draft-ietf-6lo-backbone-router-17.txt   draft-ietf-6lo-backbone-router-18.txt 
6lo P. Thubert, Ed. 6lo P. Thubert, Ed.
Internet-Draft Cisco Systems Internet-Draft Cisco Systems
Updates: 6775, 8505 (if approved) C.E. Perkins Updates: 6775, 8505 (if approved) C.E. Perkins
Intended status: Standards Track Blue Meadow Networking Intended status: Standards Track Blue Meadow Networking
Expires: 23 August 2020 E. Levy-Abegnoli Expires: 3 September 2020 E. Levy-Abegnoli
Cisco Systems Cisco Systems
20 February 2020 2 March 2020
IPv6 Backbone Router IPv6 Backbone Router
draft-ietf-6lo-backbone-router-17 draft-ietf-6lo-backbone-router-18
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 Multi-Link Subnet. single Multi-Link 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 23 August 2020. This Internet-Draft will expire on 3 September 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.
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 (https://trustee.ietf.org/ Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document. license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
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as described in Section 4.e of the Trust Legal Provisions and are as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License. provided without warranty as described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 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 . . . . . . . . . . . . . . . . . . . . . . . 6 2.4. References . . . . . . . . . . . . . . . . . . . . . . . 7
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. Updating RFC 6775 and RFC 8505 . . . . . . . . . . . . . 10 3.1. Updating RFC 6775 and RFC 8505 . . . . . . . . . . . . . 10
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 . . . . . . . . . . . . . . . . . . . . 13 3.4. The Binding Table . . . . . . . . . . . . . . . . . . . . 14
3.5. Primary and Secondary 6BBRs . . . . . . . . . . . . . . . 14 3.5. Primary and Secondary 6BBRs . . . . . . . . . . . . . . . 15
3.6. Using Optimistic DAD . . . . . . . . . . . . . . . . . . 15 3.6. Using Optimistic DAD . . . . . . . . . . . . . . . . . . 16
4. Multi-Link Subnet Considerations . . . . . . . . . . . . . . 15 4. Multi-Link Subnet Considerations . . . . . . . . . . . . . . 16
5. Optional 6LBR serving the Multi-Link Subnet . . . . . . . . . 16 5. Optional 6LBR serving the Multi-Link Subnet . . . . . . . . . 17
6. Using IPv6 ND Over the Backbone Link . . . . . . . . . . . . 17 6. Using IPv6 ND Over the Backbone Link . . . . . . . . . . . . 18
7. Routing Proxy Operations . . . . . . . . . . . . . . . . . . 18 7. Routing Proxy Operations . . . . . . . . . . . . . . . . . . 20
8. Bridging Proxy Operations . . . . . . . . . . . . . . . . . . 20 8. Bridging Proxy Operations . . . . . . . . . . . . . . . . . . 21
9. Creating and Maintaining a Binding . . . . . . . . . . . . . 21 9. Creating and Maintaining a Binding . . . . . . . . . . . . . 22
9.1. Operations on a Binding in Tentative State . . . . . . . 22 9.1. Operations on a Binding in Tentative State . . . . . . . 23
9.2. Operations on a Binding in Reachable State . . . . . . . 23 9.2. Operations on a Binding in Reachable State . . . . . . . 24
9.3. Operations on a Binding in Stale State . . . . . . . . . 24 9.3. Operations on a Binding in Stale State . . . . . . . . . 25
10. Registering Node Considerations . . . . . . . . . . . . . . . 25 10. Registering Node Considerations . . . . . . . . . . . . . . . 26
11. Security Considerations . . . . . . . . . . . . . . . . . . . 26 11. Security Considerations . . . . . . . . . . . . . . . . . . . 27
12. Protocol Constants . . . . . . . . . . . . . . . . . . . . . 26 12. Protocol Constants . . . . . . . . . . . . . . . . . . . . . 27
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 27 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 28
15. Normative References . . . . . . . . . . . . . . . . . . . . 27 15. Normative References . . . . . . . . . . . . . . . . . . . . 28
16. Informative References . . . . . . . . . . . . . . . . . . . 28 16. Informative References . . . . . . . . . . . . . . . . . . . 29
Appendix A. Possible Future Extensions . . . . . . . . . . . . . 31 Appendix A. Possible Future Extensions . . . . . . . . . . . . . 32
Appendix B. Applicability and Requirements Served . . . . . . . 31 Appendix B. Applicability and Requirements Served . . . . . . . 33
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 33 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 34
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.
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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 broadcast at the Because IPv6 ND messages sent to the SNMA group are broadcast at the
radio MAC Layer, wireless nodes that do not belong to the SNMA group radio MAC Layer, wireless nodes that do not belong to the SNMA group
still have to keep their radio turned on to listen to multicast NS still have to keep their radio turned on to listen to multicast NS
messages, which is a total waste of energy for them. In order to messages, which is a waste of energy for them. In order to reduce
reduce their power consumption, certain battery-operated devices such their power consumption, certain battery-operated devices such as IoT
as IoT sensors and smartphones ignore some of the broadcasts, making sensors and smartphones ignore some of the broadcasts, making IPv6 ND
IPv6 ND operations even less reliable. 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 routing between subnets, at the extreme by
/64 prefix to each wireless node (see [RFC8273]). assigning a /64 prefix to each wireless node (see [RFC8273]). But
deploying a single large subnet can still be attractive to avoid
renumbering in situations that involve large numbers of devices and
mobility within a bounded area.
Another way is to proxy at the boundary of the wired and wireless A way to reduce the propagation of IPv6 ND broadcast in the wireless
domains the Layer 3 protocols that rely on MAC Layer broadcast domain while preserving a large single subnet is to form a Multi-Link
operations. For instance, IEEE 802.11 [IEEEstd80211] situates proxy- Subnet (MLSN). Each Link in the MLSN, including the backbone, is its
ARP (IPv4) and proxy-ND (IPv6) functions at the Access Points (APs). own broadcast domain. A key property of MLSNs is that link-local
The 6BBR provides a proxy-ND function and can be extended for proxy- unicast traffic, link-scope multicast, and traffic with a hop limit
ARP in a continuation specification. of 1 will not transit to nodes in the same subnet on a different
link, something that may produce unexpected behavior in software that
expects a subnet to be entirely contained within a single link.
