draft-ietf-6lo-backbone-router-13.txt   draft-ietf-6lo-backbone-router-14.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: March 29, 2020 E. Levy-Abegnoli Expires: August 9, 2020 E. Levy-Abegnoli
Cisco Systems Cisco Systems
September 26, 2019 February 6, 2020
IPv6 Backbone Router IPv6 Backbone Router
draft-ietf-6lo-backbone-router-13 draft-ietf-6lo-backbone-router-14
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 MultiLink Subnet.
Status of This Memo Status of This Memo
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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 March 29, 2020. This Internet-Draft will expire on August 9, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 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.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
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include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . 4 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 . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. Updating RFC 6775 and RFC 8505 . . . . . . . . . . . . . 9 3.1. Updating RFC 6775 and RFC 8505 . . . . . . . . . . . . . 10
3.2. Access Link . . . . . . . . . . . . . . . . . . . . . . . 10 3.2. Access Link . . . . . . . . . . . . . . . . . . . . . . . 10
3.3. Route-Over Mesh . . . . . . . . . . . . . . . . . . . . . 11 3.3. Route-Over Mesh . . . . . . . . . . . . . . . . . . . . . 12
3.4. The Binding Table . . . . . . . . . . . . . . . . . . . . 12 3.4. The Binding Table . . . . . . . . . . . . . . . . . . . . 14
3.5. Primary and Secondary 6BBRs . . . . . . . . . . . . . . . 13 3.5. Primary and Secondary 6BBRs . . . . . . . . . . . . . . . 15
3.6. Using Optimistic DAD . . . . . . . . . . . . . . . . . . 14 3.6. Using Optimistic DAD . . . . . . . . . . . . . . . . . . 16
4. MultiLink Subnet Considerations . . . . . . . . . . . . . . . 14 4. MultiLink Subnet Considerations . . . . . . . . . . . . . . . 16
5. Optional 6LBR serving the MultiLink Subnet . . . . . . . . . 15 5. Optional 6LBR serving the MultiLink Subnet . . . . . . . . . 17
6. Using IPv6 ND Over the Backbone Link . . . . . . . . . . . . 15 6. Using IPv6 ND Over the Backbone Link . . . . . . . . . . . . 17
7. Routing Proxy Operations . . . . . . . . . . . . . . . . . . 16 7. Routing Proxy Operations . . . . . . . . . . . . . . . . . . 18
8. Bridging Proxy Operations . . . . . . . . . . . . . . . . . . 17 8. Bridging Proxy Operations . . . . . . . . . . . . . . . . . . 19
9. Creating and Maintaining a Binding . . . . . . . . . . . . . 18 9. Creating and Maintaining a Binding . . . . . . . . . . . . . 20
9.1. Operation on a Binding in Tentative State . . . . . . . . 19 9.1. Operation on a Binding in Tentative State . . . . . . . . 22
9.2. Operation on a Binding in Reachable State . . . . . . . . 20 9.2. Operation on a Binding in Reachable State . . . . . . . . 23
9.3. Operation on a Binding in Stale State . . . . . . . . . . 21 9.3. Operation on a Binding in Stale State . . . . . . . . . . 24
10. Registering Node Considerations . . . . . . . . . . . . . . . 22 10. Registering Node Considerations . . . . . . . . . . . . . . . 24
11. Security Considerations . . . . . . . . . . . . . . . . . . . 23 11. Security Considerations . . . . . . . . . . . . . . . . . . . 25
12. Protocol Constants . . . . . . . . . . . . . . . . . . . . . 23 12. Protocol Constants . . . . . . . . . . . . . . . . . . . . . 26
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 23 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 26
15.1. Normative References . . . . . . . . . . . . . . . . . . 24 15.1. Normative References . . . . . . . . . . . . . . . . . . 26
15.2. Informative References . . . . . . . . . . . . . . . . . 25 15.2. Informative References . . . . . . . . . . . . . . . . . 28
Appendix A. Possible Future Extensions . . . . . . . . . . . . . 28 Appendix A. Possible Future Extensions . . . . . . . . . . . . . 30
Appendix B. Applicability and Requirements Served . . . . . . . 28 Appendix B. Applicability and Requirements Served . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
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 node (STA) and
protects the wireless medium against broadcast-intensive Transparent protects the wireless medium against broadcast-intensive Transparent
Bridging reactive Lookups. In other words, the association process Bridging reactive Lookups.
is used to register the MAC Address of the STA to the AP. The AP
subsequently proxies the bridging operation and does not need to In other words, the association process is used to register the MAC
forward the broadcast Lookups over the radio. Address of the STA to the AP. The AP subsequently proxies the
bridging operation and does not need to forward the broadcast Lookups
over the radio.
