draft-ietf-6lo-backbone-router-14.txt   draft-ietf-6lo-backbone-router-15.txt 
6lo P. Thubert, Ed. 6lo P. Thubert, Ed.
Internet-Draft Cisco Systems Internet-Draft Cisco Systems
Updates: 6775, 8505 (if approved) C. Perkins Updates: 6775, 8505 (if approved) C. Perkins
Intended status: Standards Track Futurewei Intended status: Standards Track Futurewei
Expires: August 9, 2020 E. Levy-Abegnoli Expires: August 10, 2020 E. Levy-Abegnoli
Cisco Systems Cisco Systems
February 6, 2020 February 7, 2020
IPv6 Backbone Router IPv6 Backbone Router
draft-ietf-6lo-backbone-router-14 draft-ietf-6lo-backbone-router-15
Abstract Abstract
This document updates RFC 6775 and RFC 8505 in order to enable proxy This document updates RFC 6775 and RFC 8505 in order to enable proxy
services for IPv6 Neighbor Discovery by Routing Registrars called services for IPv6 Neighbor Discovery by Routing Registrars called
Backbone Routers. Backbone Routers are placed along the wireless Backbone Routers. Backbone Routers are placed along the wireless
edge of a Backbone, and federate multiple wireless links to form a edge of a Backbone, and federate multiple wireless links to form a
single MultiLink Subnet. single Multi-Link Subnet.
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 August 9, 2020. This Internet-Draft will expire on August 10, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. New Terms . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2. New Terms . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 6 2.3. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 6
2.4. References . . . . . . . . . . . . . . . . . . . . . . . 7 2.4. References . . . . . . . . . . . . . . . . . . . . . . . 7
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.1. Updating RFC 6775 and RFC 8505 . . . . . . . . . . . . . 10 3.1. Updating RFC 6775 and RFC 8505 . . . . . . . . . . . . . 11
3.2. Access Link . . . . . . . . . . . . . . . . . . . . . . . 10 3.2. Access Link . . . . . . . . . . . . . . . . . . . . . . . 11
3.3. Route-Over Mesh . . . . . . . . . . . . . . . . . . . . . 12 3.3. Route-Over Mesh . . . . . . . . . . . . . . . . . . . . . 13
3.4. The Binding Table . . . . . . . . . . . . . . . . . . . . 14 3.4. The Binding Table . . . . . . . . . . . . . . . . . . . . 15
3.5. Primary and Secondary 6BBRs . . . . . . . . . . . . . . . 15 3.5. Primary and Secondary 6BBRs . . . . . . . . . . . . . . . 16
3.6. Using Optimistic DAD . . . . . . . . . . . . . . . . . . 16 3.6. Using Optimistic DAD . . . . . . . . . . . . . . . . . . 17
4. MultiLink Subnet Considerations . . . . . . . . . . . . . . . 16 4. Multi-Link Subnet Considerations . . . . . . . . . . . . . . 17
5. Optional 6LBR serving the MultiLink Subnet . . . . . . . . . 17 5. Optional 6LBR serving the Multi-Link Subnet . . . . . . . . . 18
6. Using IPv6 ND Over the Backbone Link . . . . . . . . . . . . 17 6. Using IPv6 ND Over the Backbone Link . . . . . . . . . . . . 19
7. Routing Proxy Operations . . . . . . . . . . . . . . . . . . 18 7. Routing Proxy Operations . . . . . . . . . . . . . . . . . . 19
8. Bridging Proxy Operations . . . . . . . . . . . . . . . . . . 19 8. Bridging Proxy Operations . . . . . . . . . . . . . . . . . . 20
9. Creating and Maintaining a Binding . . . . . . . . . . . . . 20 9. Creating and Maintaining a Binding . . . . . . . . . . . . . 21
9.1. Operation on a Binding in Tentative State . . . . . . . . 22 9.1. Operations on a Binding in Tentative State . . . . . . . 23
9.2. Operation on a Binding in Reachable State . . . . . . . . 23 9.2. Operations on a Binding in Reachable State . . . . . . . 24
9.3. Operation on a Binding in Stale State . . . . . . . . . . 24 9.3. Operations on a Binding in Stale State . . . . . . . . . 25
10. Registering Node Considerations . . . . . . . . . . . . . . . 24 10. Registering Node Considerations . . . . . . . . . . . . . . . 25
11. Security Considerations . . . . . . . . . . . . . . . . . . . 25 11. Security Considerations . . . . . . . . . . . . . . . . . . . 26
12. Protocol Constants . . . . . . . . . . . . . . . . . . . . . 26 12. Protocol Constants . . . . . . . . . . . . . . . . . . . . . 27
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 27
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
15.1. Normative References . . . . . . . . . . . . . . . . . . 26 15.1. Normative References . . . . . . . . . . . . . . . . . . 27
15.2. Informative References . . . . . . . . . . . . . . . . . 28 15.2. Informative References . . . . . . . . . . . . . . . . . 29
Appendix A. Possible Future Extensions . . . . . . . . . . . . . 30 Appendix A. Possible Future Extensions . . . . . . . . . . . . . 31
Appendix B. Applicability and Requirements Served . . . . . . . 31 Appendix B. Applicability and Requirements Served . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 33
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 for wired networks; applications and and reliable broadcast service for wired networks; applications and
protocols have been built that heavily depend on that feature for protocols have been built that heavily depend on that feature for
their core operation. Unfortunately, Low-Power Lossy Networks (LLNs) their core operation. Unfortunately, Low-Power Lossy Networks (LLNs)
and local wireless networks generally do not provide the broadcast and local wireless networks generally do not provide the broadcast
capabilities of Ethernet Bridging in an economical fashion. capabilities of Ethernet Bridging in an economical fashion.
As a result, protocols designed for bridged networks that rely on As a result, protocols designed for bridged networks that rely on
multicast and broadcast often exhibit disappointing behaviours when multicast and broadcast often exhibit disappointing behaviours when
employed unmodified on a local wireless medium (see employed unmodified on a local wireless medium (see
[I-D.ietf-mboned-ieee802-mcast-problems]). [I-D.ietf-mboned-ieee802-mcast-problems]).
Wi-Fi [IEEEstd80211] Access Points (APs) deployed in an Extended Wi-Fi [IEEEstd80211] Access Points (APs) deployed in an Extended
Service Set (ESS) act as Ethernet Bridges [IEEEstd8021], with the Service Set (ESS) act as Ethernet Bridges [IEEEstd8021], with the
property that the bridging state is established at the time of property that the bridging state is established at the time of
association. This ensures connectivity to the node (STA) and association. This ensures connectivity to the end node (the Wi-Fi
protects the wireless medium against broadcast-intensive Transparent STA) and protects the wireless medium against broadcast-intensive
Bridging reactive Lookups. Transparent Bridging reactive Lookups.
In other words, the association process is used to register the MAC In other words, the association process is used to register the MAC
Address of the STA to the AP. The AP subsequently proxies the Address of the STA to the AP. The AP subsequently proxies the
bridging operation and does not need to forward the broadcast Lookups bridging operation and does not need to forward the broadcast Lookups
over the radio. over the radio.
Like Transparent Bridging, IPv6 [RFC8200] Neighbor Discovery In the same way as Transparent Bridging, IPv6 [RFC8200] Neighbor
[RFC4861] [RFC4862] Protocol (IPv6 ND) is a reactive protocol, based Discovery [RFC4861] [RFC4862] Protocol (IPv6 ND) is a reactive
on multicast transmissions to locate an on-link correspondent and protocol, based on multicast transmissions to locate an on-link
ensure the uniqueness of an IPv6 address. The mechanism for correspondent and ensure the uniqueness of an IPv6 address. The
Duplicate Address Detection (DAD) [RFC4862] was designed for the mechanism for Duplicate Address Detection (DAD) [RFC4862] was
efficient broadcast operation of Ethernet Bridging. Since broadcast designed for the efficient broadcast operation of Ethernet Bridging.
can be unreliable over wireless media, DAD often fails to discover Since broadcast can be unreliable over wireless media, DAD often
duplications [I-D.yourtchenko-6man-dad-issues]. In practice, the fails to discover duplications [I-D.yourtchenko-6man-dad-issues]. In
fact that IPv6 addresses very rarely conflict is mostly attributable practice, the fact that IPv6 addresses very rarely conflict is mostly
to the entropy of the 64-bit Interface IDs as opposed to the attributable to the entropy of the 64-bit Interface IDs as opposed to
succesful operation of the IPv6 ND duplicate address detection and the succesful operation of the IPv6 ND duplicate address detection
resolution mechanisms. and resolution mechanisms.
The IPv6 ND Neighbor Solicitation (NS) [RFC4861] message is used for The IPv6 ND Neighbor Solicitation (NS) [RFC4861] message is used for
DAD and address Lookup when a node moves, or wakes up and reconnects DAD and address Lookup when a node moves, or wakes up and reconnects
to the wireless network. The NS message is targeted to a Solicited- to the wireless network. The NS message is targeted to a Solicited-
Node Multicast Address (SNMA) [RFC4291] and should in theory only Node Multicast Address (SNMA) [RFC4291] and should in theory only
reach a very small group of nodes. But in reality, IPv6 multicast reach a very small group of nodes. But in reality, IPv6 multicast
messages are typically broadcast on the wireless medium, and so they messages are typically broadcast on the wireless medium, and so they
are processed by most of the wireless nodes over the subnet (e.g., are processed by most of the wireless nodes over the subnet (e.g.,
the ESS fabric) regardless of how few of the nodes are subscribed to the ESS fabric) regardless of how few of the nodes are subscribed to
the SNMA. As a result, IPv6 ND address Lookups and DADs over a large the SNMA. As a result, IPv6 ND address Lookups and DADs over a large
skipping to change at page 4, line 13 skipping to change at page 4, line 13
reduce their power consumption, certain battery-operated devices such reduce their power consumption, certain battery-operated devices such
as IoT sensors and smartphones ignore some of the broadcasts, making as IoT sensors and smartphones ignore some of the broadcasts, making
IPv6 ND operations even less reliable. IPv6 ND operations even less reliable.