This specification considers a special type of MLSN with a central
backbone that federates edge (LLN) links, each Link providing its own
protection against rogue access and tempering or replaying packets.
In that particular topology, ND proxies can be placed at the boundary
of the edge links and the backbone to handle IPv6 ND on behalf of
Registered Nodes and forward IPv6 packets back and forth. The ND
proxy enables the continuity of IPv6 ND operations beyond the
backbone, and enables communication using Global or Unique Local
Addresses between any pair of nodes in the MLSN.
The 6LoWPAN Backbone Router (6BBR) is a Routing Registrar [RFC8505]
that provides proxy-ND services. A 6BBR acting as a Bridging Proxy
provides a proxy-ND function with Layer-2 continuity and can be
collocated with a Wi-Fi Access Point (AP) as prescribed by IEEE Std
802.11 [IEEEstd80211]. A 6BBR acting as a Routing Proxy is
applicable to any type of LLN, including LLNs that cannot be bridged
onto the backbone, such as IEEE Std 802.15.4 [IEEEstd802154].
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] With this specification, the address to be proxied is signaled
that provides proxy services for IPv6 Neighbor Discovery. As explicitly through a registration process. A 6LoWPAN node (6LN)
represented in Figure 1, Backbone Routers federate multiple LLNs over registers all its IPv6 Addresses using NS messages with an Extended
a Backbone Link to form a Multi-Link Subnet (MLSN). The MLSN breaks Address Registration Option (EARO) as specified in [RFC8505] to a
the Layer 2 continuity and splits the broadcast domain, in a fashion 6LoWPAN Router (6LR) to which it is directly attached. If the 6LR is
that each Link, including the backbone, is its own broadcast domain. a 6BBR then the 6LN is both the Registered Node and the Registering
This means that devices that rely on a link-scope multicast on the Node. If not, then the 6LoWPAN Border Router (6LBR) that serves the
backbone will only reach other nodes on the backbone but not LLN LLN proxies the registration to the 6BBR. In that case, the 6LN is
nodes. A key property of MLSNs is that link-local traffic and the Registered Node and the 6LBR is the Registering Node. The 6BBR
traffic with a hop limit of 1 will not transit to nodes in the same performs IPv6 Neighbor Discovery (IPv6 ND) operations on its Backbone
subnet on a different link, something that may produce unexpected interface on behalf of the 6LNs that have registered addresses on its
behavior in software that expects a subnet to be entirely contained LLN interfaces without the need of a broadcast over the wireless
within a single link. In order to enable the continuity of IPv6 ND medium.
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 Registering Node that resides on the backbone does not register to
NS(EARO) as specified in [RFC8505] to the 6BBR. The 6BBR is also a the SNMA groups associated to its Registered Addresses and defers to
Border Router that performs IPv6 Neighbor Discovery (IPv6 ND) the 6BBR to answer or preferably forward to it as unicast the
operations on its Backbone interface on behalf of the 6LNs that have corresponding multicast packets.
registered addresses on its LLN interfaces without the need of a
broadcast over the wireless medium. A 6LN that resides on the
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 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
This document introduces the following terminology: This document introduces the following terminology:
Federated: A subnet that comprises a Backbone and one or more Federated: A subnet that comprises a Backbone and one or more
(wireless) access links, is said to be federated into one Multi- (wireless) access links, is said to be federated into one Multi-
Link Subnet. The proxy-ND operation of 6BBRs over the Backbone Link Subnet. The proxy-ND operation of 6BBRs over the Backbone
extends IPv6 ND operation over the access links. extends IPv6 ND operation over the access links.
Sleeping Proxy: A 6BBR acts as a Sleeping Proxy if it answers ND Sleeping Proxy: A 6BBR acts as a Sleeping Proxy if it answers IPv6
Neighbor Solicitations over the Backbone on behalf of the ND Neighbor Solicitations over the Backbone on behalf of the
Registering Node which might be in a sleep state in a low power Registering Node that is in a sleep state and cannot answer in due
network. The Sleeping Proxy that is also a Bridging Proxy will time.
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: A Routing Proxy provides IPv6 ND proxy functions and Routing Proxy: A Routing Proxy provides IPv6 ND proxy functions and
enables the MLSN operation over federated links that may not be enables the MLSN operation over federated links that may not be
compatible for bridging. The Routing Proxy advertises its own MAC compatible for bridging. The Routing Proxy advertises its own MAC
Address as the Target Link Layer Address (TLLA) in the proxied NAs Address as the Target Link Layer Address (TLLA) in the proxied NAs
over the Backbone, and routes at the Network Layer between the over the Backbone, and routes at the Network Layer between the
federated links. federated links.
Bridging Proxy: A Bridging Proxy provides IPv6 ND proxy functions Bridging Proxy: A Bridging Proxy provides IPv6 ND proxy functions
while preserving forwarding continuity at the MAC Layer. The while preserving forwarding continuity at the MAC Layer. In that
Bridging Proxy advertises the MAC Address of the Registering Node case, the MAC Address and the mobility of the Registering Node is
as the TLLA in the proxied NAs over the Backbone. In that case, visible across the bridged Backbone. The Bridging Proxy
the MAC Address and the mobility of 6LN is still visible across advertises the MAC Address of the Registering Node as the TLLA in
the bridged Backbone, and the 6BBR may be configured to proxy for the proxied NAs over the Backbone, and proxies ND for all unicast
Link Local Addresses. addresses including Link-Local Addresses. Instead of replying on
behalf of the Registering Node, a Bridging Proxy will preferably
forward the NS Lookup and NUD messages that target the Registered
Address to the Registering Node as unicast frames and let it
respond in its own.
Binding Table: The Binding Table is an abstract database that is Binding Table: The Binding Table is an abstract database that is
maintained by the 6BBR to store the state associated with its maintained by the 6BBR to store the state associated with its
registrations. registrations.
Binding: A Binding is an abstract state associated to one Binding: A Binding is an abstract state associated to one
registration, in other words one entry in the Binding Table. registration, in other words one entry in the Binding Table.
