6man WG S. Chakrabarti
Internet-Draft Ericsson
Updates: 4861 (if approved) E. Nordmark
Intended status: Standards Track P. Thubert
Expires: January 16, 2014 Cisco Systems
M. Wasserman
Painless Security
July 15, 2013
Efficiency aware IPv6 Neighbor Discovery Optimizations
draft-chakrabarti-nordmark-6man-efficient-nd-02
Abstract
IPv6 Neighbor Discovery (RFC 4861) protocol has been designed for
neighbor's address resolution, unreachability detection, address
autoconfiguration, router advertisement and solicitation. With the
progress of Internet adoption on various industries including home,
wireless, M2M and cellular networks there is a desire for optimizing
the legacy IPv6 Neighbor Discovery protocol. This document describes
a method of optimization by reducing multicast messages and
introducing an IPv6 address Registration mechanism. Efficient IPv6
Neighbor Discovery protocol is useful for energy-efficient and low-
power IPv6 networks and as well as Data Center and Home Networks.
The solution is capable of handling existing legacy IPv6 nodes in the
network with local mobility.
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 January 16, 2014.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
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document authors. All rights reserved.
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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Background . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Overview of the ND Optimization . . . . . . . . . . . . . 5
2. 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 . . . . . . . . . . . . . . . . . . . . . . . 9
6. Applicability Statement . . . . . . . . . . . . . . . . . . . 9
7. New Neighbor Discovery Options and Messages . . . . . . . . . 10
7.1. Address Registration Option . . . . . . . . . . . . . . . 10
7.2. Refresh and De-registration . . . . . . . . . . . . . . . 12
7.3. A New Router Advertisement Flag . . . . . . . . . . . . . 12
7.4. The Transaction Identification(TID) . . . . . . . . . . . 13
8. Efficiency-aware Neighbor Discovery Messages . . . . . . . . . 13
9. Efficiency-aware Host Behavior . . . . . . . . . . . . . . . . 15
10. The Energy Aware Default Router (NEAR) Behavior . . . . . . . 15
10.1. Router Configuration Modes . . . . . . . . . . . . . . . . 16
10.2. Movement Detection . . . . . . . . . . . . . . . . . . . . 17
10.2.1. Registration ownership . . . . . . . . . . . . . . . 17
11. NCE Management in efficiency-aware Routers . . . . . . . . . . 17
11.1. Handling ND DOS Attack . . . . . . . . . . . . . . . . . . 19
12. Mixed-Mode Operations . . . . . . . . . . . . . . . . . . . . 20
13. Bootstrapping . . . . . . . . . . . . . . . . . . . . . . . . 21
14. Handling Sleepy Nodes . . . . . . . . . . . . . . . . . . . . 22
15. Duplicate Address Detection . . . . . . . . . . . . . . . . . 23
16. Mobility Considerations . . . . . . . . . . . . . . . . . . . 23
17. Other Considerations . . . . . . . . . . . . . . . . . . . . . 24
17.1. Detecting Network Attachment(DNA) . . . . . . . . . . . . 24
17.2. Proxying for Efficiency-Aware hosts . . . . . . . . . . . 24
17.3. DHCPv6 Interaction . . . . . . . . . . . . . . . . . . . . 25
18. RPL Implications . . . . . . . . . . . . . . . . . . . . . . . 25
19. Updated Neighbor Discovery Constants . . . . . . . . . . . . . 26
20. Security Considerations . . . . . . . . . . . . . . . . . . . 26
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21. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
22. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 26
23. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 27
24. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
24.1. Normative References . . . . . . . . . . . . . . . . . . . 27
24.2. Informative References . . . . . . . . . . . . . . . . . . 28
Appendix A. Usecase Analysis . . . . . . . . . . . . . . . . . . 29
A.1. Data Center Routers on the link . . . . . . . . . . . . . 29
A.2. Edge Routers and Home Networks . . . . . . . . . . . . . . 29
A.3. M2M Networks . . . . . . . . . . . . . . . . . . . . . . . 29
A.4. Wi-fi Networks . . . . . . . . . . . . . . . . . . . . . . 30
A.5. 3GPP Networks . . . . . . . . . . . . . . . . . . . . . . 30
A.6. Industrial Networks . . . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30
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1. Introduction
Conceptually, IPv6 multicast messages are supposed to avoid broadcast
messages, but in practice, the multicast operation 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 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, a number of intermediate devices (such as
switches, routers and security middle boxes) host IPv6 State
Maintaining Entities (SMEs) holding information such as the location
of an IPv6 address or its mapping with a MAC address. Such
intermediate devices include Wireless Controllers that terminate a
overlay tunnel and rapidly re-enable reachability for mobile
devices(L2/L3), Network edge devices performing subscriber access,
network devices that protect the ownership of an IPv6 address,
Overlay networks in data centers, Home Networks for IPv6 clients.
