draft-ietf-6lo-backbone-router-09.txt   draft-ietf-6lo-backbone-router-10.txt 
6lo P. Thubert, Ed. 6lo P. Thubert, Ed.
Internet-Draft Cisco Systems Internet-Draft Cisco Systems
Updates: 4861, 8505 (if approved) C. Perkins Updates: 4861, 8505 (if approved) C. Perkins
Intended status: Standards Track Futurewei Intended status: Standards Track Futurewei
Expires: June 8, 2019 E. Levy-Abegnoli Expires: July 20, 2019 E. Levy-Abegnoli
Cisco Systems Cisco Systems
December 5, 2018 January 16, 2019
IPv6 Backbone Router IPv6 Backbone Router
draft-ietf-6lo-backbone-router-09 draft-ietf-6lo-backbone-router-10
Abstract Abstract
Backbone Routers are RFC8505 Routing Registrars that provide proxy This document updates RFC 4861 and RFC 8505 in order to enable proxy
services for IPv6 Neighbor Discovery. Backbone Routers federate services for IPv6 Neighbor Discovery by Routing Registrars called
multiple wireless Links over a Backbone Link to form a MultiLink Backbone Routers. Backbone Routers are placed along the wireless
Subnet. Backbone Routers placed along the wireless edge of the edge of a Backbone, and federate multiple wireless links to form a
Backbone handle IPv6 Neighbor Discovery, and route packets on behalf single MultiLink Subnet.
of registered nodes.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on June 8, 2019. This Internet-Draft will expire on July 20, 2019.
Copyright Notice Copyright Notice
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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 . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. References . . . . . . . . . . . . . . . . . . . . . . . 5 2.2. New Terms . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. New Terms . . . . . . . . . . . . . . . . . . . . . . . . 5 2.3. Acronym Definitions . . . . . . . . . . . . . . . . . . . 6
2.4. Acronym Definitions . . . . . . . . . . . . . . . . . . . 6 2.4. References . . . . . . . . . . . . . . . . . . . . . . . 7
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. Access Link . . . . . . . . . . . . . . . . . . . . . . . 9 3.1. Updating RFC 6775 and RFC 8505 . . . . . . . . . . . . . 9
3.2. Route-Over Mesh . . . . . . . . . . . . . . . . . . . . . 10 3.2. Access Link . . . . . . . . . . . . . . . . . . . . . . . 10
3.3. MultiLink Subnet Consistency . . . . . . . . . . . . . . 11 3.3. Route-Over Mesh . . . . . . . . . . . . . . . . . . . . . 11
3.4. Registering Node . . . . . . . . . . . . . . . . . . . . 11 3.4. The Binding Table . . . . . . . . . . . . . . . . . . . . 12
3.5. Using IPv6 ND Over the Backbone Link . . . . . . . . . . 12 3.5. Primary and Secondary 6BBRs . . . . . . . . . . . . . . . 13
3.6. Routing Proxy Operations . . . . . . . . . . . . . . . . 13 3.6. Using Optimistic DAD . . . . . . . . . . . . . . . . . . 13
3.7. Bridging Proxy Operations . . . . . . . . . . . . . . . . 14 4. MultiLink Subnet Considerations . . . . . . . . . . . . . . . 14
3.8. Leveraging Optimistic DAD . . . . . . . . . . . . . . . . 14 5. Optional 6LBR serving the MultiLink Subnet . . . . . . . . . 14
4. Updating RFC 4861 . . . . . . . . . . . . . . . . . . . . . . 15 6. Using IPv6 ND Over the Backbone Link . . . . . . . . . . . . 15
5. Updating RFC 8505 . . . . . . . . . . . . . . . . . . . . . . 15 7. Routing Proxy Operations . . . . . . . . . . . . . . . . . . 15
6. 6BBR detailed Operations . . . . . . . . . . . . . . . . . . 15 8. Bridging Proxy Operations . . . . . . . . . . . . . . . . . . 16
6.1. Primary and Secondary 6BBRs . . . . . . . . . . . . . . 16 9. Creating and Maintaining a Binding . . . . . . . . . . . . . 17
6.2. Binding Table . . . . . . . . . . . . . . . . . . . . . . 16 9.1. Operation on a Binding in Tentative State . . . . . . . . 19
6.3. Registration and Binding Table Entry Creation . . . . . . 17 9.2. Operation on a Binding in Reachable State . . . . . . . . 20
6.4. Defending Addresses . . . . . . . . . . . . . . . . . . . 18 9.3. Operation on a Binding in Stale State . . . . . . . . . . 21
7. Security Considerations . . . . . . . . . . . . . . . . . . . 20 10. Registering Node Considerations . . . . . . . . . . . . . . . 21
8. Protocol Constants . . . . . . . . . . . . . . . . . . . . . 20 11. Security Considerations . . . . . . . . . . . . . . . . . . . 22
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 12. Protocol Constants . . . . . . . . . . . . . . . . . . . . . 22
10. Future Work . . . . . . . . . . . . . . . . . . . . . . . . . 20 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 23
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
12.1. Normative References . . . . . . . . . . . . . . . . . . 21 15.1. Normative References . . . . . . . . . . . . . . . . . . 23
12.2. Informative References . . . . . . . . . . . . . . . . . 22 15.2. Informative References . . . . . . . . . . . . . . . . . 24
12.3. External Informative References . . . . . . . . . . . . 24 Appendix A. Possible Future Extensions . . . . . . . . . . . . . 27
Appendix A. Applicability and Requirements Served . . . . . . . 25 Appendix B. Applicability and Requirements Served . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29
1. Introduction 1. Introduction
IEEE STD. 802.1 [IEEEstd8021] Ethernet Bridging provides an efficient IEEE STD. 802.1 [IEEEstd8021] Ethernet Bridging provides an efficient
and reliable broadcast service; applications and protocols have been and reliable broadcast service for wired networks; applications and
built that heavily depend on that feature for their core operation. protocols have been built that heavily depend on that feature for
Unfortunately, Low-Power Lossy Networks (LLNs) and local wireless their core operation. Unfortunately, Low-Power Lossy Networks (LLNs)
networks generally do not provide the broadcast capabilities of and local wireless networks generally do not provide the broadcast
Ethernet Bridging in an economical fashion; protocols designed for capabilities of Ethernet Bridging in an economical fashion.
bridged networks that rely on multicast and broadcast often exhibit
disappointing behaviours when employed unmodified on a local wireless As a result, protocols designed for bridged networks that rely on
medium (see [I-D.ietf-mboned-ieee802-mcast-problems]). multicast and broadcast often exhibit disappointing behaviours when
employed unmodified on a local wireless medium (see
[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
interesting caveat that the bridging state is populated proactively property that the bridging state is established at the time of
at the association time. This ensures a solid connectivity to the association. This ensures connectivity to the node (STA) and
node (STA) and protects the wireless medium against the broadcast- protects the wireless medium against broadcast-intensive Transparent
intensive Transparent Bridging reactive lookups. In other words, the Bridging reactive Lookups. In other words, the association process
association process is used to register the MAC Address of the STA to is used to register the MAC Address of the STA to the AP. The AP
the AP. The APs subsequently proxies the bridging operation and does subsequently proxies the bridging operation and does not need to
not need to forward the broadcast lookups over the radio. forward the broadcast Lookups over the radio.
Like Transparent Bridging, the operations of the IPv6 [RFC8200] Like Transparent Bridging, IPv6 [RFC8200] Neighbor Discovery
Neighbor Discovery [RFC4861] [RFC4862] Protocol (IPv6 ND) are [RFC4861] [RFC4862] Protocol (IPv6 ND) is a reactive protocol, based
reactive and rely heavily on multicast transmissions to locate an on- on multicast transmissions to locate an on-link correspondent and
link correspondent and ensure the uniqueness of an Address. The ensure the uniqueness of an IPv6 address. The mechanism for
mechanism for Duplicate Address Detection (DAD) [RFC4862] was also Duplicate Address Detection (DAD) [RFC4862] was designed for the
designed as a natural match with the efficient broadcast operation of efficient broadcast operation of Ethernet Bridging. Since broadcast
Ethernet Bridging. However, since broadcast can be unreliable over can be unreliable over wireless media, DAD often fails to discover
wireless media, DAD often fails to discover duplications duplications [I-D.yourtchenko-6man-dad-issues]. In practice, IPv6
[I-D.yourtchenko-6man-dad-issues]. A conflict of IPv6 Address is addresses very rarely conflict because of the entropy of the 64-bit
still a very rare event, not because Address duplications are Interface IDs, not because address duplications are detected and
detected and solved as designed, but because of the sheer entropy of resolved.
the 64-bit Interface IDs.
IPv6 multicast messages are typically broadcast over the wireless The IPv6 ND Neighbor Solicitation (NS) [RFC4861] message is used for
medium; they are processed by most if not all the wireless nodes over DAD and address Lookup when a node moves, or wakes up and reconnects
the subnet - e.g., the ESS fabric - even when very few if any of the to the wireless network. The NS message is targeted to a Solicited-
nodes is subscribed to the multicast flow. The IPv6 ND Neighbor Node Multicast Address (SNMA) [RFC4291] and should in theory only
Solicitation (NS) [RFC4861] is such a message; NS messages are used reach a very small group of nodes. But in reality, IPv6 multicast
for DAD and Address lookup, and are frequently observed in a messages are typically broadcast on the wireless medium, and so they
situation of mobility and when a node wakes up and reconnects to the are processed by most of the wireless nodes over the subnet (e.g.,
wireless network. The NS message is targeted to a Sollicitated-Node the ESS fabric) regardless of how few of the nodes are subscribed to
Multicast Address (SNMA) [RFC4291] and should in theory only reach a the SNMA. As a result, IPv6 ND address Lookups and DADs over a large
very small group of nodes; but since Layer-3 multicast messages are wireless and/or a LowPower Lossy Network (LLN) can consume enough
effectively broadcasted at Layer-2, the volume of Address lookups and bandwidth to cause a substantial degradation to the unicast traffic
DADs over a large fabric can effectively consume bandwidth to the service.
point that it becomes detrimental to unicast traffic (see
[I-D.ietf-mboned-ieee802-mcast-problems]).
Additionally, wireless nodes that do not belong to the SNMA group Because IPv6 ND messages sent to the SNMA group are broadcasted at
still have to keep their radio awake and listen to broadcasted NS the radio MAC Layer, wireless nodes that do not belong to the SNMA
messages, which is a total waste of energy for them. In order to group still have to keep their radio turned on to listen to multicast
control their power consumption, battery-operated nodes such as IOT NS messages, which is a total waste of energy for them. In order to
sensors and smartphones may then elect to blindly ignore a portion of reduce their power consumption, certain battery-operated devices such
the broadcasts, which tends to make the Layer-3 protocol operations as IoT sensors and smartphones ignore some of the broadcasts, making
even less reliable. IPv6 ND operations even less reliable.
