draft-ietf-6lo-backbone-router-08.txt   draft-ietf-6lo-backbone-router-09.txt 
6lo P. Thubert, Ed. 6lo P. Thubert, Ed.
Internet-Draft cisco Internet-Draft Cisco Systems
Intended status: Standards Track C. Perkins Updates: 4861, 8505 (if approved) C. Perkins
Expires: April 25, 2019 Futurewei Intended status: Standards Track Futurewei
October 22, 2018 Expires: June 8, 2019 E. Levy-Abegnoli
Cisco Systems
December 5, 2018
IPv6 Backbone Router IPv6 Backbone Router
draft-ietf-6lo-backbone-router-08 draft-ietf-6lo-backbone-router-09
Abstract Abstract
Backbone Routers running IPv6 Neighbor Discovery can manage multiple Backbone Routers are RFC8505 Routing Registrars that provide proxy
wireless links to form a large MultiLink Subnet, but it is more services for IPv6 Neighbor Discovery. Backbone Routers federate
efficient if IPv6 Neighbor Discovery packets are not broadcast over multiple wireless Links over a Backbone Link to form a MultiLink
the wireless links. This specification specifies proxy operations Subnet. Backbone Routers placed along the wireless edge of the
for IPv6 Neighbor Discovery on behalf of devices located on Backbone handle IPv6 Neighbor Discovery, and route packets on behalf
broadcast-inefficient wireless networks. Backbone Routers placed of registered nodes.
along the wireless edge of the backbone handle IPv6 Neighbor
Discovery, and route packets on behalf of registered nodes. Wireless
nodes register, or are registered by proxy, to a Backbone Router to
establish proxy services in a fashion similar to layer-2 association.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 25, 2019. This Internet-Draft will expire on June 8, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Applicability and Requirements Served . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2. References . . . . . . . . . . . . . . . . . . . . . . . 5
5. Backbone Router Routing Operations . . . . . . . . . . . . . 8 2.3. New Terms . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Over the Backbone Link . . . . . . . . . . . . . . . . . 8 2.4. Acronym Definitions . . . . . . . . . . . . . . . . . . . 6
5.2. Proxy Operations Over the LLN Interface . . . . . . . . . 9 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.2.1. Routing Proxy Operations . . . . . . . . . . . . . . 10 3.1. Access Link . . . . . . . . . . . . . . . . . . . . . . . 9
5.2.2. Bridging Proxy Operations . . . . . . . . . . . . . . 10 3.2. Route-Over Mesh . . . . . . . . . . . . . . . . . . . . . 10
6. Backbone Router Proxy Operations . . . . . . . . . . . . . . 11 3.3. MultiLink Subnet Consistency . . . . . . . . . . . . . . 11
6.1. Primary and Secondary BBRs . . . . . . . . . . . . . . . 12 3.4. Registering Node . . . . . . . . . . . . . . . . . . . . 11
6.2. Binding Table . . . . . . . . . . . . . . . . . . . . . . 12 3.5. Using IPv6 ND Over the Backbone Link . . . . . . . . . . 12
6.3. Registration and Binding Table Entry Creation . . . . . . 13 3.6. Routing Proxy Operations . . . . . . . . . . . . . . . . 13
6.4. Defending Addresses . . . . . . . . . . . . . . . . . . . 14 3.7. Bridging Proxy Operations . . . . . . . . . . . . . . . . 14
7. Security Considerations . . . . . . . . . . . . . . . . . . . 15 3.8. Leveraging Optimistic DAD . . . . . . . . . . . . . . . . 14
8. Protocol Constants . . . . . . . . . . . . . . . . . . . . . 16 4. Updating RFC 4861 . . . . . . . . . . . . . . . . . . . . . . 15
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 5. Updating RFC 8505 . . . . . . . . . . . . . . . . . . . . . . 15
10. Future Work . . . . . . . . . . . . . . . . . . . . . . . . . 16 6. 6BBR detailed Operations . . . . . . . . . . . . . . . . . . 15
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 6.1. Primary and Secondary 6BBRs . . . . . . . . . . . . . . 16
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 6.2. Binding Table . . . . . . . . . . . . . . . . . . . . . . 16
12.1. Normative References . . . . . . . . . . . . . . . . . . 16 6.3. Registration and Binding Table Entry Creation . . . . . . 17
12.2. Informative References . . . . . . . . . . . . . . . . . 17 6.4. Defending Addresses . . . . . . . . . . . . . . . . . . . 18
12.3. External Informative References . . . . . . . . . . . . 19 7. Security Considerations . . . . . . . . . . . . . . . . . . . 20
Appendix A. Changes from revision 07 to revision 08 . . . . . . 20 8. Protocol Constants . . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
10. Future Work . . . . . . . . . . . . . . . . . . . . . . . . . 20
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 21
12.1. Normative References . . . . . . . . . . . . . . . . . . 21
12.2. Informative References . . . . . . . . . . . . . . . . . 22
12.3. External Informative References . . . . . . . . . . . . 24
Appendix A. Applicability and Requirements Served . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
1. Introduction 1. Introduction
IEEE STD. 802.1 [IEEEstd8021] Ethernet Bridging provides an efficient IEEE STD. 802.1 [IEEEstd8021] Ethernet Bridging provides an efficient
and reliable broadcast service; applications and protocols have been and reliable broadcast service; applications and protocols have been
built that heavily depend on that feature for their core operation. built that heavily depend on that feature for their core operation.
Unfortunately, many wireless networks do not economically provide the Unfortunately, Low-Power Lossy Networks (LLNs) and local wireless
broadcast capabilities of Ethernet Bridging; protocols designed for networks generally do not provide the broadcast capabilities of
bridged networks that rely on broadcast often exhibit disappointing Ethernet Bridging in an economical fashion; protocols designed for
behaviours when applied unmodified to a wireless medium (see bridged networks that rely on multicast and broadcast often exhibit
[I-D.ietf-mboned-ieee802-mcast-problems]). disappointing behaviours when employed unmodified on a local wireless
medium (see [I-D.ietf-mboned-ieee802-mcast-problems]).
WiFi [IEEEstd80211] Access Points (APs) deployed in an Extended Wi-Fi [IEEEstd80211] Access Points (APs) deployed in an Extended
Service Set (ESS) act as bridges. In order to ensure a solid Service Set (ESS) act as Ethernet Bridges [IEEEstd8021], with the
connectivity to the devices and protect the medium against harmful interesting caveat that the bridging state is populated proactively
broadcasts, they refrain from relying on broadcast-intensive at the association time. This ensures a solid connectivity to the
protocols such as Transparent Bridging on the wireless side. node (STA) and protects the wireless medium against the broadcast-
Instead, an association process is used to register the MAC addresses intensive Transparent Bridging reactive lookups. In other words, the
of the wireless device (STA) to the AP. The APs subsequently proxy association process is used to register the MAC Address of the STA to
the bridging operation and eliminate the broadcasts. the AP. The APs subsequently proxies the bridging operation and does
not need to forward the broadcast lookups over the radio.
The IPv6 [RFC8200] Neighbor Discovery [RFC4861] [RFC4862] Protocol Like Transparent Bridging, the operations of the IPv6 [RFC8200]
(IPv6 ND) operations are reactive and rely heavily on multicast Neighbor Discovery [RFC4861] [RFC4862] Protocol (IPv6 ND) are
transmissions to locate an on-link correspondent and ensure address reactive and rely heavily on multicast transmissions to locate an on-
uniqueness. Duplicate Address Detection [RFC4862] (DAD) mechanism link correspondent and ensure the uniqueness of an Address. The
was designed as a natural match with the efficient broadcast mechanism for Duplicate Address Detection (DAD) [RFC4862] was also
operation of Ethernet Bridging. However, since broadcast can be designed as a natural match with the efficient broadcast operation of
unreliable over wireless media, DAD often fails to discover Ethernet Bridging. However, since broadcast can be unreliable over
duplications [I-D.yourtchenko-6man-dad-issues]. DAD usually appears wireless media, DAD often fails to discover duplications
to work on wireless media, not because address duplication is [I-D.yourtchenko-6man-dad-issues]. A conflict of IPv6 Address is
detected and solved as designed, but because the use of 64-bit still a very rare event, not because Address duplications are
Interface IDs makes duplication into a very rare event. detected and solved as designed, but because of the sheer entropy of
the 64-bit Interface IDs.
IPv6 multicast messages are typically broadcast over the wireless IPv6 multicast messages are typically broadcast over the wireless
medium. They are processed by most if not all wireless nodes over medium; they are processed by most if not all the wireless nodes over
the ESS fabric even when very few if any of them are subscribed to the subnet - e.g., the ESS fabric - even when very few if any of the
the multicast address. A simple Neighbor Solicitation (NS) nodes is subscribed to the multicast flow. The IPv6 ND Neighbor
[RFC4861], that is supposedly targeted to a small group of nodes, can Solicitation (NS) [RFC4861] is such a message; NS messages are used
congest the wireless bandwidth for DAD and Address lookup, and are frequently observed in a
[I-D.ietf-mboned-ieee802-mcast-problems]. The IPv6 ND operation situation of mobility and when a node wakes up and reconnects to the
leads to undesirable power consumption in battery-operated devices. wireless network. The NS message is targeted to a Sollicitated-Node
Multicast Address (SNMA) [RFC4291] and should in theory only reach a
These problems suggest restricting IPv6 ND broadcasts over wireless very small group of nodes; but since Layer-3 multicast messages are
access links, which can be done by dividing up the subnet. Another effectively broadcasted at Layer-2, the volume of Address lookups and
way is to take over (proxy) the Layer-3 protocols that rely on DADs over a large fabric can effectively consume bandwidth to the
broadcast operation at the boundary of the wired and wireless point that it becomes detrimental to unicast traffic (see
domains, emulating the Layer-2 association at layer-3. For instance, [I-D.ietf-mboned-ieee802-mcast-problems]).
IEEE 802.11 [IEEEstd80211] specifies ARP and ND proxy [RFC4389]
services at the Access Points (APs).