In general, there is a need for enhancing the IPv6 ND [ND] to make it
less chatty and flexible to work with different types of networking
elements, physical and virtual networks and at the same time
maintaining the IPv6 states to avoid duplicates or denial of
services.
1.1. Background
IPv6 ND [ND] is based on multicast signaling messages on the local
link in order to avoid broadcast messages. Following power-on and
initialization of the network in IPv6 Ethernet networks, a node joins
the solicited-node multicast address on the interface and then
performs duplicate address detection (DAD) for the acquired link-
local address by sending a solicited-node multicast message to the
link. After that it sends multicast router solicitation (RS)
messages to the all-router address 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
in the router advertisement (RA). Besides this, the IPv6 routers
usually send router advertisements periodically on the network. RAs
are sent to the all-node multicast address. The minimum RA interval
range can be 3sec to 600sec depending on applications. Nodes send
Neighbor Solicitation (NS) and Neighbor Advertisement (NA) messages
to resolve the IPv6 address of the destination on the link. These
NS/NA messages are also often multicast messages and it is assumed
that the node is on the same link and relies on the fact that the
destination node is always powered and generally available.
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The 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. It requires energy for the sleepy nodes which may
otherwise be sleeping during the idle period. Non-sleepy nodes also
spends more energy since they are in continuous listening mode. With
the explosion of Internet-of-things and machine to machine
communication, more and more devices would be using IPv6 addresses in
the near future. Since Neighbor Discovery is at the heart of IPv6
protocol, there is a need to make this protocol more efficient.
1.2. Overview of the ND Optimization
IPv6 Neighbor Discovery Optimization for 6LoWPAN [6LOWPAN-ND]
addresses many of the concerns described above by optimizing the
Router advertisement, minimizing periodic multicast packets in the
network and introducing two new options - one for node registration
and another for prefix dissemination in a network where all nodes in
the network are uniquely identified by their 64-bit Interface
Identifier. EUI-64 identifiers are recommended as unique Interface
Identifiers, however if the network is isolated from the Internet,
uniqueness of the identifiers may be obtained by other mechanisms
such as a random number generator with lowest collision rate.
Although, the ND optimization [6LOWPAN-ND] applies to 6LoWPAN
[LOWPAN] network, the concept is mostly applicable to a power-aware
IPv6 network. Therefore, this document generalizes the address
registration and multicast reduction in [6LOWPAN-ND] to all IPv6
links.
Thus optimizing the regular IPv6 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 as
Home, Enterprise networks, Data Centers and Operator's Cellular/
Wireless networks.
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 of this document is to provide an efficient Neighbor
Discovery Protocol in classic IPv6 subnets and links. Research
indicates that often networked-nodes require more energy than stand-
alone nodes because a node's energy usage depends on network messages
it receives and responds. While reducing energy consumption is
essential for battery operated nodes in some machines, saving energy
actually a cost factor in business in general as the explosion of
more device usage is leading to usage of more servers and network
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infrastructure in all sectors of the society and business. Thus this
document introduces the node registration concept discussed in
6LoWPAN [LOWPAN], without handling the 'multi-level subnets'
scenarios that are not the typical usecases in classic IPv6 subnets.
In the process, the node registration method is also deemed to be
useful for preventing Neighbor Discovery denial of service ( ND DOS)
attacks.