These problems can be alleviated by reducing the IPv6 ND broadcasts These problems can be alleviated by reducing the IPv6 ND broadcasts
over wireless access links. This has been done by splitting the over wireless access links. This has been done by splitting the
broadcast domains and routes between subnets, or even by assigning a broadcast domains and routes between subnets, or even by assigning a
/64 prefix to each wireless node (see [RFC8273]). /64 prefix to each wireless node (see [RFC8273]).
Another way is to proxy at the boundary of the wired and wireless Another way is to proxy at the boundary of the wired and wireless
domains the Layer-3 protocols that rely on MAC Layer broadcast domains the Layer 3 protocols that rely on MAC Layer broadcast
operations. For instance, IEEE 802.11 [IEEEstd80211] situates proxy- operations. For instance, IEEE 802.11 [IEEEstd80211] situates proxy-
ARP (IPv4) and proxy-ND (IPv6) functions at the Access Points (APs). ARP (IPv4) and proxy-ND (IPv6) functions at the Access Points (APs).
The 6BBR provides a proxy-ND function and can be extended for proxy- The 6BBR provides a proxy-ND function and can be extended for proxy-
ARP in a continuation specification. ARP in a continuation specification.
Knowledge of which address to proxy for can be obtained by snooping Knowledge of which address to proxy for can be obtained by snooping
the IPV6 ND protocol (see [I-D.bi-savi-wlan]), but it has been found the IPV6 ND protocol (see [I-D.bi-savi-wlan]), but it has been found
to be unreliable. An IPv6 address may not be discovered immediately to be unreliable. An IPv6 address may not be discovered immediately
due to a packet loss, or if a "silent" node is not currently using due to a packet loss, or if a "silent" node is not currently using
one of its addresses. A change of state (e.g. due to movement) may one of its addresses. A change of state (e.g., due to movement) may
be missed or misordered, leading to unreliable connectivity and be missed or misordered, leading to unreliable connectivity and
incomplete knowledge of the state of the network. incomplete knowledge of the state of the network.
This specification defines the 6BBR as a Routing Registrar [RFC8505] This specification defines the 6BBR as a Routing Registrar [RFC8505]
that provides proxy services for IPv6 Neighbor Discovery. As that provides proxy services for IPv6 Neighbor Discovery. As
represented in Figure 1, Backbone Routers federate multiple LLNs over represented in Figure 1, Backbone Routers federate multiple LLNs over
a Backbone Link to form a MultiLink Subnet (MLSN). Backbone Routers a Backbone Link to form a Multi-Link Subnet (MLSN). The MLSN breaks
placed along the LLN edge of the Backbone handle IPv6 Neighbor the Layer 2 continuity and splits the broadcast domain, in a fashion
Discovery, and forward packets on behalf of registered nodes. that each Link, including the backbone, is its own broadcast domain.
This means that devices that rely on a link-scope multicast on the
backbone will only reach other nodes on the backbone but not LLN
nodes. The same goes a packet that is sent with a hop limit of 1 or
using a Link-Local destination address. This packet may reach other
nodes on the backbone but not LLN Nodes. In order to enable the
continuity of IPv6 ND operations beyond the backbone, and enable
communication using Global or Unique Local Addresses between any pair
of nodes in the MLSN, Backbone Routers placed along the LLN edge of
the Backbone handle IPv6 ND on behalf of Registered Nodes and forward
IPv6 packets back and forth.
A 6LoWPAN node (6LN) registers all its IPv6 Addresses using an A 6LoWPAN node (6LN) registers all its IPv6 Addresses using an
NS(EARO) as specified in [RFC8505] to the 6BBR. The 6BBR is also a NS(EARO) as specified in [RFC8505] to the 6BBR. The 6BBR is also a
Border Router that performs IPv6 Neighbor Discovery (IPv6 ND) Border Router that performs IPv6 Neighbor Discovery (IPv6 ND)
operations on its Backbone interface on behalf of the 6LNs that have operations on its Backbone interface on behalf of the 6LNs that have
registered addresses on its LLN interfaces without the need of a registered addresses on its LLN interfaces without the need of a
broadcast over the wireless medium. A 6LN that resides on the broadcast over the wireless medium. A 6LN that resides on the
backbone does not register to the SNMA groups associated to its backbone does not register to the SNMA groups associated to its
Registered Addresses and defers to the 6BBR to answer or preferably Registered Addresses and defers to the 6BBR to answer or preferably
forward to it as unicast the corresponding multicast packets. forward to it as unicast the corresponding multicast packets.
skipping to change at page 5, line 19 skipping to change at page 5, line 26
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2.2. New Terms 2.2. New Terms
This document introduces the following terminology: This document introduces the following terminology:
Federated Federated
A subnet that comprises a Backbone and one or more (wireless) A subnet that comprises a Backbone and one or more (wireless)
access links, is said to be federated into one MultiLink access links, is said to be federated into one Multi-Link
Subnet. The proxy-ND operation of 6BBRs over the Backbone and Subnet. The proxy-ND operation of 6BBRs over the Backbone and
the access links provides the appearance of a subnet for IPv6 the access links provides the appearance of a subnet for IPv6
ND. ND.
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
Solicitations over the Backbone on behalf of the Registering Solicitations over the Backbone on behalf of the Registering
Node. Node which might be in a sleep state in a low power network.
The Sleeping Proxy that is also a Bridging Proxy will
preferably forward the relevant messages to the Registering
Node as unicast frames in accord to the duty cycle of the
Registering Node and let it respond.
Routing Proxy Routing Proxy
A Routing Proxy provides IPv6 ND proxy functions and enables A Routing Proxy provides IPv6 ND proxy functions and enables
the MLSN operation over federated links that may not be the MLSN operation over federated links that may not be
compatible for bridging. The Routing Proxy advertises its own compatible for bridging. The Routing Proxy advertises its own
MAC Address as the TLLA in the proxied NAs over the Backbone, MAC Address as the Target Link Layer Address (TLLA) in the
and routes at the Network Layer between the federated links. proxied NAs over the Backbone, and routes at the Network Layer
between the federated links.
Bridging Proxy Bridging Proxy
A Bridging Proxy provides IPv6 ND proxy functions while A Bridging Proxy provides IPv6 ND proxy functions while
preserving forwarding continuity at the MAC Layer. The preserving forwarding continuity at the MAC Layer. The
Bridging Proxy advertises the MAC Address of the Registering Bridging Proxy advertises the MAC Address of the Registering
Node as the TLLA in the proxied NAs over the Backbone. In that Node as the TLLA in the proxied NAs over the Backbone. In that
case, the MAC Address and the mobility of 6LN is still visible case, the MAC Address and the mobility of 6LN is still visible
across the bridged Backbone, and the 6BBR may be configured to across the bridged Backbone, and the 6BBR may be configured to
proxy for Link Local Addresses. proxy for Link Local Addresses.
Binding Table Binding Table
skipping to change at page 6, line 24 skipping to change at page 6, line 36
6BBR: 6LoWPAN Backbone Router 6BBR: 6LoWPAN Backbone Router
6LBR: 6LoWPAN Border Router 6LBR: 6LoWPAN Border Router
6LN: 6LoWPAN Node 6LN: 6LoWPAN Node
6LR: 6LoWPAN Router 6LR: 6LoWPAN Router
6CIO: Capability Indication Option 6CIO: Capability Indication Option
ARO: Address Registration Option
DAC: Duplicate Address Confirmation DAC: Duplicate Address Confirmation
DAD: Duplicate Address Detection DAD: Duplicate Address Detection
DAR: Duplicate Address Request DAR: Duplicate Address Request
EARO: Extended Address Registration Option
EDAC: Extended Duplicate Address Confirmation EDAC: Extended Duplicate Address Confirmation
EDAR: Extended Duplicate Address Request EDAR: Extended Duplicate Address Request
DODAG: Destination-Oriented Directed Acyclic Graph DODAG: Destination-Oriented Directed Acyclic Graph
ID: Identifier
LLN: Low-Power and Lossy Network LLN: Low-Power and Lossy Network
NA: Neighbor Advertisement NA: Neighbor Advertisement
NCE: Neighbor Cache Entry NCE: Neighbor Cache Entry
ND: Neighbor Discovery ND: Neighbor Discovery
NDP: Neighbor Discovery Protocol NDP: Neighbor Discovery Protocol
NS: Neighbor Solicitation NS: Neighbor Solicitation
NS(DAD): NDP NS message used for the purpose of duplication
avoidance (multicast)
NS(Lookup): NDP NS message used for the purpose of address
resolution (multicast)
NS(NUD): NDP NS message used for the purpose of unreachability
detection (unicast)
NUD: Neighbor Unreachability Detection
ROVR: Registration Ownership Verifier ROVR: Registration Ownership Verifier
RPL: IPv6 Routing Protocol for LLNs RPL: IPv6 Routing Protocol for LLNs
RA: Router Advertisement RA: Router Advertisement
RS: Router Solicitation RS: Router Solicitation
SNMA: Solicited-Node Multicast Address
LLA: Link Layer Address (aka MAC address)
SLLA: Source Link Layer Address
TLLA: Target Link Layer Address
TID: Transaction ID TID: Transaction ID
2.4. References 2.4. 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 for IP version 6" [RFC4861], "IPv6 Stateless o "Neighbor Discovery for IP version 6" [RFC4861], "IPv6 Stateless
Address Autoconfiguration" [RFC4862] and "Optimistic Duplicate Address Autoconfiguration" [RFC4862] and "Optimistic Duplicate
Address Detection" [RFC4429], Address Detection" [RFC4429],
o "Neighbor Discovery Proxies (proxy-ND)" [RFC4389] and "MultiLink o "Neighbor Discovery Proxies (proxy-ND)" [RFC4389] and "Multi-Link
Subnet Issues" [RFC4903], Subnet Issues" [RFC4903],
o "Problem Statement and Requirements for IPv6 over Low-Power o "Problem Statement and Requirements for IPv6 over Low-Power
Wireless Personal Area Network (6LoWPAN) Routing" [RFC6606], and Wireless Personal Area Network (6LoWPAN) Routing" [RFC6606], and
o Neighbor Discovery Optimization for Low-Power and Lossy Networks o Neighbor Discovery Optimization for Low-Power and Lossy Networks
[RFC6775] and "Registration Extensions for 6LoWPAN Neighbor [RFC6775] and "Registration Extensions for 6LoWPAN Neighbor
Discovery" [RFC8505]. Discovery" [RFC8505].