2.3. Abbreviations 2.3. Abbreviations
This document uses the following abbreviations: This document uses the following abbreviations:
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
ARO: Address Registration 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 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 ID: Identifier
LLN: Low-Power and Lossy Network LLN: Low-Power and Lossy Network
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LLA: Link Layer Address (aka MAC address) LLA: Link Layer Address (aka MAC address)
SLLA: Source Link Layer Address SLLA: Source Link Layer Address
TLLA: Target 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:
* "Neighbor Discovery for IP version 6" [RFC4861], "IPv6 Stateless Classical IPv6 ND: "Neighbor Discovery for IP version 6" [RFC4861],
Address Autoconfiguration" [RFC4862] and "Optimistic Duplicate "IPv6 Stateless Address Autoconfiguration" [RFC4862] and
Address Detection" [RFC4429], "Optimistic Duplicate Address Detection" [RFC4429],
* "Neighbor Discovery Proxies (proxy-ND)" [RFC4389] and "Multi-Link IPv6 ND over multiple links: "Neighbor Discovery Proxies (proxy-ND)"
Subnet Issues" [RFC4903], [RFC4389] and "Multi-Link Subnet Issues" [RFC4903],
* "Problem Statement and Requirements for IPv6 over Low-Power 6LoWPAN: "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
* Neighbor Discovery Optimization for Low-Power and Lossy Networks 6LoWPAN ND: Neighbor Discovery Optimization for Low-Power and Lossy
[RFC6775] and "Registration Extensions for 6LoWPAN Neighbor Networks [RFC6775] and "Registration Extensions for 6LoWPAN
Discovery" [RFC8505]. Neighbor 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 following 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 5 skipping to change at page 8, 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:
* Multi-Link-subnet functions (provided by the 6BBR on the backbone) * Multi-Link-subnet functions (provided by the 6BBR on the backbone)
performed on behalf of registered 6LNs, and performed on behalf of Registered Nodes, and
* Routing registrar services that reduce multicast within the LLN: * 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 abstract data that
Tables of all the 6BBRs on a backbone form a distributed database of is stored in the Binding Table includes the Registered Address,
6LNs that reside in the LLNs or on the IPv6 Backbone. anchor information on the Registering Node such as connecting
interface, Link-Local Address and Link-Layer Address of the
Registering Node on that interface, the EARO including ROVR and TID,
a state that can be either Reachable, Tentative, or Stale, and other
information such as a trust level that may be configured, e.g., to
protect a server. The combined Binding Tables of all the 6BBRs on a
backbone form a distributed database of Registered Nodes 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:
* Create a new entry in a Binding Table for a new Registered Address * 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.
* Advertise a Registered Address over the Backbone using an * Advertise a Registered Address over the Backbone using an NA
unsolicited NA message, asynchronously or as a response to a NS message, either unsolicited or as a response to a NS message.
message. This includes joining the multicast group associated to This includes joining the multicast group associated to the SNMA
the SNMA derived from the Registered Address as specified in derived from the Registered Address as specified in section 7.2.1.
section 7.2.1. of [RFC4861] over the Backbone. of [RFC4861] over the Backbone.
* The 6BBR may respond immediately as a Proxy in lieu of the * The 6BBR MAY respond immediately as a Proxy in lieu of the
Registering Node, e.g., if the Registering Node has a sleeping Registering Node, e.g., if the Registering Node has a sleeping
cycle that the 6BBR does not want to interrupt, or if the 6BBR has cycle that the 6BBR does not want to interrupt, or if the 6BBR has
a recent state that is deemed fresh enough to permit the proxied a recent state that is deemed fresh enough to permit the proxied
response. It is preferred, though, that the 6BBR checks whether response. It is preferred, though, that the 6BBR checks whether
the Registering Node is still responsive on the Registered the Registering Node is still responsive on the Registered
Address. To that effect: Address. To that effect:
- as a Bridging Proxy: - as a Bridging Proxy:
the 6BBR forwards the multicast DAD and Address Lookup messages the 6BBR forwards the multicast DAD and Address Lookup messages
as a unicast MAC-Layer frames to the MAC address of the as a unicast MAC-Layer frames to the MAC address of the
skipping to change at page 9, line 11 skipping to change at page 9, line 44
* Deliver packets arriving from the LLN, using Neighbor Solicitation * 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.
* Forward or bridge packets between the LLN and the Backbone. * Forward or bridge packets between the LLN and the Backbone.
* Verify liveness for a registration, when needed. * 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 that
connecting the Multi-link IPv6 subnet to the Internet. federate the Multi-link IPv6 subnet.
The operation of IPv6 ND and of proxy-ND are not mutually exclusive The operation of IPv6 ND and of proxy-ND are not mutually exclusive
on the Backbone, meaning that nodes attached to the Backbone and on the Backbone, meaning that nodes attached to the Backbone and
using IPv6 ND can transparently interact with 6LNs that rely on a 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 6BBR to proxy ND for them, whether the 6LNs are reachable over an LLN
or directly attached to the Backbone. or directly attached to the Backbone.
The [RFC8505] registration mechanism used to learn addresses to be The [RFC8505] registration mechanism used to learn addresses to be
proxied for may co-exist in a 6BBR with a proprietary snooping or the proxied may co-exist in a 6BBR with a proprietary snooping or the
traditional bridging functionality of an Access Point, in order to traditional bridging functionality of an Access Point, in order to
support legacy LLN nodes that do not support this specification. support legacy LLN nodes that do not support this specification.
The registration to a proxy service uses an NS/NA(EARO) exchange. The registration to a proxy service uses an NS/NA exchange with EARO.
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 performs IPv6 ND functions over the backbone as follows:
in [RFC8505] as follows:
* The EARO is used in the IPv6 ND exchanges over the Backbone * The EARO [RFC8505] is used in the IPv6 ND exchanges over the
between the 6BBRs to help distinguish duplication from movement. Backbone between the 6BBRs to help distinguish duplication from
Extended Duplicate Address Messages (EDAR and EDAC) may also be movement. Extended Duplicate Address Messages (EDAR and EDAC) may
used between a 6LBR, if one is present, and the 6BBR. Address also be used to communicate with a 6LBR, if one is present.
duplication is detected using the ROVR field. Conflicting Address 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 which forms an order of
registrations.
* The Link Layer Address (LLA) that the 6BBR advertises for the * 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. This document specifies the use
registration NS(EARO) contains an Source Link Layer Address Option of those ND messages by 6BBRs over the backbone, at a high level in
(SLLAO). This specification details the use of those messages over Section 6 and in more detail in Section 9.
the backbone.