The proposed changes can be used in two different ways. In one case
all the hosts and routers on a link implement the new mechanisms,
which gives the maximum benefits. In another case the link has a
mixture of new hosts and/or routers and legacy [RFC4861] hosts and
routers, operating in a mixed-mode providing some of the benefits.
In the following sections the document describes the basic operations
of registration methods, optimization of Neighbor Discovery messages,
interoperability with legacy IPv6 implementations and provides a
section on use-case scenarios where it can be typically applicable.
This document also describes an optional feature for node mobility in
the LLN network using backbone routers(BBR) or multiple default
subnet routers. This optional feature in generating a sequence ID by
the host in the registration message will be helpful for deploying
RPL[RFC6550] with reliability in the LLN.
2. Definition Of Terms
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
multi-level Subnets:
It is 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 more 'intermediate' routers
which relays 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 Internet and
Home Network. An IPv6 router with one interface connected to IPv6
subnet and other interface connecting to a non-classic IPv6
interface such as 6LoWPAN interface. Border router is usually the
gateway to the IPv6 network or Internet.
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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.
Backbone Router:
An IPv6 router that federates the LLN using a transit link as a
backbone. A BBR acts as a 6LoWPAN Border Routers (6LBR) and an
Energy 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):
It is the default Router of the single hop IPv6 subnet. This
router 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. The EAH is the host which implements
the host functionality for optimized Neighbor Discovery mentioned
in this document.
Legacy IPv6 Host:
A host in a IPv6 network is considered a IPv6 node without routing
and forwarding capability and implements RFC 4861 host functions.
Legacy IPv6 Router:
An IPv6 Router which implements RFC 4861 Neighbor Discovery
protocols.
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:
It is a low power and lossy network where nodes are typically
constrained in system resources and energy, for instance battery
powered nodes. Alternately LLN could be a network of line-powered
nodes with radio links with lossy characteristics. Wifi, ZigBee,
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Celular networks are examples of such a network.
Extended LLN:
This is the aggregation of multiple LLNs as defined in [RFC4919]
interconnected by a Backbone Link via Backbone Routers and forming
a single IPv6 link.
3. Assumptions for efficiency-aware Neighbor Discovery
o The efficiency-aware nodes in the network carry unique interface
ID in the network in order to form 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.
o /64-bit IPv6 prefix is used for Stateless Auto-address
configuration (SLAAC). The IPv6 Prefix may be distributed with
Router Advertisement (RA) from the default router to all the nodes
in that link.
o The efficiency-aware node MAY maintain a sequence counter in
permanent memory according to section 7 of RFC 6550.
4. The set of Requirements for efficiency and optimization
o Node Registration: Node initiated Registration and address
allocation is done in order to avoid periodic multicast Router
Advertisement messages and often Neighbor Address resolution can
be skipped as all packets go via the default router which now
knows about all the registered nodes. Node Registration enables
reduction of all-node and solicited-node multicast messages in the
subnet.
o Address allocation of registered nodes [ND] are performed using
IPv6 Autoconfiguration [AUTOCONF].
o Host initiated Registration and Refresh is done by sending a
Router Solicitation and then a Neighbor Solicitation Message using
Address Registration Option (described below).
o The node registration may replace the requirement of doing
Duplicate Address Detection.
o 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 the network is an isolated one and uses ULA [ULA] as
its IPv6 address then the deployment should make sure that each
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MAC address in that network has unique address and can provide a
unique 64-bit ID for each node in the network.
o /64-bit Prefix is required 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 the host does not wait for the Router
Advertisements as the NEAR routers do not perform periodic multicast
RA as per RFC 4861. Instead, the EAH sends a multicast RS to find
out a NEAR router in the network. The RS message is the same as in
RFC 4861. The advertising routers in the link responds to the RS
message with RA with Prefix Information Option and any other options
configured in the network. If EAH hosts will look for a RA from a
NEAR (E-flag) and choose a NEAR as its default router and
consequently sends a unicast Neighbor Solicitation Message with ARO
option in order to register itself with the default router. The EAH
does not do Duplicate Address Detection or NS Resolution of
addresses. NEAR maintains a binding of registered nodes and
registration life-time information along with the neighbor Cache
information. The NEAR is responsible for forwarding all the messages
from its EAH including on-link messages from one EAH 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 the
NEAR is configured for 'mixed mode' operation, it should be able to
handle Address Registration Option(ARO) requests and send periodic
RA. Thus it should be able to serve both efficiency-aware hosts and
legacy hosts. Similarly, a legacy host compatible EAH falls back to
RFC 4861 host behavior if a NEAR is not present in the link. See the
section on 'Mixed Mode Operations' for details below.