3. Overview 3. Overview
This section and its subsections present a non-normative high level This section and its subsections present a non-normative high level
view of the operation of the 6BBR. The next sections cover the view of the operation of the 6BBR. The following sections cover the
normative part. Figure 1 illustrates a backbone link that federates normative part. Figure 1 illustrates a backbone link that federates
a collection of LLNs as a single IPv6 Subnet, with a number of 6BBRs a collection of LLNs as a single IPv6 Subnet, with a number of 6BBRs
providing proxy-ND services to their attached LLNs. providing proxy-ND services to their attached LLNs.
The LLN may be a hub-and-spoke access link such as (Low-Power) IEEE
STD. 802.11 (Wi-Fi) [IEEEstd80211] and IEEE STD. 802.15.1 (Bluetooth)
[IEEEstd802151], or a Mesh-Under or a Route-Over network [RFC8505].
The proxy state can be distributed across multiple 6BBRs attached to
the same Backbone.
| |
+-----+ +-----+ +-----+ IPv6 +-----+ +-----+ +-----+ IPv6
(default) | | (Optional) | | | | Node (default) | | (Optional) | | | | Node
Router | | 6LBR | | | | or Router | | 6LBR | | | | or
+-----+ +-----+ +-----+ 6LN +-----+ +-----+ +-----+ 6LN
| Backbone side | | | Backbone side | |
----+-------+-----------------+---+-------------+----+----- ----+-------+-----------------+---+-------------+----+-----
| | | | | |
+------+ +------+ +------+ +------+ +------+ +------+
| 6BBR | | 6BBR | | 6BBR | | 6BBR | | 6BBR | | 6BBR |
skipping to change at page 8, line 26 skipping to change at page 9, line 26
+------+ +------+ +------+ +------+ +------+ +------+
o Wireless side o o o o o o o Wireless side 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 o o o o o o o o o o o o o o o o o o LLN 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
Figure 1: Backbone Link and Backbone Routers Figure 1: Backbone Link and Backbone Routers
The LLN may be a hub-and-spoke access link such as (Low-Power) IEEE
STD. 802.11 (Wi-Fi) [IEEEstd80211] and IEEE STD. 802.15.1 (Bluetooth)
[IEEEstd802151], or a Mesh-Under or a Route-Over network [RFC8505].
The proxy state can be distributed across multiple 6BBRs attached to
the same Backbone.
The main features of a 6BBR are as follows: The main features of a 6BBR are as follows:
o Multilink-subnet functions (provided by the 6BBR on the backbone) o Multi-Link-subnet functions (provided by the 6BBR on the backbone)
performed on behalf of registered 6LNs, and performed on behalf of registered 6LNs, and
o Routing registrar services that reduce multicast within the LLN: o Routing registrar services that reduce multicast within the LLN:
* Binding Table management * Binding Table management
* failover, e.g., due to mobility * failover, e.g., due to mobility
Each Backbone Router (6BBR) maintains a data structure for its Each Backbone Router (6BBR) maintains a data structure for its
Registered Addresses called a Binding Table. The combined Binding Registered Addresses called a Binding Table. The combined Binding
Tables of all the 6BBRs on a backbone form a distributed database of Tables of all the 6BBRs on a backbone form a distributed database of
6LNs that reside in the LLNs or on the IPv6 Backbone. 6LNs that reside in the LLNs or on the IPv6 Backbone.
Unless otherwise configured, a 6BBR does the following: Unless otherwise configured, a 6BBR does the following:
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 duplicated over the Backbone and ensure that the Address is not duplicated over the Backbone
o Advertise a Registered Address over the Backbone using NA o Advertise a Registered Address over the Backbone using an
messages, asynchronously or as a response to a Neighbor unsolicited NA message, asynchronously or as a response to a NS
Solicitation messages. This includes participating to the message. This includes joining the multicast group associated to
solicited-node multicast address associated to the Registered the SNMA derived from the Registered Address as specified in
Address as specified in section 7.2.1. of [RFC4861] over the section 7.2.1. of [RFC4861] over the Backbone.
Backbone.
o Either respond using NA messages as a proxy or preferably bridge o The 6BBR may respond immediately as a Proxy in lieu of the
to the 6LN as a unicast frame the IPv6 ND messages (multicast DAD Registering Node, e.g., if the Registering Node has a sleeping
and Address Lookup, and unicast NUD) received for the Registered cycle that the 6BBR does not want to interrupt, and if the 6BR has
Address over the Backbone. This may include responding on behalf a recent state that is deemed fresh enough to permit the proxied
of a sleeping node, or checking the liveliness of the Registering response. It is preferred, though, that the 6BBR checks whether
Node before answering on its behalf. the Registering Node is still responsive on the Registered
Address. to that effect:
* as a Bridging Proxy, the 6BBR forwards the multicast DAD and
Address Lookup messages as a unicast MAC-Layer frames to the
MAC address of the Registering Node that matches the Target in
the ND message, and forwards as is the unicast Neighbor
Unreachability Detection (NUD) messages, so as to let the
Registering Node answer with the ND Message and options that it
sees fit;
* as a Routing Proxy, the 6BBR checks the liveliness of the
Registering Node, e.g., using a NUD verification, before
answering on its behalf.
o Deliver packets arriving from the LLN, using Neighbor Solicitation o Deliver packets arriving from the LLN, using Neighbor Solicitation
messages to look up the destination over the Backbone. messages to look up the destination over the Backbone.
o Forward or bridge packets between the LLN and the Backbone. o Forward or bridge packets between the LLN and the Backbone.
o Verify liveness for a registration, when needed. o Verify liveness for a registration, when needed.
The first of these functions enables the 6BBR to fulfill its role as The first of these functions enables the 6BBR to fulfill its role as
a Routing Registrar for each of its attached LLNs. The remaining a Routing Registrar for each of its attached LLNs. The remaining
skipping to change at page 10, line 18 skipping to change at page 11, line 23
registrations to different 6BBRs for the same Registered Address registrations to different 6BBRs for the same Registered Address
are resolved using the TID field. are resolved using the TID field.
o The Link Layer Address (LLA) that the 6BBR advertises for the o The Link Layer Address (LLA) that the 6BBR advertises for the
Registered Address on behalf of the Registered Node over the Registered Address on behalf of the Registered Node over the
Backbone can belong to the Registering Node; in that case, the Backbone can belong to the Registering Node; in that case, the
6BBR (acting as a Bridging Proxy (see Section 8)) bridges the 6BBR (acting as a Bridging Proxy (see Section 8)) bridges the
unicast packets. Alternatively, the LLA can be that of the 6BBR unicast packets. Alternatively, the LLA can be that of the 6BBR
on the Backbone interface, in which case the 6BBR (acting as a on the Backbone interface, in which case the 6BBR (acting as a
Routing Proxy(see Section 7)) receives the unicast packets at Routing Proxy(see Section 7)) receives the unicast packets at
Layer-3 and routes over. Layer 3 and routes over.
3.1. Updating RFC 6775 and RFC 8505 3.1. Updating RFC 6775 and RFC 8505
This specification adds the EARO as a possible option in RS, NS(DAD) This specification adds the EARO as a possible option in RS, NS(DAD)
and NA messages over the backbone. [RFC8505] requires that the and NA messages over the backbone. [RFC8505] requires that the
registration NS(EARO) contains an SLLAO. This specification details registration NS(EARO) contains an Source Link Layer Address Option
the use of those messages over the backbone. (SLLAO). This specification details the use of those messages over
the backbone.
Note: [RFC6775] requires that the registration NS(EARO) contains an Note: [RFC6775] requires that the registration NS(EARO) contains an
SLLAO and [RFC4862] that the NS(DAD) is sent from the unspecified SLLAO and [RFC4862] that the NS(DAD) is sent from the unspecified
address for which there cannot be a SLLAO. Consequently, an NS(DAD) address for which there cannot be a SLLAO. Consequently, an NS(DAD)
cannot be confused with a registration. cannot be confused with a registration.
This specification adds the capability to insert IPv6 ND options in This specification adds the capability to insert IPv6 ND options in
the EDAR and EDAC messages. In particular, a 6BBR acting as a 6LR 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 for the Registered Address can insert an SLLAO in the EDAR to the
6LBR in order to avoid a Lookup back. This enables the 6LBR to store 6LBR in order to avoid a Lookup back. This enables the 6LBR to store
the MAC address associated to the Registered Address on a Link and to the MAC address associated to the Registered Address on a Link and to
serve as a mapping server as described in serve as a mapping server as described in
[I-D.thubert-6lo-unicast-lookup]. [I-D.thubert-6lo-unicast-lookup].