Current devices rely on snooping for detecting association state,
which is failure-prone in lossy and mobile conditions. With
snooping, a state (e.g. a new IPv6 address) may not be discovered, or
a change of state (e.g. a movement) may be missed, leading to
unreliable connectivity.
WPAN devices (i.e., those implementing IEEE STD. 802.15.4
[IEEEstd802154]) can make use of Neighbor Discovery Optimization for
IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs)
[RFC6775] which treats the wireless medium as different from
Ethernet. RFC 6775 is updated as [I-D.ietf-6lo-rfc6775-update]; the
update includes changes that are required by this document.
2. Applicability and Requirements Served
This specification updates and generalizes 6LoWPAN ND to a broader
range of Low power and Lossy Networks (LLNs) with support for
Duplicate Address Detection (DAD) and address lookup that does not
require broadcasts over the LLNs. The term LLN is used loosely in
this specification to cover multiple types of WLANs and WPANs,
including Low-Power Wi-Fi, BLUETOOTH(R) Low Energy, IEEE STD.
802.11AH and IEEE STD. 802.15.4 wireless meshes, so as to address the
requirements listed in Appendix B.3 of [I-D.ietf-6lo-rfc6775-update]
"Requirements Related to the Variety of Low-Power Link types".
For the TimeSlotted Channel Hopping (TSCH) mode of [IEEEstd802154], Additionally, wireless nodes that do not belong to the SNMA group
the 6TiSCH architecture [I-D.ietf-6tisch-architecture] describes how still have to keep their radio awake and listen to broadcasted NS
a 6LoWPAN ND host could connect to the Internet via a RPL mesh messages, which is a total waste of energy for them. In order to
Network, but doing so requires extensions to the 6LOWPAN ND protocol control their power consumption, battery-operated nodes such as IOT
to support mobility and reachability in a secure and manageable sensors and smartphones may then elect to blindly ignore a portion of
environment. The extensions detailed in this document also work for the broadcasts, which tends to make the Layer-3 protocol operations
the 6TiSCH architecture, serving the requirements listed in even less reliable.
Appendix B.2 of [I-D.ietf-6lo-rfc6775-update] "Requirements Related
to Routing Protocols".
This specification also applies to wireless links such as Low-Power These problems can be alleviated by a reduction of IPv6 ND broadcasts
IEEE STD. 802.11 (Wi-Fi) and IEEE STD. 802.15.1 (Bluetooth) over wireless access links. One classical way to achieve this to
[IEEEstd802151]. It makes use of extensions to [RFC6775] to enable split the broadcast domains and route between subnets, possibly by
proxy operation by the 6BBR, as specified in assigning a /64 prefix to each wireless node (see [RFC8273]).
[I-D.ietf-6lo-rfc6775-update]. The BBR proxy operations eliminate
the need for wireless nodes to respond synchronously when a lookup is
performed for their addresses. This provides the function of a Sleep
Proxy for ND [I-D.nordmark-6man-dad-approaches].
This draft establishes a Backbone that treats multiple LLNs as a Another way is to proxy the Layer-3 protocols that rely on broadcast
single IPv6 MultiLink Subnet. Each LLN in the subnet is anchored at operations at the boundary of the wired and wireless domains, in a
an IPv6 Backbone Router (6BBR). The Backbone Routers interconnect fashion similar to the Layer-2 association but at layer-3. To that
the LLNs and advertise the addresses of the 6LNs using proxy-ND effect, IEEE 802.11 [IEEEstd80211] requires ARP and proxy-ND
operations. This specification extends IPv6 ND over the backbone to [RFC4389] services at the Access Points (APs), and this specification
distinguish address movement from duplication and eliminate stale is a possible response to that requirement.
state in the backbone routers and backbone nodes once a 6LN has
roamed. In this way, mobile nodes may roam rapidly from one 6BBR to
the next and requirements in Appendix B.1 of
[I-D.ietf-6lo-rfc6775-update] "Requirements Related to Mobility" are
met.
This specification enables any 6LN to register its IPv6 addresses and IPv6 proxy-ND services can be obtained automatically by snooping the
thereby obtain routing services including proxy-ND operations over IPV6 ND protocol (see [I-D.bi-savi-wlan]). Proprietary techniques
the backbone, providing a solution to the requirements expressed in for IPv6 ND and DHCP snooping are effectively deployed, and though
Appendix B.4 of [I-D.ietf-6lo-rfc6775-update] "Requirements Related snooping is really useful to cancel undesirable broadcast
to Proxy Operations". transmissions, it has also proven to be unreliable; An IPv6 Address
may not be discovered immediately due to a packet loss, or a silent
node that does not use the Address for a while; a change of state
(e.g. due a movement) may be missed or misordered, leading to
unreliable connectivity and a partial knowledge of the state of the
network.
The Link Layer Address (LLA) that is returned as Target LLA (TLLA) in With this specification, a wireless node proactively registers its
Neighbor Advertisements (NA) messages by the 6BBR on behalf of the IPv6 Addresses using a NS(EARO) as specified in [RFC8505] to an IPv6
Registered Node over the backbone may be that of the Registering Backbone Router (6BBR). The 6BBR is a Routing Registrar per
Node. In that case, the 6BBR needs to bridge the unicast packets [RFC8505]. It is also a Border Router that performs the IPv6 proxy
(Bridging proxy), or that of the 6BBR on the backbone, in which case Neighbor Discovery operations on its Backbone interface on behalf of
the 6BBRs needs to route the unicast packets (Routing proxy). The the 6LNs that are registered on its LLN interfaces. This effectively
IPv6 ND operation is minimized as the number of 6LNs grows in the recreates at Layer-3 the equivalent of an association such as found
LLN. This meets the requirements in Appendix B.6 of in IEEE STD. 802.11 for the purpose of providing reachability to the
[I-D.ietf-6lo-rfc6775-update] "Requirements Related to Scalability", registered Addresses without the need of a broadcast lookup over the
as long has the 6BBRs are dimensioned for the number of registrations wireless medium. Additional benefits are discussed in Appendix A.
that each needs to support.
In the case of Low-Power IEEE STD. 802.11, a 6BBR may be collocated 2. Terminology
with a standalone AP or a CAPWAP [RFC5415] wireless controller. Then
the wireless client (STA) makes use of this specification to register
its IPv6 address(es) to the 6BBR over the wireless medium. In the
case RPL, the RPL root is collocated with a 6LoWPAN Border Router
(6LBR), and either collocated with or connected to the 6BBR over an
IPv6 Link. The 6LBR makes use of this specification to register the
6LNs on their behalf to the 6BBR.
3. Terminology 2.1. BCP 14
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] . 14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here.
2.2. References
In this document, readers will encounter terms and concepts that are In this document, readers will encounter terms and concepts that are
discussed in the following documents: discussed in the following documents:
o "Neighbor Discovery Proxies (proxy-ND)" [RFC4389]
o "Optimistic Duplicate Address Detection" [RFC4429], and
o "Neighbor Discovery for IP version 6" [RFC4861], o "Neighbor Discovery for IP version 6" [RFC4861],
o "IPv6 Stateless Address Autoconfiguration" [RFC4862], o "IPv6 Stateless Address Autoconfiguration" [RFC4862],
o "Multi-Link Subnet Issues" [RFC4903], o "MultiLink Subnet Issues" [RFC4903],
o "IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs): o "IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs):
Overview, Assumptions, Problem Statement, and Goals" [RFC4919], Overview, Assumptions, Problem Statement, and Goals" [RFC4919],
o Neighbor Discovery Optimization for Low-power and Lossy Networks o Neighbor Discovery Optimization for Low-Power and Lossy Networks
[RFC6775], [RFC6775],
o ,"Mobility Support in IPv6" [RFC6275], o ,"Mobility Support in IPv6" [RFC6275],
o "Neighbor Discovery Proxies (ND Proxy)" [RFC4389] o "Problem Statement and Requirements for IPv6 over Low-Power
Wireless Personal Area Network (6LoWPAN) Routing" [RFC6606], and
mostly
o "Optimistic Duplicate Address Detection" [RFC4429], and
o "Registration Extensions for 6LoWPAN Neighbor Discovery" o "Registration Extensions for 6LoWPAN Neighbor Discovery"
[I-D.ietf-6lo-rfc6775-update] [RFC8505].
This document also uses terminology from [RFC7102] and 2.3. New Terms
[I-D.ietf-6lo-rfc6775-update], and introduces the following
terminology: This document also introduces the following terminology:
Federated
A subnet that is partitionned over a Backbone and one or more
(wireless) access links, is said to be federated into one
MultiLink Subnet by the proxy-ND operation of 6BBRs located at
the edge of the Backbone and the access links and providing a
semblance of a non-partitionned subnet for IPv6 ND over the
Backbone.
Sleeping Proxy Sleeping Proxy
A 6BBR acts as a Sleeping Proxy if it answers ND Neighbor A 6BBR acts as a Sleeping Proxy if it answers ND Neighbor
Solicitation over the backbone on behalf of the Registered Solicitation over the Backbone on behalf of the Registered
Node. Node.
Unicasting Proxy Unicasting Proxy
A Unicasting Proxy forwards NS messages to the Registering A Unicasting Proxy forwards NS messages to the Registering
Node, transforming Layer-2 multicast into unicast. Node, transforming Layer-2 multicast into unicast.
Routing proxy Routing Proxy
A routing proxy advertises its own MAC address as the TLLA in A Routing Proxy advertises its own MAC Address as the TLLA in
the proxied NAs over the backbone, as opposed to that of the the proxied NAs over the Backbone, as opposed to that of the
node that performs the registration. node that performs the registration.
Bridging proxy Bridging Proxy
A Bridging proxy advertises the MAC address of the node that A Bridging Proxy advertises the MAC Address of the node that
performs the registration as the TLLA in the proxied NAs over performs the registration as the TLLA in the proxied NAs over
the backbone. In that case, the MAC address and the mobility the Backbone. In that case, the MAC Address and the mobility
of 6LN is still visible across the bridged backbone fabric. of 6LN is still visible across the bridged Backbone fabric.