These problems can be alleviated by a reduction of IPv6 ND broadcasts These problems can be alleviated by reducing the IPv6 ND broadcasts
over wireless access links. One classical way to achieve this to over wireless access links. This has been done by splitting the
split the broadcast domains and route between subnets, possibly by broadcast domains and routes between subnets, or even by assigning a
assigning a /64 prefix to each wireless node (see [RFC8273]). /64 prefix to each wireless node (see [RFC8273]).
Another way is to proxy the Layer-3 protocols that rely on broadcast Another way is to proxy at the boundary of the wired and wireless
operations at the boundary of the wired and wireless domains, in a domains the Layer-3 protocols that rely on MAC Layer broadcast
fashion similar to the Layer-2 association but at layer-3. To that operations. For instance, IEEE 802.11 [IEEEstd80211] situates proxy-
effect, IEEE 802.11 [IEEEstd80211] requires ARP and proxy-ND ARP (IPv4) and proxy-ND (IPv6) functions at the Access Points (APs).
[RFC4389] services at the Access Points (APs), and this specification The 6BBR provides a proxy-ND function and can be extended for proxy-
is a possible response to that requirement. ARP in a continuation specification.
IPv6 proxy-ND services can be obtained automatically by snooping the IPv6 proxy-ND services can be obtained by snooping the IPV6 ND
IPV6 ND protocol (see [I-D.bi-savi-wlan]). Proprietary techniques protocol (see [I-D.bi-savi-wlan]). Proprietary techniques for IPv6
for IPv6 ND and DHCP snooping are effectively deployed, and though ND and DHCP snooping have been used; although snooping does eliminate
snooping is really useful to cancel undesirable broadcast undesirable broadcast transmissions, it has been found to be
transmissions, it has also proven to be unreliable; An IPv6 Address unreliable. An IPv6 address may not be discovered immediately due to
may not be discovered immediately due to a packet loss, or a silent a packet loss, or if a "silent" node is not currently using one of
node that does not use the Address for a while; a change of state its addresses. A change of state (e.g. due to movement) may be
(e.g. due a movement) may be missed or misordered, leading to missed or misordered, leading to unreliable connectivity and
unreliable connectivity and a partial knowledge of the state of the incomplete knowledge of the state of the network.
network.
With this specification, a wireless node proactively registers its This specification defines the 6BBR as a Routing Registrar [RFC8505]
IPv6 Addresses using a NS(EARO) as specified in [RFC8505] to an IPv6 that provide proxy services for IPv6 Neighbor Discovery. Backbone
Backbone Router (6BBR). The 6BBR is a Routing Registrar per Routers federate multiple LLNs over a Backbone Link to form a
[RFC8505]. It is also a Border Router that performs the IPv6 proxy MultiLink Subnet (MLSN). Backbone Routers placed along the LLN edge
Neighbor Discovery operations on its Backbone interface on behalf of of the Backbone handle IPv6 Neighbor Discovery, and forward packets
the 6LNs that are registered on its LLN interfaces. This effectively on behalf of registered nodes.
recreates at Layer-3 the equivalent of an association such as found
in IEEE STD. 802.11 for the purpose of providing reachability to the An LLN node (6LN) registers all its IPv6 Addresses using an NS(EARO)
registered Addresses without the need of a broadcast lookup over the as specified in [RFC8505] to the 6BBR. The 6BBR is also a Border
wireless medium. Additional benefits are discussed in Appendix A. Router that performs IPv6 Neighbor Discovery (IPv6 ND) operations on
its Backbone interface on behalf of the 6LNs that have registered
addresses on its LLN interfaces without the need of a broadcast over
the wireless medium. Additional benefits are discussed in
Appendix B.
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. References 2.2. New Terms
In this document, readers will encounter terms and concepts that are
discussed in the following documents:
o "Neighbor Discovery Proxies (proxy-ND)" [RFC4389]
o "Optimistic Duplicate Address Detection" [RFC4429], and
o "Neighbor Discovery for IP version 6" [RFC4861],
o "IPv6 Stateless Address Autoconfiguration" [RFC4862],
o "MultiLink Subnet Issues" [RFC4903],
o "IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs):
Overview, Assumptions, Problem Statement, and Goals" [RFC4919],
o Neighbor Discovery Optimization for Low-Power and Lossy Networks
[RFC6775],
o ,"Mobility Support in IPv6" [RFC6275],
o "Problem Statement and Requirements for IPv6 over Low-Power
Wireless Personal Area Network (6LoWPAN) Routing" [RFC6606], and
mostly
o "Registration Extensions for 6LoWPAN Neighbor Discovery"
[RFC8505].
2.3. New Terms
This document also introduces the following terminology: This document introduces the following terminology:
Federated Federated
A subnet that is partitionned over a Backbone and one or more A subnet that comprises a Backbone and one or more (wireless)
(wireless) access links, is said to be federated into one access links, is said to be federated into one MultiLink
MultiLink Subnet by the proxy-ND operation of 6BBRs located at Subnet. The proxy-ND operation of 6BBRs over the Backbone and
the edge of the Backbone and the access links and providing a the access links provides the appearance of a subnet for IPv6
semblance of a non-partitionned subnet for IPv6 ND over the ND.
Backbone.
Sleeping Proxy Sleeping Proxy
A 6BBR acts as a Sleeping Proxy if it answers ND Neighbor A 6BBR acts as a Sleeping Proxy if it answers ND Neighbor
Solicitation over the Backbone on behalf of the Registered Solicitations over the Backbone on behalf of a Registered Node.
Node.
Unicasting Proxy
A Unicasting Proxy forwards NS messages to the Registering
Node, transforming Layer-2 multicast into unicast.
Routing Proxy Routing Proxy
A Routing Proxy advertises its own MAC Address as the TLLA in A Routing Proxy provides IPv6 ND proxy functions and enables
the proxied NAs over the Backbone, as opposed to that of the the MLSN operation over federated links that may not be
node that performs the registration. compatible for bridging. The Routing Proxy advertises its own
MAC Address as the TLLA in the proxied NAs over the Backbone,
and routes at the Network Layer between the federated links.
Bridging Proxy Bridging Proxy
A Bridging Proxy advertises the MAC Address of the node that A Bridging Proxy provides IPv6 ND proxy functions while
performs the registration as the TLLA in the proxied NAs over preserving forwarding continuity at the MAC Layer. The
the Backbone. In that case, the MAC Address and the mobility Bridging Proxy advertises the MAC Address of the Registering
of 6LN is still visible across the bridged Backbone fabric. 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
across the bridged Backbone, and the 6BR may be configured to
proxy for Link Local Addresses.
Primary 6BBR Binding Table
The 6BBR that will defend a Registered Address for the purpose The Binding Table is an abstract database that is maintained by
of DAD over the Backbone. the 6BBR to store the state associated with its registrations.
Secondary 6BBR Binding
A 6BBR other than the Primary 6BBR to which an Address is A Binding is an abstract state associated to one registration,
registered. A Secondary Router MAY advertise the Address over in other words one entry in the Binding Table.
the Backbone and proxy for it.
2.4. Acronym Definitions 2.3. Acronym Definitions
This document uses the following acronyms: This document uses the following acronyms:
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
skipping to change at page 7, line 4 skipping to change at page 6, line 24
6LR: 6LoWPAN Router 6LR: 6LoWPAN Router
6CIO: Capability Indication Option 6CIO: Capability Indication Option
EARO: (Extended) Address Registration Option -- (E)ARO EARO: (Extended) Address Registration Option -- (E)ARO
EDAR: (Extended) Duplicate Address Request -- (E)DAR EDAR: (Extended) Duplicate Address Request -- (E)DAR
EDAC: (Extended) Duplicate Address Confirmation -- (E)DAC EDAC: (Extended) Duplicate Address Confirmation -- (E)DAC
DAD: Duplicate Address Detection DAD: Duplicate Address Detection
DODAG: Destination-Oriented Directed Acyclic Graph DODAG: Destination-Oriented Directed Acyclic Graph
IPv6 ND: IPv6 Neighbor Discovery
LLN: Low-Power and Lossy Network LLN: Low-Power and Lossy Network
NA: Neighbor Advertisement NA: Neighbor Advertisement
NCE: Neighbor Cache Entry NCE: Neighbor Cache Entry
ND: Neighbor Discovery
NDP: Neighbor Discovery Protocol
NS: Neighbor Solicitation NS: Neighbor Solicitation
ROVR: Registration Ownership Verifier (pronounced rover) ROVR: Registration Ownership Verifier
RPL: IPv6 Routing Protocol for LLNs (pronounced ripple) [RFC6550] RPL: IPv6 Routing Protocol for LLNs
RA: Router Advertisement RA: Router Advertisement
RS: Router Solicitation RS: Router Solicitation
TID: Transaction ID (a sequence counter in the EARO) TID: Transaction ID (a sequence counter in the EARO)
3. Overview 2.4. References
A 6BBR provides proxy-ND services to 6LNs attached to an LLN that is In this document, readers will encounter terms and concepts that are
anchored at the 6BBR; this way, a subnet that is located on a discussed in the following documents:
Backbone can be extended in the LLN as a MultiLink Subnet. The LLN
may be a hub-and-spoke network, a mesh-under or a route-over network.
The proxy-ND operation can co-exist with IPv6 ND over the Backbone. o "Neighbor Discovery for IP version 6" [RFC4861], "IPv6 Stateless
The proxy state can be distributed across multiple 6BBR attached to a Address Autoconfiguration" [RFC4862] and "Optimistic Duplicate
same Backbone. A 6LN may move freely from an LLN anchored at one Address Detection" [RFC4429],
6BBR to an LLN anchored at another 6BBR on the same Backbone and
retain any or all of the IPv6 Addresses that the 6LN has formed.
The registration to a proxy service is done via a NS/NA(EARO) o "Neighbor Discovery Proxies (proxy-ND)" [RFC4389] and "MultiLink
exchange. The 6BBR operation resembles that of a Mobile IPv6 (MIPv6) Subnet Issues" [RFC4903],
[RFC6275] Home Agent. The combination if a 6BBR and a MIPv6 HA
enables a full mobility support for 6LNs, inside and outside the o "Problem Statement and Requirements for IPv6 over Low-Power
links that form the subnet. Wireless Personal Area Network (6LoWPAN) Routing" [RFC6606], and
o Neighbor Discovery Optimization for Low-Power and Lossy Networks
[RFC6775] and "Registration Extensions for 6LoWPAN Neighbor
Discovery" [RFC8505].