Note: [RFC6775] requires that the registration NS(EARO) contains an Note: [RFC8505] requires that the registration NS(EARO) contains an
SLLAO and [RFC4862] that the NS(DAD) is sent from the unspecified Source Link Layer Address Option (SLLAO). [RFC4862] requires that
address for which there cannot be a SLLAO. Consequently, an NS(DAD) the NS(DAD) is sent from the unspecified address for which there
cannot be confused with a registration. cannot be a SLLAO. Consequently, an NS(DAD) cannot be confused with
a registration.
This specification adds the capability to insert IPv6 ND options in This specification allows to deploy a 6LBR on the backbone where EDAR
the EDAR and EDAC messages. In particular, a 6BBR acting as a 6LR and EDAC messages coexist with classical ND. It also adds the
for the Registered Address can insert an SLLAO in the EDAR to the capability to insert IPv6 ND options in the EDAR and EDAC messages.
6LBR in order to avoid a Lookup back. This enables the 6LBR to store A 6BBR acting as a 6LR for the Registered Address can insert an SLLAO
the MAC address associated to the Registered Address on a Link and to in the EDAR to the 6LBR in order to avoid a Lookup back. This
serve as a mapping server as described in enables the 6LBR to store the MAC address associated to the
[I-D.thubert-6lo-unicast-lookup]. Registered Address on a Link and to serve as a mapping server as
described in [I-D.thubert-6lo-unicast-lookup].
This specification allows for an address to be registered to more
than one 6BBR. Consequently a 6LBR that is deployed on the backbone
MUST be capable of maintaining state for each of the 6BBR having
registered with the same TID and same ROVR.
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.
| |
skipping to change at page 12, line 5 skipping to change at page 12, line 48
| 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
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 transmitted as a multicast The RS sent initially by the 6LN (e.g., a Wi-Fi STA) is transmitted
but since it is intercepted by the 6BBR, it is never effectively as a multicast but since it is intercepted by the 6BBR, it is never
broadcast. The multiple arrows associated to the ND messages on the effectively broadcast. The multiple arrows associated to the ND
Backbone denote a real Layer 2 broadcast. messages on the Backbone denote a real Layer 2 broadcast.
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.
| |
skipping to change at page 12, line 43 skipping to change at page 13, line 38
(6LN) (6LR) (6LN) (6LR) (6LN) (6LR) (6LR) (6LR)(6LN) (6LN) (6LR) (6LN) (6LR) (6LN) (6LR) (6LR) (6LR)(6LN)
(6LN)(6LR) (6LR) (6LN) (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) (6LR)(6LN) (6LR) (6LR)(6LR)
(6LR) (6LR) (6LR) (6LR) (6LN)(6LR) (6LR) (6LR) (6LR) (6LR) (6LR) (6LR) (6LR) (6LR) (6LN)(6LR) (6LR) (6LR) (6LR) (6LR)
(6LN) (6LN)(6LN) (6LN) (6LN) (6LN) (6LN) (6LN) (6LN) (6LN) (6LN) (6LN)(6LN) (6LN) (6LN) (6LN) (6LN) (6LN) (6LN) (6LN)
Figure 4: Route-Over Mesh Use case Figure 4: Route-Over Mesh Use case
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] using a
6LBR (the Registering Node) then proxies the [RFC8505] registration neighboring 6LR as relay. The 6LBR (the Registering Node) then
to the 6BBR to obtain proxy-ND services from the 6BBR. 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 The RS sent initially by the 6LN is a transmitted as a multicast and
multicast but since it is intercepted by the 6BBR, it is never contained within 1-hop broadcast range where hopefully a 6LR is
effectively broadcast, and the multiple arrows associated to the ND found. The 6LR is expected to be already connected to the LLN and
messages on the Backbone denote a real Layer 2 broadcast. capable to reach the 6LBR, possibly multiple hops away, using unicast
messages.
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 13, line 48 skipping to change at page 14, line 48
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 the RPL architecture [I-D.ietf-6tisch-architecture] suggests using the RPL
[RFC6550] routing protocol and collocating the RPL root with a 6LBR [RFC6550] routing protocol and collocating the RPL root with a 6LBR
that serves the LLN. The 6LBR is also either collocated with or that serves the LLN. The 6LBR is also either collocated with or
directly connected 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]. The 6BBR answers with an NA(EARO) and
active registrations in an abstract Binding Table. maintains a state for the registration 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
skipping to change at page 14, line 51 skipping to change at page 15, line 51
The operation of the Binding Table is specified in detail 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
The same address may be successfully registered to more than one The same address may be successfully registered to more than one
6BBR, in which case the Registering Node uses the same EARO in all 6BBR, in which case the Registering Node uses the same EARO in all
the parallel registrations. To allow for this, ND(DAD) and NA the parallel registrations. To allow for this, ND(DAD) and NA
messages with an EARO that indicate an identical Binding in another messages with an EARO that indicate an identical Binding in another
6BBR (same Registered address, same TID, same ROVR) are silently 6BBR (same Registered address, same TID, same ROVR) are silently
ignored. ignored but for the purpose of selecting the primary 6BBR for that
registration.
A 6BBR may optionally be primary or secondary. The primary is the A 6BBR may be either primary or secondary. The primary is the 6BBR
6BBR that has the highest EUI-64 Address of all the 6BBRs that share that has the highest EUI-64 Address of all the 6BBRs that share a
a registration for the same Registered Address, with the same ROVR registration for the same Registered Address, with the same ROVR and
and same Transaction ID, the EUI-64 Address being considered as an 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
generates unwanted traffic but no reachability issue since all 6BBRs generates unwanted traffic but no reachability issue since all 6BBRs
provide reachability from the Backbone to the 6LN. provide reachability from the Backbone to the 6LN.
skipping to change at page 16, line 5 skipping to change at page 17, line 5
Registered Address can flow immediately. Registered Address can flow immediately.
4. Multi-Link 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 Multi-Link 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 Legacy nodes located on the backbone expect that the subnet is
Discovery [RFC8201]. For that reason, the MTU MUST have the same deployed within a single link and that there is a common Maximum
value on the Backbone and all attached LLNs. As a consequence, the Transmission Unit (MTU) for intra-subnet communication, the Link MTU.
6BBR MUST use the same MTU value in RAs over the Backbone and in the They will not perform the IPv6 Path MTU Discovery [RFC8201] for a
RAs that it transmits towards the LLN links. destination within the subnet. For that reason, the MTU MUST have
the same value on the Backbone and all federated LLNs in the MLSN.