3.2. Access Link 3.2. Access Link
The simplest Multi-Link Subnet topology from the Layer-3 perspective The simplest Multi-Link Subnet topology from the Layer 3 perspective
occurs when the wireless network appears as a single hop hub-and- occurs when the wireless network appears as a single hop hub-and-
spoke network as shown in Figure 2. The Layer-2 operation may spoke network as shown in Figure 2. The Layer 2 operation may
effectively be hub-and-spoke (e.g., Wi-Fi) or Mesh-Under, with a effectively be hub-and-spoke (e.g., Wi-Fi) or Mesh-Under, with a
Layer-2 protocol handling the complex topology. Layer 2 protocol handling the complex topology.
| |
+-----+ +-----+ +-----+ IPv6 +-----+ +-----+ +-----+ IPv6
(default) | | (Optional) | | | | Node (default) | | (Optional) | | | | Node
Router | | 6LBR | | | | or Router | | 6LBR | | | | or
+-----+ +-----+ +-----+ 6LN +-----+ +-----+ +-----+ 6LN
| Backbone side | | | Backbone side | |
----+-------+-----------------+---+-------------+----+----- ----+-------+-----------------+---+-------------+----+-----
| | | | | |
+------+ +------+ +------+ +------+ +------+ +------+
skipping to change at page 11, line 30 skipping to change at page 12, line 30
Figure 3 illustrates a flow where 6LN forms an IPv6 Address and Figure 3 illustrates a flow where 6LN forms an IPv6 Address and
registers it to a 6BBR acting as a 6LR [RFC8505]. The 6BBR applies registers it to a 6BBR acting as a 6LR [RFC8505]. The 6BBR applies
ODAD (see Section 3.6) to the registered address to enable ODAD (see Section 3.6) to the registered address to enable
connectivity while the message flow is still in progress. connectivity while the message flow is still in progress.
In this example, a 6LBR is deployed on the backbone link to serve the In this example, a 6LBR is deployed on the backbone link to serve the
whole subnet, and EDAR / EDAC messages are used in combination with whole subnet, and EDAR / EDAC messages are used in combination with
DAD to enable coexistence with IPv6 ND over the backbone. DAD to enable coexistence with IPv6 ND over the backbone.
The RS sent initially by the 6LN(STA) is a transmitted as a multicast The RS sent initially by the 6LN(STA) is transmitted as a multicast
but since it is intercepted by the 6BBR, it is never effectively but since it is intercepted by the 6BBR, it is never effectively
broadcast. The multiple arrows associated to the ND messages on the broadcast. The multiple arrows associated to the ND messages on the
Backbone denote a real Layer-2 broadcast. Backbone denote a real Layer 2 broadcast.
6LN(STA) 6BBR(AP) 6LBR default GW 6LN(STA) 6BBR(AP) 6LBR default GW
| | | | | | | |
| LLN Access Link | IPv6 Backbone (e.g., Ethernet) | | LLN Access Link | IPv6 Backbone (e.g., Ethernet) |
| | | | | | | |
| RS(multicast) | | | | RS(multicast) | | |
|---------------->| | | |---------------->| | |
| RA(PIO, Unicast)| | | | RA(PIO, Unicast)| | |
|<----------------| | | |<----------------| | |
| NS(EARO) | | | | NS(EARO) | | |
skipping to change at page 12, line 47 skipping to change at page 13, line 47
| | | |
| NA(EARO) |<DAD timeout> | NA(EARO) |<DAD timeout>
|<----------------| |<----------------|
| | | |
Figure 3: Initial Registration Flow to a 6BBR acting as Routing Proxy Figure 3: Initial Registration Flow to a 6BBR acting as Routing Proxy
3.3. Route-Over Mesh 3.3. Route-Over Mesh
A more complex Multi-Link Subnet topology occurs when the wireless A more complex Multi-Link Subnet topology occurs when the wireless
network appears as a Layer-3 Mesh network as shown in Figure 4. A network appears as a Layer 3 Mesh network as shown in Figure 4. A
so-called Route-Over routing protocol exposes routes between 6LRs so-called Route-Over routing protocol exposes routes between 6LRs
towards both 6LRs and 6LNs, and a 6LBR acts as Root of the Layer-3 towards both 6LRs and 6LNs, and a 6LBR acts as Root of the Layer 3
Mesh network and proxy-registers the LLN addresses to the 6BBR. Mesh network and proxy-registers the LLN addresses to the 6BBR.
| |
+-----+ +-----+ +-----+ IPv6 +-----+ +-----+ +-----+ IPv6
(default) | | (Optional) | | | | Node (default) | | (Optional) | | | | Node
Router | | 6LBR | | | | or Router | | 6LBR | | | | or
+-----+ +-----+ +-----+ 6LN +-----+ +-----+ +-----+ 6LN
| Backbone side | | | Backbone side | |
----+-------+-----------------+---+-------------+----+----- ----+-------+-----------------+---+-------------+----+-----
| | | | | |
skipping to change at page 13, line 37 skipping to change at page 14, line 37
Figure 5 illustrates IPv6 signaling that enables a 6LN (the Figure 5 illustrates IPv6 signaling that enables a 6LN (the
Registered Node) to form a Global or a Unique-Local Address and Registered Node) to form a Global or a Unique-Local Address and
register it to the 6LBR that serves its LLN using [RFC8505]. The register it to the 6LBR that serves its LLN using [RFC8505]. The
6LBR (the Registering Node) then proxies the [RFC8505] registration 6LBR (the Registering Node) then proxies the [RFC8505] registration
to the 6BBR to obtain proxy-ND services from the 6BBR. to the 6BBR to obtain proxy-ND services from the 6BBR.
As above, the RS sent initially by the 6LN(STA) is a transmitted as a As above, the RS sent initially by the 6LN(STA) is a transmitted as a
multicast but since it is intercepted by the 6BBR, it is never multicast but since it is intercepted by the 6BBR, it is never
effectively broadcast, and the multiple arrows associated to the ND effectively broadcast, and the multiple arrows associated to the ND
messages on the Backbone denote a real Layer-2 broadcast. messages on the Backbone denote a real Layer 2 broadcast.
6LoWPAN Node 6LR 6LBR 6BBR 6LoWPAN Node 6LR 6LBR 6BBR
(mesh leaf) (mesh router) (mesh root) (mesh leaf) (mesh router) (mesh root)
| | | | | | | |
| 6LoWPAN ND |6LoWPAN ND | 6LoWPAN ND | IPv6 ND | 6LoWPAN ND |6LoWPAN ND | 6LoWPAN ND | IPv6 ND
| LLN link |Route-Over mesh|Ethernet/serial| Backbone | LLN link |Route-Over mesh|Ethernet/serial| Backbone
| | |/Internal call | | | |/Internal call |
| IPv6 ND RS | | | | IPv6 ND RS | | |
|-------------->| | | |-------------->| | |
|-----------> | | | |-----------> | | |
skipping to change at page 14, line 39 skipping to change at page 15, line 39
| | |<--------------| | | |<--------------|
| | Extended DAC | | | | Extended DAC | |
| |<--------------| | | |<--------------| |
| NA(EARO) | | | | NA(EARO) | | |
|<--------------| | | |<--------------| | |
| | | | | | | |
Figure 5: Initial Registration Flow over Route-Over Mesh Figure 5: Initial Registration Flow over Route-Over Mesh
As a non-normative example of a Route-Over Mesh, the 6TiSCH As a non-normative example of a Route-Over Mesh, the 6TiSCH
architecture [I-D.ietf-6tisch-architecture] suggests using RPL architecture [I-D.ietf-6tisch-architecture] suggests using the RPL
[RFC6550] and collocating the RPL root with a 6LBR that serves the [RFC6550] routing protocol and collocating the RPL root with a 6LBR
LLN. The 6LBR is also either collocated with or directly connected that serves the LLN. The 6LBR is also either collocated with or
to the 6BBR over an IPv6 Link. directly connected to the 6BBR over an IPv6 Link.
3.4. The Binding Table 3.4. The Binding Table
Addresses in an LLN that are reachable from the Backbone by way of Addresses in an LLN that are reachable from the Backbone by way of
the 6BBR function must be registered to that 6BBR, using an NS(EARO) the 6BBR function must be registered to that 6BBR, using an NS(EARO)
with the R flag set [RFC8505]. A 6BBR maintains a state for its with the R flag set [RFC8505]. A 6BBR maintains a state for its
active registrations in an abstract Binding Table. active registrations in an abstract Binding Table.
An entry in the Binding Table is called a "Binding". A Binding may An entry in the Binding Table is called a "Binding". A Binding may
be in Tentative, Reachable or Stale state. be in Tentative, Reachable or Stale state.
skipping to change at page 15, line 25 skipping to change at page 16, line 25
o De-registrations (newer TID, same ROVR, null Lifetime) are o De-registrations (newer TID, same ROVR, null Lifetime) are
accepted with a status of 4 ("Removed"); the entry is deleted; accepted with a status of 4 ("Removed"); the entry is deleted;
o Newer registrations (newer TID, same ROVR, non-null Lifetime) are o Newer registrations (newer TID, same ROVR, non-null Lifetime) are
accepted with a status of 0 (Success); the Binding is updated with accepted with a status of 0 (Success); the Binding is updated with
the new TID, the Registration Lifetime and the Registering Node; the new TID, the Registration Lifetime and the Registering Node;
in Tentative state the EDAC response is held and may be in Tentative state the EDAC response is held and may be
overwritten; in other states the Registration Lifetime timer is overwritten; in other states the Registration Lifetime timer is
restarted and the entry is placed in Reachable state. restarted and the entry is placed in Reachable state.
o Identical registrations (same TID, same ROVR) from a same o Identical registrations (same TID, same ROVR) from the same
Registering Node are accepted with a status of 0 (Success). In Registering Node are accepted with a status of 0 (Success). In
Tentative state, the response is held and may be overwritten, but Tentative state, the response is held and may be overwritten, but
the response is eventually produced, carrying the result of the the response is eventually produced, carrying the result of the
DAD process; DAD process;
o Older registrations (older TID, same ROVR) from the same o Older registrations (older TID, same ROVR) from the same
Registering Node are discarded; Registering Node are discarded;
o Identical and older registrations (not-newer TID, same ROVR) from o Identical and older registrations (not-newer TID, same ROVR) from
o a different Registering Node are rejected with a status of 3 o a different Registering Node are rejected with a status of 3
(Moved); this may be rate limited to avoid undue interference; (Moved); this may be rate limited to avoid undue interference;
o Any registration for the same address but with a different ROVR is o Any registration for the same address but with a different ROVR is
rejected with a status of 1 (Duplicate). rejected with a status of 1 (Duplicate).
