Security
October 22, 2013

Wired and Wireless
February 14, 2014

IPv6 Neighbor Discovery Optimizations
draft-chakrabarti-nordmark-6man-efficient-nd-04 for Wired and Wireless Networks
draft-chakrabarti-nordmark-6man-efficient-nd-05

Abstract

IPv6 Neighbor Discovery (RFC 4861) protocol has been designed for
neighbor's address resolution, unreachability detection, address
autoconfiguration, router advertisement 4861 going back to RFC 1970) was defined
at a time when link-local multicast was as reliable and solicitation. With with the
progress of Internet adoption same
network cost (send a packet on various industries including home,
wireless, M2M a yellow-coax Ethernet) as unicast and cellular networks there is
where the hosts were assumed to be always on and connected.

Since 1996 we've seen a desire significant change with both an introduction
of wireless networks and battery operated devices, which poses
significant challenges for optimizing the legacy old assumptions. We are also seeing
datacenter networks where virtual machines are not always on and
connected, and scaling of multicast can be challenging.

This specification contains extensions to IPv6 Neighbor Discovery protocol. This document describes
a method
which remove most use of optimization by reducing multicast messages and
introducing an IPv6 address Registration mechanism. make sleeping hosts more
efficient. The optimization specification includes a default mixed mode where a
link can have an arbitrary mix of IPv6 hosts and/or routers - some
implementing legacy Neighbor Discovery protocol is useful for Wirless and low-
power IPv6 networks and some implementing the
optimizations in this specification. The optimizations provide
incremental benefits to hosts as well soon as Data Centers and Home Networks.
The solution is capable of handling existing legacy IPv6 nodes in the
network with local mobility. first updated routers
are deployed on a link.

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 http://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 April 25, August 18, 2014.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://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
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described in the Simplified BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Problem Areas 5
2. Goals and Requirements . . . . . . . . . . . . . . . . . . . . 6
2.1. Mixed-Mode Operations . . . . 4
1.2. Overview of the basic ND Optimization . . . . . . . . . . 5
2. Definition Of Terms . . . . 7
3. Changes to ND state management . . . . . . . . . . . . . . . . 7
4. Definition Of Terms . . . . 6
3. Assumptions for efficiency-aware Neighbor Discovery . . . . . 8
4. The set of Requirements for efficiency and optimization . . . 8
5. Basic Operations . . . . . . . . . 7
5. Protocol Overview . . . . . . . . . . . . . . . . 9
6. Applicability Statement . . . . . . 9
5.1. Proxying to handle Mixed mode . . . . . . . . . . . . . 10
7. . 11
6. New Neighbor Discovery Options and Messages . . . . . . . . . 10
7.1. 11
6.1. Router Advertisement flag for NEARs . . . . . . . . . . . 11
6.2. Address Registration Option (ARO) . . . . . . . . . . . . 12
6.3. Registrar Address Option (RAO) . . . 10
7.2. Refresh and De-registration . . . . . . . . . . . 14
7. Conceptual Data Structures . . . . 12
7.3. A New Router Advertisement Flag . . . . . . . . . . . . . 13
7.4. The Transaction Identification(TID) . 15
8. Host Behavior . . . . . . . . . . 13
8. Efficiency-aware Neighbor Discovery Messages . . . . . . . . . 14
9. Efficiency-aware Host Behavior . . . . . 16
8.1. Host and/or Interface Initialization . . . . . . . . . . . 15
10. The Efficiency Aware Default 16
8.2. Host Receiving Router (NEAR) Behavior Advertisements . . . . . . 16
10.1. Router Configuration Modes . . . . . 16
8.3. Timing out Registrar List entries . . . . . . . . . . . . 17
10.2. Movement Detection
8.4. Sending AROs . . . . . . . . . . . . . . . . . . . . 17
10.2.1. Registration ownership . . . 17
8.5. Receiving Neighbor Advertisements . . . . . . . . . . . . 18
11. NCE
8.6. Host Management in efficiency-aware Routers of the TID . . . . . . . . . . . . . . . . 18
11.1. Handling ND DOS Attack
8.7. Refreshing a Registration . . . . . . . . . . . . . . . . 18
8.8. De-registering . . 20
12. Mixed-Mode Operations . . . . . . . . . . . . . . . . . . . . 21
13. Bootstrapping 19
8.9. Refreshing RA information . . . . . . . . . . . . . . . . 19
8.10. Sleep and Wakeup . . . . . . . . 22
14. Handling Sleepy Nodes . . . . . . . . . . . . . 21
8.11. Receiving Redirects . . . . . . . 23
15. Duplicate Address Detection . . . . . . . . . . . . 21
8.12. Movement Detection . . . . . 23
16. Mobility Considerations . . . . . . . . . . . . . . . 21
9. Router Behavior . . . . 24
17. Other Considerations . . . . . . . . . . . . . . . . . . . 21
9.1. Router and/or Interface Initialization . . 24
17.1. Detecting Network Attachment(DNA) . . . . . . . . 21
9.2. Receiving Router Solicitations . . . . 24
17.2. Proxying . . . . . . . . . . 22
9.3. Periodic Multicast RA for Efficiency-Aware legacy hosts . . . . . . . . . . 22
9.4. Multicast RA when new information . 25
17.3. DHCPv6 Interaction . . . . . . . . . . . 22
9.5. Receiving ARO . . . . . . . . . 25
18. VRRP Interaction . . . . . . . . . . . . . 23
9.6. NCE Management in NEARs . . . . . . . . . . 26
19. RPL Implications . . . . . . . 23
9.7. Sending non-zero status in ARO . . . . . . . . . . . . . . 24
9.8. Timing out Registered NCEs . . 26
20. Updated Neighbor Discovery Constants . . . . . . . . . . . . . 26
21. Security Considerations . 24
9.9. Router Advertisement Consistency . . . . . . . . . . . . . 25
9.10. Sending Redirects . . . . . 27
22. IANA Considerations . . . . . . . . . . . . . . . 25
9.11. Providing Information to Routing Protocols . . . . . . 27
23. Changelog . . 25
9.12. Creating Legacy NCEs . . . . . . . . . . . . . . . . . . . 25
9.13. Proxy Address Resolution and DAD for Legacy Hosts . . . . 25
10. Handling ND DoS Attack . . . . . . . . . . . . . . . . 27
24. Acknowledgements . . . . 26
11. Bootstrapping . . . . . . . . . . . . . . . . . . . . . . . . 27
25. References
12. Interaction with other protocols . . . . . . . . . . . . . . . 27
12.1. Detecting Network Attachment (DNA) . . . . . . . . . . . . 28
25.1. Normative References
12.2. DHCPv6 Interaction . . . . . . . . . . . . . . . . . . . . 28
25.2. Informative References
12.3. Other use of Multicast . . . . . . . . . . . . . . . . . . 28
Appendix A. Usecase Analysis
12.4. VRRP Interaction . . . . . . . . . . . . . . . . . . 30
A.1. Data Center Routers on the link . . . 28

13. Updated Neighbor Discovery Constants . . . . . . . . . . 30
A.2. Edge Routers and Home Networks . . . 29
14. Security Considerations . . . . . . . . . . . . . . . . . . . 29
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
A.3. M2M Networks
16. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 30
A.4. Wi-fi Networks
17. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 31
A.5. 3GPP Networks
18. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 31
A.6. Industrial Networks
19. References . . . . . . . . . . . . . . . . . . . . 31
A.7. Set and forget offline network . . . . . . 32
19.1. Normative References . . . . . . . . 31 . . . . . . . . . . . 32
19.2. Informative References . . . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31 34

1. Introduction

Conceptually,

IPv6 multicast messages are supposed to avoid broadcast
messages, but in practice, the multicast operation Neighbor Discovery [RFC4861] was defined at the link level
is that of a broadcast nevertheless. This did not matter much at the time ND [ND] was originally designed, when an Ethernet network local
area networks had different properties than today. A common link was
more or less a single shared wire, but since then, large scale switch
fabrics, low power sleeping devices, mobile wireless/cellular devices
and virtual machines have changed
the landscape dramatically.

In a modern switch fabric, yellow-coax shared wire Ethernet, where a number of intermediate devices (such as
switches, routers link-layer multicast
and security middle boxes) host IPv6 State
Maintaining Entities (SMEs) holding information such as unicast worked the location
of an IPv6 address or its mapping with a MAC address. Such
intermediate devices include Wireless Controllers that terminate a
overlay tunnel same - send the packet on the wire and rapidly re-enable reachability for mobile
devices(L2/L3), Network edge devices performing subscriber access, the
interested receivers will pick it up. Thus the network devices cost
(ignoring any processing cost on the receivers that might not
completely filter out Ethernet multicast addresses that protect they did not
want) and the ownership reliability of an IPv6 address,
Overlay networks in data centers, Home Networks for IPv6 clients.

In general, there is sending a need for enhancing the IPv6 ND [ND] to make it
less chatty link-layer unicast and flexible to work with different types of networking
elements, physical
multicast was the same. Furthermore, the hosts at the time was
always on and virtual networks connected. Powering on and off the workstation/PC
hosts at the same time
maintaining was slow and disruptive process.

Under the IPv6 states above assumptions it was quite efficient to avoid duplicates or denial of
services.

1.1. Problem Areas

Specifically, maintain the following are
shared state of the issues with link such as the IPv6 deployment
in many wireless prefixes and high-density IPv6 subnets today:
o The their lifetimes
using periodic RA messages in IPv6 ND [ND], and NS/NA messages
require all IPv6 nodes in the link to be in listening mode even
when they are in idle cycle. multicast Router Advertisement messages. It requires energy for the sleepy
nodes which may otherwise be sleeping during the idle period.
Non-sleepy nodes was also spends more energy since they are in
continuous listening mode. With the explosion of Internet-of-
things and machine
efficient to machine communication, more and more devices
would be using IPv6 addresses in the near future.
o With WIFI, a use multicast message will consume the wireless link on
all Access Points around Neighbor Solicitations for address
resolution as a switched fabric and will be transmitted
at the lowest speed possible in order to ensure slight improvement over the maximum
reception by all wireless nodes. This means that broadcast use in an
environment where bandwidth is scarce, a single multicast packet
may consume the bandwidth ARP.
And finally, checking for hundreds of unicast packets. Sadly,
IPv6 ND is a major source of multicast messages in wireless
devices, since such messages are triggered each time a wireless
device changes its point of attachment.

o In a datacenter, where VM mobility and VM address reslution also
trigger storms of potential duplicate IPv6 ND multicast messages, which become address using
broadcast was efficient and natural.

Since then we've seen a major
hassle as the number of VM may scale to tremedous change with the tens wide-spread
deployment of thousands in a
large Data Center. At the IETF, WiFi and other wireless network technologies. WiFi is
a WG discusses such problems with
Address Resolution case in Massive Datacenters (ARMD).

The following paragraph elaborates the source of all the multicast
messages point in IPv6 ND.

Following power-on and initialization of that it provides the same network in IPv6 service
abstraction as Ethernet
networks, a node joins and is often bridged with Ethernets, meaning
that the solicited-node multicast address Neighbor Discovery software on hosts and routers might be
unaware that WiFi is being used. Yet the
interface performance and then performs duplicate address detection (DAD) reliability
of multicast is quite different than for the
acquired link-local address by sending unicast on WiFi (see for
instance [I-D.vyncke-6man-mcast-not-efficient]). Similarly 3GPP and
M2M networks and devices will benefit from a solicited-node multicast
message standard specification
for optimized Neighbor discovery. Even wired networks have evolved
substantially with modern switch fabrics using explicit packet
replication logic to the link. After that it sends handle multicast router
solicitation (RS) messages to the all-router address packets.

The hosts and usage patterns has undergone radical changes as well.
Hosts go to solicit
router advertisements. Once the host receives a valid router
advertisement (RA) with the "A" flag, it autoconfigures the IPv6
address with the advertised prefix sleep when not in the router advertisement (RA).
Besides this, the IPv6 routers usually send router advertisements
periodically use to save on the network. RAs are sent battery power [RFC6574]
or to the all-node multicast
address. The minimum RA interval range can be 3sec to 600sec
depending on applications. Nodes send Neighbor Solicitation (NS) more energy efficient even with mains power. The
expectation is that waking up doesn't take much time and
Neighbor Advertisement (NA) messages to resolve power
otherwise the IPv6 address benefits of
the destination on the link. These NS/NA messages sleeping are also often
multicast messages and it is assumed that greatly reduced. Initially
sleeping hosts were esoteric sensor nodes, but this sleeping hosts
have become mainstream in smartphones.

