draft-ietf-6lo-backbone-router-06.txt   draft-ietf-6lo-backbone-router-07.txt 
6lo P. Thubert, Ed. 6lo P. Thubert, Ed.
Internet-Draft cisco Internet-Draft cisco
Intended status: Standards Track February 23, 2018 Intended status: Standards Track C. Perkins
Expires: August 27, 2018 Expires: March 7, 2019 Futurewei
September 3, 2018
IPv6 Backbone Router IPv6 Backbone Router
draft-ietf-6lo-backbone-router-06 draft-ietf-6lo-backbone-router-07
Abstract Abstract
This specification proposes proxy operations for IPv6 Neighbor Backbone Routers placed at the wireless edge of a backbone link
Discovery on behalf of devices located on broadcast-inefficient interconnect multiple wireless links at Layer-3 to form a large
wireless networks. A broadcast-efficient backbone running classical MultiLink Subnet, so that the broadcast domain of the backbone does
IPv6 Neighbor Discovery federates multiple wireless links to form a not extend to the wireless links. Wireless nodes register or are
large MultiLink Subnet, but the broadcast domain does not need to proxy-registered to a Backbone Router to establish IPv6 Neighbor
extend to the wireless links for the purpose of ND operation. Discovery proxy services, and the Backbone Router takes care of the
Backbone Routers placed at the wireless edge of the backbone proxy ND operation on behalf of registered nodes and ensures and routes
the ND operation and route packets from/to registered nodes, and towards the registered addresses over the wireless interface.
wireless nodes register or are proxy-registered to the Backbone
Router to setup proxy services in a fashion that is essentially
similar to a classical Layer-2 association.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 27, 2018. This Internet-Draft will expire on March 7, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Applicability and Requirements Served . . . . . . . . . . . . 4 2. Applicability and Requirements Served . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Backbone Router Routing Operations . . . . . . . . . . . . . 9 5. Backbone Router Routing Operations . . . . . . . . . . . . . 8
5.1. Over the Backbone Link . . . . . . . . . . . . . . . . . 10 5.1. Over the Backbone Link . . . . . . . . . . . . . . . . . 9
5.2. Over the LLN Link . . . . . . . . . . . . . . . . . . . . 11 5.2. Over the LLN Link . . . . . . . . . . . . . . . . . . . . 10
6. BackBone Router Proxy Operations . . . . . . . . . . . . . . 13 6. Backbone Router Proxy Operations . . . . . . . . . . . . . . 11
6.1. Registration and Binding State Creation . . . . . . . . . 15 6.1. Registration and Binding State Creation . . . . . . . . . 14
6.2. Defending Addresses . . . . . . . . . . . . . . . . . . . 17 6.2. Defending Addresses . . . . . . . . . . . . . . . . . . . 15
7. Security Considerations . . . . . . . . . . . . . . . . . . . 18 7. Security Considerations . . . . . . . . . . . . . . . . . . . 16
8. Protocol Constants . . . . . . . . . . . . . . . . . . . . . 18 8. Protocol Constants . . . . . . . . . . . . . . . . . . . . . 16
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
11.1. Normative References . . . . . . . . . . . . . . . . . . 19 11.1. Normative References . . . . . . . . . . . . . . . . . . 17
11.2. Informative References . . . . . . . . . . . . . . . . . 20 11.2. Informative References . . . . . . . . . . . . . . . . . 18
11.3. External Informative References . . . . . . . . . . . . 23 11.3. External Informative References . . . . . . . . . . . . 22
Appendix A. Requirements . . . . . . . . . . . . . . . . . . . . 24 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
A.1. Requirements Related to Mobility . . . . . . . . . . . . 24
A.2. Requirements Related to Routing Protocols . . . . . . . . 25
A.3. Requirements Related to the Variety of Low-Power Link
types . . . . . . . . . . . . . . . . . . . . . . . . . . 26
A.4. Requirements Related to Proxy Operations . . . . . . . . 26
A.5. Requirements Related to Security . . . . . . . . . . . . 27
A.6. Requirements Related to Scalability . . . . . . . . . . . 28
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 29
1. Introduction 1. Introduction
One of the key services provided by IEEE std. 802.1 [IEEEstd8021] One of the key services provided by IEEE STD. 802.1 [IEEEstd8021]
Ethernet Bridging is an efficient and reliable broadcast service, and Ethernet Bridging is an efficient and reliable broadcast service, and
multiple applications and protocols have been built that heavily multiple applications and protocols have been built that heavily
depend on that feature for their core operation. But a wide range of depend on that feature for their core operation. Unfortunately, a
wireless networks do not provide the solid and cheap broadcast wide range of wireless networks do not provide economical broadcast
capabilities of Ethernet Bridging, and protocols designed for bridged capabilities of Ethernet Bridging; protocols designed for bridged
networks that rely on broadcast often exhibit disappointing networks that rely on broadcast often exhibit disappointing
behaviours when applied unmodified to a wireless medium. behaviours when applied unmodified to a wireless medium.