3. Overview
Figure 1 illustrates backbone link federating a collection of LLNs as
a single IPv6 Subnet, with a number of 6BBRs providing proxy-ND
services to their attached LLNs.
| |
+-----+ +-----+
| | Gateway (default) Router | | Gateway (default) Router
| | | |
+-----+ +-----+
| |
| Backbone Link | Backbone side
+-------------------------+----------------------+ +-------------------------+----------------------+
| | | | | |
+------+ +------+ +------+ +------+ +------+ +------+
| 6BBR | | 6BBR | | 6BBR | | 6BBR | | 6BBR | | 6BBR |
| | | | | | | | | | | |
+------+ +------+ +------+ +------+ +------+ +------+
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 o o o o
LLN LLN LLN LLN LLN LLN
Figure 1: Backbone Link and Backbone Routers Figure 1: Backbone Link and Backbone Routers
Each Backbone Router (6BBR) maintains an abstract Binding Table of The LLN may be a hub-and-spoke access link such as (Low-Power) IEEE
its Registered Nodes. The Binding Tables form a distributed database STD. 802.11 (Wi-Fi) [IEEEstd80211] and IEEE STD. 802.15.1 (Bluetooth)
of 6LNs that reside on the LLNs or on the IPv6 Backbone, and use an [IEEEstd802151], or a Mesh-Under or a Route-Over network [RFC8505].
extension to IPv6 ND to exchange that information across the The proxy state can be distributed across multiple 6BBRs attached to
Backbone. In that process: the same Backbone.
The Extended Address Registration Option (EARO) defined in The main features of a 6BBR are as follows:
[RFC8505] is used in the ND exchanges over the Backbone between
the 6BBRs to help distinguish duplication from movement.
Optionally, Extended Duplicate Address Messages (EDAR and EDAC)
can also be used between the 6BBR and a 6LBR if one is present on
the Backbone. Address duplication is detected using the ROVR
field, and conflicting registrations to different 6BBRs by a same
owner 6LR are resolved using the TID field.
The Link Layer Address (LLA) that the 6BBR advertises for the o Multilink-subnet functions (provided by the 6BBR on the backbone)
performed on behalf of registered 6LNs, and
o Routing registrar services that reduce multicast within the LLN:
* Binding Table management
* failover, e.g., due to mobility
Each Backbone Router (6BBR) maintains a data structure for its
Registered Nodes called a Binding Table. The combined Binding Tables
of all the 6BBRs on a backbone form a distributed database of 6LNs
that reside in the LLNs or on the IPv6 Backbone.
Unless otherwise configured, a 6BBR does the following:
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
o Defend a Registered Address over the Backbone using NA messages on
behalf of the sleeping 6LN
o Advertise a Registered Address over the Backbone using NA
messages, asynchronously or as a response to a Neighbor
Solicitation messages.
o Deliver packets arriving from the LLN, using Neighbor Solicitation
messages to look up the destination over the Backbone.
o Forward or bridge packets between the LLN and the Backbone.
o Verify liveness for a registration, when needed.
The first of these functions enables the 6BBR to fulfill its role as
a Routing Registrar for each of its attached LLNs. The remaining
functions fulfill the role of the 6BBRs as the border routers
connecting the Multi-link IPv6 subnet to the Internet.
The proxy-ND operation can co-exist with IPv6 ND over the Backbone.
The 6BBR may co-exist with a proprietary snooping or a traditional
bridging functionality in an Access Point, in order to support legacy
nodes that do not support this specification. In the case, the co-
existing function may turn multicastsinto a series of unicast to the
legacy nodes.
The registration to a proxy service uses an NS/NA(EARO) exchange.
The 6BBR operation resembles that of a Mobile IPv6 (MIPv6) [RFC6275]
Home Agent (HA). The combination of a 6BBR and a MIPv6 HA enables
full mobility support for 6LNs, inside and outside the links that
form the subnet.
The 6BBRs use the Extended Address Registration Option (EARO) defined
in [RFC8505] as follows:
o The EARO is used in the IPv6 ND exchanges over the Backbone
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
duplication is detected using the ROVR field. Conflicting
registrations to different 6BBRs for the same 6LR address are
resolved using the TID field.
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 may be that of the Registering Node; in that case, the Backbone can belong to the Registering Node; in that case, the
6BBR needs to bridge the unicast packets (Bridging Proxy). 6BBR (acting as a Bridging Proxy (see Section 8)) bridges the
Alternatively, the LLA can be that of the 6BBR on the Backbone unicast packets. Alternatively, the LLA can be that of the 6BBR
interface, in which case the 6BBRs receives at Layer-2 and and on the Backbone interface, in which case the 6BBR (acting as a
needs to route at Layer-3 the unicast packets (Routing Proxy). Routing Proxy(see Section 7)) receives the unicast packets at
This is discussed in more details in Section 3.6 and Section 3.7, Layer-2 and routes them.
respectively.
3.1. Access Link 3.1. Updating RFC 6775 and RFC 8505
This specification also applies to (hub-and-spoke) Access Links such This specification adds the EARO as a possible option in RS, NS(DAD)
as (Low-Power) IEEE STD. 802.11 (Wi-Fi) [IEEEstd80211] and IEEE STD. and NA messages over the backbone. [RFC8505] requires that the
802.15.1 (Bluetooth) [IEEEstd802151]. Figure 2 illustrates an ODAD- registration NS(EARO) contains an SLLAO. This specification details
complient (see Section 3.8) example of a 6LN that forms an IPv6 the use of those messages over the backbone.
Address and registers it to a 6BBR acting as a 6LR [RFC8505].
6LoWPAN Node 6BBR 6LBR default Note: [RFC6775] requires that the registration NS(EARO) contains an
(STA) (AP) Router SLLAO and [RFC4862] that the NS(DAD) is sent from the unspecified
|(Wireless) LLN | IPv6 ND Backbone | address for which there cannot be a SLLAO. Consequently, an NS(DAD)
| | (Ethernet) | cannot be confused with a registration.
| RS | | |
|-------------->| | |
| (multicast) | | |
| | | |
| RA(PIO) | | |
|<--------------| | |
| (L2 unicast) | | |
| | | |
| NS(EARO) | | |
|-------------->| | |
| (optimistic) | | |
| | Extended DAR | |
| |------------->| |
| | Extended DAC | |
| |<-------------| |
| | NS-DAD(EARO) |
| |------------------------------>|
| |-------> (multicast) |
| |---------------------> |
| | RS(no SLLAO, for ODAD) |
| |------------------------------>|
| | (if no BCE) NS-LOOKUP |
| |<------------------------------|
| | NA(SLLAO, not(O), EARO) |
| |------------------------------>|
| | RA(unicast) |
| |<------------------------------|
| | | |
| IPv6 Packets in optimistic mode |
|<--------------------------------------------->|
| | | |
| NA(EARO) |DAD <timeout> | |
|<--------------| | |
| | | |
Figure 2: Initial Registration Flow to a 6BBR acting as Routing Proxy This specification adds the capability to insert IPv6 ND options in
the EDAR and EDAC messages. In particular, a 6BBR acting as a 6LR
for the Registered Address can insert an SLLAO in the EDAR to the
6LBR in order to avoid a Lookup back.
3.2. Route-Over Mesh 3.2. Access Link
In the case of a Route-Over Mesh, e.g., using RPL [RFC6550], the Figure 2 illustrates a flow where 6LN forms an IPv6 Address and
6TiSCH architecture [I-D.ietf-6tisch-architecture] suggests to registers it to a 6BBR acting as a 6LR [RFC8505]. The 6BBRs applies
collocate the RPL root with a 6LoWPAN Border Router (6LBR), which is ODAD (see Section 3.6) to the registered address to enable
either collocated with or connected to the 6BBR over an IPv6 Link. connectivity while the message flow is still in progress. In that
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
enable coexistence with IPv6 ND over the backbone.
Figure 3 illustrates the initial IPv6 signaling that enables a 6LN to 6LN(STA) 6BBR(AP) 6LBR default GW
form a Global or a Unique-Local Address and register it to the 6LBR | | | |
using [RFC8505]. The 6LBR also leverages [RFC8505] to register the | LLN Access Link | IPv6 Backbone (e.g., Ethernet) |
6LNs on their behalf to the 6BBR and obtain proxy-ND services. | | | |
| RS(multicast) | | |
|---------------->| | |
| RA(PIO, Unicast)| | |
|<----------------| | |
| NS(EARO) | | |
|---------------->| | |
| | Extended DAR | |
| |--------------->| |
| | Extended DAC | |
| |<---------------| |
| | |
| | NS-DAD(EARO, multicast) |
| |--------> |
| |-------------------------------->|
| | |
| | RS(no SLLAO, for ODAD) |
| |-------------------------------->|
| | (if no fresher Binding) NS(Lookup) |
| | <-------------|
| |<--------------------------------|
| | NA(SLLAO, not(O), EARO) |
| |-------------------------------->|
| | RA(unicast) |
| |<--------------------------------|
| | |
| IPv6 Packets in optimistic mode |
|<------------------------------------------------->|
| | |
| |
| NA(EARO) |<DAD timeout>
|<----------------|
| |
Figure 2: Initial Registration Flow to a 6BBR acting as Routing Proxy
3.3. Route-Over Mesh
Figure 3 illustrates IPv6 signaling that enables a 6LN to form a
Global or a Unique-Local Address and register it to the 6LBR that
serves its LLN using [RFC8505]. The 6LBR (acting as Registering
Node) proxies the registration to the 6BBR, using [RFC8505] to
register the addresses the 6LN (Registered Node) on its behalf to the
6BBR, and obtain proxy-ND services from the 6BBR.
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+RPL | 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 | | |
|-------------->| | | |-------------->| | |
|-----------> | | | |-----------> | | |
|------------------> | | |------------------> | |
| IPv6 ND RA | | | | IPv6 ND RA | | |
|<--------------| | | |<--------------| | |
| | <once> | | | | <once> | |
| NS(EARO) | | | | NS(EARO) | | |
skipping to change at page 11, line 5 skipping to change at page 11, line 47
| | | NA(EARO) |<timeout> | | | NA(EARO) |<timeout>
| | |<--------------| | | |<--------------|
| | Extended DAC | | | | Extended DAC | |
| |<--------------| | | |<--------------| |
| NA(EARO) | | | | NA(EARO) | | |
|<--------------| | | |<--------------| | |
| | | | | | | |
Figure 3: Initial Registration Flow over Route-Over Mesh Figure 3: Initial Registration Flow over Route-Over Mesh
3.3. MultiLink Subnet Consistency As a non-normative example of a Route-Over Mesh, the 6TiSCH
architecture [I-D.ietf-6tisch-architecture] suggests using RPL
[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
IPv6 Link.
3.4. The Binding Table
Addresses in a LLN that are reachable from the Backbone by way of 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 active
registrations in an abstract Binding Table.
An entry in the Binding Table Entry is called a "Binding". A Binding
may be in Tentative, Reachable or Stale state.
The 6BBR uses a combination of [RFC8505] and IPv6 ND over the
Backbone to advertise the registration and avoid a duplication.
Conflicting registrations are solved by the 6BBRs transparently to
the Registering Nodes.