Some of the node is above trends were observed early (e.g., Ohta-san
commented on the same
link and relies Neighbor Discovery being inefficient on WiFi a long time
back) but the fact that issues were not broadly understood. The issues were
raised in the destination node is always
powered and generally available.

1.2. Overview of 6LowPAN context where the basic ND Optimization

In desire was to run IPv6 over
low-power radio networks and battery operated devices. That lead to
defining a nutshell, the following basic set of optimizations [RFC6775] for that specific category
of links. However, the trends are made not limited to such specific link
types.

This document applies what we have learned from the
original IPv6 6LowPAN to all link
types, by reusing existing support from base Neighbor Discovery protocol [ND]:
o Adds Node Registration at the default subnet-router
o Introduces a EUI-64 identifier for identification during
initiation
o Does not require unsolicited periodic Router Advertisements
o No multicast messages required for address resolution (such
as Redirect) and DAD for
non-link-local IP addresses
o Introduces a short-lived temporary NCE entry for unregistered
nodes that turns into a regular NCE upon registration
o Supports mixed mode operations where legacy IPv6 nodes from 6LowPAN (Address Registration Option) and
enahnced optimized routers can co-exist during
adding pieces to import the transition
period.

EUI-64 identifiers robustness with redundant routers.

The optimizations are recommended done in a way to provide incremental benefits.
As soon as unique Interface Identifiers,
however if the network there is isolated from the Internet, uniqueness of
the identifiers may be obtained by other mechanisms such as at least one router on a random
number generator with lowest collision rate. Although, the ND
optimization [6LOWPAN-ND] applies to 6LoWPAN [LOWPAN] networks, link which supports
these optimizations, then the
concept is mostly applicable to power-aware IPv6 networks.
Therefore, this document generalizes updated hosts on the address registration link can sleep
better.

2. Goals and
multicast reduction in [6LOWPAN-ND] Requirements

The goal is to all IPv6 links.

Thus optimizing the regular IPv6 remove as much Neighbor Discovery [ND] to minimize
total number of related signaling messages without losing generality
of Neighbor Discovery, autoconfiguration and reliable host-router
communication, are desirable in any modern IPv6 networks such multicast traffic on
the link as
Home, Enterprise networks, Data Centers possible, and Operator's Cellular/
Wireless networks. handle Duplicate Address Detection (DAD)
without requiring the hosts to always be awake.

The optimization will be highly effective for links and nodes which
do not support multicast and as well as for a multicast network
without MLD snooping switches. Moreover, in the MLD-snooping
networks the MLD switches will deal with less number of multicasts.

The goal problems that will be addresses are:

Remove the use of this document is multicast for DAD and Address Resolution (no
multicast NS messages), and remove periodic multicast RAs. Some
multicast RS and RA are needed to provide an efficient Neighbor
Discovery Protocol in classic IPv6 subnets in wireless/wired links.
In the process, handle the node registration method is also deemed to be
useful for preventing Neighbor Discovery denial arrival of service ( ND DOS)
attacks.

The proposed changes can be used in two different ways. In one case
all the new hosts
and routers on a link implement the new mechanisms,
which gives link since they need to bootstrap to find each
other.

Remove the maximum benefits. In another case need for hosts to always be awake to defend their
addresses by responding to any DAD probes.

Ensure that the link has a
mixture protocol is robust against single points of new hosts and/or routers
failure and uses soft state which is automatically rebuilt after a
state loss.

A router which does not support legacy [RFC4861] hosts and
routers, operating in will always maintain
a mixed-mode providing some complete set of Neighbor Cache Entries (NCEs) for all hosts on
the benefits.

In link. Hence there is no need for it to send Neighbor
Solicitations. Thus it can avoid the following sections problem specified in
[RFC6583].

The optimized solution SHOULD be independent of the document describes addresses
allocation mechanism. In addition to supporting SLAAC [RFC4862]
and DHCPv6 [RFC3315] it SHOULD also work with hosts with 'Privacy
Extensions for Stateless Address Autoconfiguration in
IPv6'[RFC4941] and with stable IPv6 private addresses
[I-D.ietf-6man-stable-privacy-addresses].

2.1. Mixed-Mode Operations

Mixed-Mode operation is the basic operations
of registration methods, optimization protocol behavior when the IPv6 subnet is
composed of Neighbor Discovery messages,
interoperability with legacy IPv6 implementations Neighbor Discovery compliant nodes and provides a
section
efficiency-aware IPv6 nodes implementing this specification.

The mixed-mode model SHOULD support arbitrary combinations of legacy
[RFC4861] hosts and/or routers with new hosts and/or routers on use-case scenarios where it can a
link. The introduction of one new router SHOULD provide improved
services to a new host, allowing the new host to avoid multicast and
not requring the host to be typically applicable. awake to defend its IPv6 addresses using
DAD.

This document also describes assumes that an optional feature for enabling node
mobility implementation will have configuration
knobs to determine whether it is running in the LLN network using backbone routers(BBR) legacy IPv6 ND [RFC4861]
or multiple
default subnet routers. This optional feature generates Efficiency Aware only mode (no-legacy mode) or both (Mixed mode).

3. Changes to ND state management

These optimizations change some fundamental aspects of Neighbor
Discovery. Firstly, it moves the distributed address resolution
state (each node responding to a sequence
ID by multicast NS for its own addresses)
to a set of routers which maintain a list of Address Registrations
for the host in hosts. Secondly, the registration message for deploying some routing
protocols (example: RPL [RFC6550]) with reliability information distributed in Router
Advertisements changes from being periodically flooded by the LLN.

2. routers
to explicit requests from the hosts for refreshed information using
Router Solicitations.

4. Definition Of Terms

The key words keywords "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].

multi-level Subnets:
A wireless link determined by one IPv6 off-link prefix in a
network where in order to reach a destination with same prefix a
packet may have to travel through one or more 'intermediate'
routers which relay the packet to the next 'intermediate' router
or the host in its own.
Border Router(BR):
A border router is typically located at the junction of Internet
and Home Network. An IPv6 router with one interface connected to
an IPv6 subnet and other interface connecting to a non-classic
IPv6 interface such as 6LoWPAN interface. A Border router is
usually the gateway between the IPv6 network and Internet.
Backbone:
This is an IPv6 transit link that interconnects 2 or more Low
Power Lossy Networks (LLNs). It is expected to be deployed as a
high speed backbone in order to federate a potentially large set
of LLN nodes. Also referred to as a LLN backbone or Backbone
network in this document.
Backbone Router:
An IPv6 router that federates the LLN using a transit link as a
backbone. A BBR acts as a 6LoWPAN Border Router (6LBR) and an
Efficiency Aware Default Router (NEAR).
Efficiency-Aware Network:
An Efficiency-Aware network is composed of network elements that
are sensitive to energy usage or number of signaling messages in
the network. An efficiency-aware network may also contain links
that do not support multicast or it does not have MLD snooping
capabilities and yet the network likes to communicate most
efficiently with minimum number of signaling messages. Data
center networks with virtual machines, cellular IPv6 networks, any
IPv6 networks with energy-sensitive nodes are examples of
Efficiency-Aware networks.

IPv6 ND-efficiency-aware Router(NEAR):
The default Router of the single hop IPv6 subnet. This (NEAR):
A router that implements the optimizations specified in this
document. This router should be able to handle both legacy IPv6
nodes and nodes that sends registration request.

Efficiency-Aware Host(EAH):
A host in a IPv6 network is considered a IPv6 node without routing
and forwarding capability. Host (EAH):
The EAH is the host which implements the host functionality for
optimized Neighbor Discovery mentioned in this document. At least
initially implementations are likely to have a fallback to legacy
Neighbor Discovery when no NEAR is on the link.

Legacy IPv6 Host:
A IPv6 host that implements [RFC4861] without the extensions in a
this dociument.

Legacy IPv6 network is considered a Router:
A IPv6 node router that implements [RFC4861] without routing the extensions in
this dociument.

Mixed mode
A NEAR supports both legacy hosts and forwarding capability EAH, with a configuration
knob to disable the support for legacy hosts. Some routers on the
link can be legacy and implements RFC 4861 host functions.

Legacy some can be NEAR.

No-legacy mode
A mode configured on a NEAR to not support any legacy [RFC4861]
hosts or routers. Opposite of mixed mode.

IPv6 Router:
An Address Registrar
Normally the default router(s) on the link will act as IPv6 Router which implements RFC 4861 Neighbor Discovery
protocols.
Address Registrars tracking all the EAHs. But in some cases it is
more efficient to use a different set of routers as Address
Registrars. The hosts are informed of the address registrars
using router advertisement messages, and register with the
available registrars.

EUI-64:
It is the IEEE defined 64-bit extended unique identifier formed by
concatenation of 24-bit or 36-bit company id value by IEEE
Registration Authority and the extension identifier within that
company-id assignment. The extension identifiers are 40-bit (for
24-bit company-id) or 28-bit (for the 36-bit company-id)
respectively.
LLN: The protocol supports EUI-64 for compatibility with
[RFC6775].

DUID
It is a low power DHCP Unique ID of a device [RFC3315]. The DUID is assumed
to be stable in a given IPv6 subnet. A device which does not have
an EUI-64 can form and lossy network where nodes are typically
constrained use a DUID in system resources its address registrations.

NCE
Neighbor Cache Entry. It is a conceptual data structure
introduced in section 5.1 of [RFC4861] and energy, further elaborated in
[RFC6775].

TID
The Transaction ID is a device generated sequence number used for instance battery
powered nodes. Alternately LLN could be
registration. This number is used to allow a network of line-powered
nodes host to have
concurrent registrations with radio links different routers, while also being
able to robustly replace a registration with lossy characteristics. Wifi, ZigBee,
Celular networks are examples of such a network.
Extended LLN:
This is the aggregation of multiple LLNs as defined in [RFC4919]
interconnected by new one. It
facilitates interoperation with protocols like RPL [RFC6550] which
use a Backbone Link via Backbone Routers and forming TID internally to handle host movement.

5. Protocol Overview

In a single nutshell, the following basic optimizations are made from the
original IPv6 link.

3. Assumptions for efficiency-aware Neighbor Discovery protocol [RFC4861]:

o The efficiency-aware nodes in the network carry unique interface
ID in the network in order to form Adds Node Registration with the auto-configured IPv6
address uniquely. An EUI-64 interface ID required for global
communication.
o All nodes are single IPv6-hop away from their default router in
the subnet. router(s).

o /64-bit IPv6 prefix is used Address Resolution and DAD uses the registered addresses instead
of multicast Neighbor Solicitation messages for Stateless Auto-address
configuration (SLAAC). The non-link-local
IPv6 Prefix may be distributed with addresses.

o Does not require unsolicited periodic Router Advertisement (RA) from the default router to all Advertisements.

o Supports mixed-mode operation where legacy IPv6 hosts and routers
and NEARs and EAHs can co-exist on the nodes
in that same link.
o The efficiency-aware node MAY maintain This support
can be configured off.

When a sequence counter host powers on it behaves conforms to legacy ND [RFC4861] by
multicasting up to MAX_RTR_SOLICITATIONS Router Solicitations and
receives Router Advertisements. The additional information in
permanent memory according the
Router Advertisements by the NEARs is used by the EAH to section 7 build a list
of RFC 6550.

4. The set IPv6 Address Registrars. As the host is forming its IPv6
addresses (using any of Requirements for efficiency and optimization

o Node Registration: Node initiated Registration the many statless and stateful IPv6 address
allocation is done in order to avoid periodic mechanism) then, instead of using a multicast Router
Advertisement messages and often DAD message,
it unicasts an Neighbor Solicitation with the new Address resolution can
Registration Option (ARO) to the Registrars. Assuming an IPv6
addresses are not duplicate the EAH receives a Neighbor Advertisement
with the ARO option from the NEARs. The EAH refreshes the registered
addresses before they expire, thereby removing the need for the EAH
to be skipped awake to defend its addresses using DAD as all specified in
[RFC4862] as the NEARs will handle DAD.