Like Transparent Bridging, IPv6 [RFC8200] Neighbor Discovery Like Transparent Bridging, IPv6 [RFC8200] Neighbor Discovery
[RFC4861] [RFC4862] Protocol (IPv6 ND) is a reactive protocol, based [RFC4861] [RFC4862] Protocol (IPv6 ND) is a reactive protocol, based
on multicast transmissions to locate an on-link correspondent and on multicast transmissions to locate an on-link correspondent and
ensure the uniqueness of an IPv6 address. The mechanism for ensure the uniqueness of an IPv6 address. The mechanism for
Duplicate Address Detection (DAD) [RFC4862] was designed for the Duplicate Address Detection (DAD) [RFC4862] was designed for the
efficient broadcast operation of Ethernet Bridging. Since broadcast efficient broadcast operation of Ethernet Bridging. Since broadcast
can be unreliable over wireless media, DAD often fails to discover can be unreliable over wireless media, DAD often fails to discover
duplications [I-D.yourtchenko-6man-dad-issues]. In practice, IPv6 duplications [I-D.yourtchenko-6man-dad-issues]. In practice, the
addresses very rarely conflict because of the entropy of the 64-bit fact that IPv6 addresses very rarely conflict is mostly attributable
Interface IDs, not because address duplications are detected and to the entropy of the 64-bit Interface IDs as opposed to the
resolved. succesful operation of the IPv6 ND duplicate address detection 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
wireless and/or a LowPower Lossy Network (LLN) can consume enough wireless and/or a LowPower Lossy Network (LLN) can consume enough
bandwidth to cause a substantial degradation to the unicast traffic bandwidth to cause a substantial degradation to the unicast traffic
service. service.
Because IPv6 ND messages sent to the SNMA group are broadcasted at Because IPv6 ND messages sent to the SNMA group are broadcast at the
the radio MAC Layer, wireless nodes that do not belong to the SNMA radio MAC Layer, wireless nodes that do not belong to the SNMA group
group still have to keep their radio turned on to listen to multicast still have to keep their radio turned on to listen to multicast NS
NS messages, which is a total waste of energy for them. In order to messages, which is a total waste of energy for them. In order to
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
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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 provide proxy services for IPv6 Neighbor Discovery. Backbone that provides proxy services for IPv6 Neighbor Discovery. As
Routers federate multiple LLNs over a Backbone Link to form a represented in Figure 1, Backbone Routers federate multiple LLNs over
MultiLink Subnet (MLSN). Backbone Routers placed along the LLN edge a Backbone Link to form a MultiLink Subnet (MLSN). Backbone Routers
of the Backbone handle IPv6 Neighbor Discovery, and forward packets placed along the LLN edge of the Backbone handle IPv6 Neighbor
on behalf of registered nodes. Discovery, and forward packets on behalf of registered nodes.
An LLN node (6LN) registers all its IPv6 Addresses using an NS(EARO) A 6LoWPAN node (6LN) registers all its IPv6 Addresses using an
as specified in [RFC8505] to the 6BBR. The 6BBR is also a Border NS(EARO) as specified in [RFC8505] to the 6BBR. The 6BBR is also a
Router that performs IPv6 Neighbor Discovery (IPv6 ND) operations on Border Router that performs IPv6 Neighbor Discovery (IPv6 ND)
its Backbone interface on behalf of the 6LNs that have registered operations on its Backbone interface on behalf of the 6LNs that have
addresses on its LLN interfaces without the need of a broadcast over registered addresses on its LLN interfaces without the need of a
the wireless medium. Additional benefits are discussed in broadcast over the wireless medium. A 6LN that resides on the
Appendix B. backbone does not register to the SNMA groups associated to its
Registered Addresses and defers to the 6BBR to answer or preferably
forward to it as unicast the corresponding multicast packets.
2. Terminology Additional benefits are discussed in Appendix B.
2. Terminology
2.1. BCP 14 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] [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
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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 MultiLink
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 a Registered Node. Solicitations over the Backbone on behalf of the Registering
Node.
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 TLLA in the proxied NAs over the Backbone,
and routes at the Network Layer between the federated links. 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 6BR 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
The Binding Table is an abstract database that is maintained by The Binding Table is an abstract database that is maintained by
the 6BBR to store the state associated with its registrations. the 6BBR to store the state associated with its registrations.