6. Applicability Statement
This document aims to guide the implementers to choose an appropriate
IPv6 neighbor discovery and Address configuration procedures suitable
for any efficient IPv6 network. These optimization is equally useful
for 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 will reduce cost and increase
bandwidth availability.
The address registration mechanism and associated extension on
Neighbor Discovery protocol allow a low-power host to move between
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the LLN and the classic IPv6 networks as well as movement from one
Border 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 for backward compatibility and transitioning
to a complete efficiency-aware network of hosts and routers. Though
the efficiency-aware only nodes will minimize the ND signaling and
DOS attacks in the LAN.
Applicability of this solution is limited to 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 the hosts in the network.
7.1. Address Registration Option
The Address Registration Option(ARO) is useful for avoiding Duplicate
Address Detection messages since it requires a unique EUI-64 ID for
registration. The address registration is used for maintaining
reachability of the node or host by the router. This option is
exactly the same as in [6LOWPAN-ND] which is reproduced here for the
benefits of the readers. Additionally a Transaction ID field and a
corresponding bit have been introduced in order to detect duplicate
address registration and local mobility of a node.
The routers keep track of host IP addresses that are directly
reachable and their corresponding link-layer addresses. This is
useful for lossy and lowpower networks(LLN) and as well as wired
networks. 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 default router. 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
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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 by hosts an SLLA option MUST be included and the
address that is to be registered MUST be the IPv6 source address of
the Neighbor Solicitation message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length = 2 | Status | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reservd |T| TID | Registration Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ EUI-64 or equivalent +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fields:
Type: 33 ( See [6LOWPAN-ND] )
Length: 8-bit unsigned integer. The length of the option in
units of 8 bytes. Always 2.
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.
Reserved: This field is unused. It MUST be initialized to zero
by the sender and MUST be ignored by the receiver.
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 to
detect 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.
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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 to uniquely identify the
interface of the registered address by including the
EUI-64 identifier assigned to it unmodified.
T bit: One bit flag. Set if the TID octet is present for
processing.
The Status values used in Neighbor Advertisements are:
+--------+--------------------------------------------+
| Status | Description |
+--------+--------------------------------------------+
| 0 | Success |
| 1 | Duplicate Address |
| 2 | Neighbor Cache Full |
| 3 | Registration Ownership Response |
| 4-255 | Allocated using Standards Action [RFC2434] |
+--------+--------------------------------------------+
Table 1
7.2. Refresh and De-registration
A host SHOULD send a Registration message in order to renew its
registration before its registration lifetime expires in order to
continue its connectivity with the network. If anytime, the node
decides that it does not need the default router's service anymore,
it MUST send a de-registration message - i,e, a registration message
with lifetime being set to zero. A mobile host SHOULD first de-
register with the default router before it moves away from the
subnet.
7.3. A New Router Advertisement Flag
A new Router Advertisement flag [RF] is needed in order to
distinguish a router advertisement from a efficiency-aware default
router or a legacy IPv6 router. This flag is ignored by the legacy
IPv6 hosts. EAH hosts use this flag in order to discover a NEAR
router if it receives multiple RA from both legacy and NEAR routers.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|M|O|H|Prf|P|E|R|
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+-+-+-+-+-+-+-+-+
The 'E' bit above MUST be 1 when a IPv6 router implements and
configures the efficiency-aware Router behavior for Neighbor
Discovery as per this document. All other cases E bit is 0.
The legacy IPv6 hosts will ignore the E bit in RA advertisement. All
EAH MUST look for E bit in RA in order to determine the efficiency-
aware support in the default router in the link.