The routers on the link advertise the prefixes without setting the L
flag. Thus only the IPv6 link-local addresses are considered on-
link. Thus the hosts will send packets go via to a default router, and the
default routers maintain all the registrations. Hence a router which now
knows about will
know the link-layer addresses of all the registered nodes. Node Registration hosts. This
enables
reduction of all-node the router to forward the packet (without needing any Address
Resolution with the multicast Neighbor Solicitation), and solicited-node also to
send a Redirect to the originating host informing the host of the
link-layer address.

Instead of relying on periodic multicast messages in RAs to refresh the
subnet.

o Address allocation lifetimes
of registered nodes [ND] are performed using
IPv6 Autoconfiguration [AUTOCONF].
o Host initiated Registration and Refresh prefixes etc, the model in efficiency-aware networks is done for the
hosts to ask for refreshed information by sending unicasting a Router
Solicitation and then before the information expires.

The periodic multicast RAs are also used to provide new information
such as additional prefixes, radical reduction in the preferred
and/or valid lifetime for a Neighbor Solicitation Message prefix. A host does not know to ask for
such information. Thus a router that wishes to quickly disseminate
such change can resort to a few multicast RAs, or wait for the hosts
to request a refresh using a Router Solicitation.

The routers can crash and loose all their state, including the
Address Registration Option (described below).
o Registrations. On router initialization the router will
multicast a few initial RAs. The node registration may replace protocol has a Router Epoch
mechanism which is used by the requirement hosts to detect that the router has
lost state. In that case the hosts will immediately re-register
allowing the router to quickly rebuild its Address Registration
state.

Normally it is sufficient for the hosts to register with all the
default routers on the link. However, in some cases such as
simplistic VRRP deployment the hosts should register with all the
VRRP routers even though they only know of doing
Duplicate one virtual router IPv6
address. And in other cases it would be more efficient to only
register with one router even though there are multiple default
routers. The RAs can contain a Registrar Address Detection.
o Option to
explicitly tell the hosts where to register.

Sleepy hosts are supported by this Neighbor Discovery procedures as
they are not woken up periodically by Router Advertisement multicast
messages or Neighbor Solicitation multicast messages. Sleepy nodes
may wake up in its own schedule and send unicast registration refresh
messages when needed.
o Since this document requires formation of an IPv6 address with an
unique 64-bit Interface ID(EUI-64) is required for global IPv6
addresses, if before the network registration lifetime expiration. The
recommended procedure on wakeup is an isolated one and uses ULA [ULA] as
its IPv6 address then the deployment should make sure that each
MAC address in that network has unique address and can provide to unicast a
unique 64-bit ID for each node in the network.
o A /64-bit Prefix is required Neighbor Solicitation
to form the IPv6 address.
o MTU requirement is same as IPv6 network.

5. Basic Operations

In the efficient-nd IPv6 Network, the NEAR routers are the default
routers for the efficiency-aware hosts (EAH). During the startup or
joining the network router(s), which serves as DNA check [RFC6059] that
the host does not wait for is on the Router
Advertisements as same link, performs NUD against the NEAR routers do not perform periodic multicast
RA as per RFC 4861. Instead, router, and
includes the EAH sends a multicast RS Address Registration Option to find
out a NEAR router in the network. The RS message is refresh the same as in
RFC 4861. The advertising registration.

5.1. Proxying to handle Mixed mode

When there are one or more legacy routers in on the link responds then the
recommendation is to configure those to advertise the RS
message with RA prefixes with Prefix Information Option and any other options
configured
L=0 just as the NEARs. That results in the network. If EAH hosts will look for a RA from a
NEAR (E-flag) and choose sending all packets
to a NEAR as its default router and
consequently sends unless/until they receive a unicast Neighbor Solicitation Message with ARO
option in order to register itself with Redirect. However,
the default router. The EAH
does not legacy routers do Duplicate Address Detection or NS Resolution of
addresses. NEAR maintains a binding of registered nodes and
registration life-time information along with not maintain the neighbor Cache
information. The NEAR is responsible for forwarding address registrations. Thus
even though all the messages
from its EAH including on-link messages from one EAH hosts send the packets to another. For
details of protocol operations please see the sections below.

When a IPv6 network consists of both legacy hosts and EAH, and if routers, the
NEAR is configured for 'mixed mode' operation, it should be able legacy
routers might in turn need to
handle perform Address Registration Option(ARO) requests and send periodic
RA. Thus it should be able to serve both efficiency-aware Resolution by
multicasting a Neighbor Solicitation per [RFC4861]. In addition,
legacy hosts and legacy hosts. Similarly, routers will perform DAD as specified in
[RFC4862] that is, by sending a legacy host compatible EAH falls back to
RFC 4861 host behavior if multicast NS and waiting for a NEAR is NS or
NA which indicates a conflict. A EAH will not present in the link. See receive and respond to
such messages.

If the
section on 'Mixed Mode Operations' for details below.

6. Applicability Statement

This document aims NEARs have been configured to guide implementers operate in mixed-mode, then they
will respond to choose an appropriate
IPv6 neighbor discovery multicast NS messages from legacy nodes for both DAD
and Address configuration procedures suitable
for any efficient IPv6 network. These optimizations are equally
useful for Resolution. They will respond with the energy-sensitive, non-multicast links and for
classical IPv6 networks i.e. home networks, Data-Center IPv6 overlay
networks where saving Neighbor Discovery messages Target Link Layer
Address being that of the registered host, so that subsequent
communication will reduce cost
and increase bandwidth availability.

The not go via the routers. (Implementations of
"Neighbor Discovery Proxies (ND Proxy)" [RFC4389] might proxy using
their own MAC address registration mechanism and associated extension to as TLLA, but that is outside of the scope of
this document.)

6. New Neighbor Discovery protocol allow Options and Messages

This specification introduces a low-power host to move between new flag in the LLN RAs, reuses and
extends the classic IPv6 networks as well as movement ARO option from one
Border [RFC6775] and introduces a new Registrar
Address option.

6.1. Router registration area to another while staying within the
same IPv6 subnet.

Note that the specification allows 'Mixed-mode' operation in the
efficiency-aware nodes Advertisement flag for backward compatibility and transitioning NEARs

A new Router Advertisement flag is needed in order to distinguish a complete efficiency-aware network of hosts and routers. Though
the efficiency-aware only nodes
router advertisement sent by a NEAR, which will minimize the ND signaling and
DOS attacks in trigger an EAH to
register with the LAN.

Applicability of this solution NEAR. This flag is limited to ignored by the legacy IPv6 nodes
and subnets and it optimizes the generic IPv6 signaling activities at
network layer. However, further optimization at the application
layers are possible for increased efficiency based on particular use-
cases and applications.

7. New Neighbor Discovery Options and Messages

This section will discuss the registration and de-registration
procedure of
hosts.

The current flags field in RA is reproduced here with the hosts added 'E'
bit.

0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|M|O|H|Prf|P|E|R|
+-+-+-+-+-+-+-+-+

The 'E' bit is set to 1 in a RA sent by a NEAR. In all other cases
the network.

7.1. E bit MUST be 0.

6.2. Address Registration Option (ARO)

The Address Registration Option(ARO) is useful Option was defined in [RFC6775] for avoiding Duplicate
Address Detection messages since the
purposes of 6LowPAN and this document extends it requires in a backwards
compatible way by using some of the reserved fields. The extensions
are to handle different unique identifiers than EUI-64 ID for
registration. (this document
specifies how to use DHCP Unique Identifiers with the ability do use
other identifier namespaces in the future) and a Transaction Id.

The address registration Unique Interface Identifier is used for maintaining
reachability of by the node or NEARs to distinguish
between a refresh of an existing registration and a different host
trying to register an IPv6 address which is already registered by
some other host. Thus the router. This option requirement is
almost that the same ARO as in [6LOWPAN-ND]. A Transaction ID field unique id is
unique per link, but due to the potential for host mobility across
links and subnets it should be globally unique. Both an EUI-64 and a
corresponding bit have been introduced in order
DUID satisfies that requirement.

The TID is used by the NEARs to detect duplicate
address handle the case when due to packet
loss one NEAR might have a old registration and local mobility of another NEAR has a node.
newer registration. The routers keep track of host IP addresses that are directly
reachable and their corresponding link-layer addresses. This TID allows them to determine which is
useful for lossy and lowpower networks(LLN) and as well as wired IPv6
networks. more
recent. The TID also facilitates the interaction with RPL.

An Address Registration Option (ARO) can be included in unicast Neighbor
Solicitation (NS) messages sent by hosts. Thus it can be included in
the unicast NS messages that a host sends as part of Neighbor
Unreachability Detection to determine that it can still reach a the
default router. router(s). The ARO is used by the receiving router to
reliably maintain its Neighbor Cache. The same option is included in
corresponding Neighbor Advertisement (NA) messages with a Status
field indicating the success or failure of the registration. This
option is always host initiated.

The ARO is required for reliability and power saving. The lifetime
field provides flexibility to the host to register an address which
should be usable (the reachability information may be propagated to
the routing protocols) during its intended sleep schedule of nodes
that switches to frequent sleep mode.

The sender of the NS also includes the EUI-64 of the interface it is
registering an address from. This is used as a unique ID for the
detection of duplicate addresses. It is used to tell the difference
between the same node re-registering its address and a different node
(with a different EUI-64) registering an address that is already in
use by someone else. The EUI-64 is also used to deliver an NA
carrying an error Status code to the EUI-64 based link-local IPv6
address of the host.

When the ARO is used sent by hosts and a host then, for links which have link-layer
addresses, a SLLA option MUST be included [
except for the point-to-point links (example: IP-in-IP tunnel)] and
the target included. The address for to-be that is
registered node MUST be is the IPv6 source address of the Neighbor Solicitation
message.

Note that Typically a node should be able host would have several addresses to register register,
with each one being registered using a default router
with multiple IPv6 addresses (including privacy addresses). separate NS containing an ARO.
(This approach facilitates applying SeND [RFC3971].)
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 = 2 | Status | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reservd Res | IDS |T| TID | Registration Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ EUI-64 or equivalent +
~ Unique Interface Identifier (variable length) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Fields:

Type: 33 ( See [6LOWPAN-ND] ) [RFC6775]

Length: 8-bit unsigned integer. The length of the option
(including the type and lenth fields) in units of 8
bytes. Always 2.
Status: The value 0 is invalid.

Status: 8-bit unsigned integer. Indicates the status of a
registration in the NA response. MUST be set to 0 in
NS messages. See below. [RFC6775].

Reserved: 8 bits. This field is unused. It MUST be initialized
to zero by the sender and MUST be ignored by the
receiver.

Res: 4 bits. This field is unused. It MUST be initialized
to zero by the sender and MUST be ignored by the
receiver.

IDS: 3 bits. Identifier name Space. Indicates whether the
Unique Interface Identifier is a DUID or or a IEEE
assigned EUI-64 with room to define additional name
spaces.

T bit: One bit flag. Set if the TID octet is valid.

TID: 8-bit integer. It is a transaction id maintained by
the host and incremented with each registration. it is
recommended that the node maintains a persistent
storage for TID. TID is used as a sequence counter by the NEARs to
detect determine the most
recent registration request from a
host and its mobility within the same subnet across
multiple default Border Routers. Its operation
follows section 7 of RPL [RFC6550] for sequence
counters. registration.

Registration Lifetime: 16-bit unsigned integer. The amount of time
in a unit of 60 seconds that the router should retain
the Neighbor Cache entry for the sender of the NS that
includes this option.
EUI-64: 64 bits. This field is used A value of zero means to uniquely identify remove
the
interface registration.

Unique Interface Identifier: Variable length in multiples of 8
bytes. If the registered address by including the
EUI-64 identifier assigned IDS=000, then it is an 8 byte (64 bit)
unmodified EUI-64. If IDS=0011 then it is a variable
length DUID. A DUID MUST be zero padded to a multiple
of 8 bytes.