Primary BBR Primary 6BBR
The BBR that will defend a Registered Address for the purpose The 6BBR that will defend a Registered Address for the purpose
of DAD over the backbone. of DAD over the Backbone.
Secondary BBR Secondary 6BBR
A BBR other than the Primary BBR to which an address is A 6BBR other than the Primary 6BBR to which an Address is
registered. A Secondary Router MAY advertise the address over registered. A Secondary Router MAY advertise the Address over
the backbone and proxy for it. the Backbone and proxy for it.
4. Overview 2.4. Acronym Definitions
The services specified in this document assist a 6LN to move freely This document uses the following acronyms:
from an LLN anchored at one 6BBR to an LLN anchored at another 6BBR
on the same backbone and keep any or all of the IPv6 addresses that 6BBR: 6LoWPAN Backbone Router
the 6LN has formed.
6LBR: 6LoWPAN Border Router
6LN: 6LoWPAN Node
6LR: 6LoWPAN Router
6CIO: Capability Indication Option
EARO: (Extended) Address Registration Option -- (E)ARO
EDAR: (Extended) Duplicate Address Request -- (E)DAR
EDAC: (Extended) Duplicate Address Confirmation -- (E)DAC
DAD: Duplicate Address Detection
DODAG: Destination-Oriented Directed Acyclic Graph
LLN: Low-Power and Lossy Network
NA: Neighbor Advertisement
NCE: Neighbor Cache Entry
ND: Neighbor Discovery
NDP: Neighbor Discovery Protocol
NS: Neighbor Solicitation
ROVR: Registration Ownership Verifier (pronounced rover)
RPL: IPv6 Routing Protocol for LLNs (pronounced ripple) [RFC6550]
RA: Router Advertisement
RS: Router Solicitation
TID: Transaction ID (a sequence counter in the EARO)
3. Overview
A 6BBR provides proxy-ND services to 6LNs attached to an LLN that is
anchored at the 6BBR; this way, a subnet that is located on a
Backbone can be extended in the LLN as a MultiLink Subnet. The LLN
may be a hub-and-spoke network, a mesh-under or a route-over network.
The proxy-ND operation can co-exist with IPv6 ND over the Backbone.
The proxy state can be distributed across multiple 6BBR attached to a
same Backbone. A 6LN may move freely from an LLN anchored at one
6BBR to an LLN anchored at another 6BBR on the same Backbone and
retain any or all of the IPv6 Addresses that the 6LN has formed.
The registration to a proxy service is done via a NS/NA(EARO)
exchange. The 6BBR operation resembles that of a Mobile IPv6 (MIPv6)
[RFC6275] Home Agent. The combination if a 6BBR and a MIPv6 HA
enables a full mobility support for 6LNs, inside and outside the
links that form the subnet.
| |
+-----+ +-----+
| | Gateway (default) Router | | Gateway (default) Router
| | | |
+-----+ +-----+
| |
| Backbone Link | Backbone Link
+-------------------------+----------------------+ +-------------------------+----------------------+
| | | | | |
skipping to change at page 7, line 28 skipping to change at page 8, line 28
o o o o o o o o o o o o
o o o o o o o o o o o o o o o o o o o o o o o o o o o o
o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o
o o o o o o o o o o o o o o o o o o o o
o o o o o o o o o o o o o o
LLN LLN LLN LLN LLN LLN
Figure 1: Backbone Link and Backbone Routers Figure 1: Backbone Link and Backbone Routers
Each Backbone Router (6BBR) maintains a Binding Table of its Each Backbone Router (6BBR) maintains an abstract Binding Table of
Registered Nodes. The Binding Tables form a distributed database of its Registered Nodes. The Binding Tables form a distributed database
wireless 6LNs that reside on the LLNs or on the backbone, and use an of 6LNs that reside on the LLNs or on the IPv6 Backbone, and use an
extension to IPv6 ND to exchange that information across the Backbone extension to IPv6 ND to exchange that information across the
as described below. Backbone. In that process:
The Extended Address Registration Option (EARO) defined in The Extended Address Registration Option (EARO) defined in
[I-D.ietf-6lo-rfc6775-update] is used in the ND exchanges over the [RFC8505] is used in the ND exchanges over the Backbone between
backbone between the 6BBRs to enable the registration for routing and the 6BBRs to help distinguish duplication from movement.
proxy services, as well as distinguish duplication from movement. Optionally, Extended Duplicate Address Messages (EDAR and EDAC)
can also be used between the 6BBR and a 6LBR if one is present on
the Backbone. Address duplication is detected using the ROVR
field, and conflicting registrations to different 6BBRs by a same
owner 6LR are resolved using the TID field.
Address duplication is detected using the ROVR field in the EARO. In The Link Layer Address (LLA) that the 6BBR advertises for the
case of conflicting registrations to multiple 6BBRs from the same Registered Address on behalf of the Registered Node over the
node, the Transaction ID (TID) in the EARO enables 6BBRs to determine Backbone may be that of the Registering Node; in that case, the
the latest registration for that 6LN. 6BBR needs to bridge the unicast packets (Bridging Proxy).
Alternatively, the LLA can be that of the 6BBR on the Backbone
interface, in which case the 6BBRs receives at Layer-2 and and
needs to route at Layer-3 the unicast packets (Routing Proxy).
This is discussed in more details in Section 3.6 and Section 3.7,
respectively.
6BBRs perform ND proxy operations over the backbone, on behalf of 3.1. Access Link
their Registered Nodes. Registration to a proxy service is done via
a NS/NA(EARO) exchange. 6BBR operation resembles that of a Mobile
IPv6 (MIPv6) [RFC6275] Home Agent. This enables mobility support for
6LNs; if they move outside of the network delimited by the Backbone
link, then they make use of a Home Agent. Home Agent functionality
can easily be collocated with a 6BBR on the same backbone interface
of a router.
The Optimistic Duplicate Address Detection [RFC4429] (ODAD) This specification also applies to (hub-and-spoke) Access Links such
specification details how an address can be used before a Duplicate as (Low-Power) IEEE STD. 802.11 (Wi-Fi) [IEEEstd80211] and IEEE STD.
Address Detection (DAD) is complete, and mandates that an address 802.15.1 (Bluetooth) [IEEEstd802151]. Figure 2 illustrates an ODAD-
that is TENTATIVE should not be associated to a Source Link-Layer complient (see Section 3.8) example of a 6LN that forms an IPv6
Address Option in a Neighbor Solicitation message. This Address and registers it to a 6BBR acting as a 6LR [RFC8505].
specification makes use of ODAD to create a temporary proxy state in
the 6BBR until DAD is completed over the backbone. This way, the
specification allows proxy state distribution across multiple 6BBR
and co-existence with IPv6 ND over the backbone.
5. Backbone Router Routing Operations 6LoWPAN Node 6BBR 6LBR default
(STA) (AP) Router
|(Wireless) LLN | IPv6 ND Backbone |
| | (Ethernet) |
| RS | | |
|-------------->| | |
| (multicast) | | |
| | | |
| RA(PIO) | | |
|<--------------| | |
| (L2 unicast) | | |
| | | |
| NS(EARO) | | |
|-------------->| | |
| (optimistic) | | |
| | Extended DAR | |
| |------------->| |
| | Extended DAC | |
| |<-------------| |
| | NS-DAD(EARO) |
| |------------------------------>|
| |-------> (multicast) |
| |---------------------> |
| | RS(no SLLAO, for ODAD) |
| |------------------------------>|
| | (if no BCE) NS-LOOKUP |
| |<------------------------------|
| | NA(SLLAO, not(O), EARO) |
| |------------------------------>|
| | RA(unicast) |
| |<------------------------------|
| | | |
| IPv6 Packets in optimistic mode |
|<--------------------------------------------->|
| | | |
| NA(EARO) |DAD <timeout> | |
|<--------------| | |
| | | |
| Figure 2: Initial Registration Flow to a 6BBR acting as Routing Proxy
+-----+
| | Gateway (default) Router
| |
+-----+
| /64
| Backbone Link
+-------------------+-------------------+
| /64 | /64 | /64
+------+ +------+ +------+
| 6BBR | | 6BBR | | 6BBR |
| | | | | |
+------+ +------+ +------+
o o o o o o
o o o o o o o o o o o o o o
o o o o o o o o o o o o o o o
o o o o o o o o o o
o o o o o o o
LLN: N*/128 LLN: M*/128 LLN: P*/128 3.2. Route-Over Mesh
Figure 2: Example Routing Configuration for 3 LLNs in the ML Subnet In the case of a Route-Over Mesh, e.g., using RPL [RFC6550], the
6TiSCH architecture [I-D.ietf-6tisch-architecture] suggests to
collocate the RPL root with a 6LoWPAN Border Router (6LBR), which is
either collocated with or connected to the 6BBR over an IPv6 Link.
5.1. Over the Backbone Link Figure 3 illustrates the initial IPv6 signaling that enables a 6LN to
form a Global or a Unique-Local Address and register it to the 6LBR
using [RFC8505]. The 6LBR also leverages [RFC8505] to register the
6LNs on their behalf to the 6BBR and obtain proxy-ND services.
A 6BBR is a specific kind of Border Router that performs proxy 6LoWPAN Node 6LR 6LBR 6BBR
Neighbor Discovery on its backbone interface on behalf of registered (mesh leaf) (mesh router) (mesh root)
6LNs on its LLN interfaces. | | | |
| 6LoWPAN ND |6LoWPAN ND+RPL | 6LoWPAN ND | IPv6 ND
| LLN link |Route-Over mesh|Ethernet/serial| Backbone
| | |/Internal call |
| IPv6 ND RS | | |
|-------------->| | |
|-----------> | | |
|------------------> | |
| IPv6 ND RA | | |
|<--------------| | |
| | <once> | |
| NS(EARO) | | |
|-------------->| | |
| 6LoWPAN ND | Extended DAR | |
| |-------------->| |
| | | NS(EARO) |
| | |-------------->|
| | | (proxied) | NS-DAD
| | | |------>
| | | | (EARO)
| | | |
| | | NA(EARO) |<timeout>
| | |<--------------|
| | Extended DAC | |
| |<--------------| |
| NA(EARO) | | |
|<--------------| | |
| | | |
On the backbone side, the 6BBR advertises the prefixes of the LLNs Figure 3: Initial Registration Flow over Route-Over Mesh
for which it serves as a proxy. Some restrictions of the attached
LLNs will apply to the backbone. In particular, the MTU SHOULD be
set to the same value on the backbone and all attached LLNs. The
scalability of the multilink subnet [RFC4903] requires that broadcast
operations are avoided as much as possible on the backbone as well.