Binding Binding
A Binding is an abstract state associated to one registration, A Binding is an abstract state associated to one registration,
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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
EDAC: Extended Duplicate Address Confirmation EDAC: Extended Duplicate Address Confirmation
EDAR: Extended Duplicate Address Request EDAR: Extended Duplicate Address Request
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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
Figure 1 illustrates backbone link federating a collection of LLNs as This section and its subsections present a non-normative high level
a single IPv6 Subnet, with a number of 6BBRs providing proxy-ND view of the operation of the 6BBR. The next sections cover the
services to their attached LLNs. normative part. Figure 1 illustrates a backbone link that federates
a collection of LLNs as a single IPv6 Subnet, with a number of 6BBRs
providing proxy-ND services to their attached LLNs.
| |
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ IPv6
(default) | | (Optional) | | | | IPv6 (default) | | (Optional) | | | | Node
Router | | 6LBR | | | | Node Router | | 6LBR | | | | or
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+ 6LN
| Backbone side | | | Backbone side | |
----+-------+-----------------+---+-------------+----+----- ----+-------+-----------------+---+-------------+----+-----
| | | | | |
+------+ +------+ +------+ +------+ +------+ +------+
| 6BBR | | 6BBR | | 6BBR | | 6BBR | | 6BBR | | 6BBR |
| | | | | | | | | | | |
+------+ +------+ +------+ +------+ +------+ +------+
o Wireless side 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 o o o o o o o o o o o o
o o o
LLN LLN LLN
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 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) STD. 802.11 (Wi-Fi) [IEEEstd80211] and IEEE STD. 802.15.1 (Bluetooth)
[IEEEstd802151], or a Mesh-Under or a Route-Over network [RFC8505]. [IEEEstd802151], or a Mesh-Under or a Route-Over network [RFC8505].
The proxy state can be distributed across multiple 6BBRs attached to The proxy state can be distributed across multiple 6BBRs attached to
the same Backbone. the same Backbone.
The main features of a 6BBR are as follows: The main features of a 6BBR are as follows:
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o Multilink-subnet functions (provided by the 6BBR on the backbone) o Multilink-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 Nodes called a Binding Table. The combined Binding Tables Registered Addresses called a Binding Table. The combined Binding
of all the 6BBRs on a backbone form a distributed database of 6LNs Tables of all the 6BBRs on a backbone form a distributed database of
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 NA
messages, asynchronously or as a response to a Neighbor messages, asynchronously or as a response to a Neighbor
Solicitation messages. This includes participating to the Solicitation messages. This includes participating to the
solicited-node multicast address associated to the Registered solicited-node multicast address associated to the Registered
Address as specified in section 7.2.1. of [RFC4861] over the Address as specified in section 7.2.1. of [RFC4861] over the
Backbone. Backbone.
o Either respond using NA messages as a proxy or bridge as a unicast o Either respond using NA messages as a proxy or preferably bridge
frame the IPv6 ND messages (multicast DAD and Address Lookup, and to the 6LN as a unicast frame the IPv6 ND messages (multicast DAD
unicast NUD) received for the Registered Address over the and Address Lookup, and unicast NUD) received for the Registered
Backbone. This may include responding on behalf of a sleeping Address over the Backbone. This may include responding on behalf
node, or checking the liveliness of the Registering Node before of a sleeping node, or checking the liveliness of the Registering
answering on its behalf. Node 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
functions fulfill the role of the 6BBRs as the border routers functions fulfill the role of the 6BBRs as the border routers
connecting the Multi-link IPv6 subnet to the Internet. connecting the Multi-link IPv6 subnet to the Internet.
The proxy-ND operation can co-exist with IPv6 ND over the Backbone. The operation of IPv6 ND and of proxy-ND are not mutually exclusive
on the Backbone, meaning that nodes attached to the Backbone and
using IPv6 ND can transparently interact with 6LNs that rely on a
6BBR to proxy ND for them, whether the 6LNs are reachable over an LLN
or directly attached to the Backbone.
The 6BBR may co-exist with a proprietary snooping or a traditional The [RFC8505] registration mechanism used to learn addresses to be
bridging functionality in an Access Point, in order to support legacy proxied for may co-exist in a 6BBR with a proprietary snooping or the
nodes that do not support this specification. In the case, the co- traditional bridging functionality of an Access Point, in order to
existing function may turn multicasts into a series of unicast to the support legacy LLN nodes that do not support this specification.
legacy nodes.
The registration to a proxy service uses an NS/NA(EARO) exchange. The registration to a proxy service uses an NS/NA(EARO) exchange.
The 6BBR operation resembles that of a Mobile IPv6 (MIPv6) [RFC6275] The 6BBR operation resembles that of a Mobile IPv6 (MIPv6) [RFC6275]
Home Agent (HA). The combination of a 6BBR and a MIPv6 HA enables Home Agent (HA). The combination of a 6BBR and a MIPv6 HA enables
full mobility support for 6LNs, inside and outside the links that full mobility support for 6LNs, inside and outside the links that
form the subnet. form the subnet.
The 6BBRs use the Extended Address Registration Option (EARO) defined The 6BBRs use the Extended Address Registration Option (EARO) defined
in [RFC8505] as follows: in [RFC8505] as follows:
o The EARO is used in the IPv6 ND exchanges over the Backbone o The EARO is used in the IPv6 ND exchanges over the Backbone
between the 6BBRs to help distinguish duplication from movement. between the 6BBRs to help distinguish duplication from movement.