When a node includes ARO option in a Neighbor Solicitation it unmodified.
T bit: One bit flag. Set MUST,
on links that have link-layer addresses, also include a SLLA option.
That option is needed so that the registrar can record the link-layer
address on success and send back an error if the TID octet address is present for
processing. a
duplicate.

6.3. Registrar Address Option (RAO)

Normally the Registrars are the Default Routers. However, there are
cases (like some approaches to handle VRRP, or coordinated separate
routers) where there is a need to have different (and either more or
less) Registrars than Default Routers. Furthermore, to robustly
handle NEAR state state loss this option carries a Router Epoch which
triggers the EAHs to re-register on a router epoch change. The Status values used in Neighbor Advertisements are:

+--------+--------------------------------------------+
| Status | Description |
+--------+--------------------------------------------+
| RAO
contains the information for both of those.

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Success Type | Length | 1 Num Addresses | Duplicate Address
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | 2 Router Epoch | Neighbor Cache Full
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | 3
~ IPv6 registratr addresses ~
| Registration Ownership Response (Num Addresses) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 4-255 | Allocated using Standards Action [RFC2434]
~ Reserved for future extensions ~
|
+--------+--------------------------------------------+

Table 1

7.2. Refresh |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Fields:

Type: TBD (IANA)

Length: 8-bit unsigned integer. The length of the option
(including the type and De-registration

A host SHOULD send a Registration message lenth fields) in order to renew its
registration before its registration lifetime expires in order units of 8
bytes. The value 0 is invalid.

Num Addresses 16-bit unsigned integer. Set to
continue its connectivity with zero if there are no
addresses i.e., when the network. If anytime, option is used to only carry
the node
decides that it does router epoch. NumAdressses*2 + 1 must not need exceed
the default router's service anymore,
it Length.

Reserved 16-bit unused field. It MUST send a de-registration message - i,e, a registration message
with lifetime being set be initialized to zero. A mobile host SHOULD first de-
register with zero
by the default router before it moves away from sender and MUST be ignored by the
subnet.

7.3. A New receiver.

Router Advertisement Flag epoch 16-bit integer. A new Router Advertisement flag [RF] is needed in order to
distinguish a router advertisement from MUST pick a efficiency-aware default
router or new epoch after
a legacy IPv6 router. This flag is ignored state loss, either by keeping the legacy
IPv6 hosts. EAH hosts use this flag epoch in order to discover a NEAR
router if it receives multiple RA from both legacy stable
storage and NEAR routers.

0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|M|O|H|Prf|P|E|R|
+-+-+-+-+-+-+-+-+ incrementing it, or picking a good random
number.

IPv6 registrar addresses Zero or more IPv6 addresses, typically of
link-local scope.

The 'E' bit above receiver MUST be 1 when a silently ignore any data after the IPv6 router implements and
configures registrar
addresses field (such data is present when the efficiency-aware Length is greater than
NumAdressses*2 + 1).

The Registrar Addresses have their lifetime be the Default Router behavior for Neighbor
Discovery as per this document. All other cases
Lifetime even when they come from the E bit MUST be 0.

The legacy IPv6 hosts will ignore RAO (thus there is no explicit
lifetime in the E bit RAO).

7. Conceptual Data Structures

In addition to the Conceptual Data structures in RA advertisement. All [RFC4861] a EAH MUST look for E bit in RA in order
needs to determine maintain the efficiency-
aware support in new Registrar List for each interface. The
Registrar List contains the default set of IP addresses to which the host
needs to send Address Registrations. Each IP address has a Router
Epoch (used to determine when a router in might have lost state). Also,
the link.

7.4. The Transaction Identification(TID)

The TID field is used together host MAY use this data structure to track when it needs to
refresh its registrations with age the registrar.

The use of a registration explicit registrations with lifetimes plus the desire to
not multicast Neighbor Solicitation messages for
arbitration between hosts imply that we
manage the Neighbor Cache entries slightly differently than in
[RFC4861]. This results in two routers (default or backbone) to ensure
freshness and ownership different types of NCEs and the registration of a given target
address. Same value of TID indicates types
specify how those entries can be removed:

Legacy: Entries that both states of
registration are valid. In case of a mismatch between comparable
TIDs, subject to the most recent TID wins. The TID definition used normal rules in section
6.4.1 of RFC 6550 for DAOSequence number would be applicable for here
[RFC4861] that allow for TID in ARO message.

It is 8 bit field. TID garbage collection
when low on memory. Legacy entries are created
only when there is generated by the host at no duplicate NCE. The
legacy entries are converted to the time registered
entries upon successful processing of a new
registraton request.

This document assumes ARO.
Legacy type can be considered as union of
garbage-collectible and Tentative Type NCEs
described in [RFC6775].

Registered: Entries that an implementation will have configuration
knobs to determine whether it is running in classical IPv6 ND [ND] or
Efficiency Aware ND (this document) mode an explicit registered
lifetime and are kept until this lifetime
expires or both(Mixed mode).

8. Efficiency-aware Neighbor Discovery Messages

Router Advertisement(RA): Periodic RAs SHOULD be avoided. Only
solicited RAs they are RECOMMENDED. An RA MUST
contain explicitly unregistered.

Note that the Source Link-layer Address option
containing Router's link-layer address (this type of the NCE is optional orthogonal to the states specified
in [ND]. An RA MUST carry Prefix
information option with L bit being unset, so
that hosts do not multicast any NS messages
as part [RFC4861]. There can only be one type of NCE for an IP address resolution. at
a time.

8. Host Behavior

A new flag
(E-flag) is introduced in the RA EAH follows [RFC4861] and applicable parts of [RFC6775] as follows
in order this section./

A EAH implementation MAY be able to
characterize fall back to [RFC4861] host
behavior if there is no NEAR on the efficiency-aware mode
support. Unlike RFC4861 which suggests
multicast link.

8.1. Host and/or Interface Initialization

A host multicasts Router Advertisements, this
specification optimizes the exchange by
always unicasting RAs Solicitation at system startup or interface
initialization as specified in response to RS.
This is possible since [RFC4861] and its updates such as
[I-D.ietf-6man-resilient-rs].

Unlike RFC4861 the RS always includes MUST (on link layers which have addresses)
include a SLLA option, which is used by the router to unicast the RA.
Router Solicitation(RS): Upon system startup, the node sends a
multicast or link broadcast (when multicast

The host is not supported at the link-layer) RS required to
find out join the available routers in solicited-node multicast
address(es) but it MUST join the link.
An RS may be sent at other times all-nodes multicast address.

8.2. Host Receiving Router Advertisements

The RA is validated and processed as described specified in section 6.3.7 of RFC 4861. A Router
Solicitation MUST carry Source Link-layer
Address option except [RFC4861] with
additional behavior for RAO and the point-to-point
links. Since Registrar List as follows.

When a RA is received without a RAO (but with the E flag set), or the
RAO contains no periodic RAs are allowed Registrar Addresses, then the IPv6 source address is
added/updated in the efficiency-aware Registrar List. When a RA is received with a
RAO then the IPv6 network, Registrar Addresses in that option are added/
updated in the data structure.

If those Registrar List (or entries) already exist and the Router
Epoch in the RAO differs from the Router Epoch in the Registrar List
entry, or if the entry does not exist, then the host
may send periodic unicast RS will initiate
sending NS messages with ARO options to the routers.
The time-periods new/updated Registration
List entries. Note that if the RA contains no RAO (but the E flag is
set) then for the RS varies on purposes of the
deployment scenarios and epoch comparison one should use a
zero Router Epoch.

However, if the Default Router Lifetime advertised in the RAs.
Default Router Selection: Same as in section 6.3.6 of RFC 4861[ND].
Neighbor Solicitation (NS): Neighbor solicitation RA is used between zero, then any
matching Registration List entry (or entries) are instead deleted
from the hosts and Registration List. It is OPTIONAL for the default-router host to de-
register when an entry is deleted from the Registration List.

The host can form its IPv6 address using any available mechanism -
SLAAC, DHCPv6, temporary addresses, etc - as part of
NUD and registering the host's address(es).
An NS message MUST use registration
mechanism is orthogonal and independent of the address allocation.
The Address Registration option procedure replaces the DAD procedure in order to accomplish
[RFC4862].

8.3. Timing out Registrar List entries

The lifetime for the registration.
Neighbor Advertisement (NA): As defined Registrar List entries are taken from the
Default Router Lifetime in [ND] and ARO option.
Redirect Messages: A router SHOULD NOT the RA. When an entry is removed the host
MAY send AROs with a Redirect message zero Regisration Lifetime to the removed
Registrar Addresses.

8.4. Sending AROs

When a host since the link has non-transitive
reachability. The formed a new IPv6 address, or when the host behavior is same as
described in section 8.3 learns of RFC 4861[ND],
i,e.
a host MUST NOT send new NEAR and has existing IPv6 addresses, then it would register
the new things (could be new addresses to all the existing
Registrars, or accept redirect
messages when in efficiency-aware mode.

Same as in RFC 4861[ND]
MTU option: As per the RFC 4861.
Address Resolution: No NS/NA are sent as all the prefixes IPv6 addresses with the new Registrar.
IPv6 link-local addresses are treated registered as well as off-link. Thus no address resolution is
performed at the hosts. The routers keep
track of Neighbor Solicitations with Address
Registration options(ARO) gobals and create an
extended neighbor cache of reachable
addresses. The router also knows
ULA.

If the nexthop
link-local address and corresponding link-
layer address when it wants to route EAH has a
packet.
Neighbor Unreachability Detection(NUD): NUD is performed in
"forward-progress" fashion as described TID then it sets the T-bit and includes the TID in
section 7.3.1 of RFC 4861[ND].
the ARO. When the host registers its addresses with multiple
Registrars it uses the same TID. However, if
Address Registration Option the host has moved
(lost its network attachment and determines it is used, attached to a
different link using e.g., DNA [RFC6059]), then it will increment the NUD
SHOULD be combined with
TID value and use the Re-registration
of new value for subsequent registrations.

The host places its Unique Interface Identifier (whether it is a DUID
or EUI-64) in the node. ARO. This way no extra message for
NUD identifier is required.

9. Efficiency-aware Host Behavior

A typically kept in stable
storage so that the host sends Router Solicitation at can use the system startup and also same identifier over time. It
MUST use the same identifer when it suspects that one of re-registers its default routers have become
unreachable(after NUD fails). The EAH MUST process the E-bit in RA address, since
otherwise all those will be returned as described in this document. duplicates.

The EAH MUST use NS which includes the ARO option to
register MUST include a SLLA option on
link layers that have link-layer addresses.

The EAH retransmits NS messages with ARO as specified in [RFC6775]
until it receives a NA message from the neighboring NEAR router.

A host Registrar containing an ARO.

The number of such retransmissions SHOULD be able configurable.

8.5. Receiving Neighbor Advertisements

The Neighbor Advertisement are validated and processed as specified
in [RFC4861] for example to autoconfigure its IPv6 addresses using handle Neighbor Unreachability Detection
(NUD). In addition, the
IPv6 prefix obtained from Router Advertisement. The host SHOULD form
its link-local address from the EUI-64 processes any received ARO as specified by IEEE
Registration Authority and RFC 2373. follows.

If this draft feature is
implemented and configured, the ARO has status code 0 (Success), then the host MUST NOT re-direct Neighbor
Discovery messages. The host is not required to join updates the solicited-
node multicast address but it MUST join
information in the all-node multicast
address.

A host always sends packets Registrar List to (one of) its default router(s). This know when it next needs to
refresh the registered address with this Registrar. No further
processing is accomplished by needed of the routers never setting ARO.

If the 'L' flag in ARO has status code 1 (Duplicate), then the
Prefix options. host can not use
the IPv6 address. The EAH host may register with more than one default routers in a
subnet but follows the address allocation protocol
it SHOULD use one default primary router for used to pick a source IP- new address at a time. - be that DHCPv6, tempororary
addresses, etc.

If an EAH receives the ARO has a status code 2 (Neighbor Cache Full) in response to
its registration request from a NEAR router, Registrar, then the node MUST be able to choose another
router SHOULD
continue to register the address with other Registrars (when
available).

TBD: What about other not yet defined status code values?