7.4. The Transaction Identification(TID)
The TID field is used together with age of a registration for
arbitration between two routers (default or backbone) to ensure
freshness and ownership of the registration of a given target
address. Same value of TID indicates that both states of
registration are valid. In case of a mismatch between comparable
TIDs, the most recent TID wins. The TID definition used in section
6.4.1 of RFC 6550 for DAOSequence number would be applicable for here
for TID in ARO message.
It is 8 bit field. TID is generated by the host at the time of a new
registraton request.
This document assumes that an implementation will have configuration
knobs to determine whether it is running in classical IPv6 ND [ND] or
Optimized Energy Aware ND (this document) mode or both(Mixed mode).
8. Efficiency-aware Neighbor Discovery Messages
Router Advertisement(RA): Periodic RAs SHOULD be avoided. Only
solicited RAs are RECOMMENDED. An RA MUST
contain the Source Link-layer Address option
containing Router's link-layer address (this
is optional 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 of address resolution. A new flag
(E-flag) is introduced in the RA in order to
characterize the efficiency-aware mode
support. Unlike RFC4861 which suggests
multicast Router Advertisements, this
specification optimizes the exchange by
always unicasting RAs in response to RS.
This is possible since the RS always includes
a SLLA option, which is used by the router to
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unicast the RA.
Router Solicitation(RS): Upon system startup, the node sends a
multicast or link broadcast (when multicast
is not supported at the link-layer) RS to
find out the available routers in the link.
An RS may be sent at other times as described
in section 6.3.7 of RFC 4861. A Router
Solicitation MUST carry Source Link-layer
Address option. Since no periodic RAs are
allowed in the efficiency-aware IPv6 network,
the host may send periodic unicast RS to the
routers. The time-periods for the RS varies
on the deployment scenarios and 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 is used between
the hosts and the default-router as part of
NUD and registering the host's address(es).
An NS message MUST use the Address
Registration option in order to accomplish
the registration.
Neighbor Advertisement (NA): As defined in [ND] and ARO option.
Redirect Messages: A router SHOULD NOT send a Redirect message
to a host since the link has non-transitive
reachability. The host behavior is same as
described in section 8.3 of RFC 4861[ND],
i,e. a host MUST NOT send 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 the prefixes are treated
as off-link. Thus no address resolution is
performed at the hosts. The routers keep
track of Neighbor Solicitations with Address
Registration options(ARO) and create an
extended neighbor cache of reachable
addresses. The router also knows the nexthop
link-local address and corresponding link-
layer address when it wants to route a
packet.
Neighbor Unreachability Detection(NUD): NUD is performed in
"forward-progress" fashion as described in
section 7.3.1 of RFC 4861[ND]. However, if
Address Registration Option is used, the NUD
SHOULD be combined with the Re-registration
of the node. This way no extra message for
NUD is required.
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9. Efficiency-aware Host Behavior
A host sends Router Solicitation at the system startup and also when
it suspects that one of its default routers have become
unreachable(after NUD fails). The EAH MUST process the E-bit in RA
as described in this document. The EAH MUST use ARO option to
register with the neighboring NEAR router.
A host SHOULD be able to autoconfigure its IPv6 addresses using the
IPv6 prefix obtained from Router Advertisement. The host SHOULD form
its link-local address from the EUI-64 as specified by IEEE
Registration Authority and RFC 2373. If this draft feature is
implemented and configured, the host MUST NOT re-direct Neighbor
Discovery messages. The host is not required to join the solicited-
node multicast address but it MUST join the all-node multicast
address.
A host always sends packets to (one of) its default router(s). This
is accomplished by the routers never setting the 'L' flag in the
Prefix options.
The host is unable to forward routes or participate in a routing
protocol. A legacy IPv6 Host compliant EAH SHOULD be able to fall
back to RFC 4861 host behavior if there is no efficiency-aware router
(NEAR) in the link.
The efficiency-aware host MUST NOT send or accept re-direct messages.
It does not join solicited node multicast address.
If the EAH is capable of generating TID and configured for this
operation, the EAH MUST use the TID field and appropriate associated
operation bits in the ARO message during registration and refresh.
10. The Energy Aware Default Router (NEAR) Behavior
The main purpose of the default router in the context of this
document is to receive and process the registration request, forward
packets from one neighbor to the other, informs the routing protocol
about the un-availability of the registered nodes if the routing
protocol requires this information for the purpose of mobility or
fast convergence. A default router (NEAR) behavior may be observed
in one or more interfaces of a Border Router(BR).