Only one 6LN may register a given Address, but the Address may be
registered to Multiple 6BBRs for higher availability.
Over the LLN, Binding Table management is as follows:
o De-registrations (newer TID, same ROVR, null Lifetime) are
accepted with a status of 4 ("Removed"); the entry is deleted;
o Newer registrations (newer TID, same ROVR, non-null Lifetime) are
accepted with a status of 0 (Success); the Binding is updated with
the new TID, the Registration Lifetime and the Registering Node;
in Tentative state the EDAC response is held and may be
overwritten; in other states the Registration Lifetime timer is
restarted and the entry is placed in Reachable state.
o Identical registrations (same TID, same ROVR) from a same
Registering Node are accepted with a status of 0 (Success). In
Tentative state, the response is held and may be overwritten, but
the response MUST be eventually produced, carrying the result of
the DAD process;
o Older registrations (older TID, same ROVR) from the same
Registering Node are discarded;
o Identical and older registrations (not-newer TID, same ROVR) from
a different Registering Node are rejected with a status of 3
(Moved); this may be rate limited to avoid undue interference;
o Any registration for the same address but with a different ROVR is
rejected with a status of 1 (Duplicate).
3.5. Primary and Secondary 6BBRs
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
parallel registrations. To allow for this, ND(DAD) and NA messages
with an EARO that indicate an identical Binding in another 6BBR (same
Registered address, same TID, same ROVR) as silently ignored.
A 6BBR MAY be primary or secondary. The primary is the 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 and same
Transaction ID, the EUI-64 Address being considered as an unsigned
64bit integer. A given 6BBR can be primary for a given Address and
secondary for another Address, regardless of whether or not the
Addresses belong to the same 6LN.
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
of primary. More than one 6BBR claiming or defending an address
generates unwanted traffic but no reachability issue since all 6BBRs
provide reachability from the Backbone to the 6LN.
3.6. Using Optimistic DAD
Optimistic Duplicate Address Detection [RFC4429] (ODAD) specifies how
an IPv6 Address can be used before completion of Duplicate Address
Detection (DAD). ODAD guarantees that this behavior will not cause
harm if the new Address is a duplicate.
Support for ODAD avoids delays in installing the Neighbor Cache Entry
(NCE) in the 6BBRs and the default router, enabling immediate
connectivity to the registered node. As shown in Figure 2, if the
6BBR is aware of the Link-Layer Address (LLA) of a router, then the
6BBR sends a Router Solicitation (RS), using the Registered Address
as the IP Source Address, to the known router(s). The RS MUST be
sent without a Source LLA Option (SLLAO), to avoid invalidating a
preexisting NCE in the router.
Following ODAD, the router may then send a unicast RA to the
Registered Address, and it may resolve that Address using an
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
then determine the freshest EARO in case of a conflicting NA(EARO)
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
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 Registered Address can flow immediately.
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
a same 6BBR. Multicast ND messages are link-scoped and MUST NOT be the same 6BBR. ND messages are link-scoped and are not forwarded by
forwarded across the Backbone Routers. the 6BBR between the backbone and the LLNs though some packets may be
reinjected in Bridging Proxy mode (see Section 8).
A prefix that is used across a MultiLink Subnet may still be Nodes located inside the subnet do not perform the IPv6 Path MTU
advertised as on-link over the Backbone, by setting the "L" bit in Discovery [RFC8201]. For that reason, the MTU must have a same value
the Prefix Information Option (PIO) in RA messages ([RFC4861]), in on the Backbone and all attached LLNs. To achieve this, the 6BBR
order to support classical IPv6 hosts; but the MultiLink Subnet MUST use the same MTU value in RAs over the Backbone and in the RAs
prefix MUST be advertised as not-onlink in RAs sent towards the LLN. that it transmits towards the LLN links.
Nodes located inside the subnet will not perform the IPv6 Path MTU 5. Optional 6LBR serving the MultiLink Subnet
Discovery [RFC8201] between one another. For that reason, the MTU
must have a same value on the Backbone and all attached LLNs. To
achieve this, the 6BBR MUST use the same MTU value that is used in
RAs over the Backbone in the RAs that it transmits towards the LLN
links.
3.4. Registering Node 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
advertisement (see section 4.3. of [RFC8505]) in RA messages.
A Registering Node MUST implement [RFC6775] as updated by [RFC8505] When a 6LBR is present, the 6BBR uses an EDAR/EDAC message exchange
in order to interact with a 6BBR. As such, it does not depend on with the 6LBR to check for duplication or movement. This is done
multicast RAs to discover the 6LR(s). prior to the NS(DAD) process, which may be avoided of the 6LBR
already maintains a conflicting state for the Registered Address.
The Registering Node MUST accept multicast RAs, but those are This specification enables an address to be registered to more than
expected to be rare within in the LLN is the best practices one 6BBR. It results that a 6LBR MUST be capable to maintain a state
([RFC7772]) are followed. for each of the 6BBR having registered with a same TID and same ROVR.
The Registering Node SHOULD comply with the Simple Procedures for If this registration is duplicate or not the freshest, then the 6LBR
Detecting Network Attachment in IPv6 [RFC6059] (DNA procedures) to replies with an EDAC message with a status code of 1 ("Duplicate
assert movements, and support Packet-Loss Resiliency for Router Address") or 3 ("Moved"), respectively. If this registration is the
Solicitations [RFC7559] in order to make the unicast RS messages more freshest, then the 6LBR replies with a status code of 0. In that
reliable. case, if this registration is fresher than an existing registration
for another 6BBR, then the 6LBR also sends an asynchronous EDAC with
a status of 4 ("Removed") to that other 6BBR.
The Registering Node signals that it requires IPv6 proxy-ND services The EDAC message SHOULD carry the SLLAO used in NS messages by the
from a 6BBR by registering the corresponding IPv6 Address with an 6BBR for that Binding, and the EDAR message SHOULD carry the TLLAO
NS(EARO) message with the 'R' flag set ([RFC8505]). It may be the associated with the currently accepted registration. This enables a
actual owner of the IPv6 Address or a 6LBR that performs the 6BBR to locate the new position of a mobile 6LN in the case of a
registration on its behalf in a Route-Over mesh. Routing Proxy operation, and opens the capability for the 6LBR to
serve as a mapping server in the future.
The Registering Node SHOULD register all of its Global Unicast and Note that if Link Local addresses are registered, then the scope of
Unique-Local IPv6 Addresses to the 6BBRs. Failure to register a uniqueness on which the address duplication is checked is the total
subset of Addresses may result in those Addresses being unreachable collection of links that the 6LBR serves as opposed to the sole link
by other parties if the 6BBR cancels the NS(LOOKUP) over the LLN or on which the Link Local address is assigned.
to selected LLN nodes that are known to register their addresses.
3.5. 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 that On the Backbone side, the 6BBR MUST join the SNMA group corresponding
corresponds to a Registered Address as soon as it creates an entry to a Registered Address as soon as it creates a Binding for that
for that Address, and conserve its SNMA membership as long as it Address, and maintain that SNMA membership as long as it maintains
maintains the associated entry. The 6BBR uses either the SNMA or the registration.
plain unicast to defend the Registered Addresses in its Binding
Table over the Backbone. The 6BBR uses either the SNMA or plain unicast to defend the
Registered Addresses in its Binding Table over the Backbone (as
specified in [RFC4862]).
The 6BBR advertises and defends the Registered Addresses over the The 6BBR advertises and defends the Registered Addresses over the
Backbone using the IPv6 ND protocol [RFC4861]. It MUST uses an EARO Backbone Link using RS, NS(DAD) and NA messages with the Registered
in the NS(DAD) and NA messages that it generates over the Backbone Address as the Source or Target address, respectively.
Link for the Registered Address. A NA message generated in response
to a NS(LOOKUP) MUST NOT have the override (O) bit set. A proxied NS
MUST NOT contain an SLLAO to avoid the confusion with a registration.
A 6BBR may asynchronously update the NCEs in correspondent nodes over The 6BBR MUST place an EARO in the IPv6 ND messages that it generates
the Backbone, e.g., in case of a movement. This is achieved using a on behalf of the Registered Node. Note that an NS(DAD) does not
gratuitous NA with the override (O) bit set, that may be sent unicast contain an SLLAO and cannot be confused with a proxy registration
to each individual correspondent, or multicast to all nodes (more in such as performed by a 6LBR.
Section 3.7 and Section 3.6).
A 6LBR may optionally be deployed over the Backbone. When that is An NA message generated in response to an NS(DAD) MUST have the
the case, the 6BBR uses an EDAR/EDAC echange to check for duplication Override flag set and a status of 1 (Duplicate) or 3 (Moved) in the
or movement as prescribed in [RFC8505]. If this registration is EARO. An NA message generated in response to an NS(Lookup) or an
duplicate or not the freshest, then the 6LBR replies with a status NS(NUD) MUST NOT have the Override flag set.
code of 1 ("Duplicate Address") or 3 ("Moved"), respectively. If
this registration is the freshest, then the 6LBR replies with a
status code of 0; in that case, if there was an existing registration
on an old 6BBR, then the 6LBR also sends an asynchronous EDAC with a
status of 4 ("Removed") to the old 6BBR. Note that an alternate
protocol such as LISP [RFC6830] may be used to provide an equivalent
service.
Nodes implementing this specification is expected to co-exist on a This specification enables proxy operation for the IPv6 ND resolution
same Backbone Link with nodes implementing classical IPv6 ND of LLN devices and a prefix that is used across a MultiLink Subnet
[RFC4861] and snooping [I-D.bi-savi-wlan]. It results that the fact MAY be advertised as on-link over the Backbone. This is done for
that there is a 6LBR or an alternate protocol that is deployed on the backward compatibility with existing IPv6 hosts by setting the L flag
Backbone does not mean that all IPv6 addresses are known there; the in the Prefix Information Option (PIO) of RA messages [RFC4861].
fact that a unicast DAD succeeds with the 6LBR does not mean that the
address is not duplicate, and, unless administratively overridden,
6BBRs must still perform classical IPv6 ND DAD after an EDAC with a
status code of 0.
For slow movements, the Neighbor Unreachability Detection (NUD) For movement involving a slow reattachment, the Neighbor
procedure defined in [RFC4861] may time out too quickly, and the Unreachability Detection (NUD) defined in [RFC4861] may time out too
support of [RFC7048] is recommended for all nodes in the subnet. quickly. Nodes on the backbone SHOULD support [RFC7048] whenever
possible.
3.6. Routing Proxy Operations 7. Routing Proxy Operations
When operating as a Routing Proxy, the 6BBR MUST use the Layer-2 A Routing Proxy provides IPv6 ND proxy functions for Global and
Address on its Backbone Interface in the TLLA and SLLA options, when Unique Local addresses between the LLN and the backbone, but not for
present, of the RS, NS and NA messages that it generates to advertise Link-Local addresses. It operates as an IPv6 border router and
the Registered Addresses. In that case, the MAC Addresses of the provides a full Link-Layer isolation.