The operation of the Binding Table is specified in details in The operation of the Binding Table is specified in detail in
Section 9. Section 9.
3.5. Primary and Secondary 6BBRs 3.5. Primary and Secondary 6BBRs
A same address may be successfully registered to more than one 6BBR, The same address may be successfully registered to more than one
in which case the Registering Node uses the same EARO in all the 6BBR, in which case the Registering Node uses the same EARO in all
parallel registrations. To allow for this, ND(DAD) and NA messages the parallel registrations. To allow for this, ND(DAD) and NA
with an EARO that indicate an identical Binding in another 6BBR (same messages with an EARO that indicate an identical Binding in another
Registered address, same TID, same ROVR) as silently ignored. 6BBR (same Registered address, same TID, same ROVR) are silently
ignored.
A 6BBR may optionally be primary or secondary. The primary is the A 6BBR may optionally be primary or secondary. The primary is the
6BBR that has the highest EUI-64 Address of all the 6BBRs that share 6BBR that has the highest EUI-64 Address of all the 6BBRs that share
a registration for the same Registered Address, with the same ROVR a registration for the same Registered Address, with the same ROVR
and same Transaction ID, the EUI-64 Address being considered as an and same Transaction ID, the EUI-64 Address being considered as an
unsigned 64bit integer. A given 6BBR can be primary for a given 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. not the Addresses belong to the same 6LN.
In the following sections, is is expected that an NA is sent over the In the following sections, is is expected that an NA is sent over the
skipping to change at page 16, line 46 skipping to change at page 17, line 46
Registered Address, and it may resolve that Address using an Registered Address, and it may resolve that Address using an
NS(Lookup) message. In response, the 6BBR sends an NA with an EARO NS(Lookup) message. In response, the 6BBR sends an NA with an EARO
and the Override (O) flag [RFC4861] that is not set. The router can and the Override (O) flag [RFC4861] that is not set. The router can
then determine the freshest EARO in case of conflicting NA(EARO) then determine the freshest EARO in case of conflicting NA(EARO)
messages, using the method described in section 5.2.1 of [RFC8505]. messages, using the method described in section 5.2.1 of [RFC8505].
If the NA(EARO) is the freshest answer, the default router creates a If the NA(EARO) is the freshest answer, the default router creates a
Binding with the SLLAO of the 6BBR (in Routing Proxy mode) or that of Binding with the SLLAO of the 6BBR (in Routing Proxy mode) or that of
the Registering Node (in Bridging Proxy mode) so that traffic from/to the Registering Node (in Bridging Proxy mode) so that traffic from/to
the Registered Address can flow immediately. the Registered Address can flow immediately.
4. MultiLink Subnet Considerations 4. Multi-Link Subnet Considerations
The Backbone and the federated LLN Links are considered as different The Backbone and the federated LLN Links are considered as different
links in the MultiLink Subnet, even if multiple LLNs are attached to links in the Multi-Link Subnet, even if multiple LLNs are attached to
the same 6BBR. ND messages are link-scoped and are not forwarded by the same 6BBR. ND messages are link-scoped and are not forwarded by
the 6BBR between the backbone and the LLNs though some packets may be the 6BBR between the backbone and the LLNs though some packets may be
reinjected in Bridging Proxy mode (see Section 8). reinjected in Bridging Proxy mode (see Section 8).
Nodes located inside the subnet do not perform the IPv6 Path MTU Nodes located inside the subnet do not perform the IPv6 Path MTU
Discovery [RFC8201]. For that reason, the MTU MUST have a same value Discovery [RFC8201]. For that reason, the MTU MUST have the same
on the Backbone and all attached LLNs. As a consequence, the 6BBR value on the Backbone and all attached LLNs. As a consequence, the
MUST use the same MTU value in RAs over the Backbone and in the RAs 6BBR MUST use the same MTU value in RAs over the Backbone and in the
that it transmits towards the LLN links. RAs that it transmits towards the LLN links.
5. Optional 6LBR serving the MultiLink Subnet 5. Optional 6LBR serving the Multi-Link Subnet
A 6LBR can be deployed to serve the whole MLSN. It may be attached A 6LBR can be deployed to serve the whole MLSN. It may be attached
to the backbone, in which case it can be discovered by its capability to the backbone, in which case it can be discovered by its capability
advertisement (see section 4.3. of [RFC8505]) in RA messages. advertisement (see section 4.3. of [RFC8505]) in RA messages.
This specification allows for an address to be registered to more This specification allows for an address to be registered to more
than one 6BBR. It results that a 6LBR MUST be capable of maintaining than one 6BBR. Consequently a 6LBR MUST be capable of maintaining
a state for each of the 6BBR having registered with a same TID and state for each of the 6BBR having registered with the same TID and
same ROVR. same ROVR.
When a 6LBR is present, the 6BBR uses an EDAR/EDAC message exchange When a 6LBR is present, the 6BBR uses an EDAR/EDAC message exchange
with the 6LBR to check if the new registration corresponds to a with the 6LBR to check if the new registration corresponds to a
duplication or a movement. This is done prior to the NS(DAD) duplication or a movement. This is done prior to the NS(DAD)
process, which may be avoided of the 6LBR already maintains a process, which may be avoided if the 6LBR already maintains a
conflicting state for the Registered Address. conflicting state for the Registered Address.
If this registration is duplicate or not the freshest, then the 6LBR If this registration is duplicate or not the freshest, then the 6LBR
replies with an EDAC message with a status code of 1 ("Duplicate replies with an EDAC message with a status code of 1 ("Duplicate
Address") or 3 ("Moved"), respectively. If this registration is the Address") or 3 ("Moved"), respectively. If this registration is the
freshest, then the 6LBR replies with a status code of 0. In that freshest, then the 6LBR replies with a status code of 0. In that
case, if this registration is fresher than an existing registration case, if this registration is fresher than an existing registration
for another 6BBR, then the 6LBR also sends an asynchronous EDAC with for another 6BBR, then the 6LBR also sends an asynchronous EDAC with
a status of 4 ("Removed") to that other 6BBR. a status of 4 ("Removed") to that other 6BBR.
The EDAR message SHOULD carry the SLLAO used in NS messages by the The EDAR message SHOULD carry the SLLAO used in NS messages by the
6BBR for that Binding, and the EDAC message SHOULD carry the TLLAO 6BBR for that Binding, and the EDAC message SHOULD carry the Target
associated with the currently accepted registration. This enables a Link Layer Address Option (TLLAO) associated with the currently
6BBR to locate the new position of a mobile 6LN in the case of a accepted registration. This enables a 6BBR to locate the new
Routing Proxy operation, and opens the capability for the 6LBR to position of a mobile 6LN in the case of a Routing Proxy operation,
serve as a mapping server in the future. and opens the capability for the 6LBR to serve as a mapping server in
the future.
Note that if Link Local addresses are registered, then the scope of Note that if Link Local addresses are registered, then the scope of
uniqueness on which the address duplication is checked is the total uniqueness on which the address duplication is checked is the total
collection of links that the 6LBR serves as opposed to the sole link collection of links that the 6LBR serves as opposed to the sole link
on which the Link Local address is assigned. on which the Link Local address is assigned.
6. Using IPv6 ND Over the Backbone Link 6. Using IPv6 ND Over the Backbone Link
On the Backbone side, the 6BBR MUST join the SNMA group corresponding On the Backbone side, the 6BBR MUST join the SNMA group corresponding
to a Registered Address as soon as it creates a Binding for that to a Registered Address as soon as it creates a Binding for that
skipping to change at page 18, line 26 skipping to change at page 19, line 31
on behalf of the Registered Node. Note that an NS(DAD) does not on behalf of the Registered Node. Note that an NS(DAD) does not
contain an SLLAO and cannot be confused with a proxy registration contain an SLLAO and cannot be confused with a proxy registration
such as performed by a 6LBR. such as performed by a 6LBR.
An NA message generated in response to an NS(DAD) MUST have the An NA message generated in response to an NS(DAD) MUST have the
Override flag set and a status of 1 (Duplicate) or 3 (Moved) in the Override flag set and a status of 1 (Duplicate) or 3 (Moved) in the
EARO. An NA message generated in response to an NS(Lookup) or an EARO. An NA message generated in response to an NS(Lookup) or an
NS(NUD) MUST NOT have the Override flag set. NS(NUD) MUST NOT have the Override flag set.
This specification enables proxy operation for the IPv6 ND resolution This specification enables proxy operation for the IPv6 ND resolution
of LLN devices and a prefix that is used across a MultiLink Subnet of LLN devices and a prefix that is used across a Multi-Link Subnet
MAY be advertised as on-link over the Backbone. This is done for MAY be advertised as on-link over the Backbone. This is done for
backward compatibility with existing IPv6 hosts by setting the L flag backward compatibility with existing IPv6 hosts by setting the L flag
in the Prefix Information Option (PIO) of RA messages [RFC4861]. in the Prefix Information Option (PIO) of RA messages [RFC4861].
For movement involving a slow reattachment, the Neighbor For movement involving a slow reattachment, the NUD procedure defined
Unreachability Detection (NUD) defined in [RFC4861] may time out too in [RFC4861] may time out too quickly. Nodes on the backbone SHOULD
quickly. Nodes on the backbone SHOULD support [RFC7048] whenever support [RFC7048] whenever possible.
possible.
7. Routing Proxy Operations 7. Routing Proxy Operations
A Routing Proxy provides IPv6 ND proxy functions for Global and A Routing Proxy provides IPv6 ND proxy functions for Global and
Unique Local addresses between the LLN and the backbone, but not for Unique Local addresses between the LLN and the backbone, but not for
Link-Local addresses. It operates as an IPv6 border router and Link-Local addresses. It operates as an IPv6 border router and
provides a full Link-Layer isolation. provides a full Link-Layer isolation.