Extended Duplicate Address Messages (EDAR and EDAC) MAY also be
used with a 6LBR, if one is present, and the 6BBR. Address Extended Duplicate Address Messages (EDAR and EDAC) may also be
used between a 6LBR, if one is present, and the 6BBR. Address
duplication is detected using the ROVR field. Conflicting duplication is detected using the ROVR field. Conflicting
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
skipping to change at page 10, line 17 skipping to change at page 10, line 42
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
Figure 2 illustrates a flow where 6LN forms an IPv6 Address and The simplest Multi-Link Subnet topology from the Layer-3 perspective
registers it to a 6BBR acting as a 6LR [RFC8505]. The 6BBRs applies occurs when the wireless network appears as a single hop hub-and-
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
Layer-2 protocol handling the complex topology.
|
+-----+ +-----+ +-----+ IPv6
(default) | | (Optional) | | | | Node
Router | | 6LBR | | | | or
+-----+ +-----+ +-----+ 6LN
| Backbone side | |
----+-------+-----------------+---+-------------+----+-----
| | |
+------+ +------+ +------+
| 6BBR | | 6BBR | | 6BBR |
| 6LR | | 6LR | | 6LR |
+------+ +------+ +------+
(6LN) (6LN) (6LN) (6LN) (6LN) (6LN) (6LN) (6LN)
Figure 2: Access Link Use case
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
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. In that connectivity while the message flow is still in progress.
example, a 6LBR is deployed on the backbone link to serve the whole
subnet, and EDAR / EDAC messages are used in combination with DAD to In this example, a 6LBR is deployed on the backbone link to serve the
enable coexistence with IPv6 ND over the backbone. whole subnet, and EDAR / EDAC messages are used in combination with
DAD to enable coexistence with IPv6 ND over the backbone.
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 effectively
broadcast. The multiple arrows associated to the ND messages on the
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 11, line 42 skipping to change at page 12, line 42
| |<-----------------------------------| | |<-----------------------------------|
| | | | | |
| IPv6 Packets in optimistic mode | | IPv6 Packets in optimistic mode |
|<---------------------------------------------------->| |<---------------------------------------------------->|
| | | | | |
| | | |
| NA(EARO) |<DAD timeout> | NA(EARO) |<DAD timeout>
|<----------------| |<----------------|
| | | |
Figure 2: 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
Figure 3 illustrates IPv6 signaling that enables a 6LN to form a A more complex Multi-Link Subnet topology occurs when the wireless
Global or a Unique-Local Address and register it to the 6LBR that network appears as a Layer-3 Mesh network as shown in Figure 4. A
serves its LLN using [RFC8505]. The 6LBR (acting as Registering so-called Route-Over routing protocol exposes routes between 6LRs
Node) proxies the registration to the 6BBR, using [RFC8505] to towards both 6LRs and 6LNs, and a 6LBR acts as Root of the Layer-3
register the addresses the 6LN (Registered Node) on its behalf to the Mesh network and proxy-registers the LLN addresses to the 6BBR.
6BBR, and obtain proxy-ND services from the 6BBR.
|
+-----+ +-----+ +-----+ IPv6
(default) | | (Optional) | | | | Node
Router | | 6LBR | | | | or
+-----+ +-----+ +-----+ 6LN
| Backbone side | |
----+-------+-----------------+---+-------------+----+-----
| | |
+------+ +------+ +------+
| 6BBR | | 6BBR | | 6BBR |
+------+ +------+ +------+
| | |
+------+ +------+ +------+
| 6LBR | | 6LBR | | 6LBR |
+------+ +------+ +------+
(6LN) (6LR) (6LN) (6LR) (6LN) (6LR) (6LR) (6LR)(6LN)
(6LN)(6LR) (6LR) (6LN) (6LN) (6LR)(6LN) (6LR) (6LR) (6LR) (6LN)
(6LR)(6LR) (6LR) (6LR) (6LR)(6LN) (6LR) (6LR)(6LR)
(6LR) (6LR) (6LR) (6LR) (6LN)(6LR) (6LR) (6LR) (6LR) (6LR)
(6LN) (6LN)(6LN) (6LN) (6LN) (6LN) (6LN) (6LN) (6LN) (6LN)
Figure 4: Route-Over Mesh Use case
Figure 5 illustrates IPv6 signaling that enables a 6LN (the
Registered Node) to form a Global or a Unique-Local Address and
register it to the 6LBR that serves its LLN using [RFC8505]. The
6LBR (the Registering Node) then proxies the [RFC8505] registration
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
multicast but since it is intercepted by the 6BBR, it is never
effectively broadcast, and the multiple arrows associated to the ND
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 12, line 36 skipping to change at page 14, line 36
| | | | (EARO) | | | | (EARO)
| | | | | | | |
| | | NA(EARO) |<timeout> | | | NA(EARO) |<timeout>
| | |<--------------| | | |<--------------|
| | Extended DAC | | | | Extended DAC | |
| |<--------------| | | |<--------------| |
| NA(EARO) | | | | NA(EARO) | | |
|<--------------| | | |<--------------| | |
| | | | | | | |
Figure 3: 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 RPL
[RFC6550] and collocating the RPL root with a 6LBR that serves the [RFC6550] and collocating the RPL root with a 6LBR that serves the
LLN, and is either collocated with or connected to the 6BBR over an LLN. The 6LBR is also either collocated with or directly connected
IPv6 Link. to the 6BBR over an IPv6 Link.