As a consequence, the 6BBR MUST use the same MTU value in RAs over
the Backbone and in the RAs that it transmits towards the LLN links.
5. Optional 6LBR serving the Multi-Link 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
than one 6BBR. Consequently a 6LBR MUST be capable of maintaining
state for each of the 6BBR having registered with the same TID and
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 if 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
skipping to change at page 16, line 44 skipping to change at page 17, line 42
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 Target 6BBR for that Binding, and the EDAC message SHOULD carry the Target
Link Layer Address Option (TLLAO) associated with the currently Link Layer Address Option (TLLAO) associated with the currently
accepted registration. This enables a 6BBR to locate the new accepted registration. This enables a 6BBR to locate the new
position of a mobile 6LN in the case of a Routing Proxy operation, position of a mobile 6LN in the case of a Routing Proxy operation,
and opens the capability for the 6LBR to serve as a mapping server in and opens the capability for the 6LBR to serve as a mapping server in
the future. 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
Address, and maintain that SNMA membership as long as it maintains Address, and maintain that SNMA membership as long as it maintains
the registration. The 6BBR uses either the SNMA or plain unicast to the registration. The 6BBR uses either the SNMA or plain unicast to
defend the Registered Addresses in its Binding Table over the defend the Registered Addresses in its Binding Table over the
Backbone (as specified in [RFC4862]). The 6BBR advertises and Backbone (as specified in [RFC4862]). The 6BBR advertises and
defends the Registered Addresses over the Backbone Link using RS, defends the Registered Addresses over the Backbone Link using RS,
NS(DAD) and NA messages with the Registered Address as the Source or NS(DAD) and NA messages with the Registered Address as the Source or
Target address, respectively. Target address.
The 6BBR MUST place an EARO in the IPv6 ND messages that it generates The 6BBR MUST place an EARO in the IPv6 ND messages that it generates
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.
IPv6 ND operates as follows on the backbone: IPv6 ND operates as follows on the backbone:
* Section 7.2.8 of [RFC4861] specifies that an NA message generated * Section 7.2.8 of [RFC4861] specifies that an NA message generated
as a proxy does not have the Override flag set in order to ensure as a proxy does not have the Override flag set in order to ensure
that if the real owner is present on the link, its own NA will that if the real owner is present on the link, its own NA will
take precedence, and that this NA does not update the NCE for the take precedence, and that this NA does not update the NCE for the
real owner if one exists. real owner if one exists.
* A node that receives multiple NA messages updates an existing NCE * A node that receives multiple NA messages updates an existing NCE
only if the Override flag is set; otherwise the node will probe only if the Override flag is set; otherwise the node will probe
the cached address. the cached address.
* When an NS(DAD) is received for a tentative address, which means * When an NS(DAD) is received for a tentative address, which means
that 2 nodes form the same address at nearly the same time, that two nodes form the same address at nearly the same time,
section 5.4.3 of [RFC4862] cannot sort out the first come and the section 5.4.3 of [RFC4862] cannot detect which node first claimed
address is abandoned. the address and the address is abandoned.
* In any fashion, [RFC4862] indicates that a node never responds to * In any case, [RFC4862] indicates that a node never responds to a
a Neighbor Solicitation for a tentative address. Neighbor Solicitation for a tentative address.
This specification adds information about proxied addresses that This specification adds information about proxied addresses that
helps sort out a duplication (different ROVR) from a movement (same helps sort out a duplication (different ROVR) from a movement (same
ROVR, different TID), and in the latter case the older registration ROVR, different TID), and in the latter case the older registration
from the fresher one (by comparing TIDs). from the fresher one (by comparing TIDs).
When a Registering Node moves from one 6BBR to the next, the new 6BBR When a Registering Node moves from one 6BBR to the next, the new 6BBR
sends NA messages to update the NCE in node over the backbone. The sends NA messages over the backbone to update existing NCEs. A node
6BBR may set the Override flag in the NA messages if it is known that that supports this specification and that receives multiple NA
the Registering Node will not connect directly to the backbone (e.g.,
the Registering Node is attached using a different type of
interface).
A node that supports this specification and that receives multiple NA
messages with an EARO option and the same ROVR MUST favor the NA with messages with an EARO option and the same ROVR MUST favor the NA with
the freshest EARO over the others. the freshest EARO over the others.
When the Binding is in Tentative state: The 6BBR MAY set the Override flag in the NA messages if it does not
compete with the Registering Node for the NCE in backbone nodes.
This is assured if the Registering Node is attached via an interface
that cannot be bridged onto the backbone, making it impossible for
the Registering Node to defend its own addresses there. This may
also be signaled by the Registering Node through a protocol extension
that is not in scope for this specification.
When the Binding is in Tentative state, the 6BBR acts as follows:
* an NS(DAD) that indicates a duplication can still not be asserted * an NS(DAD) that indicates a duplication can still not be asserted
for first come, but the situation can be avoided using a 6LBR on for first come, but the situation can be avoided using a 6LBR on
the backbone that will serialize the order of appearance of the the backbone that will serialize the order of appearance of the
address and ensure first-come/first-serve. address and ensure first-come/first-serve.
* an NS or an NA that denotes an older registration for the same * an NS or an NA that denotes an older registration for the same
Registered Node is not interpreted as a duplication as specified Registered Node is not interpreted as a duplication as specified
in section 5.4.3 and 5.4.4 of [RFC4862], respectively. in section 5.4.3 and 5.4.4 of [RFC4862], respectively.
When the Binding is no more in Tentative state: When the Binding is no longer in Tentative state, the 6BBR acts as
follows:
* an NS or an NA with an EARO that denotes a duplicate registration * an NS or an NA with an EARO that denotes a duplicate registration
(different ROVR) is answered with an NA message that carries an (different ROVR) is answered with an NA message that carries an
EARO with a status of 1 (Duplicate), unless the received message EARO with a status of 1 (Duplicate), unless the received message
is an NA that carries an EARO with a status of 1. is an NA that carries an EARO with a status of 1.
In any state: In any state, the 6BBR acts as follows:
* an NS or an NA with an EARO that denotes an older registration * an NS or an NA with an EARO that denotes an older registration
(same ROVR) is answered with an NA message that carries an EARO (same ROVR) is answered with an NA message that carries an EARO
with a status of 3 (Moved) to ensure that the stale state is with a status of 3 (Moved) to ensure that the stale state is
removed rapidly. removed rapidly.