In this mode, it is not required that the MAC addresses of the 6LNs In this mode, it is not required that the MAC addresses of the 6LNs
are visible at Layer-2 over the Backbone. It is thus useful when the are visible at Layer 2 over the Backbone. It is thus useful when the
messaging over the Backbone that is associated to wireless mobility messaging over the Backbone that is associated to wireless mobility
becomes expensive, e.g., when the Layer-2 topology is virtualized becomes expensive, e.g., when the Layer 2 topology is virtualized
over a wide area IP underlay. over a wide area IP underlay.
This mode is definitely required when the LLN uses a MAC address This mode is definitely required when the LLN uses a MAC address
format that is different from that on the Backbone (e.g., EUI-64 vs. format that is different from that on the Backbone (e.g., EUI-64 vs.
EUI-48). Since a 6LN may not be able to resolve an arbitrary EUI-48). Since a 6LN may not be able to resolve an arbitrary
destination in the MLSN directly, the MLSN prefix MUST NOT be destination in the MLSN directly, the MLSN prefix MUST NOT be
advertised as on-link in RA messages sent towards the LLN. advertised as on-link in RA messages sent towards the LLN.
In order to maintain IP connectivity, the 6BBR installs a connected In order to maintain IP connectivity, the 6BBR installs a connected
Host route to the Registered Address on the LLN interface, via the 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. option in the NS(EARO) messages.
When operating as a Routing Proxy, the 6BBR MUST use its Layer-2 When operating as a Routing Proxy, the 6BBR MUST use its Layer 2
Address on its Backbone Interface in the SLLAO of the RS messages and Address on its Backbone Interface in the SLLAO of the RS messages and
the TLLAO of the NA messages that it generates to advertise the the TLLAO of the NA messages that it generates to advertise the
Registered Addresses. Registered Addresses.
For each Registered Address, multiple peers on the Backbone may have For each Registered Address, multiple peers on the Backbone may have
resolved the Address with the 6BBR MAC Address, maintaining that resolved the Address with the 6BBR MAC Address, maintaining that
mapping in their Neighbor Cache. The 6BBR SHOULD maintain a list of mapping in their Neighbor Cache. The 6BBR SHOULD maintain a list of
the peers on the Backbone which have associated its MAC Address with the peers on the Backbone which have associated its MAC Address with
the Registered Address. If that Registered Address moves to a new the Registered Address. If that Registered Address moves to a new
6BBR, the previous 6BBR SHOULD unicast a gratuitous NA with the 6BBR, the previous 6BBR SHOULD unicast a gratuitous NA with the
skipping to change at page 19, line 41 skipping to change at page 20, line 45
registered. Since the previous 6BBR removed its Host route to the registered. Since the previous 6BBR removed its Host route to the
Registered Address, it will look up the address over the backbone, Registered Address, it will look up the address over the backbone,
resolve the address with the LLA of the new 6BBR, and forward the resolve the address with the LLA of the new 6BBR, and forward the
packet to the correct 6BBR. The previous 6BBR SHOULD also issue a packet to the correct 6BBR. The previous 6BBR SHOULD also issue a
redirect message [RFC4861] to update the cache of the correspondent. redirect message [RFC4861] to update the cache of the correspondent.
8. Bridging Proxy Operations 8. Bridging Proxy Operations
A Bridging Proxy provides IPv6 ND proxy functions between the LLN and A Bridging Proxy provides IPv6 ND proxy functions between the LLN and
the backbone while preserving the forwarding continuity at the MAC the backbone while preserving the forwarding continuity at the MAC
Layer. It acts as a Layer-2 Bridge for all types of unicast packets Layer. It acts as a Layer 2 Bridge for all types of unicast packets
including link-scoped, and appears as an IPv6 Host on the Backbone. including link-scoped, and appears as an IPv6 Host on the Backbone.
The Bridging Proxy registers any Binding including for a Link-Local The Bridging Proxy registers any Binding including for a Link-Local
address to the 6LBR (if present) and defends it over the backbone in address to the 6LBR (if present) and defends it over the backbone in
IPv6 ND procedures. IPv6 ND procedures.
To achieve this, the Bridging Proxy intercepts the IPv6 ND messages To achieve this, the Bridging Proxy intercepts the IPv6 ND messages
and may reinject them on the other side, respond directly or drop and may reinject them on the other side, respond directly or drop
them. For instance, an ND(Lookup) from the backbone that matches a them. For instance, an ND(Lookup) from the backbone that matches a
Binding can be responded directly, or turned into a unicast on the Binding can be responded directly, or turned into a unicast on the
LLN side to let the 6LN respond. LLN side to let the 6LN respond.
As a Bridging Proxy, the 6BBR MUST use the Registering Node's Layer-2 As a Bridging Proxy, the 6BBR MUST use the Registering Node's Layer 2
Address in the SLLAO of the NS/RS messages and the TLLAO of the NA Address in the SLLAO of the NS/RS messages and the TLLAO of the NA
messages that it generates to advertise the Registered Addresses. messages that it generates to advertise the Registered Addresses.
The Registering Node's Layer-2 address is found in the SLLA of the The Registering Node's Layer 2 address is found in the SLLA of the
registration NS(EARO), and maintained in the Binding Table. registration NS(EARO), and maintained in the Binding Table.
The MultiLink Subnet prefix SHOULD NOT be advertised as on-link in RA The Multi-Link Subnet prefix SHOULD NOT be advertised as on-link in
messages sent towards the LLN. If a destination address is seen as RA messages sent towards the LLN. If a destination address is seen
on-link, then a 6LN may use NS(Lookup) messages to resolve that as on-link, then a 6LN may use NS(Lookup) messages to resolve that
address. In that case, the 6BBR MUST either answer the NS(Lookup) address. In that case, the 6BBR MUST either answer the NS(Lookup)
message directly or reinject the message on the backbone, either as a message directly or reinject the message on the backbone, either as a
Layer-2 unicast or a multicast. Layer 2 unicast or a multicast.
If the Registering Node owns the Registered Address, then its If the Registering Node owns the Registered Address, then its
mobility does not impact existing NCEs over the Backbone. Otherwise, mobility does not impact existing NCEs over the Backbone. Otherwise,
when the 6LN selects another Registering Node, the new Registering when the 6LN selects another Registering Node, the new Registering
Node SHOULD send a multicast NA with the Override flag set to fix the Node SHOULD send a multicast NA with the Override flag set to fix the
existing NCEs across the Backbone. existing NCEs across the Backbone.
This method can fail if the multicast message is not received; one or This method can fail if the multicast message is not received; one or
more correspondent nodes on the Backbone might maintain an stale NCE, more correspondent nodes on the Backbone might maintain an stale NCE,
and packets to the Registered Address may be lost. When this and packets to the Registered Address may be lost. When this
condition happens, it is eventually discovered and resolved using condition happens, it is eventually discovered and resolved using NUD
Neighbor Unreachability Detection (NUD) as defined in [RFC4861]. as defined in [RFC4861].
9. Creating and Maintaining a Binding 9. Creating and Maintaining a Binding
Upon receiving a registration for a new Address (i.e., an NS(EARO) Upon receiving a registration for a new Address (i.e., an NS(EARO)
with the R flag set), the 6BBR creates a Binding and operates as a with the R flag set), the 6BBR creates a Binding and operates as a
6LR according to [RFC8505], interacting with the 6LBR if one is 6LR according to [RFC8505], interacting with the 6LBR if one is
present. present.
An implementation of a Routing Proxy that creates a Binding MUST also An implementation of a Routing Proxy that creates a Binding MUST also
create an associated Host route pointing to the registering node in create an associated Host route pointing to the registering node in
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This specification enables nodes on a Backbone Link to co-exist along This specification enables nodes on a Backbone Link to co-exist along
with nodes implementing IPv6 ND [RFC4861] as well as other non- with nodes implementing IPv6 ND [RFC4861] as well as other non-
normative specifications such as [I-D.bi-savi-wlan]. It is possible normative specifications such as [I-D.bi-savi-wlan]. It is possible
that not all IPv6 addresses on the Backbone are registered and known that not all IPv6 addresses on the Backbone are registered and known
to the 6LBR, and an EDAR/EDAC echange with the 6LBR might succeed to the 6LBR, and an EDAR/EDAC echange with the 6LBR might succeed
even for a duplicate address. Consequently, and unless even for a duplicate address. Consequently, and unless
administratively overridden, the 6BBR still needs to perform IPv6 ND administratively overridden, the 6BBR still needs to perform IPv6 ND
DAD over the backbone after an EDAC with a status code of 0 or 9. DAD over the backbone after an EDAC with a status code of 0 or 9.
For the DAD operation, the Binding is placed in Tentative state for a For the DAD operation, the Binding is placed in Tentative state for a
duration of TENTATIVE_DURATION, and an NS(DAD) message is sent as a duration of TENTATIVE_DURATION (Section 12), and an NS(DAD) message
multicast message over the Backbone to the SNMA associated with the is sent as a multicast message over the Backbone to the SNMA
registered Address [RFC4862]. The EARO from the registration MUST be associated with the registered Address [RFC4862]. The EARO from the
placed unchanged in the NS(DAD) message. registration MUST be placed unchanged in the NS(DAD) message.
If a registration is received for an existing Binding with a non-null If a registration is received for an existing Binding with a non-null
Registration Lifetime and the registration is fresher (same ROVR, Registration Lifetime and the registration is fresher (same ROVR,
fresher TID), then the Binding is updated, with the new Registration fresher TID), then the Binding is updated, with the new Registration
Lifetime, TID, and possibly Registering Node. In Tentative state Lifetime, TID, and possibly Registering Node. In Tentative state
(see Section 9.1), the current DAD operation continues unaltered. In (see Section 9.1), the current DAD operation continues unaltered. In
other states (see Section 9.2 and Section 9.3 ), the Binding is other states (see Section 9.2 and Section 9.3 ), the Binding is
placed in Reachable state for the Registration Lifetime, and the 6BBR placed in Reachable state for the Registration Lifetime, and the 6BBR
returns an NA(EARO) to the Registering Node with a status of 0 returns an NA(EARO) to the Registering Node with a status of 0
(Success). (Success).
skipping to change at page 22, line 5 skipping to change at page 23, line 9
binding MUST remove the associated Host route pointing on the binding MUST remove the associated Host route pointing on the
registering node. It MAY preserve a temporary state in order to registering node. It MAY preserve a temporary state in order to
forward packets in flight. The state may be a NCE formed based on a forward packets in flight. The state may be a NCE formed based on a
received NA message, or a Binding in Stale state and pointing at the received NA message, or a Binding in Stale state and pointing at the
new 6BBR on the backbone. new 6BBR on the backbone.