IEEE std. 802.11 [IEEEstd80211] Access Points (APs) deployed in an Wi-Fi [IEEEstd80211] Access Points (APs) deployed in an Extended
Extended Service Set (ESS) effectively act as bridges, but, in order Service Set (ESS) act as bridges. However, in order to ensure a
to ensure a solid connectivity to the devices and protect the medium solid connectivity to the devices and protect the medium against
against harmful broadcasts, they refrain from relying on broadcast- harmful broadcasts, they refrain from relying on broadcast-intensive
intensive protocols such as Transparent Bridging on the wireless protocols such as Transparent Bridging on the wireless side.
side. Instead, an association process is used to register Instead, an association process is used to register proactively the
proactively the MAC addresses of the wireless device (STA) to the AP, MAC addresses of the wireless device (STA) to the AP. Then, the APs
and then the APs proxy the bridging operation and cancel the proxy the bridging operation and cancel the broadcasts.
broadcasts.
Classical IPv6 [RFC8200] Neighbor Discovery [RFC4861] [RFC4862] The IPv6 [RFC8200] Neighbor Discovery [RFC4861] [RFC4862] Protocol
Protocol (NDP) operations are reactive and rely heavily on multicast (NDP) operations are reactive and rely heavily on multicast
operations to locate an on-link correspondent and ensure address transmissions to locate an on-link correspondent and ensure address
uniqueness, which is a pillar that sustains the whole IP uniqueness. When the Duplicate Address Detection [RFC4862] (DAD)
architecture. When the Duplicate Address Detection [RFC4862] (DAD)
mechanism was designed, it was a natural match with the efficient mechanism was designed, it was a natural match with the efficient
broadcast operation of Ethernet Bridging, but with the unreliable broadcast operation of Ethernet Bridging. However, since broadcast
broadcast that is typical of wireless media, DAD is bound to fail to can be unreliable over wireless media, DAD often fails to discover
discover duplications [I-D.yourtchenko-6man-dad-issues]. In other duplications [I-D.yourtchenko-6man-dad-issues]. DAD usually appears
words, because the broadcast service is unreliable, DAD appears to to work on wireless media, not because address duplication is
work on wireless media not because address duplication is detected detected and solved as designed, but because the use of 64-bit
and solved as designed, but because the duplication is a very rare Interface IDs makes duplication into a very rare event.
event as a side effect of the sheer amount of entropy in 64-bits
Interface IDs.
In the real world, IPv6 multicast messages are effectively broadcast, IPv6 multicast messages are usually broadcast over the wireless
so they are processed by most if not all wireless nodes over the ESS medium. They are processed by most if not all wireless nodes over
fabric even when very few if any of the nodes is effectively the ESS fabric even when very few if any of the nodes are subscribed
listening to the multicast address. It results that a simple to the multicast address. Consequently a simple Neighbor
Neighbor Solicitation (NS) lookup message [RFC4861], that is Solicitation (NS) lookup message [RFC4861], that is supposedly
supposedly targeted to a very small group of nodes, ends up polluting targeted to a very small group of nodes, can consume the whole
the whole wireless bandwidth across the fabric wireless bandwidth across the fabric
[I-D.vyncke-6man-mcast-not-efficient]. In other words, the reactive [I-D.vyncke-6man-mcast-not-efficient]. The reactive IPv6 ND
IPv6 ND operation leads to undesirable power consumption in battery- operation leads to undesirable power consumption in battery-operated
operated devices. devices.