This behavior is specified in more details in Section 9. This behavior is specified in more detail in Section 9.
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 Multi-Link 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 NUD procedure defined For movement involving a slow reattachment, the NUD procedure defined
in [RFC4861] may time out too quickly. Nodes on the backbone SHOULD in [RFC4861] may time out too quickly. Nodes on the backbone SHOULD
support [RFC7048] whenever possible. support [RFC7048] whenever possible.
skipping to change at page 19, line 14 skipping to change at page 20, line 21
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, a prefix that is used across a MLSN
advertised as on-link in RA messages sent towards the LLN. MUST NOT be 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.
skipping to change at page 21, line 33 skipping to change at page 22, line 35
* An EDAC message with a status of 9 (6LBR Registry Saturated) is * 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
even for a duplicate address. Consequently, and unless even for a duplicate address. Consequently the 6BBR still needs to
administratively overridden, the 6BBR still needs to perform IPv6 ND perform IPv6 ND DAD over the backbone after an EDAC with a status
DAD over the backbone after an EDAC with a status code of 0 or 9. 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 (Section 12), and an NS(DAD) message duration of TENTATIVE_DURATION (Section 12), and an NS(DAD) message
is sent as a multicast message over the Backbone to the SNMA is sent as a multicast message over the Backbone to the SNMA
associated with the registered Address [RFC4862]. The EARO from the associated with the registered Address [RFC4862]. The EARO from the
registration MUST be 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).
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 does not alter its current state. In
Registering Node with a status of 0 (Success). A registration that Reachable State it returns an NA(EARO) back to the Registering Node
is not as fresh (same ROVR, older TID) is ignored. with a status of 0 (Success). A registration that is not as fresh
(same ROVR, older TID) is ignored.
If a registration is received for an existing Binding and a If a registration is received for an existing Binding and a
registration Lifetime of zero, then the Binding is removed, and the registration Lifetime of zero, then the Binding is removed, and the
6BBR returns an NA(EARO) back to the Registering Node with a status 6BBR returns an NA(EARO) back to the Registering Node with a status
of 0 (Success). An implementation of a Routing Proxy that removes a of 0 (Success). An implementation of a Routing Proxy that removes a
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.
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
new 6BBR on the backbone.
The old 6BBR SHOULD also use REDIRECT messages as specified in The old 6BBR removes its Binding Table entry and notifies the
[RFC4861] to update the correspondents for the Registered Address, Registering Node with a status of 3 (Moved) if a new 6BBR claims a
pointing to the new 6BBR. fresher registration (same ROVR, fresher TID) for the same address.
The old 6BBR MAY preserve a temporary state in order to forward
packets in flight. The state may for instance be a NCE formed based
on a received NA message. It may also be a Binding Table entry in
Stale state and pointing at the new 6BBR on the backbone, or any
other abstract cache entry that can be used to resolve the Link-Layer
Address of the new 6BBR. The old 6BBR SHOULD also use REDIRECT
messages as specified in [RFC4861] to update the correspondents for
the Registered Address, pointing to the new 6BBR.
9.1. Operations 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:
* The Binding MUST be removed if an NA message is received over the * 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 that indicates an existing registration owned by a different EARO that indicates an existing registration owned by a different
Registering Node (different ROVR). An NA MUST be sent back to the Registering Node (different ROVR). In that case, an NA is sent
Registering Node with a status of 1 (Duplicate). This behavior back to the Registering Node with a status of 1 (Duplicate) to
might be overridden by policy, in particular if the registration indicate that the binding has been rejected. This behavior might
is trusted, e.g., based on the validation of the ROVR field (see be overridden by 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]). [I-D.ietf-6lo-ap-nd]).
* The Binding MUST be removed if an NS(DAD) message is received over * The Binding MUST be removed if an NS(DAD) message is received over
the Backbone for the Registered Address with no EARO, or the Backbone for the Registered Address with no EARO, or
containing an EARO with a different ROVR that indicates a containing an EARO with a different ROVR that indicates a
tentative registration by a different Registering Node. In that tentative registration by a different Registering Node. In that
case, an NA MUST be sent back to the Registering Node with a case, an NA is sent back to the Registering Node with a status of
status of 1 (Duplicate). This behavior might be overridden by 1 (Duplicate). This behavior might be overridden by policy, in
policy, in particular if the registration is trusted, e.g., based particular if the registration is trusted, e.g., based on the
on the validation of the ROVR field (see [I-D.ietf-6lo-ap-nd]). validation of the ROVR field (see [I-D.ietf-6lo-ap-nd]).
* The Binding MUST be removed if an NA or an NS(DAD) message is * 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 with a that indicates a fresher registration ([RFC8505]) an EARO with a that indicates a fresher registration ([RFC8505])
for the same Registering Node (same ROVR). A status of 3 is for the same Registering Node (same ROVR). In that case, an NA
returned in the NA(EARO) back to the Registering Node. MUST be sent back to the Registering Node with a status of 3
(Moved).
* The Binding MUST be kept unchanged if an NA or an NS(DAD) message * The Binding MUST be kept unchanged if an NA or an NS(DAD) message
is received over the Backbone for the Registered Address is received over the Backbone for the Registered Address
containing an EARO with a that indicates an older registration containing an EARO with a that indicates an older registration
([RFC8505]) for the same Registering Node (same ROVR). The ([RFC8505]) for the same Registering Node (same ROVR). The
message SHOULD be answered with an NA that carries an EARO with a message is answered with an NA that carries an EARO with a status
status of 3 (Moved) and the Override flag not set. This behavior of 3 (Moved) and the Override flag not set. This behavior might
might be overridden by policy, in particular if the registration be overridden by policy, in particular if the registration is not
is not trusted. trusted.
* Other NS(DAD) and NA messages from the Backbone are ignored. * Other NS(DAD) and NA messages from the Backbone are ignored.
* NS(Lookup) and NS(NUD) messages SHOULD be optimistically answered * 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). If optimistic DAD is
disabled, then they SHOULD be queued to be answered when the disabled, then they SHOULD be queued to be answered when the
Binding goes to Reachable state. Binding goes to Reachable state.