The implementation should also use REDIRECT messages as specified in The implementation should also use REDIRECT messages as specified in
[RFC4861] to update the correspondents for the Registered Address, [RFC4861] to update the correspondents for the Registered Address,
pointing the new 6BBR. pointing the new 6BBR.
9.1. Operation on a Binding in Tentative State 9.1. Operations on a Binding in Tentative State
The Tentative state covers a DAD period over the backbone during The Tentative state covers a DAD period over the backbone during
which an address being registered is checked for duplication using which an address being registered is checked for duplication using
procedures defined in [RFC4862]. procedures defined in [RFC4862].
For a Binding in Tentative state: For a Binding in Tentative state:
o The Binding MUST be removed if an NA message is received over the o The Binding MUST be removed if an NA message is received over the
Backbone for the Registered Address with no EARO, or containing an Backbone for the Registered Address with no EARO, or containing an
EARO with a status of 1 (Duplicate) that indicates an existing EARO with a status of 1 (Duplicate) that indicates an existing
registration owned by a different Registering Node. In that case, registration owned by a different Registering Node. In that case,
an NA MUST be sent back to the Registering Node with a status of 1 an NA MUST be sent back to the Registering Node with a status of 1
(Duplicate) in the EARO. This behavior might be overriden by (Duplicate) in the EARO. This behavior might be overriden by
policy, in particular if the registration is trusted, e.g., based policy, in particular if the registration is trusted, e.g., based
on the validation of the ROVR field (see [I-D.ietf-6lo-ap-nd]). on the validation of the ROVR field (see [I-D.ietf-6lo-ap-nd]).
o
o An NS(DAD) with no EARO or with an EARO that indicates a duplicate o An NS(DAD) with no EARO or with an EARO that indicates a duplicate
registration (i.e. different ROVR) MUST be answered with an NA registration (i.e., different ROVR) MUST be answered with an NA
message containing an EARO with a status of 1 (Duplicate) and the message containing an EARO with a status of 1 (Duplicate) and the
Override flag not set. This behavior might be overriden by Override flag not set. This behavior might be overriden by
policy, in particular if the registration is not trusted. policy, in particular if the registration is not trusted.
o The Binding MUST be removed if an NA message is received over the o The Binding MUST be removed if an NA message is received over the
Backbone for the Registered Address containing an EARO with a Backbone for the Registered Address containing an EARO with a
status of 3 (Moved), or an NS(DAD) with an EARO that indicates a status of 3 (Moved), or an NS(DAD) with an EARO that indicates a
fresher registration ([RFC8505]) for the same Registered Node fresher registration ([RFC8505]) for the same Registered Node
(i.e. same ROVR). A status of 3 is returned in the NA(EARO) back (i.e., same ROVR). A status of 3 is returned in the NA(EARO) back
to the Registering Node. to the Registering Node.
o NS(DAD) and NA messages containing an EARO that indicates a o NS(DAD) and NA messages containing an EARO that indicates a
registration for the same Registered Node that is not as fresh as registration for the same Registered Node that is not as fresh as
this SHOULD be answered with an NA message containing an EARO with this SHOULD be answered with an NA message containing an EARO with
a status of 3 (Moved) in order to clean up the situation a status of 3 (Moved) in order to clean up the situation
immediately. immediately.
o Other NS(DAD) and NA messages from the Backbone are ignored. o Other NS(DAD) and NA messages from the Backbone are ignored.
o NS(Lookup) and NS(NUD) messages SHOULD be optimistically answered o NS(Lookup) and NS(NUD) messages SHOULD be optimistically answered
with an NA message containing an EARO with a status of 0 and the with an NA message containing an EARO with a status of 0 and the
Override flag not set (see Section 3.6). Override flag not set (see Section 3.6).
o If optimistic DAD is disabled, then they SHOULD be queued to be o If optimistic DAD is disabled, then they SHOULD be queued to be
answered when the Binding goes to Reachable state. answered when the Binding goes to Reachable state.
When the TENTATIVE_DURATION timer elapses, the Binding is placed in When the TENTATIVE_DURATION (Section 12) timer elapses, the Binding
Reachable state for the Registration Lifetime, and the 6BBR returns is placed in Reachable state for the Registration Lifetime, and the
an NA(EARO) to the Registering Node with a status of 0 (Success). 6BBR returns an NA(EARO) to the Registering Node with a status of 0
(Success).
The 6BBR also attempts to take over any existing Binding from other The 6BBR also attempts to take over any existing Binding from other
6BBRs and to update existing NCEs in backbone nodes. This is done by 6BBRs and to update existing NCEs in backbone nodes. This is done by
sending an NA message with an EARO and the Override flag set over the sending an NA message with an EARO and the Override flag set over the
backbone (see Section 7 and Section 8). backbone (see Section 7 and Section 8).
9.2. Operation on a Binding in Reachable State 9.2. Operations on a Binding in Reachable State
The Reachable state covers an active registration after a successful The Reachable state covers an active registration after a successful
DAD process. DAD process.
If the Registration Lifetime is of a long duration, an implementation If the Registration Lifetime is of a long duration, an implementation
might be configured to reassess the availability of the Registering might be configured to reassess the availability of the Registering
Node at a lower period, using a NUD procedure as specified in Node at a lower period, using a NUD procedure as specified in
[RFC7048]. If the NUD procedure fails, the Binding SHOULD be placed [RFC7048]. If the NUD procedure fails, the Binding SHOULD be placed
in Stale state immediately. in Stale state immediately.
For a Binding in Reachable state: For a Binding in Reachable state:
o The Binding MUST be removed if an NA or an NS(DAD) message is o The Binding MUST be removed if an NA or an NS(DAD) message is
received over the Backbone for the Registered Address containing received over the Backbone for the Registered Address containing
an EARO that indicates a fresher registration ([RFC8505]) for the an EARO that indicates a fresher registration ([RFC8505]) for the
same Registered Node (i.e. same ROVR). A status of 4 (Removed) is same Registered Node (i.e., same ROVR). A status of 4 (Removed)
returned in an asynchronous NA(EARO) to the Registering Node. is returned in an asynchronous NA(EARO) to the Registering Node.
Based on configuration, an implementation may delay this operation Based on configuration, an implementation may delay this operation
by a small timer in order to a allow for a parallel registration by a timer with a short setting, e.g., a few seconds to a minute,
to reach this node, in which case the NA might be ignored. in order to a allow for a parallel registration to reach this
node, in which case the NA might be ignored.
o An NS(DAD) with no EARO or with an EARO that indicates a duplicate o An NS(DAD) with no EARO or with an EARO that indicates a duplicate
registration (i.e. different ROVR) MUST be answered with an NA registration (i.e., different ROVR) MUST be answered with an NA
message containing an EARO with a status of 1 (Duplicate) and the message containing an EARO with a status of 1 (Duplicate) and the
Override flag not set. Override flag not set.
o NS(DAD) and NA messages containing an EARO that indicates a o NS(DAD) and NA messages containing an EARO that indicates a
registration for the same Registered Node that is not as fresh as registration for the same Registered Node that is not as fresh as
this binding MUST be answered with an NA message containing an this binding MUST be answered with an NA message containing an
EARO with a status of 3 (Moved). EARO with a status of 3 (Moved).
o Other NS(DAD) and NA messages from the Backbone are ignored. o Other NS(DAD) and NA messages from the Backbone are ignored.
o NS(Lookup) and NS(NUD) messages SHOULD be answered with an NA o NS(Lookup) and NS(NUD) messages SHOULD be answered with an NA
message containing an EARO with a status of 0 and the Override message containing an EARO with a status of 0 and the Override
flag not set. The 6BBR MAY check whether the Registering Node is flag not set. The 6BBR MAY check whether the Registering Node is
still available using a NUD procedure over the LLN prior to still available using a NUD procedure over the LLN prior to
answering; this behaviour depends on the use case and is subject answering; this behaviour depends on the use case and is subject
to configuration. to configuration.
When the Registration Lifetime timer elapses, the Binding is placed When the Registration Lifetime timer elapses, the Binding is placed
in Stale state for a duration of STALE_DURATION. in Stale state for a duration of STALE_DURATION (Section 12).
9.3. Operation on a Binding in Stale State 9.3. Operations on a Binding in Stale State
The Stale state enables tracking of the Backbone peers that have a The Stale state enables tracking of the Backbone peers that have a
NCE pointing to this 6BBR in case the Registered Address shows up NCE pointing to this 6BBR in case the Registered Address shows up
later. later.
If the Registered Address is claimed by another 6LN on the Backbone, If the Registered Address is claimed by another 6LN on the Backbone,
with an NS(DAD) or an NA, the 6BBR does not defend the Address. with an NS(DAD) or an NA, the 6BBR does not defend the Address.
For a Binding in Stale state: For a Binding in Stale state:
skipping to change at page 24, line 43 skipping to change at page 25, line 44
o If the 6BBR receives an NS(Lookup) or an NS(NUD) message for the o If the 6BBR receives an NS(Lookup) or an NS(NUD) message for the
Registered Address, the 6BBR MUST attempt a NUD procedure as Registered Address, the 6BBR MUST attempt a NUD procedure as
specified in [RFC7048] to the Registering Node, targeting specified in [RFC7048] to the Registering Node, targeting
o the Registered Address, prior to answering. If the NUD procedure o the Registered Address, prior to answering. If the NUD procedure
succeeds, the operation in Reachable state applies. If the NUD succeeds, the operation in Reachable state applies. If the NUD
fails, the 6BBR refrains from answering. fails, the 6BBR refrains from answering.
o Other NS(DAD) and NA messages from the Backbone are ignored. o Other NS(DAD) and NA messages from the Backbone are ignored.