The 6BBR uses an EARO in the NS-DAD and the multicast NA messages 3.3. MultiLink Subnet Consistency
that it generates over the Backbone Link on behalf of a Registered
Node. The 6BBR places an EARO in its unicast NA messages, if and
only if the NS/NA that stimulates it had an EARO in it and the 'R'
bit set.
The 6BBR SHOULD use unicast or the solicited-node multicast address The Backbone and the federated LLN Links are considered as different
(SNMA) [RFC4291] to defend its Registered Addresses in its Binding Links in the MultiLink Subnet, even if multiple LLNs are attached to
Table over the backbone. In particular, the 6BBR MUST join the SNMA a same 6BBR. Multicast ND messages are link-scoped and MUST NOT be
group that corresponds to a Registered Address as soon as it creates forwarded across the Backbone Routers.
an entry for that address, and maintain its SNMA membership as long
as it maintains that entry.
Optimistic DAD (ODAD) [RFC4429] SHOULD be supported by the 6BBRs in A prefix that is used across a MultiLink Subnet may still be
their proxy activity over the backbone. A 6BBR supporting ODAD MUST advertised as on-link over the Backbone, by setting the "L" bit in
join the SNMA of a Tentative address. the Prefix Information Option (PIO) in RA messages ([RFC4861]), in
order to support classical IPv6 hosts; but the MultiLink Subnet
prefix MUST be advertised as not-onlink in RAs sent towards the LLN.
A 6BBR in Routing Proxy mode MAY advertise the Registered IPv6 Nodes located inside the subnet will not perform the IPv6 Path MTU
Address with the 6BBR Link Layer Address, and update Neighbor Cache Discovery [RFC8201] between one another. For that reason, the MTU
Entries (NCE) in correspondent nodes over the backbone, using must have a same value on the Backbone and all attached LLNs. To
gratuitous NA(Override). This method may fail if the multicast achieve this, the 6BBR MUST use the same MTU value that is used in
message is not received, and correspondent nodes may maintain an RAs over the Backbone in the RAs that it transmits towards the LLN
incorrect neighbor state, which they will eventually discover through links.
Neighbor Unreachability Detection (NUD). For slow movements, the NUD
procedure defined in [RFC4861] may time out too quickly, and the
support of [RFC7048] is recommended in all 6LNs in the network.
Multicast should be avoided as much as possible even on the backbone 3.4. Registering Node
[I-D.ietf-mboned-ieee802-mcast-problems]. Although hosts can
participate using legacy IPv6 ND, all 6LNs connected to the backbone
SHOULD support [I-D.ietf-6man-rs-refresh], which also requires the
support of [RFC7559].
5.2. Proxy Operations Over the LLN Interface A Registering Node MUST implement [RFC6775] as updated by [RFC8505]
in order to interact with a 6BBR. As such, it does not depend on
multicast RAs to discover the 6LR(s).
6LNs on the LLN follow [RFC6775] and do not depend on multicast RAs The Registering Node MUST accept multicast RAs, but those are
to discover routers. 6LNs SHOULD accept multicast RAs [RFC7772], but expected to be rare within in the LLN is the best practices
those are expected to be rare within in the LLN. Nodes SHOULD follow ([RFC7772]) are followed.
the Simple Procedures for Detecting Network Attachment in IPv6
[RFC6059] (DNA procedures) to assert movements, and support Packet-
Loss Resiliency for Router Solicitations [RFC7559] to make the
unicast RS more reliable.
A 6LN signals that it requires IPv6 ND proxy services from a 6BBR by The Registering Node SHOULD comply with the Simple Procedures for
registering the corresponding IPv6 Address with an NS(EARO) message Detecting Network Attachment in IPv6 [RFC6059] (DNA procedures) to
with the 'R' flag set. The 6LN that performs the registration (the assert movements, and support Packet-Loss Resiliency for Router
Registering Node) may be the owner of the IPv6 Address (the Solicitations [RFC7559] in order to make the unicast RS messages more
Registered Node) or a 6LBR that performs the registration on its reliable.
behalf.
5.2.1. Routing Proxy Operations The Registering Node signals that it requires IPv6 proxy-ND services
from a 6BBR by registering the corresponding IPv6 Address with an
NS(EARO) message with the 'R' flag set ([RFC8505]). It may be the
actual owner of the IPv6 Address or a 6LBR that performs the
registration on its behalf in a Route-Over mesh.
When operating as a Routing Proxy, the BBR installs host routes The Registering Node SHOULD register all of its Global Unicast and
(/128) to the Registered Addresses within the LLN, via the Unique-Local IPv6 Addresses to the 6BBRs. Failure to register a
subset of Addresses may result in those Addresses being unreachable
by other parties if the 6BBR cancels the NS(LOOKUP) over the LLN or
to selected LLN nodes that are known to register their addresses.
3.5. Using IPv6 ND Over the Backbone Link
On the Backbone side, the 6BBR MUST join the SNMA group that
corresponds to a Registered Address as soon as it creates an entry
for that Address, and conserve its SNMA membership as long as it
maintains the associated entry. The 6BBR uses either the SNMA or
plain unicast to defend the Registered Addresses in its Binding
Table over the Backbone.
The 6BBR advertises and defends the Registered Addresses over the
Backbone using the IPv6 ND protocol [RFC4861]. It MUST uses an EARO
in the NS(DAD) and NA messages that it generates over the Backbone
Link for the Registered Address. A NA message generated in response
to a NS(LOOKUP) MUST NOT have the override (O) bit set. A proxied NS
MUST NOT contain an SLLAO to avoid the confusion with a registration.
A 6BBR may asynchronously update the NCEs in correspondent nodes over
the Backbone, e.g., in case of a movement. This is achieved using a
gratuitous NA with the override (O) bit set, that may be sent unicast
to each individual correspondent, or multicast to all nodes (more in
Section 3.7 and Section 3.6).
A 6LBR may optionally be deployed over the Backbone. When that is
the case, the 6BBR uses an EDAR/EDAC echange to check for duplication
or movement as prescribed in [RFC8505]. If this registration is
duplicate or not the freshest, then the 6LBR replies with a status
code of 1 ("Duplicate Address") or 3 ("Moved"), respectively. If
this registration is the freshest, then the 6LBR replies with a
status code of 0; in that case, if there was an existing registration
on an old 6BBR, then the 6LBR also sends an asynchronous EDAC with a
status of 4 ("Removed") to the old 6BBR. Note that an alternate
protocol such as LISP [RFC6830] may be used to provide an equivalent
service.
Nodes implementing this specification is expected to co-exist on a
same Backbone Link with nodes implementing classical IPv6 ND
[RFC4861] and snooping [I-D.bi-savi-wlan]. It results that the fact
that there is a 6LBR or an alternate protocol that is deployed on the
Backbone does not mean that all IPv6 addresses are known there; the
fact that a unicast DAD succeeds with the 6LBR does not mean that the
address is not duplicate, and, unless administratively overridden,
6BBRs must still perform classical IPv6 ND DAD after an EDAC with a
status code of 0.
For slow movements, the Neighbor Unreachability Detection (NUD)
procedure defined in [RFC4861] may time out too quickly, and the
support of [RFC7048] is recommended for all nodes in the subnet.
3.6. Routing Proxy Operations
When operating as a Routing Proxy, the 6BBR MUST use the Layer-2
Address on its Backbone Interface in the TLLA and SLLA options, when
present, of the RS, NS and NA messages that it generates to advertise
the Registered Addresses. In that case, the MAC Addresses of the
6LNs do not need to be visible at Layer-2 over the Backbone to
maintain end-to-end IP connectivity, but the NCEs of the
correspondents must be updated when the owner registers to a
different 6BBR.
This technique is useful when the churn on the Backbone fabric
associated to wireless mobility becomes expensive, e.g., when the
Layer-2 topology is virtualized over a wide area IP underlay. In
order to maintain IP connectivity, the 6BBR installs a connected host
route to the Registered Address on the LLN interface, via the
Registering Node as identified by the Source Address and the SLLA Registering Node as identified by the Source Address and the SLLA
option in the NS(EARO) messages. In that case, the MAC address of option in the NS(EARO) messages.
the 6LN is not visible at Layer-2 over the backbone. The 6BBR
installs a host route towards the Registered Node over the interface
toward the 6LN, and routes unicast packets to the 6LN.
The Routing Proxy 6BBR handles the ND protocol over the backbone on This technique is also useful when the LLN uses a MAC address format
behalf of the Registered Nodes, using its own MAC address in the TLLA that is different from that on the Backbone (e.g., EUI-64 vs. EUI-
and SLLA options in proxied NS and NA messages. For each Registered 48).
Address, multiple peer Nodes on the backbone may have resolved the
address with the 6BBR MAC address, maintaining that mapping in their
Neighbor cache.
For each Registered Address, the 6BBR SHOULD maintain a list of the For each Registered Address, multiple peer Nodes on the Backbone may
peers on the backbone which have associated its MAC address with the have resolved the Address with the 6BBR MAC Address, maintaining that
Registered Address. If that Registered Address moves to a different mapping in their Neighbor cache. The 6BBR SHOULD maintain a list of
6BBR, the first 6BBR SHOULD unicast a gratuitous NA(Override) to each the peers on the Backbone which have associated its MAC Address with
such peer, to supply the MAC address of the new 6BBR in the TLLA the Registered Address. If that Registered Address moves from an old
option for the Address. to a new 6BBR, the old 6BBR SHOULD unicast a gratuitous NA with the
Override (O) bit set to each such peer, to supply the LLA of the new
6BBR in the TLLA option for the Address.