8.6. Host Management of the TID

It is RECOMMENDED that the EAH MAY maintain a sequence counter (TID)
instable storage according to section 7 of [RFC6550]. The host TID is unable
used to forward routes or participate in a routing
protocol. A legacy resolve conflicts between different registrations issues by
the same host for the same IPv6 Host compliant EAH SHOULD address. Conflicts can be able due to fall
back
different link-layer addresses, but it can also be due to RFC 4861 host behavior registering
with different NEARs/Registrars and those routers connect use
protocols like RPL for routing, and RPL uses a TID to habdle movement
vs. multi-homing.

Thus the same TID should be used if there the host is no efficiency-aware router
(NEAR) in registering its
addresses with multiple Registrars at the same time. But if the link.

The efficiency-aware host MUST NOT
might have moved to a different attachment point, then it should
increment its TID for subsequent registrations.

8.7. Refreshing a Registration

A host SHOULD send or accept re-direct messages.
It a Registration message in order to renew its
registration before its registration lifetime expires in order to
continue its connectivity with the network.

This specification does not join solicited node multicast address.

If constrain the EAH implementation. One
possible implementation strategy is capable to attempt re-register at 1/3rd
of generating TID the registration lifetime, and configured for this
operation, if no response try again at 2/3rd
of the EAH MUST use lifetime, etc. Another possible strategy is to wait until the TID field and appropriate associated
operation bits in
end of the ARO message during registration lifetime and refresh.

In some cases, hosts may need to send MAX_RTR_SOLICITATIONS(3) to
receive then do the reply back from same relatively
rapid retransmissions as for the default router. initial registration [RFC6775]. In
all cases the host SHOULD apply a lossy link or
due random factor to sleepy default router, the hosts may have its re-
registration timeout to send more than 3
solicitations [Resilient-RS]. But this can easily increase the
number avoid self-synchronizing behavior across lots
of siganling traffic in hosts. Sleeping hosts would re-register when they are waking up
to do other work.

8.8. De-registering

If anytime, the network. Thus it is RECOMMENDED node decides that the EAH nodes start with the default MAX_RTR_SOLICITATION [ND]
value in it does not need a low power network.

However, in some scenarios the packet loss resilient router
solicitation method may be applicable [Resilient-RS].

10. The Efficiency Aware Default Router (NEAR) Behavior

The main purpose of the particular
default router in the context of this
document is to receive and process router's service anymore, the it SHOULD send a de-
registration request, forward
packets from one neighbor message to that NEAR/Registrar. Similarly if the other, informs the routing protocol
about the un-availability of host
stops using a particular IPv6 address, then it SHOULD de-register
that address with all the Registrars it had registered nodes with. This
applies even if the routing
protocol requires this information for host was using the purpose of mobility or
fast convergence. A default router (NEAR) behavior may be observed
in one or more interfaces IPv6 address, then went to
sleep, and then picked a different set of IPv6 addresses. In such a Border Router(BR).
case it is preferred if the host de-registers before going to sleep.
A Border Router normally may have multiple interfaces and connects mobile host SHOULD first de-register its addresses before it moves
away from the nodes subnet (if the mobile host can know that in advance of
moving.)

De-registration is performed by unicasting a link Neighbor Solicitation
with an ARO where the Registration Lifetime is zero to zero. Such an
ARO should have an incremented TID. De-registration AROs are
retransmitted just like a regular IPv6 subnet(s) or acts as a
gateway between separate networks such other AROs as Internet and home networks
. specified above.

8.9. Refreshing RA information

The Border Router EAH is responsible for distributing one or more /64
prefixes to asking the nodes to identify a packet belonging routers for updates to the
particular network. One or more of the interfaces of
information contained in the Border Router may be connected with Advertisements, since the efficiency-aware hosts or a
efficiency-aware router(NEAR).

The efficiency-aware default router MUST NEARs
will not send periodic RA unless
it multicast such updates. That is configured done by sending unicast RSs
to support both legacy IPv6 and efficiency-aware
hosts. If the Router router(s) which will result in unicast RAs. However,
significant care is configured for efficiency-aware hosts
support, it MUST send Router Advertisements with E-bit flag ON and
MUST NOT set 'L' bit required in determining when the advertisements.

The router SHOULD NOT garbage collect Registered Neighbor Cache
entries since they need to retain them until RSs should be
transmitted.

As part of normal operation the Registration
Lifetime expires. If a NEAR receives Default Routers, Prefixes, and other
RA information have lifetimes, and there are a NS message from few common cases:

1. The advertised lifetimes are constant i.e., the same host
one with ARO and another without ARO then routers keep on
advancing the NS message with ARO
gets time when the precedence and information will expire.

2. The routers decrement the NS without ARO is ignored. This behavior
protects advertised lifetimes in real time i.e.,
the information is set to expire at a determined time and
subsequent RAs have lower and lower lifetimes.

3. The routers forceably expire some information by advertising it
with a zero lifetime for a while, and then stop advertising it.

4. A router crashes or is silently removed from Denial Of Service attacks. Similarly, if
Neighbor Unreachability Detection on the router determines network and as a
result there are no more updates. For example, that the
host default
router will expire and there is UNREACHABLE (based on the logic little benefit in [ND]), trying to
refresh it by sending lots of RSs.

The host's logic for refreshing the Neighbor Cache
entry SHOULD NOT be deleted but information needs to be retained until the Registration
Lifetime expires. If an ARO arrives for an NCE careful
to not send a large number of RSs, in particular if there is
information that is supposed to expire at a fixed time i.e., the
lifetime decrements in
UNCREACHABLE state, real time.

A host MUST NOT try to refresh information because its lifetime is
near zero, since that NCE should would cause unnecessary RSs. Instead the
refresh needs to be marked as STALE.

A default router keeps a cache for all based on when the nodes' IP addresses,
created information was most recently
received from the router. A lifetime of 10 minutes that was heard
from the Address Registration processing.

The NEAR router SHOULD deny registration to 10 minutes ago might be normal as part of expiring
some information. But a new registration
request remaining lifetime of 10 minutes for a
prefix that was last heard 24 hours ago with a lifetime of 24 hours
means that a refresh is in order.

It is RECOMMENDED that the status code 2 host track the expiry time (the wall clock
time when some information will expire) and when it reaches the maximum capacity
for handling receives an RA
with that information check whether the neighbor cache.

10.1. Router Configuration Modes

An efficiency-aware Router(NEAR) MUST be able expiry time is moving
forward, or appears to configure be frozen in
efficiency-aware-only mode where it will expect all hosts register
with time. That can tell the router following RS; thus NEAR will not support legacy
hosts. However,
difference between he first two cases above, and avoid unneccesary
RSs as some information naturally expires. Furthermore it will create legacy NCE for the routers in is
RECOMMENDED that the
network assuming host track which information was received from
which router, so that it can see when a router used to provide the routers do not register with
information no longer provides it. This mode
is able That helps to prevent ND flooding on see if the link.

An efficiency-aware Router(NEAR) SHOULD third
case above might be able in play. Finally, if a router has not responded
to have configuration
knob a few (e.g., MAX_RTR_SOLICITATIONS) attempts to configure itself in Mixed-Mode where it will support both
efficiency-aware hosts get a refresh,
then the router might be unreachable or dead, and legacy hosts. However even there is little
benefit in mixed-mode sending further RSs to that router. When the router comes
back it will multicast a few RAs.

When the hosts determines that case 1 above is likely, then it should check
pick a reasonable time to ask for duplicate entries refreshes. The exact refresh
behavior is not mandated by this specification, but the same
implemention strategies as for refreshing address registrations in
Section 8.7 can be considered.

If the NCE before
creating a new ones host is unable to refresh the information and it should rate-limit creating new NCE based
on requests from as a result ends
up with an empty default router list, or all the default routers are
marked as UNREACHABLE by NUD, then the same host MAC address. MAY switch to sending
initial multicast Router Solicitations as in Section 8.1.

8.10. Sleep and Wakeup

The RECOMMENDED default mode protocol allows the sleepy nodes to complete its sleep schedule
without waking up due to periodic Router Advertisement messages or
due to Multicast Neighbor Solicitation for address resolution. The
node registration lifetime SHOULD be related with its sleep interval
period in order to avoid waking up in the middle of operation sleep for
registration refresh. Depending on the efficiency-aware
router is Mixed-mode. Though it cannot reap application, the full benefit registration
lifetime SHOULD be equal to or integral multiple of
efficiency related optimization described a node's sleep
interval period.

When a host wakes up it can combine movement detecting (DNA), NUD,
and refreshing its Address Registration by sending a unicast NS with
an ARO to its existing default router(s).

8.11. Receiving Redirects

An EAH handles Redirect messages as specified in this document.

10.2. [RFC4861].

8.12. Movement Detection

When a host moves from one subnet to another its IPv6 prefix changes
and the movement detection is determined according to the existing
IPv6 movement detection described in [DNA].

However, if the movement happens across different default routers [RFC6059].

9. Router Behavior

A NEAR follows [RFC4861] and applicable parts of [RFC6775] as follows
in
the subnet this section.

A NEAR SHOULD support legacy hosts and the node likes mixed mode as specified in
this section by being able to register with one proxy Address Resolution and DAD. The
NEAR SHOULD implement a knob to be able to disable this behavior.
That knob can either be set to "mixed-mode" or to "no-legacy-mode".

The RECOMMENDED default mode of operation for the default
routers closest NEAR is Mixed-mode.

A NEAR should be configured to its present location, it MUST send another
registration request advertise prefixes without the on-link
(L-bit) unset. Furthermore, any legacy routers attached to the new default router. The new default
router then first sends same
link as a NEAR should be configured the same way. That reduces the
cases in mixed mode when multicast NS to messages are needed between
legacy hosts and routers.

9.1. Router and/or Interface Initialization

A NEAR multicasts some initial Router Advertisements at system
startup or interface initialization as specified in [RFC4861] and its peers with a link scope
updates.

The NEAR MUST join the all-nodes and all-routers multicast
message to IPv6 address ff02::2 with addresses.
In mixed mode it MUST also join the ARO option.

10.2.1. Registration ownership

The subnet-local-routers check their respective NCE table solicited-node multicast
address(es) for its addresses and also for all the
particular registration. If Registered NCEs.

A NEAR picks a new Router Epoch if it has lost the registration entry exists, Registered NCEs,
which is typically the NEAR
default case for router then calculates initialization. Either the 'age' of
Router Epoch can be stored in stable storage and incremented on each
router initialization, or the registration by
subtracting NEAR can pick a good random number on
router initialization. The effect of occasionally picking the present time from same
Router Epoch as before the registration received time
recorded at state loss is that it will take longer for
the NCE. The NEAR router then responds with a NA with
ARO option Status being equal to 3 and replaces build up its state of Registered NCEs.

9.2. Receiving Router Solicitations

Periodic RAs SHOULD be avoided. Only solicited RAs are RECOMMENDED.
An RA MUST contain the 'registration
lifetime' field Source Link-layer Address option containing
Router's link-layer address (this is optional in [RFC4861]. An RA
MUST carry any Prefix information option with the 'age' L bit being unset, so
that hosts do not multicast any NS messages as part of registration. Upon receiving address
resolution. A new flag (E-flag) is introduced in the
NA from RA which the neighboring routers
hosts use to distinguish a NEAR from a legacy router.

Unlike [RFC4861] which suggests multicast Router Advertisements, this
specification optimizes the prospective default router
determines its registration ownership. If exchange by always unicasting RAs in
response to RSs. This is possible since the other router
registration age RS always includes a
SLLA option, which is higher than its own registration age, then used by the
current router is considered to have unicast the most recent registration
ownership. RA.

If both routers registration age are zero or within
MAX_REG_AGE_DIFFERENCE window, then the TID field is used NEAR has been configured to
determine the ownership. The higher value send an explicit set of TID wins. Note that IPv6
Registrar Addresses, or implements a Router Epoch, then the registration ownership and local movement detection behavior in NEAR router MUST be optionally configured.
includes a RAO in all its RAs.