3.4. The Binding Table 3.4. The Binding Table
Addresses in a LLN that are reachable from the Backbone by way of the Addresses in an LLN that are reachable from the Backbone by way of
6BBR function must be registered to that 6BBR, using an NS(EARO) with the 6BBR function must be registered to that 6BBR, using an NS(EARO)
the R flag set [RFC8505]. A 6BBR maintains a state for its active with the R flag set [RFC8505]. A 6BBR maintains a state for its
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.
The 6BBR uses a combination of [RFC8505] and IPv6 ND over the The 6BBR uses a combination of [RFC8505] and IPv6 ND over the
Backbone to advertise the registration and avoid a duplication. Backbone to advertise the registration and avoid a duplication.
Conflicting registrations are solved by the 6BBRs transparently to Conflicting registrations are solved by the 6BBRs, transparently to
the Registering Nodes. the Registering Nodes.
Only one 6LN may register a given Address, but the Address may be Only one 6LN may register a given Address, but the Address may be
registered to Multiple 6BBRs for higher availability. registered to Multiple 6BBRs for higher availability.
Over the LLN, Binding Table management is as follows: Over the LLN, Binding Table management is as follows:
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 a 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 MUST be eventually produced, carrying the result of the response is eventually produced, carrying the result of the
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
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
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, A same address may be successfully registered to more than one 6BBR,
in which case the Registering Node uses the same EARO in all the in which case the Registering Node uses the same EARO in all the
parallel registrations. To allow for this, ND(DAD) and NA messages parallel registrations. To allow for this, ND(DAD) and NA messages
with an EARO that indicate an identical Binding in another 6BBR (same with an EARO that indicate an identical Binding in another 6BBR (same
Registered address, same TID, same ROVR) as silently ignored. Registered address, same TID, same ROVR) as 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
backbone only if the node is primary or does not support the concept backbone only if the node is primary or does not support the concept
of primary. More than one 6BBR claiming or defending an address of primary. More than one 6BBR claiming or defending an address
skipping to change at page 14, line 23 skipping to change at page 16, line 28
3.6. Using Optimistic DAD 3.6. Using Optimistic DAD
Optimistic Duplicate Address Detection [RFC4429] (ODAD) specifies how Optimistic Duplicate Address Detection [RFC4429] (ODAD) specifies how
an IPv6 Address can be used before completion of Duplicate Address an IPv6 Address can be used before completion of Duplicate Address
Detection (DAD). ODAD guarantees that this behavior will not cause Detection (DAD). ODAD guarantees that this behavior will not cause
harm if the new Address is a duplicate. harm if the new Address is a duplicate.
Support for ODAD avoids delays in installing the Neighbor Cache Entry Support for ODAD avoids delays in installing the Neighbor Cache Entry
(NCE) in the 6BBRs and the default router, enabling immediate (NCE) in the 6BBRs and the default router, enabling immediate
connectivity to the registered node. As shown in Figure 2, if the connectivity to the registered node. As shown in Figure 3, if the
6BBR is aware of the Link-Layer Address (LLA) of a router, then the 6BBR is aware of the Link-Layer Address (LLA) of a router, then the
6BBR sends a Router Solicitation (RS), using the Registered Address 6BBR sends a Router Solicitation (RS), using the Registered Address
as the IP Source Address, to the known router(s). The RS MUST be as the IP Source Address, to the known router(s). The RS is sent
sent without a Source LLA Option (SLLAO), to avoid invalidating a without a Source LLA Option (SLLAO), to avoid invalidating a
preexisting NCE in the router. preexisting NCE in the router.
Following ODAD, the router may then send a unicast RA to the Following ODAD, the router may then send a unicast RA to the
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 a 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. MultiLink 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 MultiLink 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 a same value
on the Backbone and all attached LLNs. To achieve this, the 6BBR on the Backbone and all attached LLNs. As a consequence, the 6BBR
MUST use the same MTU value in RAs over the Backbone and in the RAs MUST use the same MTU value in RAs over the Backbone and in the RAs
that it transmits towards the LLN links. that it transmits towards the LLN links.