5.2.2. Bridging Proxy Operations If the 6BBR fails to maintain this list, then it MAY send the
gratuitous NA with the Override (O) bit set as a multicast message
that will possibly hit all the nodes on the Backbone, whether they
maintain an NCE or not for the Registered Address.
If a correspondent fails to receive the gratuitous NA, it will keep
sending traffic to a 6BBR to which the node was previously
registered. That old 6BBR having removed its host route to the
Registered Address, it will look it up over the backbone, resolve the
with the LLA of the new 6BBR, and forward the packet to the correct
6BBR. The old 6BBR SHOULD also issue a redirect message [RFC4861] is
order to update the cache of the correspondent.
3.7. Bridging Proxy Operations
A Bridging Proxy can be implemented in a Layer-3 switch, or in a A Bridging Proxy can be implemented in a Layer-3 switch, or in a
wireless Access Point that acts as an IPv6 Host. In the latter case, wireless Access Point or wireless Controller that acts as a Layer-2
the SLLA option in the proxied NA messages is that of the Registering Bridge for unicast packets from/to the Registered Address. The
Node, and the 6BBR acts as a Layer-2 bridge for unicast packets to Bridging Proxy appears as an IPv6 Host on the Backbone whereas the
the Registered Address. The MAC address in the S/TLLA is that of the Routing Proxy described in Section 3.6 is an IPv6 router operating as
Registering Node, which is not necessarily the Registered Node. When a border router between Links of a MultiLink Subnet.
a 6LN moves within a LLN mesh, it may attach to a different 6LBR
acting as Registering Node, and the MAC address advertised over the
backbone might change.
If a registration moves from one 6BBR to the next, but the When operating as a Bridging Proxy, the 6BBR MUST use the Registering
Registering Node does not change, as indicated by the S/TLLA option Node's Layer-2 Address in the TLLA and SLLA options, when present,
in the ND exchanges, there is no need to update the Neighbor Caches of, respectively, the RS, NS and NA messages that it generates to
of the peer's Nodes on the backbone. On the other hand, if the LLA advertise the Registered Addresses. The Registering Node's Layer-2
changes, the 6BBR SHOULD inform all the relevant peers as described address is found in the SLLA of the registration NS(EARO), and
above, to update the affected Neighbor Caches. In the same fashion, maintained in the abstract Binding Table.
if the Registering Node changes with a new registration, the 6BBR
SHOULD also update the affected Neighbor Caches over the backbone.
6. Backbone Router Proxy Operations If the Registering Node is the owner of the Registered Address, then
its mobility does not impact existing NCEs over the Backbone. If it
is not, then when the 6LN selects another Registering Node, the new
Registering Node SHOULD send a multicast NA with the Override (O) bit
set to fix the existing NCEs across the Backbone. This method may
fail if the multicast message is not received, in which case one or
more correspondent nodes on the Backbone may maintain an obsolete NCE
and traffic to the Registered Address may be lost for a while. When
this condition happens, it is eventually be discovered and solved
through the Neighbor Unreachability Detection (NUD) procedure defined
in [RFC4861].
The LLNs attached to each 6BBR are considered different Links in a 3.8. Leveraging Optimistic DAD
multi-link subnet. The prefix that is used may still be advertised
as on-link on the backbone to support legacy 6LNs. Multicast ND The Optimistic Duplicate Address Detection [RFC4429] (ODAD)
messages are link-scoped and not forwarded across the backbone specification details how an IPv6 Address can be used before a
routers. Duplicate Address Detection (DAD) is complete.
ODAD provides a set of rules that guarantee that this behavior may
not harm an existing state should the new Address effectively be a
duplicate. This specification leverages ODAD to avoid delays in
installing the Neighbor Cache Entry (NCE) in the 6BBRs and the
default router in order to obtain immediate connectivity to the
registered node.
This specification RECOMMENDS to support ODAD to create an optimistic
proxy state in the 6BBR until DAD is completed over the Backbone. As
shown in Figure 2, if the 6BBR is aware of the Link-Layer Address
(LLA) of a router, then the 6BBR sends a Router Sollicitation (RS),
sourced with the Registered Address, to the known router(s). The RS
MUST be sent without a Source LLA Option (SLLAO), to ensure that a
preexisting NCE in the router is not affected.
Following the ODAD flows, the router may then send a unicast RA to
the Registered Address, and in the process of doing so, it may
resolve it using an NS(LOOKUP) message. In response, the 6BBR sends
a NA with the override (O) bit that is not set (per [RFC4429]), and
an EARO option. If the router supports this specification, then it
can determine the freshest EARO option in case of a conflicting
NA(EARO) messages, using section 5.2.1 of [RFC8505]. If the NA(EARO)
is the freshest or only answer then the default router creates a BCE
with the SLLAO of the 6BBR (in Routing Proxy mode) or that of the
Registering Node (in Bridging Proxy mode) and traffic from/to the
Registered Address can flow immediately.
4. Updating RFC 4861
This specification adds the EARO as a possible option in RS, NS(DAD)
and NA messages over the backbone. Note that [RFC8505] requires that
the registration NS(EARO) contains an SLLAO. Note that an NS(DAD)
does not contain an SLLAO and thus cannot be confused with a
registration.
5. Updating RFC 8505
This specification adds the capability to insert IPv6 ND options in
the EDAR and EDAC messages. In particular, a 6BBR acting as a 6LR
for the Registered Address can insert an SLLAO in the EDAR to the
6LBR in order to avoid a lookup back.
6. 6BBR detailed Operations
By default, a 6BBR operates as a Sleeping Proxy, as follows: By default, a 6BBR operates as a Sleeping Proxy, as follows:
o Create a new entry in a Binding Table for a new Registered Address o Create a new entry in a Binding Table for a new Registered Address
and ensure that the address is not a duplicate over the backbone and ensure that the Address is not a duplicate over the Backbone
o Defend a Registered Address over the backbone using NA messages o Defend a Registered Address over the Backbone using NA messages
with the Override bit set on behalf of the sleeping 6LN with the Override bit set on behalf of the sleeping 6LN
o Advertise a Registered Address over the backbone using NA o Advertise a Registered Address over the Backbone using NA
messages, asynchronously or as a response to a Neighbor messages, asynchronously or as a response to a Neighbor
Solicitation messages. Solicitation messages.
o To deliver packets arriving from the LLN, use Neighbor o To deliver packets arriving from the LLN, use Neighbor
Solicitation messages to look up the destination over the Solicitation messages to look up the destination over the
backbone. Backbone.
o Forward packets between the LLN and the backbone. o Forward packets between the LLN and the Backbone.
o Verify liveliness when needed for a stale registration. o Verify liveliness when needed for a stale registration.
A 6BBR may act as a Sleeping Proxy only for a Registered Address that A 6BBR may act as a Sleeping Proxy only for a Registered Address that
is REACHABLE, or TENTATIVE in which case the answer is delayed. In is REACHABLE, or TENTATIVE in which case the answer is delayed. In
any other state, the Sleeping Proxy operates as a Unicasting Proxy. any other state, the Sleeping Proxy operates as a Unicasting Proxy.
The 6BBR does not act on ND Messages over the backbone unless they The 6BBR does not act on ND Messages over the Backbone unless they
are relevant to a Registered Node on the LLN side, saving wireless are relevant to a Registered Node on the LLN side, saving wireless
interference. On the LLN side, the prefixes associated to the interference. On the LLN side, the prefixes associated to the
MultiLink Subnet are presented as not on-link, so address resolution MultiLink Subnet are presented as not on-link, so Address resolution
for other hosts do not occur. for other hosts do not occur.
As a Unicasting Proxy, the 6BBR forwards NS lookup messages to the As a Unicasting Proxy, the 6BBR forwards NS lookup messages to the
Registering Node, transforming Layer-2 multicast into unicast. This Registering Node, transforming Layer-2 multicast into unicast. This
is not possible in UNREACHABLE state, so the NS messages are is not possible in UNREACHABLE state, so the NS messages are
multicasted, and rate-limited. Retries are possible, using an multicasted, and rate-limited. Retries are possible, using an
exponential back-off to protect the medium. In other states, the exponential back-off to protect the medium. In other states, the
messages are forwarded to the Registering Node as unicast Layer-2 messages are forwarded to the Registering Node as unicast Layer-2
messages. In TENTATIVE state, the NS message is either held till DAD messages. In TENTATIVE state, the NS message is either held till DAD
completes, or dropped if DAD does not complete. completes, or dropped if DAD does not complete.
6.1. Primary and Secondary BBRs 6.1. Primary and Secondary 6BBRs
A 6BBR MAY be primary or secondary. The primary is the backbone A 6BBR MAY be primary or secondary. The primary is the Backbone
router that has the highest EUI-64 address of all the 6BBRs that router that has the highest EUI-64 Address of all the 6BBRs that
share a registration for a same Registered Address, with the same share a registration for a same Registered Address, with the same
ROVR and same Transaction ID, the EUI-64 address being considered as ROVR and same Transaction ID, the EUI-64 Address being considered as
an unsigned 64bit integer. A given 6BBR can be primary for a given an unsigned 64bit integer. A given 6BBR can be primary for a given
address and secondary for another address, regardless of whether or Address and secondary for another Address, regardless of whether or
not the addresses belong to the same 6LN. The primary Backbone not the Addresses belong to the same 6LN. The primary Backbone
Router is in charge of protecting the address for DAD over the Router is in charge of protecting the Address for DAD over the
Backbone. Any of the Primary and Secondary 6BBR may claim the Backbone. Any of the Primary and Secondary 6BBR may claim the
address over the backbone, since they are all capable to route from Address over the Backbone, since they are all capable to route from
the backbone to the 6LN; the address appears on the backbone as an the Backbone to the 6LN; the Address appears on the Backbone as an
anycast address. anycast Address.