9.3. Periodic Multicast RA for legacy hosts

The NEAR routers MAY
implement this feature. Configuring this option is needed when MUST NOT send periodic RA in no-legacy mode. In mixed mode
the NEAR routers are used needs to send periodic multicast RAs as specified in
[RFC4861] to support legacy hosts.

9.4. Multicast RA when new information

When a low power and lossy network environment.

11. NCE Management in efficiency-aware Routers

The use of explicit registrations with lifetimes plus the desire router has new information to
not share (new prefixes, prefixes
that should be immediately deprecated, etc) it MAY multicast Neighbor Solicitation messages for hosts imply up to
MAX_INITIAL_RTR_ADVERTISEMENTS number of Router Advertisements. Note
that we
manage such new information is not likely to reach sleeping hosts until
those hosts refresh by sending a RS.

9.5. Receiving ARO

The NEAR follows the Neighbor Cache entries slightly differently than in [ND].
This results logic in two different types of [RFC6775] for managing the NCEs and the types specify how
those entries can be removed:

Legacy: Entries that are subject
responding to NS messages with the normal rules in
[ND] ARO option. The slight
modification is that allow instead of using an EUI-64 as the key to check
for garbage collection when low
on memory. Legacy entries are created only
when there is no duplicate NCE. duplicates, the NEAR uses the IDS value plus the variable length
Unique Interface Identifier value as the key. In mixed-mode
and efficiency-aware mode addition the legacy entries
are converted NEAR
checks the new TID field as follows.

The TID field is used together with age of a registration for
arbitration between two routers to ensure freshness of the registered entries upon
successful processing
registration of ARO. Legacy type can
be considered as union a given target address. Same value of garbage-collectible
and Tentative Type NCEs described in

[6LOWPAN-ND].
Registered: Entries TID indicates
that have an explicit registered
lifetime and are kept until this lifetime
expires or they both states of registration are explicitly unregistered.

Note that the type valid. In case of a mismatch
between comparable TIDs, the NCE is orthogonal to the states most recent TID wins. The TIDs are
compared as specified in [ND]. section 7 of [RFC6550].

9.6. NCE Management in NEARs

When a host interacts with a router by sending Router Solicitations
that does not match with the existing NCE entry of any type, a Legacy
NCE is first created. Once a node successfully registers with a
Router the result is a Registered NCE. As Routers send RAs to legacy
hosts, or receive multicast NS messages from other Routers the result
is Legacy NCEs. There can only be one kind of NCE for an IP address
at a time.

A Router Solicitation might be received from a host that has not yet
registered its address with the router or from a legacy[ND] legacy [RFC4861]
host in the Mixed-mode of operation.

In the 'Efficiency-aware' only mode the

The router MUST NOT modify an existing Registered Neighbor Cache
entry based on the SLLA option from the Router Solicitation. Thus, a
router SHOULD create a tentative Legacy Neighbor Cache entry based on
SLLA option when there is no match with the existing NCE. Such a
legacy Neighbor Cache entry SHOULD be timed out in
TENTATIVE_LEGACY_NCE_LIFETIME seconds unless a registration converts
it into a Registered NCE.

However, in 'Mixed-mode' operation, the router does not require to
keep track of TENTATIVE_LEGACY_NCE_LIFETIME as it does not know if
the RS request is from a legacy host or the efficiency-aware hosts. from a EAH. However, it
creates the legacy type of NCE and updates it to a registered NCE if
the ARO NS request arrives corresponding to the
legacy Legacy NCE.
Successful processing of ARO will complete the NCE creation phase.

If ARO did not result in a duplicate address being detected, and the
registration life-time is non-zero, the router creates and or updates the registered
Registered NCE for the IPv6 address. If the Neighbor Cache is full
and new entries need to be created, then the router SHOULD respond
with a NA with status field set to 2. For successful creation of
NCE, the router SHOULD include a copy of ARO and send NA to the
requestor with the status field 0. A TLLA(Target TLLA (Target Link Layer) Option
is not required with this NA.

Typically for efficiency-aware routers (NEAR), the registration life-
time Registration
Lifetime and EUI-64 IDS plus Unique Interface Identifier are recorded in the
Neighbor Cache Entry along with the existing information described in [ND].
[RFC4861]. The registered NCE are meant to be ready and reachable
for communication and no address resolution is required in the link. The efficiency-aware hosts
An EAH will renew their its registration to keep maintain the state of reachability
of the Registered NCE at the router.
However the router may do perform NUD to towards the idle
or unreachable EAH hosts as per [ND].

In addition,
[RFC4861]. Should NUD fail the NEAR default routers MUST associate NOT remove the Registered
NCE. Instead it marks it as UNREACHABLE.

9.7. Sending non-zero status in ARO

If the Registration fails (due to it being a record of duplicate or the age
of
Neighbor Cache being full), then the registration. 'Age' is NEAR will send an NA with ARO
having a simple way non-zero status. However, it needs to detect movement send that back to the
originator of the failing ARO, and that host and link-layer address
will not be present in the Neighbor Cache.

The NEAR forms a
node from local default router NA with ARO, and then forms the link-layer address
by using the content of the SLLA option in the NS, bypassing the
Neighbor Cache to another. 'Age' information send this error.

9.8. Timing out Registered NCEs

The router SHOULD
contain System-time when NOT garbage collect Registered Neighbor Cache
entries since they need to retain them until the registration Registration
Lifetime expires. If a NEAR receives a NS message from the same host
one with ARO and another without ARO then the NS message with ARO
gets the precedence and the NS without ARO is first created or last
refreshed. This system-time ignored.

Similarly, if Neighbor Unreachability Detection on the router
determines that the host is deducted UNREACHABLE (based on the logic in
[RFC4861]), the Neighbor Cache entry SHOULD NOT be deleted but be
retained until the Registration Lifetime expires. If an ARO arrives
for an NCE that is in UNCREACHABLE state, that NCE should be marked
as STALE.

The NEAR router SHOULD deny registration to a new registration
request with the status code 2 when it reaches the maximum capacity
for handling the neighbor cache.

9.9. Router Advertisement Consistency

The NEAR follows section 6.2.7 in [RFC4861] by receiving RAs from
other routers (NEAR and legacy) on the current system-time link. In addition to determine the "age"
checks in that section it verifies that the prefixes to not have the
L flag set, and that the Registrar Address options are consistent.
Two RAOs are inconsistent if they contain the have a different Router
Epoch and have some IPv6 Registration Addresses in common.

9.10. Sending Redirects

A NEAR sends redirects (with target=destination) to inform the hosts
of the registration link-layer address of the nodes on the link.

This can be disabled on specific link types for instance, radio link
technologies with hidden terminal issues.

9.11. Providing Information to Routing Protocols

If there is a routing protocols like RPL which wants visibility into
the location of each IPv6 address, then this can be retrived from the
Registered NCEs on the NEAR.

9.12. Creating Legacy NCEs

In mixed-mode a NEAR will create Legacy NCEs when receiving RA, RS,
and NS messages based on the source of those packets. When not it is used
mixed-mode it needs to create Legacy NCEs for age
reporting with other routers by
looking at those packets.

9.13. Proxy Address Resolution and DAD for Legacy Hosts

This section applies in mixed mode. It does not apply in no-legacy
mode.

A NEAR in mixed mode MUST join all solicited-node for all Registered
NCEs.

The efficient-ND SHOULD continue to support the legacy IPv6 Neighbor advertisement
Solicitation requests in the mixed mode. The NEAR router SHOULD act
as the ND proxy on behalf of EAH hosts for the legacy nodes' NS
requests for selection EAH. This form of registration
ownership among proxying is to respond with a NA that
has a TLLAO taken from the default-router contenders Registered NCE for the target. Thus it is
unlike ND Proxy as specified in case [RFC4389].(Implementations of local
movement
"Neighbor Discovery Proxies (ND Proxy)" [RFC4389] might proxy using
their own MAC address as TLLA, but that is outside of the host from one default-router scope of
this document.)
In the context of this specification, proxy means:

o Responding to another in DAD probes for a registered NCE. A DAD probe from a
legacy host would not contain any ARO, hence the same
subnet. 'Age' NEAR will assume
it is always considered zero for a fresh registration duplicate if the IPv6 target address has a
Registered NCE.

o Defending a registered address using NA messages with and ARO
option and the Override bit set if the ARO option in the NS
indicates either a different node (different IDS+Unique Interface
Id) or a older registration refresh message.

11.1. (when comparing the TID).

o Advertising a registered address using NA messages, asynchronously
or as a response to a Neighbor Solicitation messages.

o Looking up a destination on the link using Neighbor Solicitation
messages in order to deliver packets arriving for the EAH.

10. Handling ND DOS DoS Attack

IETF community has discussed possible issues with /64 DOS DoS attacks on
the ND networks when an attacker host can send thousands of packets
to the router with an on-link destination address or sending RS
messages to initiate a Neighbor Solicitation from the neighboring
router which will create a number of INCOMPLETE NCE entries for non-
existent nodes in the network resulting in table overflow and denial
of service of the existing communications.

The efficiency-aware behavior documented in this specification avoids
the ND DOS DoS attacks by:

o Having the hosts register with the default router router(s).

o Having the hosts send their packets via the default router router(s).

o Not resolving addresses for the Routing Solicitor routing solicitor by mandating
SLLA option along with RS

o Checking for duplicates in NCE before the registration

o Checking against the MAC-address and EUI-64 id is possible now for
NCE matches
o On-link IPv6-destinations on a particular link must be registered
else these packets are not resolved and extra NCEs are not created

It is RECOMMENDED that Mixed-mode operation and legacy hosts SHOULD
NOT be mixed in the IPv6 link in

In order to avoid the ND DOS attacks.
For the general case of Mixed-mode the router does not create
INCOMPLETE NCEs for the registered hosts, but it follows the [ND]
steps of NCE states for legacy hosts.

12. Mixed-Mode Operations

Mixed-Mode operation discusses the protocol behavior where the IPv6
subnet is composed with legacy IPv6 Neighbor Discovery compliant
nodes and efficiency-aware IPv6 nodes implementing this
specification.

The mixed-mode model SHOULD support get maximal benefits from the following configurations in ND-DoS protection from
Address Registrations, the IPv6 link:
o The legacy IPv6 hosts and efficiency-aware-hosts in the network
and a NEAR router
o legacy IPv6 default-router and efficiency-aware hosts(EAH) in the
link
o one router is in mixed mode and routers on the link contains both legacy IPv6
hosts and EAH
o A link contains both efficiency-aware IPv6 router and hosts and
legacy IPv6 routers and hosts and each host should be able need to
communicate with each other.

In mixed-mode operation, a NEAR MUST be configured for mixed-mode in
order
upgraded to support the legacy IPv6 hosts in the network. In mixed-
mode, the NEAR MUST act as proxy for Neighbor Solicitation for DAD
and Address Resolution on behalf of its registered hosts on that
link. It should follow the NCE management for the EAH as described
in this document NEARs and follow RFC 4861 NCE management for the EAHs, respectively. With some legacy
IPv6 hosts. Both in mixed-mode and efficiency-aware mode, the NEAR
sets E-bit flag in the RA and does not set 'L' on-link bit.

If a NEAR receives NS message from the same host one with ARO and
another without ARO then the NS message with ARO gets hosts the precedence.

An efficiency-aware Host implementation SHOULD support falling back
to legacy IPv6 node behavior when no efficiency-aware
routers are
available in the network during the startup. If the EAH was
operational in efficiency-aware mode will still need to create INCOMPLETE NCEs and it determines that the NEAR
is no longer available, then it should send a RS and find an
alternate default router in the link. If no efficiency-aware router
is indicated from the RA, then the EAH SHOULD fall back into RFC 4861
behavior. On the other hand, in the efficiency-aware mode EAH SHOULD
ignore multicast Router Advertisements(RA) sent by NSs, which
keeps the DoS opportunity open. However, with fewer legacy and
Mixed-mode routers in the link.

In mixed mode operation, hosts the Router SHOULD
lower rate limits can be able to do local
movement detection based applied on ARO from EAH hosts. For the legacy
hosts, the mixed-mode router MAY follow classical IPv6 methods creation of
movement detection and MAY act as ND proxy by sending NA with 'O'
bit.[RFC 3775]
The routers that are running on efficiency-aware mode or legacy mode
SHOULD NOT dynamically switch the mode without flushing the Neighbor
Cache Entries.