5. Optional 6LBR serving the MultiLink Subnet 5. Optional 6LBR serving the MultiLink 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.
When a 6LBR is present, the 6BBR uses an EDAR/EDAC message exchange This specification allows for an address to be registered to more
with the 6LBR to check for duplication or movement. This is done than one 6BBR. It results that a 6LBR MUST be capable of maintaining
prior to the NS(DAD) process, which may be avoided of the 6LBR a state for each of the 6BBR having registered with a same TID and
already maintains a conflicting state for the Registered Address. same ROVR.
This specification enables an address to be registered to more than When a 6LBR is present, the 6BBR uses an EDAR/EDAC message exchange
one 6BBR. It results that a 6LBR MUST be capable to maintain a state with the 6LBR to check if the new registration corresponds to a
for each of the 6BBR having registered with a same TID and same ROVR. duplication or a movement. This is done prior to the NS(DAD)
process, which may be avoided of the 6LBR already maintains a
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
skipping to change at page 16, line 32 skipping to change at page 18, line 38
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 Neighbor
Unreachability Detection (NUD) defined in [RFC4861] may time out too Unreachability Detection (NUD) defined in [RFC4861] may time out too
quickly. Nodes on the backbone SHOULD support [RFC7048] whenever quickly. Nodes on the backbone SHOULD support [RFC7048] whenever
possible. possible.
7. Routing Proxy Operations 7. Routing Proxy Operations
A Routing Proxy provides IPv6 ND proxy functions for Global including 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.
skipping to change at page 17, line 34 skipping to change at page 19, line 41
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 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
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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 MultiLink Subnet prefix SHOULD NOT be advertised as on-link in RA
messages sent towards the LLN. If a destination address is seen as messages sent towards the LLN. If a destination address is seen as
on-link, then a 6LN may use NS(Lookup) messages to resolve that on-link, then a 6LN may use NS(Lookup) messages to resolve that
address. In that case, the 6BBR MUST either answer directly to the address. In that case, the 6BBR MUST either answer the NS(Lookup)
NS(Lookup) message or reinject the message on the backbone, either as message directly or reinject the message on the backbone, either as a
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. This method can fail if the existing NCEs across the Backbone.
multicast message is not received; one or more correspondent nodes on
the Backbone might maintain an stale NCE, and packets to the This method can fail if the multicast message is not received; one or
Registered Address may be lost. When this condition happens, it is more correspondent nodes on the Backbone might maintain an stale NCE,
eventually be discovered and resolved using Neighbor Unreachability and packets to the Registered Address may be lost. When this
Detection (NUD) as defined in [RFC4861]. condition happens, it is eventually discovered and resolved using
Neighbor Unreachability Detection (NUD) 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 on the registering node in create an associated Host route pointing to the registering node in
the LLN interface from which the registration was received. the LLN interface from which the registration was received.
The 6LR operation is modified as follows: The 6LR operation is modified as follows:
o EDAR and EDAC messages SHOULD carry a SLLAO and a TLLAO, o EDAR and EDAC messages SHOULD carry a SLLAO and a TLLAO,
respectively. respectively.
o A Bridging Proxy MAY register Link Local addresses to the 6BBR and o A Bridging Proxy MAY register Link Local addresses at the 6BBR and
proxy ND for those addresses over the backbone. proxy ND for these addresses over the backbone.
o An EDAC message with a status of 9 (6LBR Registry Saturated) is o An EDAC message with a status of 9 (6LBR Registry Saturated) is
assimilated as a status of 0 if a following DAD process protects assimilated as a status of 0 if a following DAD process protects
the address against duplication. the address against duplication.
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
skipping to change at page 19, line 17 skipping to change at page 21, line 28
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, and an NS(DAD) message is sent as a
multicast message over the Backbone to the SNMA associated with the multicast message over the Backbone to the SNMA associated with the
registered Address [RFC4862]. The EARO from the registration MUST be registered Address [RFC4862]. The EARO from the registration MUST be
placed unchanged in the NS(DAD) message. 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 as it was. 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).
Upon a registration that is identical (same ROVR, TID, and Upon a registration that is identical (same ROVR, TID, and
Registering Node), the 6BBR returns an NA(EARO) back to the Registering Node), the 6BBR returns an NA(EARO) back to the
Registering Node with a status of 0 (Success). A registration that Registering Node with a status of 0 (Success). A registration that
is not as fresh (same ROVR, older TID) is ignored. is not as fresh (same ROVR, older TID) is ignored.
skipping to change at page 20, line 11 skipping to change at page 22, line 22
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
skipping to change at page 20, line 34 skipping to change at page 22, line 47
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). If optimistic DAD is Override flag not set (see Section 3.6).
disabled, then they SHOULD be queued to be answered when the
Binding goes to Reachable state. o If optimistic DAD is disabled, then they SHOULD be queued to be
answered when the Binding goes to Reachable state.