A Border Router normally may have multiple interfaces and connects
the nodes in a link like a regular IPv6 subnet(s) or acts as a
gateway between separate networks such as Internet and home networks
. The Border Router is responsible for distributing one or more /64
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prefixes to the nodes to identify a packet belonging to the
particular network. One or more of the interfaces of the Border
Router may be connected with the efficiency-aware hosts or a
efficiency-aware router(NEAR).
The efficiency-aware default router MUST not send periodic RA unless
it is configured to support both legacy IPv6 and efficiency-aware
hosts. If the Router is configured for efficiency-aware hosts
support, it MUST send Router Advertisements with E-bit flag ON and
MUST NOT set 'L' bit in the advertisements.
The router SHOULD NOT garbage collect Registered Neighbor Cache
entries since they need to retain them until the 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 ignored. This behavior
protects the router from Denial Of Service attacks. Similarly, if
Neighbor Unreachability Detection on the router determines that the
host is UNREACHABLE (based on the logic in [ND]), 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.
A default router keeps a cache for all the nodes' IP addresses,
created from the Address Registration processing.
10.1. Router Configuration Modes
An efficiency-aware Router(NEAR) MUST be able to configure in
efficiency-aware-only mode where it will expect all hosts register
with the router following RS; thus will not support legacy hosts.
However, it will create legacy NCE for NS messages for other routers
in the network. This mode is able to prevent ND flooding on the
link.
An efficiency-aware Router(NEAR) SHOULD be able to have configuration
knob to configure itself in Mixed-Mode where it will support both
efficiency-aware hosts and legacy hosts. However even in mixed-mode
the router should check for duplicate entries in the NCE before
creating a new ones and it should rate-limit creating new NCE based
on requests from the same host MAC address.
The RECOMMENDED default mode of operation for the efficiency-aware
router is Mixed-mode. Though it cannot reap the full benefit of
efficiency related optimization described in this document.
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10.2. 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 in
the subnet and the node likes to register with one of the default
routers closest to its present location, it must send another
registration request to the new default router. The new default
router then first send an NS to its peers with a link scope multicast
message to IPv6 address ff02::2 with the ARO option.
10.2.1. Registration ownership
The subnet-local-routers check their respective NCE table for the
particular registration. If the registration entry exists, the NEAR
default router then calculates the 'age' of the registration by
subtracting the present time from the registration received time
recorded at the NCE. The NEAR router then responds with a NA with
ARO option Status being equal to 3 and replaces the 'registration
lifetime' field with the 'age' of registration. Upon receiving the
NA from the neighboring routers the prospective default router
determines its registration ownership. If the other router
registration age is higher than its own registration age, then the
current router is considered to have the most recent registration
ownership.
If both routers registration age are zero or within a 50msec window,
then the TID field is used to determine the ownership. The higher
value of TID wins. Note that the registration ownership and local
movement detection behavior in NEAR router MUST be optionally
configured. The NEAR routers MAY implement this feature.
Configuring this option is needed when the NEAR routers are used in a
low power and lossy network environment.
11. NCE Management in efficiency-aware Routers
The use of explicit registrations with lifetimes plus the desire to
not multicast Neighbor Solicitation messages for hosts imply that we
manage the Neighbor Cache entries slightly differently than in [ND].
This results in two different types of NCEs and the types specify how
those entries can be removed:
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Legacy: Entries that are subject to the normal rules in
[ND] that allow for garbage collection when low
on memory. Legacy entries are created only
when there is no duplicate NCE. In mixed-mode
and efficiency-aware mode the legacy entries
are converted to the registered entries upon
successful processing of ARO. Legacy type can
be considered as union of garbage-collectible
and Tentative Type NCEs described in
[6LOWPAN-ND].
Registered: Entries that have an explicit registered
lifetime and are kept until this lifetime
expires or they are explicitly unregistered.
Note that the type of the NCE is orthogonal to the states specified
in [ND].
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] host in
the Mixed-mode of operation.