In mixed mode, the NEAR SHOULD have a configurable interval for
periodic unsolicited router advertisements based on the media type.

13. INCOMPLETE NCEs.

11. Bootstrapping

The bootstrapping mechanism described here is applicable for the
efficiency-aware hosts and routers. At the start, the host uses its
link-local address to send Router Solicitation and then it sends the
Node
Address Registration message Option as described in this document in order to
form
verify the IPv6 address.

The Duplicate address detection process should following step 3 and 4 SHOULD be
skipped if repeated for all the network is guaranteed to have unique interface
identifiers which is used to form an IPv6 address.
addresses that are used for communications.

Node Router

0. |[Forms LL IPv6 addr] |

1. | ---------- Router Solicitation --------> |

| [SLLAO] |

2. | <-------- Router Advertisement --------- |

| [PIO + SLLAO] |
| |

3. | ----- Address Registration (NS) --------> |

| [ARO + SLLAO] |

4. | <-------- Neighbor Advertisement ------- |

| [ARO with Status code] |

5. ====> Address Assignment Complete

Figure 1: Neighbor Discovery Address Registration and bootstrapping

In the mixed mode operation, it is expected that logically there will
be at least one legacy IPv6 router and another NEAR router present in
the link. The legacy IPv6 router will follow RFC 4861 behavior and
NEAR router will follow the efficiency-aware behavior for
registration, NCE maintenance, forwarding packets from a EAH and it
will also act as a ND proxy for the legacy IPv6 hosts querying to
resolve a EAH node.

A legacy IPv6 host and EAH are not expected to see a difference in
their bootstrapping if both legacy and efficiency-aware
functionalities of rotuers are available in the network. It is
RECOMMENDED that the EAH implementation SHOULD be able to behave like
a legacy IPv6 host if it discovers that no efficiency-aware routing
support is present in the link.

14. Handling Sleepy Nodes

The solution allows the sleepy nodes to complete its sleep schedule
without waking up due to periodic Router Advertisement messages or
due to Multicast Neighbor Solicitation for address resolution. The
node registration lifetime SHOULD be synchronized with its sleep
interval period in order to avoid waking up in the middle of sleep
for registration refresh. Depending on the application, the
registration lifetime SHOULD be equal to or integral multiple of a
node's sleep interval period.

15. Duplicate Address Detection

In efficiency-aware mode, there is no need for Duplicate Address
Detection(DAD) assuming that the deployment ensures unique 64bit
identification availability for each registered host. In the event
of collision of EUI64 field of ARO by two registration requests, the
later request is denied if the first one is a valid request. The
denied EAH node SHOULD pick another alternative IPv6 address to
register to prevent further registration denial. The method of
assignment of alternate IPv6 address is out of scope of this
document.

In some networks there are multiple default routers and the
registering node may move from one default router (where it was
registered before) to another default router in the same subnet.
Thus in order to differentiate between the duplicate request and the
movement, the router checks the 64-bit MAC address and 'age' of the
request. If there is an entry in the node already with 0 < 'age' <
registration-life-time and the TID field of the existing entry and
the new request is same

12. Interaction with TID of the new request, it is a
duplicate.

If the default router does not have a registered entry for this host,
it should check whether it is a local movement. Please see 'Mobility
Consideration section' for details.

16. Mobility Considerations

If the hosts move from one subnet to another, they MUST first de-
register and then register themselves in the new subnet or network.
If a node moves away without de-registration and returns to the
network before the registration lifetime expires, its registration is
still considered valid. For run-away nodes the registration expires
after the lifetime expiry or due to unreachablity whichever comes
first. Otherwise, the regular IPv6 Mobility [IPV6M]behavior applies.

In the multiple default router scenario, a node may move from its
current primary default router to a prospective primary default
router. At this point, the default routers use Neighbor
Advertisements(NA) to arbitrate the latest ownership of the
registration of host. The ownership of registration is useful for
the Border Routers if they participate in a routing protocol which
advertises proximity preferences or adjusts its own forwarding
preference based on the host registration. This kind of forwarding
or routing mechanisms are useful for energy efficiency and
performance of the networks. See 'Movement Detection' section for
details.

17. Other Considerations

17.1. other protocols
12.1. Detecting Network Attachment(DNA) Attachment (DNA)

IPv6 DNA[DNA] DNA [RFC6059] uses unicast ND NS probes and link-layer indications
to detect movement of its network attachments. Upon detecting link-
layer indication, it sends a all-routers Solicitation message. When That is consistent
with the node implements mechanism in this document along with DNA, it MUST send ARO
option with its Neighbor Solicitation specification to unicast message if the
candidate router advertisement indicates that the router is a NEAR
router. If the candiate router is NS when a legacy router then and it is the
only choice then the EAH host SHOULD adapt to
wakes up - this document recommends adding the legacy behavior.
However if EAH node implements DNA host capability as well, then it
SHOULD give preference ARO to the NEAR routers in its candidate list of
routers. that NS
message.

Thus the ND optimization solution will work seamlessly with DNA
implementations and no change is required in DNA solution because of
Neighbor Discovery updates. It is a deployment and configuration
consideration as to run the network in mixed mode or efficient-mode.

17.2. Proxying for Efficiency-Aware hosts

12.2. DHCPv6 Interaction

The efficient-ND SHOULD continue to support the legacy IPv6 Neighbor
Solicitation requests protocol mechanisms in the mixed mode. The NEAR router SHOULD act
as the ND proxy on behalf of EAH hosts for the legacy nodes' NS
requests for EAH.

In the context of this specification, proxy ND means: defending a
registered address over the backbone using NA messages with and ARO
option and the Override bit set if the ARO option in the NS indicates
either a different node (different EUI-64) or a older registration
(when comparing the TID).

o advertising a registered address over the backbone using NA
messages, asynchronously or as a response to a Neighbor
Solicitation messages.
o Looking up a destination over the backbone in order to deliver
packets arriving from the EAH host using Neighbor Solicitation
messages.
o Forwarding packets from the EAH over the backbone, and the other
way around at a time if the devide has known sleeping periods or
resides on a different link such as an LLN attached document are orthogonal to the
backbone.
Eventually triggering a look-up for a destination EAH that would not
be registered at a given point of time, or as a verification of a
registration.

17.3. DHCPv6 Interaction

Co-existence with DHCP: For classical IPv6, if DHCPv6 or central
address allocation assignment mechanism in use. If DHCPv6 is used, then Neighbor Discovery
autoconfiguration is not used for global address allocation.
However, link-local duplicate address detection, Neighbor
solicitation, Neighbor unreachability detection are still used. Upon
assignment of by an EAH then, if there are one or more NEARs on the
subnet, the IPv6-address from DHCPv6, a EAH node SHOULD then
register will replace the IP-address DAD check specified in [RFC3315]
with the default router for avoiding
Duplicate address detection and Address Resolution. For Legacy
DHCPv6 nodes there is no change Registration as specified in behavior. NOTE: DHCPv6 Server
MUST be notified by NEAR for its efficiency-aware service interfaces.
DHCPv6 server then SHOULD inform the DHCP requestor node about the
default-rotuer capability during the address assignment period. this document.

12.3. Other use of Multicast

Although the solution described in this document prevents unnecesary
multicast messages in the IPv6 ND procedure, it does not affect
normal IPv6 multicast packets and nor the ability of nodes to join and
leave the multicast group or forwarding multicast traffic or
responding to multicast queries.

18.

12.4. VRRP Interaction

TBD: This section will discuss if efficient ND mixed mode and
efficiency mode require any special consideration with

A VRRP function.

19. RPL Implications

RPL [RFC6550] does not provide means for duplicate address detection
and in particular does not have a concept set of unique identifier. On routers can operate with efficient-nd in two different
ways:

o Provide the other hand, RPL is designed illusion to discover and resolve conflicts hosts that arise when they are a mobile device changes its point single router for
the purposes of attachment, with
a sequence counter that registrations. No RAO is owned by needed in that case.
But the device and incremented at
each new registration, called a DAOSequence. As we extend 6LoWPAN ND
operation over pair needs some mechanism to synchronize their neighbor
caches. Such a backbone and scale, there mechanism is a similar need to
resolve the latest point out of attachment scope of a device, whether this
device moves at layer 2 over a WIFI infrastructure, or at layer 3
within a RPL DODAG or from a DODAG to another one attached to document.

o Have the
same backbone. hosts register with each router independently. In order to cover all cases in a consistent fashion,
this document requires that a sequence counter call TID for
Transaction ID and with
case the similar rules as VRRP router includes the RPL DAOSequence is
added to RAO with the ND registration. This document defines individual IP
addresses of the TID
operations and RPL may use routers in the reserved fields for their purpose
inside pair. No synchronization of the LLN.

20.
neighbor caches are needed in that case.

13. Updated Neighbor Discovery Constants

This section discusses the updated default values of ND constants
based on [ND] [RFC4861] section 10. New and changed constants are listed
only for efficiency-aware-nd implementation. These values SHOULD be
configurable and tunable to fit implementations and deployment.

Router Constants:

MAX_RTR_ADVERTISEMENTS(NEW) 3 transmissions

MIN_DELAY_BETWEEN_RAS(CHANGED) 1 second

TENTATIVE_LEGACY_NCE_LIFETIME(NEW) 30 seconds
MAX_REG_AGE_DIFFERENCE(NEW) 50 mseconds

Host Constants:

MAX_RTR_SOLICITATION_INTERVAL(NEW) 60 seconds

Also refer to [ENH-ND] [RFC6583] , [IMPAT-ND] [RFC7048] and [6LOWPAN-ND] [RFC6775] for further tuning
of ND constants.

21.

14. Security Considerations

These optimizations are not known to introduce any new threats
against Neighbor Discovery beyond what is already documented for IPv6
[RFC 3756].
[RFC3756].

Section 11.2 of [ND] [RFC4861] applies to this document as well.

This mechanism minimizes the possibility of ND /64 DOS DoS attacks in
efficiency-aware mode. See Section 11.1.

22. 10.

The mechanisms in this document work with SeND [RFC3971] in the no-
legacy mode. In the mixed mode operation when a NEAR needs to
respond to a legacy host sending a NS for a EAH, then SeND would not
automatically fit. Potentially proxy SeND [RFC6496] could be used,
but that would require explicit awareness and setup between the proxy
and the proxied EAHs which seems impractical.

The mechanisms in this specification are orthogonal to the address
allocation thus works as well with SLAAC and DHCPv6 as the various
privacy-enhanced address allocation specifications. In particular,
using an EUI-64 for the Unique Interface Identifier in this protocol
does not require or assume that the IPv6 addresses will be formed
using the modified EUI-64 format.

The mechanism uses a Unique Interface Identifier for the purposes of
telling apart a re-registration from the same host and a duplicate/
conflicting registration from a different host. That unique ID is
not globally visible. Currently the protocol supports DHCPv6 DUID
and EUI-64 format for this I-D, but other formats which facilitate
non-linkability (such as strong random numbers large enough to be
unlikely to cause collisions) can be defined.

15. IANA Considerations

A new flag (E-bit) in RA has been introduced. IANA assignment of the
E-bit flag is required upon approval of this document.

23.

This document needs a new Neighbor Discovery option type for the RAO.

16. Changelog

Changes from draft-chakrabarti-nordmark-energy-aware-nd-02: draft-chakrabarti-nordmark-energy-aware-nd-04:

o Significantly simplified the description of the protocol.

o Added clarification that SLLA is not required for ARO in a
point-to-point link on problem statement

o Clarified that privacy and temporary addresses will be supported

o Added an IDS field in the document is indeed ARO to allow a DHCP Unique ID (DUID) as
an optimization alternative to EUI-64, with room to define other (pseudo)
unique identifiers.

o Allowed router redirects for legacy
IPv6 ND NEAR.

o Adressed editorial Addressed some of comments made in the 6man list.

o Added RAO to handle VRRP and fixed typoes. Some more
editorial work is needed similar cases when the default router
list and registrar list needs to be different.

o Added another usecase for Z-Wave example. Clarified 3GPP
Networks related comments Router Epoch to cause re-registration on existing ND optimizations.