When the TENTATIVE_DURATION (Section 12) timer elapses, the Binding When the TENTATIVE_DURATION (Section 12) timer elapses, the Binding
skipping to change at page 25, line 34 skipping to change at page 26, line 46
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 MUST register all of its IPv6 Addresses to its A 6LN MUST register all of its IPv6 Addresses to its 6LR, which is
6LR, which is the 6BBR when they are connected at Layer 2. Failure the 6BBR when they are connected at Layer 2. Failure to register an
to register an address may result in the address being unreachable by address may result in the address being unreachable by other parties.
other parties if the 6BBR cancels the NS(Lookup) over the LLN or to This would happen for instance if the 6BBR propagates the NS(Lookup)
selected LLN nodes that are known to register their addresses. from the backbone only to the LLN nodes that do not 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 BCP 202 [RFC7772] in order to
the use of multicast RAs. It SHOULD also implement Simple Procedures limit the use of multicast RAs. It SHOULD also implement Simple
for Detecting Network Attachment in IPv6 [RFC6059] (DNA procedures) Procedures for Detecting Network Attachment in IPv6 [RFC6059] (DNA
to detect movements, and support Packet-Loss Resiliency for Router procedures) to detect movements, and support Packet-Loss Resiliency
Solicitations [RFC7559] in order to improve reliability for the for Router Solicitations [RFC7559] in order to improve reliability
unicast RS messages. for the unicast RS messages.
11. Security Considerations 11. Security Considerations
This specification applies to LLNs and a backbone in which the This specification applies to LLNs and a backbone in which the
individual links are protected against rogue access, e.g., by individual links are protected against rogue access, e.g., by
authenticating a node that attaches to the network and encrypting at authenticating a node that attaches to the network and encrypting at
the MAC layer the transmissions that may be overheard. In the MAC layer the transmissions that may be overheard. In
particular, the LLN MAC is required to provide secure unicast to/from particular, the LLN MAC is required to provide secure unicast to/from
the Backbone Router and secure Broadcast from the Backbone Router in the Backbone Router and secure Broadcast from the Backbone Router in
a way that prevents tampering with or replaying the RA messages. a way that prevents tampering with or replaying the RA messages.
skipping to change at page 27, line 44 skipping to change at page 28, line 48
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, Address Autoconfiguration", RFC 4862,
DOI 10.17487/RFC4862, September 2007, DOI 10.17487/RFC4862, September 2007,
<https://www.rfc-editor.org/info/rfc4862>. <https://www.rfc-editor.org/info/rfc4862>.
[RFC6059] Krishnan, S. and G. Daley, "Simple Procedures for [RFC6059] Krishnan, S. and G. Daley, "Simple Procedures for
Detecting Network Attachment in IPv6", RFC 6059, Detecting Network Attachment in IPv6", RFC 6059,
DOI 10.17487/RFC6059, November 2010, DOI 10.17487/RFC6059, November 2010,
<https://www.rfc-editor.org/info/rfc6059>. <https://www.rfc-editor.org/info/rfc6059>.
[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012,
<https://www.rfc-editor.org/info/rfc6550>.
[RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C. [RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
Bormann, "Neighbor Discovery Optimization for IPv6 over Bormann, "Neighbor Discovery Optimization for IPv6 over
Low-Power Wireless Personal Area Networks (6LoWPANs)", Low-Power Wireless Personal Area Networks (6LoWPANs)",
RFC 6775, DOI 10.17487/RFC6775, November 2012, RFC 6775, DOI 10.17487/RFC6775, November 2012,
<https://www.rfc-editor.org/info/rfc6775>. <https://www.rfc-editor.org/info/rfc6775>.
[RFC7048] Nordmark, E. and I. Gashinsky, "Neighbor Unreachability [RFC7048] Nordmark, E. and I. Gashinsky, "Neighbor Unreachability
Detection Is Too Impatient", RFC 7048, Detection Is Too Impatient", RFC 7048,
DOI 10.17487/RFC7048, January 2014, DOI 10.17487/RFC7048, January 2014,
<https://www.rfc-editor.org/info/rfc7048>. <https://www.rfc-editor.org/info/rfc7048>.
[RFC7559] Krishnan, S., Anipko, D., and D. Thaler, "Packet-Loss
Resiliency for Router Solicitations", RFC 7559,
DOI 10.17487/RFC7559, May 2015,
<https://www.rfc-editor.org/info/rfc7559>.
[RFC7772] Yourtchenko, A. and L. Colitti, "Reducing Energy
Consumption of Router Advertisements", BCP 202, RFC 7772,
DOI 10.17487/RFC7772, February 2016,
<https://www.rfc-editor.org/info/rfc7772>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200, (IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017, DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>. <https://www.rfc-editor.org/info/rfc8200>.
[RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed., [RFC8201] McCann, J., Deering, S., Mogul, J., and R. Hinden, Ed.,
skipping to change at page 28, line 49 skipping to change at page 30, line 7
[RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903, [RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903,
DOI 10.17487/RFC4903, June 2007, DOI 10.17487/RFC4903, June 2007,
<https://www.rfc-editor.org/info/rfc4903>. <https://www.rfc-editor.org/info/rfc4903>.
[RFC5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley, [RFC5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley,
Ed., "Control And Provisioning of Wireless Access Points Ed., "Control And Provisioning of Wireless Access Points
(CAPWAP) Protocol Specification", RFC 5415, (CAPWAP) Protocol Specification", RFC 5415,
DOI 10.17487/RFC5415, March 2009, DOI 10.17487/RFC5415, March 2009,
<https://www.rfc-editor.org/info/rfc5415>. <https://www.rfc-editor.org/info/rfc5415>.
[RFC5568] Koodli, R., Ed., "Mobile IPv6 Fast Handovers", RFC 5568,
DOI 10.17487/RFC5568, July 2009,
<https://www.rfc-editor.org/info/rfc5568>.
[RFC6606] Kim, E., Kaspar, D., Gomez, C., and C. Bormann, "Problem [RFC6606] Kim, E., Kaspar, D., Gomez, C., and C. Bormann, "Problem
Statement and Requirements for IPv6 over Low-Power Statement and Requirements for IPv6 over Low-Power
Wireless Personal Area Network (6LoWPAN) Routing", Wireless Personal Area Network (6LoWPAN) Routing",
RFC 6606, DOI 10.17487/RFC6606, May 2012, RFC 6606, DOI 10.17487/RFC6606, May 2012,
<https://www.rfc-editor.org/info/rfc6606>. <https://www.rfc-editor.org/info/rfc6606>.
[RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility [RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
2011, <https://www.rfc-editor.org/info/rfc6275>. 2011, <https://www.rfc-editor.org/info/rfc6275>.
[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012,
<https://www.rfc-editor.org/info/rfc6550>.
[RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
Locator/ID Separation Protocol (LISP)", RFC 6830, Locator/ID Separation Protocol (LISP)", RFC 6830,
DOI 10.17487/RFC6830, January 2013, DOI 10.17487/RFC6830, January 2013,
<https://www.rfc-editor.org/info/rfc6830>. <https://www.rfc-editor.org/info/rfc6830>.
[RFC7559] Krishnan, S., Anipko, D., and D. Thaler, "Packet-Loss
Resiliency for Router Solicitations", RFC 7559,
DOI 10.17487/RFC7559, May 2015,
<https://www.rfc-editor.org/info/rfc7559>.
[RFC7772] Yourtchenko, A. and L. Colitti, "Reducing Energy
Consumption of Router Advertisements", BCP 202, RFC 7772,
DOI 10.17487/RFC7772, February 2016,
<https://www.rfc-editor.org/info/rfc7772>.
[RFC8273] Brzozowski, J. and G. Van de Velde, "Unique IPv6 Prefix [RFC8273] Brzozowski, J. and G. Van de Velde, "Unique IPv6 Prefix
per Host", RFC 8273, DOI 10.17487/RFC8273, December 2017, per Host", RFC 8273, DOI 10.17487/RFC8273, December 2017,
<https://www.rfc-editor.org/info/rfc8273>. <https://www.rfc-editor.org/info/rfc8273>.
[I-D.yourtchenko-6man-dad-issues] [I-D.yourtchenko-6man-dad-issues]
Yourtchenko, A. and E. Nordmark, "A survey of issues Yourtchenko, A. and E. Nordmark, "A survey of issues
related to IPv6 Duplicate Address Detection", Work in related to IPv6 Duplicate Address Detection", Work in
Progress, Internet-Draft, draft-yourtchenko-6man-dad- Progress, Internet-Draft, draft-yourtchenko-6man-dad-
issues-01, 3 March 2015, <https://tools.ietf.org/html/ issues-01, 3 March 2015, <https://tools.ietf.org/html/
draft-yourtchenko-6man-dad-issues-01>. draft-yourtchenko-6man-dad-issues-01>.
skipping to change at page 31, line 27 skipping to change at page 32, line 33
IEEE standard for Information Technology, "IEEE Standard IEEE standard for Information Technology, "IEEE Standard
for Local and metropolitan area networks -- Part 15.4: for Local and metropolitan area networks -- Part 15.4:
Low-Rate Wireless Personal Area Networks (LR-WPANs)". Low-Rate Wireless Personal Area Networks (LR-WPANs)".
Appendix A. Possible Future Extensions Appendix A. Possible Future Extensions
With the current specification, the 6LBR is not leveraged to avoid With the current specification, the 6LBR is not leveraged to avoid
multicast NS(Lookup) on the Backbone. This could be done by adding a multicast NS(Lookup) on the Backbone. This could be done by adding a
lookup procedure in the EDAR/EDAC exchange. lookup procedure in the EDAR/EDAC exchange.
By default the specification does not have a trust model, e.g., By default the specification does not have a fine-grained trust
whereby nodes that associate their address with a proof-of-ownership model: all nodes that can authenticate to the LLN MAC or attach to
[I-D.ietf-6lo-ap-nd] should be more trusted than nodes that do not. the backbone are equally trusted. It would be desirable to provide a
Such a trust model and related signaling could be added in the future stronger authorization model, e.g., whereby nodes that associate
to override the default operation and favor trusted nodes. their address with a proof-of-ownership [I-D.ietf-6lo-ap-nd] should
be more trusted than nodes that do not. Such a trust model and
related signaling could be added in the future to override the
default operation and favor trusted nodes.
Future documents may extend this specification by allowing the 6BBR Future documents may extend this specification by allowing the 6BBR
to redistribute Host routes in routing protocols that would operate to redistribute Host routes in routing protocols that would operate
over the Backbone, or in MIPv6, or FMIP, or the Locator/ID Separation over the Backbone, or in MIPv6 [RFC6275], or FMIP [RFC5568], or the
Protocol (LISP) [RFC6830] to support mobility on behalf of the 6LNs, Locator/ID Separation Protocol (LISP) [RFC6830] to support mobility
etc... LISP may also be used to provide an equivalent to the EDAR/ on behalf of the 6LNs, etc... LISP may also be used to provide an
EDAC exchange using a Map Server / Map Resolver as a replacement to equivalent to the EDAR/EDAC exchange using a Map Server / Map
the 6LBR. Resolver as a replacement to 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
Multi-Link Subnet. The proxy-ND functions enable IPv6 ND services Multi-Link Subnet. The proxy-ND functions enable IPv6 ND services
for 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,
skipping to change at page 32, line 24 skipping to change at page 33, line 36
Backbone routers and Backbone nodes once a 6LN has roamed. This way, Backbone routers and Backbone nodes once a 6LN has roamed. This 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 impact if the IPv6 ND operation is limited to one of the The negative impact of the IPv6 ND-related broadcasts can be limited
federated LLNs, enabling the number of 6LNs to grow. The Routing to one of the federated links, enabling the number of 6LNs to grow.
Proxy operation avoids the need to expose the MAC addresses of the The Routing Proxy operation avoids the need to expose the MAC
6LNs onto the backbone, keeping the Layer 2 topology simple and addresses of the 6LNs onto the backbone, keeping the Layer 2 topology
stable. This meets the requirements in Appendix B.6 of [RFC8505] simple and stable. This meets the requirements in Appendix B.6 of
"Requirements Related to Scalability", as long has the 6BBRs are [RFC8505] "Requirements Related to Scalability", as long has the
dimensioned for the number of registrations that each needs to 6BBRs are dimensioned for the number of registrations that each needs
support. to 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. The 6BBR proxy-ND operations eliminate the need for
wireless nodes to respond synchronously when a Lookup is performed wireless nodes to respond synchronously when a Lookup is performed
for their IPv6 Addresses. This provides the function of a Sleep for their IPv6 Addresses. This provides the function of a Sleep
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