6LNs do not need to be visible at Layer-2 over the Backbone to
maintain end-to-end IP connectivity, but the NCEs of the
correspondents must be updated when the owner registers to a
different 6BBR.
This technique is useful when the churn on the Backbone fabric In this mode, it is not required that the MAC addresses of the 6LNs
associated to wireless mobility becomes expensive, e.g., when the are visible at Layer-2 over the Backbone. It is thus useful when the
Layer-2 topology is virtualized over a wide area IP underlay. In messaging over the Backbone that is associated to wireless mobility
order to maintain IP connectivity, the 6BBR installs a connected host becomes expensive, e.g., when the Layer-2 topology is virtualized
route to the Registered Address on the LLN interface, via the over a wide area IP underlay.
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.
EUI-48). Since a 6LN may not be able to resolve an arbitrary
destination in the MLSN directly, the MLSN prefix 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
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.
This technique is also useful when the LLN uses a MAC address format When operating as a Routing Proxy, the 6BBR MUST use its Layer-2
that is different from that on the Backbone (e.g., EUI-64 vs. EUI- Address on its Backbone Interface in the SLLAO of the RS messages and
48). the TLLAO of the NA messages that it generates to advertise the
Registered Addresses.
For each Registered Address, multiple peer Nodes on the Backbone may For each Registered Address, multiple peers on the Backbone may have
have resolved the Address with the 6BBR MAC Address, maintaining that resolved the Address with the 6BBR MAC Address, maintaining that
mapping in their Neighbor cache. The 6BBR SHOULD maintain a list of mapping in their Neighbor Cache. The 6BBR SHOULD maintain a list of
the peers on the Backbone which have associated its MAC Address with the peers on the Backbone which have associated its MAC Address with
the Registered Address. If that Registered Address moves from an old the Registered Address. If that Registered Address moves to a new
to a new 6BBR, the old 6BBR SHOULD unicast a gratuitous NA with the 6BBR, the previous 6BBR SHOULD unicast a gratuitous NA with the
Override (O) bit set to each such peer, to supply the LLA of the new Override flag set to each such peer, to supply the LLA of the new
6BBR in the TLLA option for the Address. 6BBR in the TLLA option for the Address. A 6BBR that does not
maintain this list MAY multicast a gratuitous NA with the Override
If the 6BBR fails to maintain this list, then it MAY send the flag; this NA will possibly hit all the nodes on the Backbone,
gratuitous NA with the Override (O) bit set as a multicast message whether or not they maintain an NCE for the Registered Address.
that will possibly hit all the nodes on the Backbone, whether they
maintain an NCE or not for the Registered Address.
If a correspondent fails to receive the gratuitous NA, it will keep If a correspondent fails to receive the gratuitous NA, it will keep
sending traffic to a 6BBR to which the node was previously sending traffic to a 6BBR to which the node was previously
registered. That old 6BBR having removed its host route to the registered. Since the previous 6BBR removed its Host route to the
Registered Address, it will look it up over the backbone, resolve the Registered Address, it will look up the address over the backbone,
with the LLA of the new 6BBR, and forward the packet to the correct resolve the address with the LLA of the new 6BBR, and forward the
6BBR. The old 6BBR SHOULD also issue a redirect message [RFC4861] is packet to the correct 6BBR. The previous 6BBR SHOULD also issue a
order to update the cache of the correspondent. redirect message [RFC4861] to update the cache of the correspondent.
3.7. Bridging Proxy Operations 8. Bridging Proxy Operations
A Bridging Proxy can be implemented in a Layer-3 switch, or in a A Bridging Proxy provides IPv6 ND proxy functions between the LLN and
wireless Access Point or wireless Controller that acts as a Layer-2 the backbone while preserving the forwarding continuity at the MAC
Bridge for unicast packets from/to the Registered Address. The Layer. It acts as a Layer-2 Bridge for all types unicast packets
Bridging Proxy appears as an IPv6 Host on the Backbone whereas the including link-scoped, and appears as an IPv6 Host on the Backbone.
Routing Proxy described in Section 3.6 is an IPv6 router operating as
a border router between Links of a MultiLink Subnet.
When operating as a Bridging Proxy, the 6BBR MUST use the Registering The Bridging Proxy registers any Binding including for a Link-Local
Node's Layer-2 Address in the TLLA and SLLA options, when present, address to the 6LBR (if present) and defends it over the backbone in
of, respectively, the RS, NS and NA messages that it generates to IPv6 ND procedures.
advertise the Registered Addresses. The Registering Node's Layer-2
address is found in the SLLA of the registration NS(EARO), and
maintained in the abstract Binding Table.
If the Registering Node is the owner of the Registered Address, then To achieve this, the Bridging Proxy intercepts the IPv6 ND messages
its mobility does not impact existing NCEs over the Backbone. If it and may reinject them on the other side, respond directly or drop
is not, then when the 6LN selects another Registering Node, the new them. For instance, an ND(Lookup) from the backbone that matches a
Registering Node SHOULD send a multicast NA with the Override (O) bit Binding can be responded directly, or turned into a unicast on the
set to fix the existing NCEs across the Backbone. This method may LLN side to let the 6LN respond.
fail if the multicast message is not received, in which case one or
more correspondent nodes on the Backbone may maintain an obsolete NCE
and traffic to the Registered Address may be lost for a while. When
this condition happens, it is eventually be discovered and solved
through the Neighbor Unreachability Detection (NUD) procedure defined
in [RFC4861].
3.8. Leveraging Optimistic DAD 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
messages that it generates to advertise the Registered Addresses.
The Registering Node's Layer-2 address is found in the SLLA of the
registration NS(EARO), and maintained in the Binding Table.
The Optimistic Duplicate Address Detection [RFC4429] (ODAD) The MultiLink Subnet prefix SHOULD NOT be advertised as on-link in RA
specification details how an IPv6 Address can be used before a messages sent towards the LLN. If a destination address is seen as
Duplicate Address Detection (DAD) is complete. 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
NS(Lookup) message or reinject the message on the backbone, either as
a Layer-2 unicast or a multicast.
ODAD provides a set of rules that guarantee that this behavior may If the Registering Node owns the Registered Address, then its
not harm an existing state should the new Address effectively be a mobility does not impact existing NCEs over the Backbone. Otherwise,
duplicate. This specification leverages ODAD to avoid delays in when the 6LN selects another Registering Node, the new Registering
installing the Neighbor Cache Entry (NCE) in the 6BBRs and the Node SHOULD send a multicast NA with the Override flag set to fix the
default router in order to obtain immediate connectivity to the existing NCEs across the Backbone. This method can fail if the
registered node. multicast message is not received; one or more correspondent nodes on
the Backbone might maintain an stale NCE, and packets to the
Registered Address may be lost. When this condition happens, it is
eventually be discovered and resolved using Neighbor Unreachability
Detection (NUD) as defined in [RFC4861].
This specification RECOMMENDS to support ODAD to create an optimistic 9. Creating and Maintaining a Binding
proxy state in the 6BBR until DAD is completed over the Backbone. As
shown in Figure 2, if the 6BBR is aware of the Link-Layer Address
(LLA) of a router, then the 6BBR sends a Router Sollicitation (RS),
sourced with the Registered Address, to the known router(s). The RS
MUST be sent without a Source LLA Option (SLLAO), to ensure that a
preexisting NCE in the router is not affected.
Following the ODAD flows, the router may then send a unicast RA to Upon receiving a registration for a new Address (i.e., an NS(EARO)
the Registered Address, and in the process of doing so, it may with the R flag set), the 6BBR creates a Binding and operates as a
resolve it using an NS(LOOKUP) message. In response, the 6BBR sends 6LR according to [RFC8505], interacting with the 6LBR if one is
a NA with the override (O) bit that is not set (per [RFC4429]), and present.
an EARO option. If the router supports this specification, then it
can determine the freshest EARO option in case of a conflicting
NA(EARO) messages, using section 5.2.1 of [RFC8505]. If the NA(EARO)
is the freshest or only answer then the default router creates a BCE
with the SLLAO of the 6BBR (in Routing Proxy mode) or that of the
Registering Node (in Bridging Proxy mode) and traffic from/to the
Registered Address can flow immediately.
4. Updating RFC 4861 An implementation of a Routing Proxy that creates a Binding MUST also
create an associated Host route pointing on the registering node in
the LLN interface from which the registration was received.
This specification adds the EARO as a possible option in RS, NS(DAD) The 6LR operation is modified as follows:
and NA messages over the backbone. Note that [RFC8505] requires that
the registration NS(EARO) contains an SLLAO. Note that an NS(DAD)
does not contain an SLLAO and thus cannot be confused with a
registration.
5. Updating RFC 8505 o EDAR and EDAC messages SHOULD carry a SLLAO and a TLLAO,
respectively.
This specification adds the capability to insert IPv6 ND options in o A Bridging Proxy MAY register Link Local addresses to the 6BBR and
the EDAR and EDAC messages. In particular, a 6BBR acting as a 6LR proxy ND for those addresses over the backbone.
for the Registered Address can insert an SLLAO in the EDAR to the
6LBR in order to avoid a lookup back.
6. 6BBR detailed Operations 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
the address against duplication.
By default, a 6BBR operates as a Sleeping Proxy, as follows: This specification enables nodes on a Backbone Link to co-exist along
with nodes implementing IPv6 ND [RFC4861] as well as other non-
normative specifications such as [I-D.bi-savi-wlan]. It is possible
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
even for a duplicate address. Consequently, and unless
administratively overridden, the 6BBR still needs to perform IPv6 ND
DAD over the backbone after an EDAC with a status code of 0 or 9.
o Create a new entry in a Binding Table for a new Registered Address For the DAD operation, the Binding is placed in Tentative state for a
and ensure that the Address is not a duplicate over the Backbone duration of TENTATIVE_DURATION, and an NS(DAD) message is sent as a
multicast message over the Backbone to the SNMA associated with the
registered Address [RFC4862]. The EARO from the registration MUST be
placed unchanged in the NS(DAD) message.
o Defend a Registered Address over the Backbone using NA messages If a registration is received for an existing Binding with a non-null
with the Override bit set on behalf of the sleeping 6LN Registration Lifetime and the registration is fresher (same ROVR,
fresher TID), then the Binding is updated, with the new Registration
Lifetime, TID, and possibly Registering Node. In Tentative state
(see Section 9.1), the current DAD operation continues as it was. In
other states (see Section 9.2 and Section 9.3 ), the Binding is
placed in Reachable state for the Registration Lifetime, and the 6BBR
returns an NA(EARO) to the Registering Node with a status of 0
(Success).
o Advertise a Registered Address over the Backbone using NA Upon a registration that is identical (same ROVR, TID, and
messages, asynchronously or as a response to a Neighbor Registering Node), the 6BBR returns an NA(EARO) back to the
Solicitation messages. Registering Node with a status of 0 (Success). A registration that
is not as fresh (same ROVR, older TID) is ignored.
o To deliver packets arriving from the LLN, use Neighbor If a registration is received for an existing Binding and a
Solicitation messages to look up the destination over the registration Lifetime of zero, then the Binding is removed, and the
Backbone. 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
binding MUST remove the associated Host route pointing on the
registering node. It MAY preserve a temporary state in order to
forward packets in flight. The state may be a NCE formed based on a
received NA message, or a Binding in Stale state and pointing at the
new 6BBR on the backbone.
o Forward packets between the LLN and the Backbone. The implementation should also use REDIRECT messages as specified in
[RFC4861] to update the correspondents for the Registered Address,
pointing the new 6BBR.
o Verify liveliness when needed for a stale registration. 9.1. Operation on a Binding in Tentative State
A 6BBR may act as a Sleeping Proxy only for a Registered Address that The Tentative state covers a DAD period over the backbone during
is REACHABLE, or TENTATIVE in which case the answer is delayed. In which an address being registered is checked for duplication using
any other state, the Sleeping Proxy operates as a Unicasting Proxy. procedures defined in [RFC4862].