When the TENTATIVE_DURATION timer elapses, the Binding is placed in When the TENTATIVE_DURATION timer elapses, the Binding is placed in
Reachable state for the Registration Lifetime, and the 6BBR returns Reachable state for the Registration Lifetime, and the 6BBR returns
an NA(EARO) to the Registering Node with a status of 0 (Success). 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. Operation 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.
An NS(DAD) with no EARO or with an EARO that indicates a duplicate If If the Registration Lifetime is of a long duration, an implementation
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) is
returned in an asynchronous NA(EARO) to the Registering Node. 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 small timer in order to a allow for a parallel registration
to arrive to this node, in which case the NA might be ignored. 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 MUST be answered with an NA message containing an EARO with a this binding MUST be answered with an NA message containing an
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.
skipping to change at page 22, line 20 skipping to change at page 24, line 34
for the same Registered Node or a duplicate registration. A for the same Registered Node or a duplicate registration. A
status of 4 (Removed) MAY be returned in an asynchronous NA(EARO) status of 4 (Removed) MAY be returned in an asynchronous NA(EARO)
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 MUST be answered with an NA message containing an EARO with a this MUST be answered with an NA message containing an EARO with a
status of 3 (Moved). status of 3 (Moved).
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 attempts a NUD procedure as Registered Address, the 6BBR MUST attempt a NUD procedure as
specified in [RFC7048] to the Registering Node, targeting the specified in [RFC7048] to the Registering Node, targeting
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 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
skipping to change at page 23, line 14 skipping to change at page 25, line 29
The Registering Node SHOULD also follow [RFC7772] in order to limit The Registering Node SHOULD also follow [RFC7772] in order to limit
the use of multicast RAs. It SHOULD also implement Simple Procedures the use of multicast RAs. It SHOULD also implement Simple Procedures
for Detecting Network Attachment in IPv6 [RFC6059] (DNA procedures) for Detecting Network Attachment in IPv6 [RFC6059] (DNA procedures)
to detect movements, and support Packet-Loss Resiliency for Router to detect movements, and support Packet-Loss Resiliency for Router
Solicitations [RFC7559] in order to improve reliability for the Solicitations [RFC7559] in order to improve reliability for the
unicast RS messages. unicast RS messages.
11. Security Considerations 11. Security Considerations
This specification applies to LLNs in which the link layer is This specification applies to LLNs and a backbone in which the
protected, either by means of physical or IP security for the individual links are protected against rogue access, e.g., by
Backbone Link or MAC-layer security. In particular, the LLN MAC is authenticating a node that attaches to the network and encrypting at
required to provide secure unicast to/from the Backbone Router and the MAC layer the transmissions that may be overheard.
secure Broadcast from the Backbone Router in a way that prevents
tampering with or replaying the RA messages. In particular, the LLN MAC is required to provide secure unicast to/
from the Backbone Router and secure Broadcast from the Backbone
Router in a way that prevents tampering with or replaying the RA
messages.
A possible attack over the backbone can be done by sending an NS with
an EARO and expecting the NA(EARO) back to contain the TID and ROVR
fields of the existing state. With that information, the attacker
can easily increase the TID and take over the Binding.
[I-D.ietf-6lo-ap-nd] guarantees the ownership of a registered address [I-D.ietf-6lo-ap-nd] guarantees the ownership of a registered address
based on a proof-of-ownership encoded in the ROVR field and protects based on a proof-of-ownership encoded in the ROVR field and protects
against address theft and impersonation. against address theft and impersonation inside the LLN, because the
6LR can challenge the Registered Node for a proof-of-ownership. This
method does not extend over the backbone since the 6BBR cannot
provide the proof-of-ownership. A possible attack over the backbone
can be done by sending an NS with an EARO and expecting the NA(EARO)
back to contain the TID and ROVR fields of the existing state. With
that information, the attacker can easily increase the TID and take
over the Binding.
12. Protocol Constants 12. Protocol Constants
This Specification uses the following constants: This Specification uses the following constants:
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, by default 24 SHOULD be configured with a relatively long value to cover an
hours. In LLNs where addresses are renewed rapidly, e.g. for privacy interval when the address may be reused, and before it is safe to
reasons, STALE_DURATION SHOULD be configured with a relatively long expect that the address was definitively released. A good default
value, by default 5 minutes. value can be 24 hours. In LLNs where addresses are renewed rapidly,
e.g. for privacy reasons, STALE_DURATION SHOULD be configured with a
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.
skipping to change at page 25, line 34 skipping to change at page 28, line 9
[RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C. [RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C.