6.2. Binding Table 6.2. Binding Table
Each 6BBR maintains a Binding Table, using IPv6 ND over the backbone Each 6BBR maintains a Binding Table, using IPv6 ND over the Backbone
to detect duplication. Another document to detect duplication. Another document [RFC8505] provides details
[I-D.ietf-6lo-rfc6775-update] provides details about how the EARO is about how the EARO is used between 6LRs and 6LBRs by way of DAR/DAC
used between 6LRs and 6LBRs by way of DAR/DAC messages within the messages within the LLN. Addresses in a LLN that can be reachable
LLN. Addresses in a LLN that can be reachable from the backbone by from the Backbone by way of a 6BBR MUST be registered to that 6BBR.
way of a 6BBR MUST be registered to that 6BBR.
A false positive duplicate detection may arise over the backbone, for A false positive duplicate detection may arise over the Backbone, for
instance if a 6LN's Registered Address is registered to more than one instance if a 6LN's Registered Address is registered to more than one
LBR, or if the 6LN has moved. Both situations are handled by the LBR, or if the 6LN has moved. Both situations are handled by the
6BBR transparently to the 6LN. In the former case, one LBR becomes 6BBR transparently to the 6LN. In the former case, one LBR becomes
primary to defend the address over the backbone while the others primary to defend the Address over the Backbone while the others
become secondary and may still forward packets. In the latter case become secondary and may still forward packets. In the latter case
the LBR that receives the newest registration becomes primary because the LBR that receives the newest registration becomes primary because
of the TID. of the TID.
Only one 6LN may register a given Address at a particular 6BBR. Only one 6LN may register a given Address at a particular 6BBR.
However, that Registered Address may be registered to Multiple 6BBRs However, that Registered Address may be registered to Multiple 6BBRs
for higher availability. for higher availability.
Over the LLN, Binding Table management is as follows: Over the LLN, Binding Table management is as follows:
skipping to change at page 13, line 26 skipping to change at page 17, line 43
Identical and older registrations (not-newer TID, same ROVR) from Identical and older registrations (not-newer TID, same ROVR) from
a different Registering Node are acknowledged with a status of 3 a different Registering Node are acknowledged with a status of 3
(moved); this may be rate limited to protect the medium; (moved); this may be rate limited to protect the medium;
Any registration for a different Registered Node (different ROVR) Any registration for a different Registered Node (different ROVR)
are acknowledged with a status of 1 (duplicate). are acknowledged with a status of 1 (duplicate).
6.3. Registration and Binding Table Entry Creation 6.3. Registration and Binding Table Entry Creation
Upon receiving a registration for a new address with an NS(EARO) with Upon receiving a registration for a new Address with an NS(EARO) with
the 'R' bit set, the 6BBR performs DAD over the backbone, placing the the 'R' bit set, the 6BBR performs DAD over the Backbone, placing the
new address as target in the NS-DAD message. The EARO from the new Address as target in the NS(DAD) message. The EARO from the
registration MUST be placed unchanged in the NS-DAD message, and an registration MUST be placed unchanged in the NS(DAD) message, and an
Neighbor Cache entry created in TENTATIVE state for a duration of Neighbor Cache entry created in TENTATIVE state for a duration of
TENTATIVE_DURATION. The NS-DAD message is sent multicast over the TENTATIVE_DURATION. The NS(DAD) message is sent multicast over the
backbone to the SNMA associated with the registered address, unless Backbone to the SNMA associated with the registered Address, unless
that operation is known to be costly, and the 6BBR has an indication that operation is known to be costly, and the 6BBR has an indication
from another source (such as a Neighbor Cache entry) that the from another source (such as a Neighbor Cache entry) that the
Registered Address was known on the backbone; in the latter case, an Registered Address was known on the Backbone; in the latter case, an
NS-DAD message may be sent as a Layer-2 unicast to the MAC Address NS(DAD) message may be sent as a Layer-2 unicast to the MAC Address
that was associated with the Registered Address. that was associated with the Registered Address.
In TENTATIVE state after EARO with 'R' bit set: In TENTATIVE state after EARO with 'R' bit set:
1. The entry is removed if an NA is received over the backbone for 1. The entry is removed if an NA is received over the Backbone for
the Registered Address with no EARO, or containing an EARO with a the Registered Address with no EARO, or containing an EARO with a
status of 1 (duplicate) that indicates an existing registration status of 1 (duplicate) that indicates an existing registration
for another 6LN. The ROVR and TID fields in the EARO received for another 6LN. The ROVR and TID fields in the EARO received
over the backbone are ignored. A status of 1 is returned in the over the Backbone are ignored. A status of 1 is returned in the
EARO of the NA back to the Registering Node; EARO of the NA back to the Registering Node;
2. The entry is also removed if an NA with an ARO option with a 2. The entry is also removed if an NA with an ARO option with a
status of 3 (moved), or a NS with an ARO option that indicates a status of 3 (moved), or a NS with an ARO option that indicates a
newer registration for the same Registered Node, is received over newer registration for the same Registered Node, is received over
the backbone for the Registered Address. A status of 3 is the Backbone for the Registered Address. A status of 3 is
returned in the NA(EARO) back to the Registering Node; returned in the NA(EARO) back to the Registering Node;
3. When a registration is updated but not deleted, e.g. from a newer 3. When a registration is updated but not deleted, e.g. from a newer
registration, the DAD process on the backbone continues and the registration, the DAD process on the Backbone continues and the
running timers are not restarted; running timers are not restarted;
4. Other NS (including DAD with no EARO) and NA from the backbone 4. Other NS (including DAD with no EARO) and NA from the Backbone
are not acknowledged in TENTATIVE state. To cover legacy 6LNs are not acknowledged in TENTATIVE state. To cover legacy 6LNs
that do not support ODAD, the list of their origins MAY be stored that do not support ODAD, the list of their origins MAY be stored
and then, if the TENTATIVE_DURATION timer elapses, the 6BBR MAY and then, if the TENTATIVE_DURATION timer elapses, the 6BBR MAY
send each such legacy 6LN a unicast NA. send each such legacy 6LN a unicast NA.
5. When the TENTATIVE_DURATION timer elapses, a status 0 (success) 5. When the TENTATIVE_DURATION timer elapses, a status 0 (success)
is returned in a NA(EARO) back to the Registering Node(s), and is returned in a NA(EARO) back to the Registering Node(s), and
the entry goes to REACHABLE state for the Registration Lifetime. the entry goes to REACHABLE state for the Registration Lifetime.
The 6BBR MUST send a multicast NA(EARO) to the SNMA associated to The 6BBR MUST send a multicast NA(EARO) to the SNMA associated to
the Registered Address over the backbone with the Override bit the Registered Address over the Backbone with the Override bit
set so as to take over the binding from other 6BBRs. set so as to take over the binding from other 6BBRs.
6.4. Defending Addresses 6.4. Defending Addresses
If a 6BBR has an entry in REACHABLE state for a Registered Address: If a 6BBR has an entry in REACHABLE state for a Registered Address:
o If the 6BBR is primary, or does not support the function of o If the 6BBR is primary, or does not support the function of
primary, it MUST defend that address over the backbone upon primary, it MUST defend that Address over the Backbone upon
receiving NS, either if the NS does not carry an EARO, or if an receiving NS, either if the NS does not carry an EARO, or if an
EARO is present that indicates a different Registering Node EARO is present that indicates a different Registering Node
(different ROVR). The 6BBR sends a NA message with the Override (different ROVR). The 6BBR sends a NA message with the Override
bit set and the NA carries an EARO if and only if the NS-DAD did bit set and the NA carries an EARO if and only if the NS(DAD) did
so. When present, the EARO in the NA(Override) that is sent in so. When present, the EARO in the NA(Override) that is sent in
response to the NS(EARO) carries a status of 1 (duplicate), and response to the NS(EARO) carries a status of 1 (duplicate), and
the ROVR and TID fields in the EARO are obfuscated with null or the ROVR and TID fields in the EARO are obfuscated with null or
random values to avoid network scanning and impersonation attacks. random values to avoid network scanning and impersonation attacks.
o If the 6BBR receives an NS(EARO) for a newer registration, the o If the 6BBR receives an NS(EARO) for a newer registration, the
6BBR updates the entry and the routing state to forward packets to 6BBR updates the entry and the routing state to forward packets to
the new 6BBR, but keeps the entry REACHABLE. Afterwards, the 6BBR the new 6BBR, but keeps the entry REACHABLE. Afterwards, the 6BBR
MAY use REDIRECT messages to reroute traffic for the Registered MAY use REDIRECT messages to reroute traffic for the Registered
Address to the new 6BBR. Address to the new 6BBR.
o If the 6BBR receives an NA(EARO) for a newer registration, the o If the 6BBR receives an NA(EARO) for a newer registration, the
6BBR removes its entry and sends a NA(EARO) with a status of 3 6BBR removes its entry and sends a NA(EARO) with a status of 3
(MOVED) to the Registering Node, if the Registering Node is (MOVED) to the Registering Node, if the Registering Node is
different from the Registered Node. The 6BBR cleans up existing different from the Registered Node. The 6BBR cleans up existing
Neighbor Cache entries in peer nodes as discussed in Section 5.1, Neighbor Cache entries in peer nodes as discussed in Section 3.5,
by unicasting to each such peer, or one broadcast NA(Override). by unicasting to each such peer, or one broadcast NA(Override).
o If the 6BBR receives a NS(LOOKUP) for a Registered Address, it o If the 6BBR receives a NS(LOOKUP) for a Registered Address, it
answers immediately with an NA on behalf of the Registered Node, answers immediately with an NA on behalf of the Registered Node,
without polling it. There is no need of an EARO in that exchange. without polling it. There is no need of an EARO in that exchange.
o When the Registration-Lifetime timer elapses, the entry goes to o When the Registration-Lifetime timer elapses, the entry goes to
STALE state for a duration of STABLE_STALE_DURATION in LLNs that STALE state for a duration of STABLE_STALE_DURATION in LLNs that
keep stable addresses such as LWPANs, and UNSTABLE_STALE_DURATION keep stable Addresses such as LWPANs, and UNSTABLE_STALE_DURATION
in LLNs where addresses are renewed rapidly, e.g. for privacy in LLNs where Addresses are renewed rapidly, e.g. for privacy
reasons. reasons.