The 6BBR does not act on ND Messages over the Backbone unless they For a Binding in Tentative state:
are relevant to a Registered Node on the LLN side, saving wireless
interference. On the LLN side, the prefixes associated to the
MultiLink Subnet are presented as not on-link, so Address resolution
for other hosts do not occur.
As a Unicasting Proxy, the 6BBR forwards NS lookup messages to the o The Binding MUST be removed if an NA message is received over the
Registering Node, transforming Layer-2 multicast into unicast. This Backbone for the Registered Address with no EARO, or containing an
is not possible in UNREACHABLE state, so the NS messages are EARO with a status of 1 (Duplicate) that indicates an existing
multicasted, and rate-limited. Retries are possible, using an registration owned by a different Registering Node. In that case,
exponential back-off to protect the medium. In other states, the an NA MUST be sent back to the Registering Node with a status of 1
messages are forwarded to the Registering Node as unicast Layer-2 (Duplicate) in the EARO. This behavior might be overriden by
messages. In TENTATIVE state, the NS message is either held till DAD policy, in particular if the registration is trusted, e.g., based
completes, or dropped if DAD does not complete. on the validation of the ROVR field (see [I-D.ietf-6lo-ap-nd]).
6.1. Primary and Secondary 6BBRs 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
message containing an EARO with a status of 1 (Duplicate) and the
Override flag not set. This behavior might be overriden by
policy, in particular if the registration is not trusted.
A 6BBR MAY be primary or secondary. The primary is the Backbone o The Binding MUST be removed if an NA message is received over the
router that has the highest EUI-64 Address of all the 6BBRs that Backbone for the Registered Address containing an EARO with a
share a registration for a same Registered Address, with the same status of 3 (Moved), or an NS(DAD) with an EARO that indicates a
ROVR and same Transaction ID, the EUI-64 Address being considered as fresher registration ([RFC8505]) for the same Registered Node
an unsigned 64bit integer. A given 6BBR can be primary for a given (i.e. same ROVR). A status of 3 is returned in the NA(EARO) back
Address and secondary for another Address, regardless of whether or to the Registering Node.
not the Addresses belong to the same 6LN. The primary Backbone
Router is in charge of protecting the Address for DAD over the
Backbone. Any of the Primary and Secondary 6BBR may claim the
Address over the Backbone, since they are all capable to route from
the Backbone to the 6LN; the Address appears on the Backbone as an
anycast Address.
6.2. Binding Table o NS(DAD) and NA messages containing an EARO that indicates a
registration for the same Registered Node that is not as fresh as
this SHOULD be answered with an NA message containing an EARO with
a status of 3 (Moved) in order to clean up the situation
immediately.
Each 6BBR maintains a Binding Table, using IPv6 ND over the Backbone o Other NS(DAD) and NA messages from the Backbone are ignored.
to detect duplication. Another document [RFC8505] provides details
about how the EARO is used between 6LRs and 6LBRs by way of DAR/DAC
messages within the LLN. Addresses in a LLN that can be reachable
from the Backbone by way of a 6BBR MUST be registered to that 6BBR.
A false positive duplicate detection may arise over the Backbone, for o NS(Lookup) and NS(NUD) messages SHOULD be optimistically answered
instance if a 6LN's Registered Address is registered to more than one with an NA message containing an EARO with a status of 0 and the
LBR, or if the 6LN has moved. Both situations are handled by the Override flag not set (see Section 3.6). If optimistic DAD is
6BBR transparently to the 6LN. In the former case, one LBR becomes disabled, then they SHOULD be queued to be answered when the
primary to defend the Address over the Backbone while the others Binding goes to Reachable state.
become secondary and may still forward packets. In the latter case
the LBR that receives the newest registration becomes primary because
of the TID.
Only one 6LN may register a given Address at a particular 6BBR. When the TENTATIVE_DURATION timer elapses, the Binding is placed in
However, that Registered Address may be registered to Multiple 6BBRs Reachable state for the Registration Lifetime, and the 6BBR returns
for higher availability. an NA(EARO) to the Registering Node with a status of 0 (Success).
Over the LLN, Binding Table management is as follows: 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
sending an NA message with an EARO and the Override flag set over the
backbone (see Section 7 and Section 8).
De-registrations (newer TID, same ROVR, null Lifetime) are 9.2. Operation on a Binding in Reachable State
accepted and acknowledged with a status of 4 (TBD); the entry is
deleted;
Newer registrations (newer TID, same ROVR, non-null Lifetime) are The Reachable state covers an active registration after a successful
acknowledged with a status of 0 (success); the binding is updated DAD process.
with the new TID, the Registration Lifetime and the Registering
Node; in TENTATIVE state the acknowledgement is held and may be
overwritten; in other states the Registration-Lifetime timer is
restarted and the entry is placed in REACHABLE state.
Identical registrations (same TID, same ROVR) from a same An NS(DAD) with no EARO or with an EARO that indicates a duplicate If
Registering Node are acknowledged with a status of 0 (success). the Registration Lifetime is of a long duration, an implementation
If they are not identical, an error SHOULD be logged. In might be configured to reassess the availability of the Registering
TENTATIVE state, the response is held and may be overwritten, but Node at a lower period, using a NUD procedure as specified in
it MUST be eventually produced and it carries the result of the [RFC7048]. If the NUD procedure fails, the Binding SHOULD be placed
DAD process; in Stale state immediately.
Older registrations (older TID, same ROVR) from a Registering Node For a Binding in Reachable state:
are ignored;
Identical and older registrations (not-newer TID, same ROVR) from o The Binding MUST be removed if an NA or an NS(DAD) message is
a different Registering Node are acknowledged with a status of 3 received over the Backbone for the Registered Address containing
(moved); this may be rate limited to protect the medium; an EARO that indicates a fresher registration ([RFC8505]) for the
same Registered Node (i.e. same ROVR). A status of 4 (Removed) is
returned in an asynchronous NA(EARO) to the Registering Node.
Based on configuration, an implementation may delay this operation
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.
Any registration for a different Registered Node (different ROVR) o An NS(DAD) with no EARO or with an EARO that indicates a duplicate
are acknowledged with a status of 1 (duplicate). registration (i.e. different ROVR) MUST be answered with an NA
message containing an EARO with a status of 1 (Duplicate) and the
Override flag not set.
6.3. Registration and Binding Table Entry Creation o NS(DAD) and NA messages containing an EARO that indicates a
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
status of 3 (Moved).
Upon receiving a registration for a new Address with an NS(EARO) with o Other NS(DAD) and NA messages from the Backbone are ignored.
the 'R' bit set, the 6BBR performs DAD over the Backbone, placing the
new Address as target in the NS(DAD) message. The EARO from the
registration MUST be placed unchanged in the NS(DAD) message, and an
Neighbor Cache entry created in TENTATIVE state for a duration of
TENTATIVE_DURATION. The NS(DAD) message is sent multicast over the
Backbone to the SNMA associated with the registered Address, unless
that operation is known to be costly, and the 6BBR has an indication
from another source (such as a Neighbor Cache entry) that the
Registered Address was known on the Backbone; in the latter case, an
NS(DAD) message may be sent as a Layer-2 unicast to the MAC Address
that was associated with the Registered Address.
In TENTATIVE state after EARO with 'R' bit set: 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
flag not set. The 6BBR MAY check whether the Registering Node is
still available using a NUD procedure over the LLN prior to
answering; this behaviour depends on the use case and is subject
to configuration.
1. The entry is removed if an NA is received over the Backbone for When the Registration Lifetime timer elapses, the Binding is placed
the Registered Address with no EARO, or containing an EARO with a in Stale state for a duration of STALE_DURATION.
status of 1 (duplicate) that indicates an existing registration
for another 6LN. The ROVR and TID fields in the EARO received
over the Backbone are ignored. A status of 1 is returned in the
EARO of the NA back to the Registering Node;
2. The entry is also removed if an NA with an ARO option with a 9.3. Operation on a Binding in Stale State
status of 3 (moved), or a NS with an ARO option that indicates a
newer registration for the same Registered Node, is received over
the Backbone for the Registered Address. A status of 3 is
returned in the NA(EARO) back to the Registering Node;
3. When a registration is updated but not deleted, e.g. from a newer The Stale state enables tracking of the Backbone peers that have a
registration, the DAD process on the Backbone continues and the NCE pointing to this 6BBR in case the Registered Address shows up
running timers are not restarted; later.
4. Other NS (including DAD with no EARO) and NA from the Backbone If the Registered Address is claimed by another 6LN on the Backbone,
are not acknowledged in TENTATIVE state. To cover legacy 6LNs with an NS(DAD) or an NA, the 6BBR does not defend the Address.
that do not support ODAD, the list of their origins MAY be stored
and then, if the TENTATIVE_DURATION timer elapses, the 6BBR MAY
send each such legacy 6LN a unicast NA.
5. When the TENTATIVE_DURATION timer elapses, a status 0 (success) For a Binding in Stale state:
is returned in a NA(EARO) back to the Registering Node(s), and
the entry goes to REACHABLE state for the Registration Lifetime.
The 6BBR MUST send a multicast NA(EARO) to the SNMA associated to
the Registered Address over the Backbone with the Override bit
set so as to take over the binding from other 6BBRs.
6.4. Defending Addresses o The Binding MUST be removed if an NA or an NS(DAD) message is
received over the Backbone for the Registered Address containing
no EARO or an EARO that indicates either a fresher registration
for the same Registered Node or a duplicate registration. A
status of 4 (Removed) MAY be returned in an asynchronous NA(EARO)
to the Registering Node.