The inefficiencies of using radio broadcasts to support IPv6 NDP lead The inefficiencies of using radio broadcasts to support IPv6 NDP
the community to consider (again) splitting the broadcast domain suggest restricting broadcast transmissions over the wireless access
between the wired and the wireless access links. One classical way links. This can be done by splitting the subnet in multiple ones,
to achieve this is to split the subnet in multiple ones, and at the and in extreme cases providing a /64 per wireless device. Another
extreme provide a /64 per wireless device. Another is to proxy the way is to take over (proxy) the Layer-3 protocols that rely on
Layer-3 protocols that rely on broadcast operation at the boundary of broadcast operation at the boundary of the wired and wireless
the wired and wireless domains, effectively emulating the Layer-2 domains, emulating the Layer-2 association at Layer-3. Indeed, the
association at layer-3. To that effect, the current IEEE std. 802.11 IEEE STD. 802.11 [IEEEstd80211] specifications require ARP and ND
specifications require the capability to perform ARP and ND proxy proxy [RFC4389] functions at the Access Points (APs) but the
[RFC4389] functions at the Access Points (APs). specification for the ND proxy operations is still missing.
But for the lack a comprehensive specification for the ND proxy and Current devices rely on snooping for detecting association state,
in particular the lack of an equivalent to an association process, which is unsatisfactory in a lossy and mobile conditions. With
implementations have to rely on snooping for acquiring the related snooping, a state (e.g. a new IPv6 address) may not be discovered or
state, which is unsatisfactory in a lossy and mobile conditions. a change of state (e.g. a movement) may be missed, leading to
With snooping, a state (e.g. a new IPv6 address) may not be unreliable connectivity.
discovered or a change of state (e.g. a movement) may be missed,
leading to unreliable connectivity.
In the context of IEEE std. 802.15.4 [IEEEstd802154], the step of WPAN devices (i.e., those implementing IEEE STD. 802.15.4
considering the radio as a medium that is different from Ethernet was [IEEEstd802154]) can make use of Neighbor Discovery Optimization for
already taken with the publication of Neighbor Discovery Optimization IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs)
for IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs) [RFC6775] which treats the wireless medium as different from
[RFC6775]. RFC 6775 is updated as [I-D.ietf-6lo-rfc6775-update]; the Ethernet. RFC 6775 is updated as [I-D.ietf-6lo-rfc6775-update]; the
update includes changes that are required by this document. update includes changes that are required by this document.
This specification applies that same thinking to other wireless links This specification applies to other wireless links such as Low-Power
such as Low-Power IEEE std. 802.11 (Wi-Fi) and IEEE std. 802.15.1 IEEE STD. 802.11 (Wi-Fi) and IEEE STD. 802.15.1 (Bluetooth)
(Bluetooth) [IEEEstd802151], and extends [RFC6775] to enable proxy [IEEEstd802151], and extends [RFC6775] to enable proxy operation by
operation by the 6BBR so as to decouple the broadcast domain in the the 6BBR. The proxy operation on the BBR eliminates the need for
backbone from the wireless links. The proxy operation can be low-power nodes or nodes that are deep in a mesh to respond
maintained asynchronous so that low-power nodes or nodes that are synchronously when a lookup is performed for their addresses. This
deep in a mesh do not need to be bothered synchronously when a lookup provides the function of a Sleep Proxy for ND
is performed for their addresses, effectively implementing the ND
contribution to the concept of a Sleep Proxy
[I-D.nordmark-6man-dad-approaches]. [I-D.nordmark-6man-dad-approaches].
2. Applicability and Requirements Served 2. Applicability and Requirements Served
Efficiency aware IPv6 Neighbor Discovery Optimizations Efficiency aware IPv6 Neighbor Discovery Optimizations
[I-D.chakrabarti-nordmark-6man-efficient-nd] suggests that 6LoWPAN ND [I-D.chakrabarti-nordmark-6man-efficient-nd] suggests that 6LoWPAN ND
[RFC6775] can be extended to other types of links beyond IEEE std. [RFC6775] can be extended to other types of links beyond IEEE STD.