24. NEAR state loss.

o Specified considerations for when to refresh address
registrations.

o Specified considerations for when to refresh RA information.

17. Acknowledgements

The primary idea of this document are from 6LoWPAN Neighbor Discovery
document [6LOWPAN-ND] [RFC6775] and the discussions from the 6lowpan working group
members, chairs Carsten Bormann and Geoff Mulligan and through our
discussions with Zach Shelby, editor of the [6LOWPAN-ND]. [RFC6775].

The inspiration of such a IPv6 generic document came from Margaret
Wasserman who saw a need for such a document at the IOT workshop at
Prague IETF.

The authors acknowledge the ND denial of service issues and key
causes mentioned in the draft-halpern-6man-nddos-mitigation document
by Joel Halpern. Thanks to Joel Halpern for pinpointing the problems
that are now addressed in the NCE management section. discussion in this
document.

The authors like to thank Dave Thaler, Stuart Cheshire, Jari Arkko,
Ylva Jading, Niklas J. Johnsson, Reda Nedjar, Purvi Shah, Jaume Rius
Riu, Fredrik Garneij, Andrew Yourtchenko, Jouni Korhonen, Suresh
Krishnan, Brian Haberman, Anders Brandt, Mark Smith, Lorenzo Colitti,
David Miles Miles, Eric Vyncke, Mark ZZZ Smith, Mikael Abrahammsson, Eric
Levy-Abignoli, and Carsten Bormann for their useful comments and
suggestions on this work.

25.

18. Open Issues

The known open issues are:

o IPv6 link-local addresses are always on-link and in this version
of the document that results in multicast NS messages. The
techique used in 6LowPAN-ND is too restrictive (extract the link-
layer address from the IID). Should we send link-locals to
routers and depend on Redirect?

o If the Router Epoch is critical then we will see a RAO in all the
RAs sent by NEARs. In such a case we don't need the E-bit in the
RA.

o Editorial: Add Comparison with 6lowpan-nd and 4861?

o When a router has new information for the RA, currently it takes a
while to dissemitate that to sleeping nodes as this depends on
when the hosts send a RS. We could potentially improve this is we
could have an "information epoch number" in the ARO sent in the
NA. But that only helps if the registrations are refreshed more
frequently that the RA information.

o Future? Currently if a router changes its information, a sleeping
host would not find out when it wakes up and sends the NS with
ARO. That could be improved if we fit the Router Epoch in NA/ARO.
But there is no room for 16 bits.

o A separate but related problem is with unused NCEs due to frequent
IPv6 address change e.g., hosts which pick a different set of
addresses each time they wake up. This document recommends that
they be de-registered by the host. That could be made simpler by
introducing some Host Epoch counter in the NS/ARO.

19. References

25.1.

19.1. Normative References

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

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

[6LOWPAN-ND]
Shelby, Z., Chakrabarti, S., Nordmark, E.,

[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and C. Bormann,
"ND Optimizations M. Carney, "Dynamic Host Configuration Protocol for 6LoWPAN",
IPv6 (DHCPv6)", RFC 6775, November 2012.

[ND] 3315, July 2003.

[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6", 6 (IPv6)", RFC 4861,
September 2007.

[LOWPAN]

[RFC4944] Montenegro, G. and N. G., Kushalnagar, N., Hui, J., and D. Culler,
"Transmission of IPv6 Packets over IEEE 802.15.4 networks",
Networks", RFC 4944, September 2007.

[LOWPANG] Kushalnagar, N. and G. Montenegro, "6LoWPAN: Overview,
Assumptions, Problem Statement

[RFC6775] Shelby, Z., Chakrabarti, S., Nordmark, E., and Goals", C. Bormann,
"Neighbor Discovery Optimization for IPv6 over Low-Power
Wireless Personal Area Networks (6LoWPANs)", RFC 4919,
August 2007.

25.2. 6775,
November 2012.

19.2. Informative References

[IPV6]

[I-D.ietf-6man-resilient-rs]
Krishnan, S., Anipko, D., and D. Thaler, "Packet loss
resiliency for Router Solicitations",
draft-ietf-6man-resilient-rs-02 (work in progress),
October 2013.

[I-D.ietf-6man-stable-privacy-addresses]
Gont, F., "A Method for Generating Semantically Opaque
Interface Identifiers with IPv6 Stateless Address
Autoconfiguration (SLAAC)",
draft-ietf-6man-stable-privacy-addresses-17 (work in
progress), January 2014.

[I-D.vyncke-6man-mcast-not-efficient]
Vyncke, E., Thubert, P., Levy-Abegnoli, E., and A.
Yourtchenko, "Why Network-Layer Multicast is Not Always
Efficient At Datalink Layer",
draft-vyncke-6man-mcast-not-efficient-01 (work in
progress), February 2014.

[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6),
(IPv6) Specification", RFC 2460, December 1998.

[DNA] Krishnan, S. and G. Daley, "Simple Procedures for
Detecting Network Attachments in IPv6", RFC 6059,
November 2010.

[RFC6550] "RPL: IPv6 Routing Protocol for Low-Power and Lossy
Networks", RFC 6550, March 2012.

[AUTOCONF]
Thomson, S., Narten, T.,

[RFC3756] Nikander, P., Kempf, J., and T. Jinmei, E. Nordmark, "IPv6 Stateless
Autoconfiguration", Neighbor
Discovery (ND) Trust Models and Threats", RFC 4862, September 2007.

[SEND] 3756,
May 2004.

[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "Secure "SEcure
Neighbor Discovery", Discovery (SEND)", RFC 3971, March 2005.

[AUTOADHOC]
Baccelli, E.

[RFC4193] Hinden, R. and M. Townsley, "IP Addressing Model in
Adhoc Networks", B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 5889, September 2010.

[NDDOS-halpern]
Halpern, J., "IP Addressing Model in Adhoc Networks",
draft-halpern-6man-nddos-mitigation-00.txt (work in
progress), 4193, October 2011.

[ENH-ND] Kumari, W., Gashinsky, I., Jaeggli, J., 2005.

[RFC4389] Thaler, D., Talwar, M., and K.
Chittimaneni, C. Patel, "Neighbor Discovery Enhancement for DOS
mitigation", draft-gashinsky-6man-v6nd-enhance-02 (work in
progress), October 2012.

[IMPAT-ND]
Nordmark, E. and I. Gashinsky, "Neighbor Unreachability
Detection is too impatient",
draft-ietf-6man-impatient-nud-05 (work in progress),
October 2012.

[IEEE] IEEE Computer Society, "IEEE Std. 802.15.4-2003", ,
October 2003.

[PD] Miwakawya,
Proxies (ND Proxy)", RFC 4389, April 2006.

[RFC4862] Thomson, S., "Requirements Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, September 2007.

[RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy
Extensions for Prefix Delegation", Stateless Address Autoconfiguration in
IPv6", RFC 3769, June 2004.

[RF] 4941, September 2007.

[RFC5175] Haberman, B. and B. R. Hinden, "IPv6 Router Advertisement
Flags option", Option", RFC 5175, March 2008.

[ULA] "Unique Local IPv6 Addresses", RFC 4193.

[Resilient-RS]

[RFC6059] Krishnan, S., Anipko, D., S. and D. Thaler, "Packet loss
resiliency G. Daley, "Simple Procedures for Router Solicitations",
draft-ietf-6man-resilient-rs-01 (work
Detecting Network Attachment in progress),
May 2013.

[IPV6M] Johnson, D., IPv6", RFC 6059,
November 2010.

[RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support
in IPv6", RFC 6275, July 2011.

Appendix A. Usecase Analysis

This section provides applicability scenarios where the efficiency-
aware Neighbor Discovery will be most beneficial. Most likely the
usecases will be detailed in a separate document.

A.1. Data Center Routers on the link

Efficiency-aware Routers and hosts are useful in IPv6 networks in the
Data Center as they produce less signaling

[RFC6496] Krishnan, S., Laganier, J., Bonola, M., and also provides ways to
minimize the A. Garcia-
Martinez, "Secure Proxy ND flood of messages. Moreover, this mechanism will
work with data-center nodes which are deliberately in sleep mode Support for
saving energy.

This solution will work well in Data Center Virtual network and VM
scenarios where number of VLANs are very high and ND signalings are
undesirably high due the multicast messaging and periodic Router
Advertisments and Neighbor Unreachability detections.

A.2. Edge Routers and Home Networks

An Edge Router in the network will also benefit implementing the
efficiency-aware Neighbor Discovery behavior in order to save the
signaling and keeping track of the registered nodes in its domain. A
BNG sits at the operator's edge network and often the BNG has to
handle a large number of home CPEs. If a BNG runs SEcure Neighbor
Discovery
protocol and acts as the default router for the CPE at home, this
solution will be helpful for reducing the control messages and
improving network performances.

The same solution can be run on CPE or Home Residential Gateways to
assign IPv6 addresses to the wired and wireless home devices without
the problem of ND flooding issues and consuming less power. It
provides mechanism for the sleepy nodes to adjust their registration
lifetime according to their sleep schedules.

A.3. M2M Networks

Any Machine-to-machine(M2M) networks such as IPv6 surveilance
networks, wireless monitoring networks and other m2m networks desire
for efficiency-aware control protocols and dynamic address
allocation. The in-built address allocation (SEND)", RFC 6496, February 2012.

[RFC6550] Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R.,
Levis, P., Pister, K., Struik, R., Vasseur, JP., and autoconfiguration
mechanism in R.
Alexander, "RPL: IPv6 along with the default router capability will be
useful for the simple small-scale networks without having the burden
of DHCPv6 service and Routing Protocols.

A.4. Wi-fi Networks

In Wi-fi networks, a multicast message will consume the wireless link
on all Access Points around a switched fabric and will be transmitted
at the lowest speed possible in order to ensure the maximum reception
by all wireless nodes. This means that in an environment where
bandwidth is scarce, a single multicast packet may consume the
bandwidth for hundreds of unicast packets.

The Wi-fi IPv6 hosts can act as efficiency-aware hosts and register
with their nearest default router with NEAR behavior. This method
reduces multicast operations in the wireless access points or routers
by using this optimization.

A.5. 3GPP Networks

Section 9.2.1.1 of TS23.060 allows periodic RA and TS 123.401 stays
silent about periodic RA while 3GPP TS29.061 recommends large values
for minimum and maximum periodic router advertisements for reduced
periodic mesages. Though RFC6459 describes best practices about IPv6
3GPP systems behavior, this ND optimization standard specification
will be a helpful reference for 3GPP documents. LTE terminals (cell
phones) may also benefit with reduced multicast messages described in
this document in the wireless mode.

A.6. Industrial Networks

RPL [RFC6550] is used Protocol for Industrial wireless networks.

A.7. Set Low-Power and forget offline network

Home control modules designed for networked environments may be
deployed in very simple settings like garden path lighting controlled
by wireless light
Lossy Networks", RFC 6550, March 2012.

[RFC6574] Tschofenig, H. and motion sensors. Once J. Arkko, "Report from the network has been
created Smart Object
Workshop", RFC 6574, April 2012.

[RFC6583] Gashinsky, I., Jaeggli, J., and sensors have been associated with the light modules, the
installer takes away the configuration tool which was used to set up
the network. Most likely a ULA prefix is used, since multiple hops
may be needed. None of the sensors W. Kumari, "Operational
Neighbor Discovery Problems", RFC 6583, March 2012.

[RFC7048] Nordmark, E. and light modules has the
capability of handing out fresh prefixes. Thus, for a set-and-forget
style off-line network to work, the nodes must be provided an
infinite prefix lifetime since they have nowhere to ask for a fresh
one. I. Gashinsky, "Neighbor Unreachability
Detection Is Too Impatient", RFC 7048, January 2014.

Authors' Addresses

Samita Chakrabarti
Ericsson
San Jose, CA
USA

Email: samita.chakrabarti@ericsson.com

Erik Nordmark
Arista Networks
San Jose,
Santa Clara, CA
USA

Email: nordmark@sonic.net

Pascal Thubert
Cisco Systems

Email: pthubert@cisco.com
Margaret Wasserman
Painless Security

Email: mrw@lilacglade.org