If a 6BBR has an entry in REACHABLE state for a Registered Address: o NS(DAD) and NA messages containing an EARO that indicates a
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
status of 3 (Moved).
o If the 6BBR is primary, or does not support the function of o If the 6BBR receives an NS(Lookup) or an NS(NUD) message for the
primary, it MUST defend that Address over the Backbone upon Registered Address, the 6BBR MUST attempts a NUD procedure as
receiving NS, either if the NS does not carry an EARO, or if an specified in [RFC7048] to the Registering Node, targeting the
EARO is present that indicates a different Registering Node Registered Address, prior to answering. If the NUD procedure
(different ROVR). The 6BBR sends a NA message with the Override succeeds, the operation in Reachable state applies. If the NUD
bit set and the NA carries an EARO if and only if the NS(DAD) did fails, the 6BBR refrains from answering.
so. When present, the EARO in the NA(Override) that is sent in
response to the NS(EARO) carries a status of 1 (duplicate), and
the ROVR and TID fields in the EARO are obfuscated with null or
random values to avoid network scanning and impersonation attacks.
o If the 6BBR receives an NS(EARO) for a newer registration, the o Other NS(DAD) and NA messages from the Backbone are ignored.
6BBR updates the entry and the routing state to forward packets to
the new 6BBR, but keeps the entry REACHABLE. Afterwards, the 6BBR
MAY use REDIRECT messages to reroute traffic for the Registered
Address to the new 6BBR.
o If the 6BBR receives an NA(EARO) for a newer registration, the When the STALE_DURATION timer elapses, the Binding MUST be removed.
6BBR removes its entry and sends a NA(EARO) with a status of 3
(MOVED) to the Registering Node, if the Registering Node is
different from the Registered Node. The 6BBR cleans up existing
Neighbor Cache entries in peer nodes as discussed in Section 3.5,
by unicasting to each such peer, or one broadcast NA(Override).
o If the 6BBR receives a NS(LOOKUP) for a Registered Address, it 10. Registering Node Considerations
answers immediately with an NA on behalf of the Registered Node,
without polling it. There is no need of an EARO in that exchange.
o When the Registration-Lifetime timer elapses, the entry goes to A Registering Node MUST implement [RFC8505] in order to interact with
STALE state for a duration of STABLE_STALE_DURATION in LLNs that a 6BBR (which acts as a routing registrar). Following [RFC8505], the
keep stable Addresses such as LWPANs, and UNSTABLE_STALE_DURATION Registering Node signals that it requires IPv6 proxy-ND services from
in LLNs where Addresses are renewed rapidly, e.g. for privacy a 6BBR by registering the corresponding IPv6 Address using an
reasons. NS(EARO) message with the R flag set.
The STALE state enables tracking of the Backbone peers that have a The Registering Node may be the 6LN owning the IPv6 Address, or a
Neighbor Cache entry pointing to this 6BBR in case the Registered 6LBR that performs the registration on its behalf in a Route-Over
Address shows up later. If the Registered Address is claimed by mesh.
another 6LN on the Backbone, with an NS(DAD) or an NA, the 6BBR does
not defend the Address. In STALE state:
o If STALE_DURATION elapses, the 6BBR removes the entry. The Registering Node SHOULD register all of its IPv6 Addresses to its
6LR, which is the 6BBR when they are connected at Layer-2. Failure
to register an address may result in the address being unreachable by
other parties if the 6BBR cancels the NS(Lookup) over the LLN or to
selected LLN nodes that are known to register their addresses.
o Upon receiving an NA(Override) the 6BBR removes its entry and The Registering Node MUST refrain from using multicast NS(Lookup)
sends a NA(EARO) with a status of 4 (removed) to the Registering when the destination is not known as on-link, e.g., if the prefix is
Node. 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.
o If the 6BBR receives a NS(LOOKUP) for a Registered Address, the The Registering Node SHOULD also follow [RFC7772] in order to limit
6BBR MUST send an NS(NUD) following rules in [RFC7048] to the the use of multicast RAs. It SHOULD also implement Simple Procedures
Registering Node targeting the Registered Address prior to for Detecting Network Attachment in IPv6 [RFC6059] (DNA procedures)
answering. If the NUD succeeds, the operation in REACHABLE state to detect movements, and support Packet-Loss Resiliency for Router
applies. If the NUD fails, the 6BBR refrains from answering the Solicitations [RFC7559] in order to improve reliability for the
lookup. The NUD SHOULD be used by the Registering Node to unicast RS messages.
indicate liveness of the Registered Node, if they are different
nodes.
7. Security Considerations 11. Security Considerations
This specification applies to LLNS in which the link layer is This specification applies to LLNs in which the link layer is
protected, either by means of physical or IP security for the protected, either by means of physical or IP security for the
Backbone Link or MAC sublayer cryptography. In particular, the LLN Backbone Link or MAC-layer security. In particular, the LLN MAC is
MAC is required to provide secure unicast to/from the Backbone Router required to provide secure unicast to/from the Backbone Router and
and secure Broadcast from the Backbone Router in a way that prevents secure Broadcast from the Backbone Router in a way that prevents
tampering with or replaying the RA messages. tampering with or replaying the RA messages.
The use of EUI-64 for forming the Interface ID in the link local A possible attack over the backbone can be done by sending an NS with
Address prevents the usage of Secure ND ([RFC3971] and [RFC3972]) and an EARO and expecting the NA(EARO) back to contain the TID and ROVR
Address privacy techniques. Additional protection against Address fields of the existing state. With that information, the attacker
theft is provided by [I-D.ietf-6lo-ap-nd], which guarantees the can easily increase the TID and take over the Binding.
ownership of the ROVR. [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
When the ownership of the ROVR cannot be assessed, this specification against address theft and impersonation.
limits the cases where the ROVR and the TID are multicasted, and
obfuscates them in responses to attempts to take over an Address.
8. 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
STABLE_STALE_DURATION: 24 hours
UNSTABLE_STALE_DURATION: 5 minutes STALE_DURATION: see below
DEFAULT_NS_POLLING: 3 times In LLNs with long-lived Addresses such as LPWANs, STALE_DURATION
SHOULD be configured with a relatively long value, by default 24
hours. In LLNs where addresses are renewed rapidly, e.g. for privacy
reasons, STALE_DURATION SHOULD be configured with a relatively long
value, by default 5 minutes.
9. IANA Considerations 13. IANA Considerations
This document has no request to IANA. This document has no request to IANA.
10. Future Work 14. Acknowledgments
Future documents may extend this specification by allowing the 6BBR
to redistribute host routes in routing protocols that would operate
over the Backbone, or in MIPv6, or FMIP, or the Locator/ID Separation
Protocol (LISP) [RFC6830] to support mobility on behalf of the 6LNs,
etc...
11. 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.
12. References 15. References
12.1. Normative References 15.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>. 2006, <https://www.rfc-editor.org/info/rfc4291>.
skipping to change at page 21, line 50 skipping to change at page 24, line 11
Low-Power and Lossy Networks", RFC 6550, Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012, DOI 10.17487/RFC6550, March 2012,
<https://www.rfc-editor.org/info/rfc6550>. <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
Detection Is Too Impatient", RFC 7048,
DOI 10.17487/RFC7048, January 2014,
<https://www.rfc-editor.org/info/rfc7048>.
[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.,
"Path MTU Discovery for IP version 6", STD 87, RFC 8201, "Path MTU Discovery for IP version 6", STD 87, RFC 8201,
DOI 10.17487/RFC8201, July 2017, DOI 10.17487/RFC8201, July 2017,
<https://www.rfc-editor.org/info/rfc8201>. <https://www.rfc-editor.org/info/rfc8201>.
[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>.
12.2. 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-16 (work in progress), November WLAN", draft-bi-savi-wlan-16 (work in progress), November
2018. 2018.
[I-D.ietf-6lo-ap-nd] [I-D.ietf-6lo-ap-nd]
Thubert, P., Sarikaya, B., Sethi, M., and R. Struik, Thubert, P., Sethi, M., Struik, R., and B. Sarikaya,
"Address Protected Neighbor Discovery for Low-power and "Address Protected Neighbor Discovery for Low-power and
Lossy Networks", draft-ietf-6lo-ap-nd-08 (work in Lossy Networks", draft-ietf-6lo-ap-nd-09 (work in
progress), October 2018. progress), December 2018.
[I-D.ietf-6man-rs-refresh] [I-D.ietf-6man-rs-refresh]
Nordmark, E., Yourtchenko, A., and S. Krishnan, "IPv6 Nordmark, E., Yourtchenko, A., and S. Krishnan, "IPv6
Neighbor Discovery Optional RS/RA Refresh", draft-ietf- Neighbor Discovery Optional RS/RA Refresh", draft-ietf-
6man-rs-refresh-02 (work in progress), October 2016. 6man-rs-refresh-02 (work in progress), October 2016.
[I-D.ietf-6tisch-architecture] [I-D.ietf-6tisch-architecture]
Thubert, P., "An Architecture for IPv6 over the TSCH mode Thubert, P., "An Architecture for IPv6 over the TSCH mode
of IEEE 802.15.4", draft-ietf-6tisch-architecture-17 (work of IEEE 802.15.4", draft-ietf-6tisch-architecture-19 (work
in progress), November 2018. in progress), December 2018.
[I-D.ietf-mboned-ieee802-mcast-problems] [I-D.ietf-mboned-ieee802-mcast-problems]
Perkins, C., McBride, M., Stanley, D., Kumari, W., and J. Perkins, C., McBride, M., Stanley, D., Kumari, W., and J.
Zuniga, "Multicast Considerations over IEEE 802 Wireless Zuniga, "Multicast Considerations over IEEE 802 Wireless
Media", draft-ietf-mboned-ieee802-mcast-problems-04 (work Media", draft-ietf-mboned-ieee802-mcast-problems-04 (work
in progress), November 2018. in progress), November 2018.
[I-D.nordmark-6man-dad-approaches] [I-D.nordmark-6man-dad-approaches]
Nordmark, E., "Possible approaches to make DAD more robust Nordmark, E., "Possible approaches to make DAD more robust
and/or efficient", draft-nordmark-6man-dad-approaches-02 and/or efficient", draft-nordmark-6man-dad-approaches-02
(work in progress), October 2015. (work in progress), October 2015.
[I-D.yourtchenko-6man-dad-issues] [I-D.yourtchenko-6man-dad-issues]
Yourtchenko, A. and E. Nordmark, "A survey of issues Yourtchenko, A. and E. Nordmark, "A survey of issues
related to IPv6 Duplicate Address Detection", draft- related to IPv6 Duplicate Address Detection", draft-
yourtchenko-6man-dad-issues-01 (work in progress), March yourtchenko-6man-dad-issues-01 (work in progress), March
2015. 2015.
[RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, [IEEEstd8021]
"SEcure Neighbor Discovery (SEND)", RFC 3971, IEEE standard for Information Technology, "IEEE Standard
DOI 10.17487/RFC3971, March 2005, for Information technology -- Telecommunications and
<https://www.rfc-editor.org/info/rfc3971>. information exchange between systems Local and
metropolitan area networks Part 1: Bridging and
Architecture".
[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", [IEEEstd80211]
RFC 3972, DOI 10.17487/RFC3972, March 2005, IEEE standard for Information Technology, "IEEE Standard
<https://www.rfc-editor.org/info/rfc3972>. for Information technology -- Telecommunications and
information exchange between systems Local and
metropolitan area networks-- Specific requirements Part
11: Wireless LAN Medium Access Control (MAC) and Physical
Layer (PHY) Specifications".
[IEEEstd802151]
IEEE standard for Information Technology, "IEEE Standard
for Information Technology - Telecommunications and
Information Exchange Between Systems - Local and
Metropolitan Area Networks - Specific Requirements. - Part
15.1: Wireless Medium Access Control (MAC) and Physical
Layer (PHY) Specifications for Wireless Personal Area
Networks (WPANs)".
[IEEEstd802154]
IEEE standard for Information Technology, "IEEE Standard
for Local and metropolitan area networks -- Part 15.4:
Low-Rate Wireless Personal Area Networks (LR-WPANs)".
[RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery
Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April
2006, <https://www.rfc-editor.org/info/rfc4389>. 2006, <https://www.rfc-editor.org/info/rfc4389>.
[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>.
[RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6
over Low-Power Wireless Personal Area Networks (6LoWPANs):
Overview, Assumptions, Problem Statement, and Goals",
RFC 4919, DOI 10.17487/RFC4919, August 2007,
<https://www.rfc-editor.org/info/rfc4919>.
[RFC5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley, [RFC5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley,
Ed., "Control And Provisioning of Wireless Access Points Ed., "Control And Provisioning of Wireless Access Points
(CAPWAP) Protocol Specification", RFC 5415, (CAPWAP) Protocol Specification", RFC 5415,
DOI 10.17487/RFC5415, March 2009, DOI 10.17487/RFC5415, March 2009,
<https://www.rfc-editor.org/info/rfc5415>. <https://www.rfc-editor.org/info/rfc5415>.
[RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility [RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
2011, <https://www.rfc-editor.org/info/rfc6275>. 2011, <https://www.rfc-editor.org/info/rfc6275>.
skipping to change at page 24, line 16 skipping to change at page 26, line 39
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>.
[RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
Locator/ID Separation Protocol (LISP)", RFC 6830, Locator/ID Separation Protocol (LISP)", RFC 6830,
DOI 10.17487/RFC6830, January 2013, DOI 10.17487/RFC6830, January 2013,
<https://www.rfc-editor.org/info/rfc6830>. <https://www.rfc-editor.org/info/rfc6830>.
[RFC7048] Nordmark, E. and I. Gashinsky, "Neighbor Unreachability
Detection Is Too Impatient", RFC 7048,
DOI 10.17487/RFC7048, January 2014,
<https://www.rfc-editor.org/info/rfc7048>.
[RFC7559] Krishnan, S., Anipko, D., and D. Thaler, "Packet-Loss [RFC7559] Krishnan, S., Anipko, D., and D. Thaler, "Packet-Loss
Resiliency for Router Solicitations", RFC 7559, Resiliency for Router Solicitations", RFC 7559,
DOI 10.17487/RFC7559, May 2015, DOI 10.17487/RFC7559, May 2015,
<https://www.rfc-editor.org/info/rfc7559>. <https://www.rfc-editor.org/info/rfc7559>.
[RFC7772] Yourtchenko, A. and L. Colitti, "Reducing Energy [RFC7772] Yourtchenko, A. and L. Colitti, "Reducing Energy
Consumption of Router Advertisements", BCP 202, RFC 7772, Consumption of Router Advertisements", BCP 202, RFC 7772,
DOI 10.17487/RFC7772, February 2016, DOI 10.17487/RFC7772, February 2016,
<https://www.rfc-editor.org/info/rfc7772>. <https://www.rfc-editor.org/info/rfc7772>.
[RFC8273] Brzozowski, J. and G. Van de Velde, "Unique IPv6 Prefix [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>.
12.3. External Informative References Appendix A. Possible Future Extensions
[IEEEstd8021]
IEEE standard for Information Technology, "IEEE Standard
for Information technology -- Telecommunications and
information exchange between systems Local and
metropolitan area networks Part 1: Bridging and
Architecture".
[IEEEstd80211] With the current specification, the 6LBR is not leveraged to avoid
IEEE standard for Information Technology, "IEEE Standard multicast NS(Lookup) on the Backbone. This could be done by adding a
for Information technology -- Telecommunications and lookup procedure in the EDAR/EDAC exchange.
information exchange between systems Local and
metropolitan area networks-- Specific requirements Part
11: Wireless LAN Medium Access Control (MAC) and Physical
Layer (PHY) Specifications".
[IEEEstd802151] By default the specification does not have a trust model, e.g.,
IEEE standard for Information Technology, "IEEE Standard whereby nodes that associate their address with a proof-of-ownership
for Information Technology - Telecommunications and [I-D.ietf-6lo-ap-nd] should be more trusted than nodes that do not.
Information Exchange Between Systems - Local and Such a trust model and related signaling could be added in the future
Metropolitan Area Networks - Specific Requirements. - Part to override the default operation and favor trusted nodes.
15.1: Wireless Medium Access Control (MAC) and Physical
Layer (PHY) Specifications for Wireless Personal Area
Networks (WPANs)".
[IEEEstd802154] Future documents may extend this specification by allowing the 6BBR
IEEE standard for Information Technology, "IEEE Standard to redistribute Host routes in routing protocols that would operate
for Local and metropolitan area networks -- Part 15.4: over the Backbone, or in MIPv6, or FMIP, or the Locator/ID Separation
Low-Rate Wireless Personal Area Networks (LR-WPANs)". Protocol (LISP) [RFC6830] to support mobility on behalf of the 6LNs,
etc... LISP may also be used to provide an equivalent to the EDAR/
EDAC exchange using a Map Server / Map Resolver as a replacement to
the 6LBR.
Appendix A. 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 loosely to cover multiple types of WLANs and The term LLN is used to cover multiple types of WLANs and WPANs,
WPANs, including (Low-Power) Wi-Fi, BLUETOOTH(R) Low Energy, IEEE including (Low-Power) Wi-Fi, BLUETOOTH(R) Low Energy, IEEE STD
STD. 802.11ah and IEEE STD. 802.15.4 wireless meshes, so as to 802.11ah and IEEE STD.802.15.4 wireless meshes, meeting the
address the requirements listed in Appendix B.3 of [RFC8505] requirements listed in Appendix B.3 of [RFC8505] "Requirements
"Requirements Related to Various Low-Power Link Types". Related to Various Low-Power Link Types".
Each LLN in the subnet is anchored at an IPv6 Backbone Router (6BBR). Each LLN in the subnet is attached at 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. In this
way, mobile nodes may roam rapidly from one 6BBR to the next and way, 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.
Any 6LN may 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, providing a solution to the requirements services over the Backbone, meeting the requirements expressed in
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 IPv6 ND operation is minimized as the number of 6LNs grows in the
LLN. This meets the requirements in Appendix B.6 of [RFC8505] LLN. 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 (Low-Power) Wi-Fi access link, a 6BBR may be In the case of a Wi-Fi access link, a 6BBR may be collocated with the
collocated with the Access Point (AP), or with a Fabric Edge (FE) or Access Point (AP), or with a Fabric Edge (FE) or a CAPWAP [RFC5415]
a CAPWAP [RFC5415] Wireless LAN Controller (WLC). In that case, the Wireless LAN Controller (WLC). In those cases, the wireless client
wireless client (STA) is the 6LN [RFC8505] that makes use of this (STA) is the 6LN that makes use of [RFC8505] to register its IPv6
specification to register its IPv6 Address(es) to the 6BBR acting as Address(es) to the 6BBR acting as Routing Registrar. The 6LBR can be
Routing Registrar. The 6LBR can be centralized and either connected centralized and either connected to the Backbone Link or reachable
to the Backbone Link or reachable over IP. The 6BBR proxy-ND over IP. The 6BBR proxy-ND operations eliminate the need for
operations eliminate the need for wireless nodes to respond wireless nodes to respond synchronously when a Lookup is performed
synchronously when a lookup is performed for their IPv6 Addresses. for their IPv6 Addresses. This provides the function of a Sleep
This provides the function of a Sleep Proxy for ND Proxy for ND [I-D.nordmark-6man-dad-approaches].
[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".
skipping to change at page 26, line 39 skipping to change at page 28, line 44
The registration mechanism may be seen as a more reliable alternate The registration mechanism may be seen as a more reliable alternate
to snooping [I-D.bi-savi-wlan]. It can be noted that registration to snooping [I-D.bi-savi-wlan]. It can be noted that registration
and snooping are not mutually exclusive. Snooping may be used in and snooping are not mutually exclusive. Snooping may be used in
conjunction with the registration for nodes that do not register conjunction with the registration for nodes that do not register
their IPv6 Addresses. The 6BBR assumes that if a node registers at their IPv6 Addresses. The 6BBR assumes that if a node registers at
least one IPv6 Address to it, then the node registers all of its least one IPv6 Address to it, then the node registers all of its
Addresses to the 6BBR. With this assumption, the 6BBR can possibly Addresses to the 6BBR. With this assumption, the 6BBR can possibly
cancel all undesirable multicast NS messages that would otherwise cancel all undesirable multicast NS messages that would otherwise
have been delivered to that node. have been delivered to that node.
The scalability of the MultiLink Subnet [RFC4903] requires that Scalability of the MultiLink Subnet [RFC4903] requires avoidance of
multicast/broadcast operations are avoided as much as possible even multicast/broadcast operations as much as possible even on the
on the Backbone [I-D.ietf-mboned-ieee802-mcast-problems]. Although Backbone [I-D.ietf-mboned-ieee802-mcast-problems]. Although hosts
hosts can connect to the Backbone using classical IPv6 ND operations, can connect to the Backbone using IPv6 ND operations, multicast RAs
multicast RAs can be saved by using [I-D.ietf-6man-rs-refresh], which can be saved by using [I-D.ietf-6man-rs-refresh], which also requires
also requires the support of [RFC7559]. the support of [RFC7559].
Authors' Addresses Authors' Addresses
Pascal Thubert (editor) Pascal Thubert (editor)
Cisco Systems, Inc Cisco Systems, Inc
Building D Building D
45 Allee des Ormes - BP1200 45 Allee des Ormes - BP1200
MOUGINS - Sophia Antipolis 06254 MOUGINS - Sophia Antipolis 06254
FRANCE FRANCE
Phone: +33 497 23 26 34 Phone: +33 497 23 26 34
Email: pthubert@cisco.com Email: pthubert@cisco.com
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