The STALE state enables tracking of the backbone peers that have a The STALE state enables tracking of the Backbone peers that have a
Neighbor Cache entry pointing to this 6BBR in case the Registered Neighbor Cache entry pointing to this 6BBR in case the Registered
Address shows up later. If the Registered Address is claimed by Address shows up later. If the Registered Address is claimed by
another 6LN on the backbone, with an NS-DAD or an NA, the 6BBR does another 6LN on the Backbone, with an NS(DAD) or an NA, the 6BBR does
not defend the address. In STALE state: not defend the Address. In STALE state:
o If STALE_DURATION elapses, the 6BBR removes the entry. o If STALE_DURATION elapses, the 6BBR removes the entry.
o Upon receiving an NA(Override) the 6BBR removes its entry and o Upon receiving an NA(Override) the 6BBR removes its entry and
sends a NA(EARO) with a status of 4 (removed) to the Registering sends a NA(EARO) with a status of 4 (removed) to the Registering
Node. Node.
o If the 6BBR receives a NS(LOOKUP) for a Registered Address, the o If the 6BBR receives a NS(LOOKUP) for a Registered Address, the
6BBR MUST send an NS(NUD) following rules in [RFC7048] to the 6BBR MUST send an NS(NUD) following rules in [RFC7048] to the
Registering Node targeting the Registered Address prior to Registering Node targeting the Registered Address prior to
skipping to change at page 15, line 46 skipping to change at page 20, line 15
7. Security Considerations 7. Security Considerations
This specification applies to LLNS in which the link layer is This specification applies to LLNS in which the link layer is
protected, either by means of physical or IP security for the protected, either by means of physical or IP security for the
Backbone Link or MAC sublayer cryptography. In particular, the LLN Backbone Link or MAC sublayer cryptography. In particular, the LLN
MAC is required to provide secure unicast to/from the Backbone Router MAC is required to provide secure unicast to/from the Backbone Router
and secure Broadcast from the Backbone Router in a way that prevents and secure Broadcast from the Backbone Router in a way that prevents
tampering with or replaying the RA messages. tampering with or replaying the RA messages.
The use of EUI-64 for forming the Interface ID in the link local The use of EUI-64 for forming the Interface ID in the link local
address prevents the usage of Secure ND ([RFC3971] and [RFC3972]) and Address prevents the usage of Secure ND ([RFC3971] and [RFC3972]) and
address privacy techniques. Additional protection against address Address privacy techniques. Additional protection against Address
theft is provided by [I-D.ietf-6lo-ap-nd], which guarantees the theft is provided by [I-D.ietf-6lo-ap-nd], which guarantees the
ownership of the ROVR. ownership of the ROVR.
When the ownership of the ROVR cannot be assessed, this specification When the ownership of the ROVR cannot be assessed, this specification
limits the cases where the ROVR and the TID are multicasted, and limits the cases where the ROVR and the TID are multicasted, and
obfuscates them in responses to attempts to take over an address. obfuscates them in responses to attempts to take over an Address.
8. Protocol Constants 8. Protocol Constants
This Specification uses the following constants: This Specification uses the following constants:
TENTATIVE_DURATION: 800 milliseconds TENTATIVE_DURATION: 800 milliseconds
STABLE_STALE_DURATION: 24 hours STABLE_STALE_DURATION: 24 hours
UNSTABLE_STALE_DURATION: 5 minutes UNSTABLE_STALE_DURATION: 5 minutes
skipping to change at page 16, line 29 skipping to change at page 20, line 44
DEFAULT_NS_POLLING: 3 times DEFAULT_NS_POLLING: 3 times
9. IANA Considerations 9. IANA Considerations
This document has no request to IANA. This document has no request to IANA.
10. Future Work 10. Future Work
Future documents may extend this specification by allowing the 6BBR Future documents may extend this specification by allowing the 6BBR
to redistribute host routes in routing protocols that would operate to redistribute host routes in routing protocols that would operate
over the backbone, or in MIPv6, or FMIP, or the Locator/ID Separation over the Backbone, or in MIPv6, or FMIP, or the Locator/ID Separation
Protocol (LISP) [RFC6830] to support mobility on behalf of the 6LNs, Protocol (LISP) [RFC6830] to support mobility on behalf of the 6LNs,
etc... etc...
11. Acknowledgments 11. Acknowledgments
Kudos to Eric Levy-Abegnoli who designed the First Hop Security Many thanks to Dorothy Stanley, Thomas Watteyne and Jerome Henry for
infrastructure at Cisco. their various contributions.
12. References 12. References
12.1. Normative References 12.1. Normative References
[I-D.ietf-6lo-rfc6775-update]
Thubert, P., Nordmark, E., Chakrabarti, S., and C.
Perkins, "Registration Extensions for 6LoWPAN Neighbor
Discovery", draft-ietf-6lo-rfc6775-update-21 (work in
progress), June 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>. 2006, <https://www.rfc-editor.org/info/rfc4291>.
[RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD) [RFC4429] Moore, N., "Optimistic Duplicate Address Detection (DAD)
skipping to change at page 17, line 28 skipping to change at page 21, line 37
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, Address Autoconfiguration", RFC 4862,
DOI 10.17487/RFC4862, September 2007, DOI 10.17487/RFC4862, September 2007,
<https://www.rfc-editor.org/info/rfc4862>. <https://www.rfc-editor.org/info/rfc4862>.
[RFC6059] Krishnan, S. and G. Daley, "Simple Procedures for [RFC6059] Krishnan, S. and G. Daley, "Simple Procedures for
Detecting Network Attachment in IPv6", RFC 6059, Detecting Network Attachment in IPv6", RFC 6059,
DOI 10.17487/RFC6059, November 2010, DOI 10.17487/RFC6059, November 2010,
<https://www.rfc-editor.org/info/rfc6059>. <https://www.rfc-editor.org/info/rfc6059>.
[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012,
<https://www.rfc-editor.org/info/rfc6550>.
[RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
Bormann, "Neighbor Discovery Optimization for IPv6 over Bormann, "Neighbor Discovery Optimization for IPv6 over
Low-Power Wireless Personal Area Networks (6LoWPANs)", Low-Power Wireless Personal Area Networks (6LoWPANs)",
RFC 6775, DOI 10.17487/RFC6775, November 2012, RFC 6775, DOI 10.17487/RFC6775, November 2012,
<https://www.rfc-editor.org/info/rfc6775>. <https://www.rfc-editor.org/info/rfc6775>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200, (IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017, DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>. <https://www.rfc-editor.org/info/rfc8200>.
[RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed.,
"Path MTU Discovery for IP version 6", STD 87, RFC 8201,
DOI 10.17487/RFC8201, July 2017,
<https://www.rfc-editor.org/info/rfc8201>.
[RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C.
Perkins, "Registration Extensions for IPv6 over Low-Power
Wireless Personal Area Network (6LoWPAN) Neighbor
Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018,
<https://www.rfc-editor.org/info/rfc8505>.
12.2. Informative References 12.2. Informative References
[I-D.bi-savi-wlan]
Bi, J., Wu, J., Wang, Y., and T. Lin, "A SAVI Solution for
WLAN", draft-bi-savi-wlan-16 (work in progress), November
2018.
[I-D.ietf-6lo-ap-nd] [I-D.ietf-6lo-ap-nd]
Thubert, P., Sarikaya, B., Sethi, M., and R. Struik, Thubert, P., Sarikaya, B., Sethi, M., and R. Struik,
"Address Protected Neighbor Discovery for Low-power and "Address Protected Neighbor Discovery for Low-power and
Lossy Networks", draft-ietf-6lo-ap-nd-08 (work in Lossy Networks", draft-ietf-6lo-ap-nd-08 (work in
progress), October 2018. progress), October 2018.
[I-D.ietf-6man-rs-refresh] [I-D.ietf-6man-rs-refresh]
Nordmark, E., Yourtchenko, A., and S. Krishnan, "IPv6 Nordmark, E., Yourtchenko, A., and S. Krishnan, "IPv6
Neighbor Discovery Optional RS/RA Refresh", draft-ietf- Neighbor Discovery Optional RS/RA Refresh", draft-ietf-
6man-rs-refresh-02 (work in progress), October 2016. 6man-rs-refresh-02 (work in progress), October 2016.
[I-D.ietf-6tisch-architecture] [I-D.ietf-6tisch-architecture]
Thubert, P., "An Architecture for IPv6 over the TSCH mode Thubert, P., "An Architecture for IPv6 over the TSCH mode
of IEEE 802.15.4", draft-ietf-6tisch-architecture-15 (work of IEEE 802.15.4", draft-ietf-6tisch-architecture-17 (work
in progress), October 2018. in progress), November 2018.
[I-D.ietf-mboned-ieee802-mcast-problems] [I-D.ietf-mboned-ieee802-mcast-problems]
Perkins, C., McBride, M., Stanley, D., Kumari, W., and J. Perkins, C., McBride, M., Stanley, D., Kumari, W., and J.
Zuniga, "Multicast Considerations over IEEE 802 Wireless Zuniga, "Multicast Considerations over IEEE 802 Wireless
Media", draft-ietf-mboned-ieee802-mcast-problems-02 (work Media", draft-ietf-mboned-ieee802-mcast-problems-04 (work
in progress), August 2018. in progress), November 2018.
[I-D.nordmark-6man-dad-approaches] [I-D.nordmark-6man-dad-approaches]
Nordmark, E., "Possible approaches to make DAD more robust Nordmark, E., "Possible approaches to make DAD more robust
and/or efficient", draft-nordmark-6man-dad-approaches-02 and/or efficient", draft-nordmark-6man-dad-approaches-02
(work in progress), October 2015. (work in progress), October 2015.