802.15.4 for which it was defined. The registration technique is 802.15.4 for which it was defined. The registration technique is
beneficial when the Link-Layer technique used to carry IPv6 multicast beneficial when the Link-Layer technique used to carry IPv6 multicast
packets is not sufficiently efficient in terms of delivery ratio or packets has poor delivery ratio or requires high energy consumption
energy consumption in the end devices, in particular to enable in the end devices, all the more in use cases that involve mobility.
energy-constrained sleeping nodes. The value of such extension is
especially apparent in the case of mobile wireless nodes, to reduce
the multicast operations that are related to classical ND ([RFC4861],
[RFC4862]) and plague the wireless medium.
This specification updates and generalizes 6LoWPAN ND to a broader This specification updates and generalizes 6LoWPAN ND to a broader
range of Low power and Lossy Networks (LLNs) with a solid support for range of Low power and Lossy Networks (LLNs) with support for
Duplicate Address Detection (DAD) and address lookup that does not Duplicate Address Detection (DAD) and address lookup that does not
require broadcasts over the LLNs. The term LLN is used loosely in require broadcasts over the LLNs. The term LLN is used loosely in
this specification to cover multiple types of WLANs and WPANs, this specification to cover multiple types of WLANs and WPANs,
including Low-Power Wi-Fi, BLUETOOTH(R) Low Energy, IEEE std. including Low-Power Wi-Fi, BLUETOOTH(R) Low Energy, IEEE STD.
802.11AH and IEEE std. 802.15.4 wireless meshes, so as to address the 802.11AH and IEEE STD. 802.15.4 wireless meshes, so as to address the
requirements listed in Appendix A.3 requirements listed in Appendix B.3 of [I-D.ietf-6lo-rfc6775-update]
The scope of this draft is a Backbone Link that federates multiple "Requirements Related to the Variety of Low-Power Link types".
LLNs as a single IPv6 MultiLink Subnet. Each LLN in the subnet is
anchored at an IPv6 Backbone Router (6BBR). The Backbone Routers The scope of this draft is a Backbone that enable the federation of
interconnect the LLNs over the Backbone Link and emulate that the LLN multiple LLNs into a IPv6 MultiLink Subnet. Each LLN in the subnet
nodes are present on the Backbone using proxy-ND operations. This is anchored at an IPv6 Backbone Router (6BBR). The Backbone Routers
specification extends IPv6 ND over the backbone to discriminate interconnect the LLNs and advertise the addresses of the LLN nodes
address movement from duplication and eliminate stale state in the using proxy-ND operations. This specification extends IPv6 ND over
backbone routers and backbone nodes once a LLN node has roamed. This the backbone to distinguish address movement from duplication and
way, mobile nodes may roam rapidly from a 6BBR to the next and eliminate stale state in the backbone routers and backbone nodes once
requirements in Appendix A.1 are met. a LLN node has roamed. In this way, mobile nodes may roam rapidly
from one 6BBR to the next and requirements in Appendix B.1 of
[I-D.ietf-6lo-rfc6775-update]"Requirements Related to Mobility" are
met.
This specification can be used by any wireless node to associate at This specification can be used by any wireless node to associate at
Layer-3 with a 6BBR and register its IPv6 addresses to obtain routing Layer-3 with a 6BBR and register its IPv6 addresses to obtain routing
services including proxy-ND operations over the backbone, effectively services including proxy-ND operations over the backbone, providing a
providing a solution to the requirements expressed in Appendix A.4. solution to the requirements expressed in Appendix B.4 of
[I-D.ietf-6lo-rfc6775-update] "Requirements Related to Proxy
Operations".