When the STALE_DURATION timer elapses, the Binding MUST be removed. When the STALE_DURATION (Section 12) timer elapses, the Binding MUST
be removed.
10. Registering Node Considerations 10. Registering Node Considerations
A Registering Node MUST implement [RFC8505] in order to interact with A Registering Node MUST implement [RFC8505] in order to interact with
a 6BBR (which acts as a routing registrar). Following [RFC8505], the a 6BBR (which acts as a routing registrar). Following [RFC8505], the
Registering Node signals that it requires IPv6 proxy-ND services from Registering Node signals that it requires IPv6 proxy-ND services from
a 6BBR by registering the corresponding IPv6 Address using an a 6BBR by registering the corresponding IPv6 Address using an
NS(EARO) message with the R flag set. NS(EARO) message with the R flag set.
The Registering Node may be the 6LN owning the IPv6 Address, or a The Registering Node may be the 6LN owning the IPv6 Address, or a
6LBR that performs the registration on its behalf in a Route-Over 6LBR that performs the registration on its behalf in a Route-Over
mesh. mesh.
The Registering Node SHOULD register all of its IPv6 Addresses to its The Registering Node SHOULD register all of its IPv6 Addresses to its
6LR, which is the 6BBR when they are connected at Layer-2. Failure 6LR, which is the 6BBR when they are connected at Layer 2. Failure
to register an address may result in the address being unreachable by to register an address may result in the address being unreachable by
other parties if the 6BBR cancels the NS(Lookup) over the LLN or to other parties if the 6BBR cancels the NS(Lookup) over the LLN or to
selected LLN nodes that are known to register their addresses. selected LLN nodes that are known to register their addresses.
The Registering Node MUST refrain from using multicast NS(Lookup) The Registering Node MUST refrain from using multicast NS(Lookup)
when the destination is not known as on-link, e.g., if the prefix is when the destination is not known as on-link, e.g., if the prefix is
advertised in a PIO with the L flag that is not set. In that case, advertised in a PIO with the L flag that is not set. In that case,
the Registering Node sends its packets directly to its 6LR. the Registering Node sends its packets directly to its 6LR.
The Registering Node SHOULD also follow [RFC7772] in order to limit The Registering Node SHOULD also follow [RFC7772] in order to limit
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TENTATIVE_DURATION: 800 milliseconds TENTATIVE_DURATION: 800 milliseconds
STALE_DURATION: see below STALE_DURATION: see below
In LLNs with long-lived Addresses such as LPWANs, STALE_DURATION In LLNs with long-lived Addresses such as LPWANs, STALE_DURATION
SHOULD be configured with a relatively long value to cover an SHOULD be configured with a relatively long value to cover an
interval when the address may be reused, and before it is safe to interval when the address may be reused, and before it is safe to
expect that the address was definitively released. A good default expect that the address was definitively released. A good default
value can be 24 hours. In LLNs where addresses are renewed rapidly, value can be 24 hours. In LLNs where addresses are renewed rapidly,
e.g. for privacy reasons, STALE_DURATION SHOULD be configured with a e.g., for privacy reasons, STALE_DURATION SHOULD be configured with a
relatively shorter value, by default 5 minutes. relatively shorter value, by default 5 minutes.
13. IANA Considerations 13. IANA Considerations
This document has no request to IANA. This document has no request to IANA.
14. Acknowledgments 14. Acknowledgments
Many thanks to Dorothy Stanley, Thomas Watteyne and Jerome Henry for Many thanks to Dorothy Stanley, Thomas Watteyne and Jerome Henry for
their various contributions. their various contributions. Also many thanks to Timothy Winters and
Erik Nordmark for their help, review and support in preparation to
the IESG cycle, and to Kyle Rose, Elwyn Davies and Dominique Barthel
for their useful contributions during the IESG review process.
15. References 15. References
15.1. Normative References 15.1. Normative References
[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>.
skipping to change at page 31, line 9 skipping to change at page 32, line 9
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... LISP may also be used to provide an equivalent to the EDAR/ etc... LISP may also be used to provide an equivalent to the EDAR/
EDAC exchange using a Map Server / Map Resolver as a replacement to EDAC exchange using a Map Server / Map Resolver as a replacement to
the 6LBR. the 6LBR.
Appendix B. Applicability and Requirements Served Appendix B. Applicability and Requirements Served
This document specifies proxy-ND functions that can be used to This document specifies proxy-ND functions that can be used to
federate an IPv6 Backbone Link and multiple IPv6 LLNs into a single federate an IPv6 Backbone Link and multiple IPv6 LLNs into a single
MultiLink Subnet. The proxy-ND functions enable IPv6 ND services for Multi-Link Subnet. The proxy-ND functions enable IPv6 ND services
Duplicate Address Detection (DAD) and Address Lookup that do not for Duplicate Address Detection (DAD) and Address Lookup that do not
require broadcasts over the LLNs. require broadcasts over the LLNs.
The term LLN is used to cover multiple types of WLANs and WPANs, The term LLN is used to cover multiple types of WLANs and WPANs,
including (Low-Power) Wi-Fi, BLUETOOTH(R) Low Energy, IEEE STD including (Low-Power) Wi-Fi, BLUETOOTH(R) Low Energy, IEEE STD
802.11ah and IEEE STD.802.15.4 wireless meshes, covering the types of 802.11ah and IEEE STD.802.15.4 wireless meshes, covering the types of
networks listed in Appendix B.3 of [RFC8505] "Requirements Related to networks listed in Appendix B.3 of [RFC8505] "Requirements Related to
Various Low-Power Link Types". Various Low-Power Link Types".
Each LLN in the subnet is attached to an IPv6 Backbone Router (6BBR). Each LLN in the subnet is attached to an IPv6 Backbone Router (6BBR).
The Backbone Routers interconnect the LLNs and advertise the The Backbone Routers interconnect the LLNs and advertise the
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Mobility" are met. Mobility" are met.
A 6LN can register its IPv6 Addresses and thereby obtain proxy-ND A 6LN can register its IPv6 Addresses and thereby obtain proxy-ND
services over the Backbone, meeting the requirements expressed in services over the Backbone, meeting the requirements expressed in
Appendix B.4 of [RFC8505], "Requirements Related to Proxy Appendix B.4 of [RFC8505], "Requirements Related to Proxy
Operations". Operations".
The impact if the IPv6 ND operation is limited to one of the The impact if the IPv6 ND operation is limited to one of the
federated LLNs, enabling the number of 6LNs to grow. The Routing federated LLNs, enabling the number of 6LNs to grow. The Routing
Proxy operation avoids the need to expose the MAC addresses of the Proxy operation avoids the need to expose the MAC addresses of the
6LNs onto the backbone, keeping the Layer-2 topology simple and 6LNs onto the backbone, keeping the Layer 2 topology simple and
stable. This meets the requirements in Appendix B.6 of [RFC8505] stable. This meets the requirements in Appendix B.6 of [RFC8505]
"Requirements Related to Scalability", as long has the 6BBRs are "Requirements Related to Scalability", as long has the 6BBRs are
dimensioned for the number of registrations that each needs to dimensioned for the number of registrations that each needs to
support. support.
In the case of a Wi-Fi access link, a 6BBR may be collocated with the In the case of a Wi-Fi access link, a 6BBR may be collocated with the
Access Point (AP), or with a Fabric Edge (FE) or a CAPWAP [RFC5415] Access Point (AP), or with a Fabric Edge (FE) or a CAPWAP [RFC5415]
Wireless LAN Controller (WLC). In those cases, the wireless client Wireless LAN Controller (WLC). In those cases, the wireless client
(STA) is the 6LN that makes use of [RFC8505] to register its IPv6 (STA) is the 6LN that makes use of [RFC8505] to register its IPv6
Address(es) to the 6BBR acting as Routing Registrar. The 6LBR can be Address(es) to the 6BBR acting as Routing Registrar. The 6LBR can be
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The registration mechanism may be seen as a more reliable alternate The registration mechanism may be seen as a more reliable alternate
to snooping [I-D.bi-savi-wlan]. It can be noted that registration to snooping [I-D.bi-savi-wlan]. It can be noted that registration
and snooping are not mutually exclusive. Snooping may be used in and snooping are not mutually exclusive. Snooping may be used in
conjunction with the registration for nodes that do not register conjunction with the registration for nodes that do not register
their IPv6 Addresses. The 6BBR assumes that if a node registers at 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 least one IPv6 Address to it, then the node registers all of its
Addresses to the 6BBR. With this assumption, the 6BBR can possibly Addresses to the 6BBR. With this assumption, the 6BBR can possibly
cancel all undesirable multicast NS messages that would otherwise cancel all undesirable multicast NS messages that would otherwise
have been delivered to that node. have been delivered to that node.
Scalability of the MultiLink Subnet [RFC4903] requires avoidance of Scalability of the Multi-Link Subnet [RFC4903] requires avoidance of
multicast/broadcast operations as much as possible even on the multicast/broadcast operations as much as possible even on the
Backbone [I-D.ietf-mboned-ieee802-mcast-problems]. Although hosts Backbone [I-D.ietf-mboned-ieee802-mcast-problems]. Although hosts
can connect to the Backbone using IPv6 ND operations, multicast RAs can connect to the Backbone using IPv6 ND operations, multicast RAs
can be saved by using [I-D.ietf-6man-rs-refresh], which also requires can be saved by using [I-D.ietf-6man-rs-refresh], which also requires
the support of [RFC7559]. the support of [RFC7559].
Authors' Addresses Authors' Addresses
Pascal Thubert (editor) Pascal Thubert (editor)
Cisco Systems, Inc Cisco Systems, Inc
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