[I-D.yourtchenko-6man-dad-issues] [I-D.yourtchenko-6man-dad-issues]
Yourtchenko, A. and E. Nordmark, "A survey of issues Yourtchenko, A. and E. Nordmark, "A survey of issues
related to IPv6 Duplicate Address Detection", draft- related to IPv6 Duplicate Address Detection", draft-
yourtchenko-6man-dad-issues-01 (work in progress), March yourtchenko-6man-dad-issues-01 (work in progress), March
skipping to change at page 19, line 15 skipping to change at page 24, line 5
[RFC5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley, [RFC5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley,
Ed., "Control And Provisioning of Wireless Access Points Ed., "Control And Provisioning of Wireless Access Points
(CAPWAP) Protocol Specification", RFC 5415, (CAPWAP) Protocol Specification", RFC 5415,
DOI 10.17487/RFC5415, March 2009, DOI 10.17487/RFC5415, March 2009,
<https://www.rfc-editor.org/info/rfc5415>. <https://www.rfc-editor.org/info/rfc5415>.
[RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility [RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
2011, <https://www.rfc-editor.org/info/rfc6275>. 2011, <https://www.rfc-editor.org/info/rfc6275>.
[RFC6606] Kim, E., Kaspar, D., Gomez, C., and C. Bormann, "Problem
Statement and Requirements for IPv6 over Low-Power
Wireless Personal Area Network (6LoWPAN) Routing",
RFC 6606, DOI 10.17487/RFC6606, May 2012,
<https://www.rfc-editor.org/info/rfc6606>.
[RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
Locator/ID Separation Protocol (LISP)", RFC 6830, Locator/ID Separation Protocol (LISP)", RFC 6830,
DOI 10.17487/RFC6830, January 2013, DOI 10.17487/RFC6830, January 2013,
<https://www.rfc-editor.org/info/rfc6830>. <https://www.rfc-editor.org/info/rfc6830>.
[RFC7048] Nordmark, E. and I. Gashinsky, "Neighbor Unreachability [RFC7048] Nordmark, E. and I. Gashinsky, "Neighbor Unreachability
Detection Is Too Impatient", RFC 7048, Detection Is Too Impatient", RFC 7048,
DOI 10.17487/RFC7048, January 2014, DOI 10.17487/RFC7048, January 2014,
<https://www.rfc-editor.org/info/rfc7048>. <https://www.rfc-editor.org/info/rfc7048>.
[RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and
Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January
2014, <https://www.rfc-editor.org/info/rfc7102>.
[RFC7559] Krishnan, S., Anipko, D., and D. Thaler, "Packet-Loss [RFC7559] Krishnan, S., Anipko, D., and D. Thaler, "Packet-Loss
Resiliency for Router Solicitations", RFC 7559, Resiliency for Router Solicitations", RFC 7559,
DOI 10.17487/RFC7559, May 2015, DOI 10.17487/RFC7559, May 2015,
<https://www.rfc-editor.org/info/rfc7559>. <https://www.rfc-editor.org/info/rfc7559>.
[RFC7772] Yourtchenko, A. and L. Colitti, "Reducing Energy [RFC7772] Yourtchenko, A. and L. Colitti, "Reducing Energy
Consumption of Router Advertisements", BCP 202, RFC 7772, Consumption of Router Advertisements", BCP 202, RFC 7772,
DOI 10.17487/RFC7772, February 2016, DOI 10.17487/RFC7772, February 2016,
<https://www.rfc-editor.org/info/rfc7772>. <https://www.rfc-editor.org/info/rfc7772>.
[RFC8273] Brzozowski, J. and G. Van de Velde, "Unique IPv6 Prefix
per Host", RFC 8273, DOI 10.17487/RFC8273, December 2017,
<https://www.rfc-editor.org/info/rfc8273>.
12.3. External Informative References 12.3. External Informative References
[IEEEstd8021] [IEEEstd8021]
IEEE standard for Information Technology, "IEEE Standard IEEE standard for Information Technology, "IEEE Standard
for Information technology -- Telecommunications and for Information technology -- Telecommunications and
information exchange between systems Local and information exchange between systems Local and
metropolitan area networks Part 1: Bridging and metropolitan area networks Part 1: Bridging and
Architecture". Architecture".
[IEEEstd80211] [IEEEstd80211]
skipping to change at page 20, line 27 skipping to change at page 25, line 19
Metropolitan Area Networks - Specific Requirements. - Part Metropolitan Area Networks - Specific Requirements. - Part
15.1: Wireless Medium Access Control (MAC) and Physical 15.1: Wireless Medium Access Control (MAC) and Physical
Layer (PHY) Specifications for Wireless Personal Area Layer (PHY) Specifications for Wireless Personal Area
Networks (WPANs)". Networks (WPANs)".
[IEEEstd802154] [IEEEstd802154]
IEEE standard for Information Technology, "IEEE Standard IEEE standard for Information Technology, "IEEE Standard
for Local and metropolitan area networks -- Part 15.4: for Local and metropolitan area networks -- Part 15.4:
Low-Rate Wireless Personal Area Networks (LR-WPANs)". Low-Rate Wireless Personal Area Networks (LR-WPANs)".
Appendix A. Changes from revision 07 to revision 08 Appendix A. Applicability and Requirements Served
This section lists the changes between draft-ietf-6lo-backbone-router This document specifies proxy-ND functions that can be used to
revisions ...-07.txt and ...-08.txt. federate an IPv6 Backbone Link and multiple IPv6 LLNs into a single
MultiLink Subnet. The proxy-ND functions enable IPv6 ND services for
Duplicate Address Detection (DAD) and Address lookup that do not
require broadcasts over the LLNs.
o Reorganized the order of presentation of some sections so that The term LLN is used loosely to cover multiple types of WLANs and
related material is closer together. WPANs, including (Low-Power) Wi-Fi, BLUETOOTH(R) Low Energy, IEEE
STD. 802.11ah and IEEE STD. 802.15.4 wireless meshes, so as to
address the requirements listed in Appendix B.3 of [RFC8505]
"Requirements Related to Various Low-Power Link Types".
o Added "Future Work" section. Each LLN in the subnet is anchored at an IPv6 Backbone Router (6BBR).
The Backbone Routers interconnect the LLNs and advertise the
Addresses of the 6LNs over the Backbone Link using proxy-ND
operations.
o Added this section detailing recent changes. This specification updates IPv6 ND over the Backbone to distinguish
Address movement from duplication and eliminate stale state in the
Backbone routers and Backbone nodes once a 6LN has roamed. In this
way, mobile nodes may roam rapidly from one 6BBR to the next and
requirements in Appendix B.1 of [RFC8505] "Requirements Related to
Mobility" are met.
o Used '6LN' when LLN node is meant. Any 6LN may register its IPv6 Addresses and thereby obtain proxy-ND
services over the Backbone, providing a solution to the requirements
expressed in Appendix B.4 of [RFC8505] "Requirements Related to Proxy
Operations".
o Updated bibliographic citations. The IPv6 ND operation is minimized as the number of 6LNs grows in the
LLN. This meets the requirements in Appendix B.6 of [RFC8505]
"Requirements Related to Scalability", as long has the 6BBRs are
dimensioned for the number of registrations that each needs to
support.
In the case of a (Low-Power) Wi-Fi access link, a 6BBR may be
collocated with the Access Point (AP), or with a Fabric Edge (FE) or
a CAPWAP [RFC5415] Wireless LAN Controller (WLC). In that case, the
wireless client (STA) is the 6LN [RFC8505] that makes use of this
specification to register its IPv6 Address(es) to the 6BBR acting as
Routing Registrar. The 6LBR can be centralized and either connected
to the Backbone Link or reachable over IP. The 6BBR proxy-ND
operations eliminate the need for wireless nodes to respond
synchronously when a lookup is performed for their IPv6 Addresses.
This provides the function of a Sleep Proxy for ND
[I-D.nordmark-6man-dad-approaches].
For the TimeSlotted Channel Hopping (TSCH) mode of [IEEEstd802154],
the 6TiSCH architecture [I-D.ietf-6tisch-architecture] describes how
a 6LoWPAN ND host could connect to the Internet via a RPL mesh
Network, but doing so requires extensions to the 6LOWPAN ND protocol
to support mobility and reachability in a secure and manageable
environment. The extensions detailed in this document also work for
the 6TiSCH architecture, serving the requirements listed in
Appendix B.2 of [RFC8505] "Requirements Related to Routing
Protocols".
The registration mechanism may be seen as a more reliable alternate
to snooping [I-D.bi-savi-wlan]. It can be noted that registration
and snooping are not mutually exclusive. Snooping may be used in
conjunction with the registration for nodes that do not register
their IPv6 Addresses. The 6BBR assumes that if a node registers at
least one IPv6 Address to it, then the node registers all of its
Addresses to the 6BBR. With this assumption, the 6BBR can possibly
cancel all undesirable multicast NS messages that would otherwise
have been delivered to that node.
The scalability of the MultiLink Subnet [RFC4903] requires that
multicast/broadcast operations are avoided as much as possible even
on the Backbone [I-D.ietf-mboned-ieee802-mcast-problems]. Although
hosts can connect to the Backbone using classical IPv6 ND operations,
multicast RAs can be saved by using [I-D.ietf-6man-rs-refresh], which
also requires the support of [RFC7559].
Authors' Addresses Authors' Addresses
Pascal Thubert (editor) Pascal Thubert (editor)
Cisco Systems, Inc Cisco Systems, Inc
Building D Building D
45 Allee des Ormes - BP1200 45 Allee des Ormes - BP1200
MOUGINS - Sophia Antipolis 06254 MOUGINS - Sophia Antipolis 06254
FRANCE FRANCE
Phone: +33 497 23 26 34 Phone: +33 497 23 26 34
Email: pthubert@cisco.com Email: pthubert@cisco.com
Charles E. Perkins Charles E. Perkins
Futurewei Futurewei
2330 Central Expressway 2330 Central Expressway
Santa Clara 95050 Santa Clara 95050
United States of America United States of America
Email: charliep@computer.org Email: charliep@computer.org
Eric Levy-Abegnoli
Cisco Systems, Inc
Building D
45 Allee des Ormes - BP1200
MOUGINS - Sophia Antipolis 06254
FRANCE
Phone: +33 497 23 26 20
Email: elevyabe@cisco.com
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