In the 'Efficiency-aware' only mode the router MUST NOT modify an
existing 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.
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 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 updates
the registered NCE for the IPv6 address. If the Neighbor Cache is
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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 Link Layer)
Option is not required with this NA.
Typically for efficiency-aware routers (NEAR), the registration life-
time and EUI-64 are recorded in the Neighbor Cache Entry along with
the existing information described in [ND]. 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 will
renew their registration to keep maintain the state of reachability
of the NCE at the router. However the router may do NUD to the idle
or unreachable hosts as per [ND].
In addition, NEAR default routers MUST associate a record of the age
of the registration. 'Age' is a simple way to detect movement of a
node from local default router to another. 'Age' information SHOULD
contain System-time when the registration is first created or last
refreshed. This system-time is deducted from the current system-time
to determine the "age" of the registration and it is used for age
reporting with Neighbor advertisement for selection of registration
ownership among the default-router contenders in case of local
movement of the host from one default-router to another in the same
subnet. 'Age' is always considered zero for a fresh registration or
a registration refresh message.
11.1. Handling ND DOS Attack
IETF community has discussed possible issues with /64 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 attacks by:
o Having the hosts register with the default router
o Having the hosts send their packets via the default router
o Not resolving addresses for the 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
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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 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 the following configurations in
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 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 to
communicate with each other.
In mixed-mode operation, a NEAR MUST be configured for mixed-mode in
order 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 and follow RFC 4861 NCE management for the 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 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 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
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behavior. On the other hand, in the efficiency-aware mode EAH SHOULD
ignore multicast Router Advertisements(RA) sent by the legacy and
Mixed-mode routers in the link.
In mixed mode operation, the Router SHOULD be able to do local
movement detection based on ARO if it is configured for that
operation for EAH hosts. For the legacy hosts, the mixed-mode router
MAY follow classical IPv6 methods of movement detection and MAY act
as ND proxy by sending NA with 'O' bit.[ Reference??]
The routers that are running on efficiency-aware mode or legacy mode
SHOULD NOT dynamically switch the mode without flushing the Neighbor
Cache Entries.
13. Bootstrapping
If the network is a efficiency-aware IPv6 subnet, and the efficiency-
aware Neighbor Discovery mechanism is used by the hosts and routers
as described in this document. At the start, the node uses its link-
local address to send Router Solicitation and then it sends the Node
Registration message as described in this document in order to form
the address. The Duplicate address detection process should be
skipped if the network is guaranteed to have unique interface
identifiers which is used to form an IPv6 address.
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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
RECOMMEDED 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
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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 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
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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. Detecting Network Attachment(DNA)
IPv6 DNA[DNA] uses unicast ND 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
the node implements this document along with DNA, it MUST send ARO
option with its Neighbor Solicitation unicast message if the
candidate router advertisement indicates that the router is a NEAR
router. If the candiate router is a legacy router then and it is the
only choice then the EAH host adapt to the legacy behavior. However
if EAH node implements DNA host capability as well, then it SHOULD
give preference to the NEAR routers in its candidate list of routers.
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
The efficient-ND SHOULD continue to support the legacy IPv6 Neighbor
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 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.
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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 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 mechanism 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 the IPv6-address from DHCPv6, a EAH node SHOULD then
register the IP-address with the default router for avoiding
Duplicate address detection and Address Resolution. For Legacy
DHCPv6 nodes there is no change 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.
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 ability of nodes to join and leave
the multicast group or forwarding multicast traffic or responding to
multicast queries.
18. RPL Implications
RPL [RFC6550] does not provide means for duplicate address detection
and in particular does not have a concept of unique identifier. On
the other hand, RPL is designed to discover and resolve conflicts
that arise when a mobile device changes its point of attachment, with
a sequence counter that is owned by the device and incremented at
each new registration, called a DAOSequence. As we extend 6LoWPAN ND
operation over a backbone and scale, there is a similar need to
resolve the latest point of attachment 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 the
same backbone. In order to cover all cases in a consistent fashion,
this document requires that a sequence counter call TID for
Transaction ID and with the similar rules as the RPL DAOSequence is
added to the ND registration. This document defines the TID
operations and RPL may use the reserved fields for their purpose
inside the LLN.