Perkins, "Registration Extensions for IPv6 over Low-Power Perkins, "Registration Extensions for IPv6 over Low-Power
Wireless Personal Area Network (6LoWPAN) Neighbor Wireless Personal Area Network (6LoWPAN) Neighbor
Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018, Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018,
<https://www.rfc-editor.org/info/rfc8505>. <https://www.rfc-editor.org/info/rfc8505>.
15.2. Informative References 15.2. Informative References
[I-D.bi-savi-wlan] [I-D.bi-savi-wlan]
Bi, J., Wu, J., Wang, Y., and T. Lin, "A SAVI Solution for Bi, J., Wu, J., Wang, Y., and T. Lin, "A SAVI Solution for
WLAN", draft-bi-savi-wlan-17 (work in progress), May 2019. WLAN", draft-bi-savi-wlan-18 (work in progress), November
2019.
[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-12 (work in Lossy Networks", draft-ietf-6lo-ap-nd-13 (work in
progress), April 2019. progress), January 2020.
[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-26 (work of IEEE 802.15.4", draft-ietf-6tisch-architecture-28 (work
in progress), August 2019. in progress), October 2019.
[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-08 (work Media", draft-ietf-mboned-ieee802-mcast-problems-11 (work
in progress), August 2019. in progress), December 2019.
[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.thubert-6lo-unicast-lookup] [I-D.thubert-6lo-unicast-lookup]
Thubert, P. and E. Levy-Abegnoli, "IPv6 Neighbor Discovery Thubert, P. and E. Levy-Abegnoli, "IPv6 Neighbor Discovery
Unicast Lookup", draft-thubert-6lo-unicast-lookup-00 (work Unicast Lookup", draft-thubert-6lo-unicast-lookup-00 (work
in progress), January 2019. in progress), January 2019.
skipping to change at page 28, line 35 skipping to change at page 31, line 15
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 MultiLink Subnet. The proxy-ND functions enable IPv6 ND services for
Duplicate Address Detection (DAD) and Address Lookup that do not 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, meeting the 802.11ah and IEEE STD.802.15.4 wireless meshes, covering the types of
requirements listed in Appendix B.3 of [RFC8505] "Requirements networks listed in Appendix B.3 of [RFC8505] "Requirements Related to
Related to Various Low-Power Link Types". Various Low-Power Link Types".
Each LLN in the subnet is attached at 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
Addresses of the 6LNs over the Backbone Link using proxy-ND Addresses of the 6LNs over the Backbone Link using proxy-ND
operations. operations.
This specification updates IPv6 ND over the Backbone to distinguish This specification updates IPv6 ND over the Backbone to distinguish
Address movement from duplication and eliminate stale state in the Address movement from duplication and eliminate stale state in the
Backbone routers and Backbone nodes once a 6LN has roamed. In this Backbone routers and Backbone nodes once a 6LN has roamed. This way,
way, mobile nodes may roam rapidly from one 6BBR to the next and mobile nodes may roam rapidly from one 6BBR to the next and
requirements in Appendix B.1 of [RFC8505] "Requirements Related to requirements in Appendix B.1 of [RFC8505] "Requirements Related to
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 IPv6 ND operation is minimized as the number of 6LNs grows in the The impact if the IPv6 ND operation is limited to one of the
LLN. This meets the requirements in Appendix B.6 of [RFC8505] federated LLNs, enabling the number of 6LNs to grow. The Routing
Proxy operation avoids the need to expose the MAC addresses of the
6LNs onto the backbone, keeping the Layer-2 topology simple and
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
centralized and either connected to the Backbone Link or reachable centralized and either connected to the Backbone Link or reachable
over IP. The 6BBR proxy-ND operations eliminate the need for over IP.
wireless nodes to respond synchronously when a Lookup is performed
for their IPv6 Addresses. This provides the function of a Sleep The 6BBR proxy-ND operations eliminate the need for wireless nodes to
Proxy for ND [I-D.nordmark-6man-dad-approaches]. 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], For the TimeSlotted Channel Hopping (TSCH) mode of [IEEEstd802154],
the 6TiSCH architecture [I-D.ietf-6tisch-architecture] describes how the 6TiSCH architecture [I-D.ietf-6tisch-architecture] describes how
a 6LoWPAN ND host could connect to the Internet via a RPL mesh a 6LoWPAN ND host could connect to the Internet via a RPL mesh
Network, but doing so requires extensions to the 6LOWPAN ND protocol Network, but doing so requires extensions to the 6LOWPAN ND protocol
to support mobility and reachability in a secure and manageable to support mobility and reachability in a secure and manageable
environment. The extensions detailed in this document also work for environment. The extensions detailed in this document also work for
the 6TiSCH architecture, serving the requirements listed in the 6TiSCH architecture, serving the requirements listed in
Appendix B.2 of [RFC8505] "Requirements Related to Routing Appendix B.2 of [RFC8505] "Requirements Related to Routing
Protocols". Protocols".
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