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19. Updated Neighbor Discovery Constants
This section discusses the updated default values of ND constants
based on [ND] 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
Host Constants:
MAX_RTR_SOLICITATION_INTERVAL(NEW) 60 seconds
Also refer to [ENH-ND] , [IMPAT-ND] and [6LOWPAN-ND] for further
tuning of ND constants.
20. Security Considerations
These optimizations are not known to introduce any new threats
against Neighbor Discovery beyond what is already documented for IPv6
[RFC 3756].
Section 11.2 of [ND] applies to this document as well.
This mechanism minimizes the possibility of ND /64 DOS attacks in
efficiency-aware mode. See Section 11.1.
21. 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.
22. Changelog
Changes from draft-chakrabarti-nordmark-energy-aware-nd-02:
o Replaced energy-aware with efficency-aware which covers both
energy efficiency and other operational efficiency
o Added consideration for DNA, ND proxy and clarified that this is
useful for networks with MLD-snooping switches as well
o Added use-cases, Support for Mixed-mode operations and a diagram
for bootstrapping scenario.
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o Clarified its applicability when DHCP is used for address
allocation.
23. Acknowledgements
The primary idea of this document are from 6LoWPAN Neighbor Discovery
document [6LOWPAN-ND] 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].
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.
The authors like to thank Dave Thaler, Jari Arkko, Ylva Jading,
Niklas J. Johnsson, Reda Nedjar, Purvi Shah, Jaume Rius Riu, Fredrik
Garneij for their useful comments on this work.
24. References
24.1. 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., and C. Bormann,
"ND Optimizations for 6LoWPAN", RFC 6775, November 2012.
[ND] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6", RFC 4861,
September 2007.
[LOWPAN] Montenegro, G. and N. Kushalnagar, "Transmission of IPv6
Packets over IEEE 802.15.4 networks", RFC 4944,
September 2007.
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[LOWPANG] Kushalnagar, N. and G. Montenegro, "6LoWPAN: Overview,
Assumptions, Problem Statement and Goals", RFC 4919,
August 2007.
24.2. Informative References
[IPV6] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(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., and T. Jinmei, "IPv6 Stateless
Autoconfiguration", RFC 4862, September 2007.
[SEND] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "Secure
Neighbor Discovery", RFC 3971, March 2005.
[AUTOADHOC]
Baccelli, E. and M. Townsley, "IP Addressing Model in
Adhoc Networks", RFC 5889, September 2010.
[NDDOS-halpern]
Halpern, J., "IP Addressing Model in Adhoc Networks",
draft-halpern-6man-nddos-mitigation-00.txt (work in
progress), October 2011.
[ENH-ND] Kumari, W., Gashinsky, I., Jaeggli, J., and K.
Chittimaneni, "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, S., "Requirements for Prefix Delegation",
RFC 3769, June 2004.
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[RF] Haberman, B. and B. Hinden, "IPv6 Router Advertisement
Flags option", RFC 5175, March 2008.
[ULA] "Unique Local IPv6 Addresses", RFC 4193.
[IPV6M] Johnson, D., Perkins, C., 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.
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 and also provides ways to
minimize the ND flood of messages. Moreover, this mechanism will
work with data-center nodes which are deliberately in sleep mode 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 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
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for efficiency-aware control protocols and dynamic address
allocation. The in-built address allocation and autoconfiguration
mechanism in 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. Though the informational drafts and
RFC6459 about 3GPP systems IPv6 behavior provides best practices,
this document provides standard based optimization that 3GPP systems
can follow to improve efficiency in the mobile nodes and 3GPP
Routers.
A.6. Industrial Networks
RPL [RFC6550] is used for Industrial wireless networks.
Authors' Addresses
Samita Chakrabarti
Ericsson
San Jose, CA
USA
Email: samita.chakrabarti@ericsson.com
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Erik Nordmark
Cisco Systems
San Jose, CA
USA
Email: nordmark@cisco.com
Pascal Thubert
Cisco Systems
Email: pthubert@cisco.com
Margaret Wasserman
Painless Security
Email: mrw@lilacglade.org
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