The Link Layer Address (LLA) that is returned as Target LLA (TLLA) in The Link Layer Address (LLA) that is returned as Target LLA (TLLA) in
Neighbor Advertisements (NA) messages by the 6BBR on behalf of the Neighbor Advertisements (NA) messages by the 6BBR on behalf of the
Registered Node over the backbone may be that of the Registering Registered Node over the backbone may be that of the Registering
Node, in which case the 6BBR needs to bridge the unicast packets Node. In that case, the 6BBR needs to bridge the unicast packets
(Bridging proxy), or that of the 6BBR on the backbone, in which case (Bridging proxy), or that of the 6BBR on the backbone, in which case
the 6BBRs needs to route the unicast packets (Routing proxy). In the the 6BBRs needs to route the unicast packets (Routing proxy). In the
latter case, the 6BBR may maintain the list of correspondents to latter case, the 6BBR maintains the list of correspondents to which
which it has advertised its own MAC address on behalf of the LLN node it has advertised its own MAC address on behalf of the LLN node. The
and the IPv6 ND operation is minimized as the number of nodes scale IPv6 ND operation is minimized as the number of nodes scale up in the
up in the LLN. This enables to meet the requirements in Appendix A.6 LLN. This meets the requirements in Appendix B.6 of
as long has the 6BBRs are dimensioned for the number of registration [I-D.ietf-6lo-rfc6775-update] "Requirements Related to Scalability",
as long has the 6BBRs are dimensioned for the number of registrations
that each needs to support. that each needs to support.
In the context of the the TimeSlotted Channel Hopping (TSCH) mode of For the TimeSlotted Channel Hopping (TSCH) mode of [IEEEstd802154],
[IEEEstd802154], the 6TiSCH architecture the 6TiSCH architecture [I-D.ietf-6tisch-architecture] describes how
[I-D.ietf-6tisch-architecture] introduces how a 6LoWPAN ND host could a 6LoWPAN ND host could connect to the Internet via a RPL mesh
connect to the Internet via a RPL mesh Network, but this requires Network, but doing so requires additions to the 6LOWPAN ND protocol
additions to the 6LOWPAN ND protocol to support mobility and to support mobility and reachability in a secure and manageable
reachability in a secured and manageable environment. This environment. This document details such additions for the 6TiSCH
specification details the new operations that are required to architecture, and serves the requirements listed in Appendix B.2 of
implement the 6TiSCH architecture and serves the requirements listed [I-D.ietf-6lo-rfc6775-update] "Requirements Related to Routing
in Appendix A.2. Protocols".
In the case of Low-Power IEEE std. 802.11, a 6BBR may be collocated In the case of Low-Power IEEE STD. 802.11, a 6BBR may be collocated
with a standalone AP or a CAPWAP [RFC5415] wireless controller, and with a standalone AP or a CAPWAP [RFC5415] wireless controller. Then
the wireless client (STA) leverages this specification to register the wireless client (STA) makes use of this specification to register
its IPv6 address(es) to the 6BBR over the wireless medium. In the its IPv6 address(es) to the 6BBR over the wireless medium. In the
case of a 6TiSCH LLN mesh, the RPL root is collocated with a 6LoWPAN case of a 6TiSCH LLN mesh, the RPL root is collocated with a 6LoWPAN
Border Router (6LBR), and either collocated with or connected to the Border Router (6LBR), and either collocated with or connected to the
6BBR over an IPv6 Link. The 6LBR leverages this specification to 6BBR over an IPv6 Link. The 6LBR makes use of this specification to
register the LLN nodes on their behalf to the 6BBR. In the case of register the LLN nodes on their behalf to the 6BBR. In the case of
BTLE, the 6BBR is collocated with the router that implements the BTLE BTLE, the 6BBR is collocated with the router that implements the BTLE
central role as discussed in section 2.2 of [RFC7668]. central role as discussed in section 2.2 of [RFC7668].
3. Terminology 3. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
skipping to change at page 6, line 32 skipping to change at page 6, line 18
Readers would benefit from reading "Multi-Link Subnet Issues" Readers would benefit from reading "Multi-Link Subnet Issues"
[RFC4903], ,"Mobility Support in IPv6" [RFC6275], "Neighbor Discovery [RFC4903], ,"Mobility Support in IPv6" [RFC6275], "Neighbor Discovery
Proxies (ND Proxy)" [RFC4389] and "Optimistic Duplicate Address Proxies (ND Proxy)" [RFC4389] and "Optimistic Duplicate Address
Detection" [RFC4429] prior to this specification for a clear Detection" [RFC4429] prior to this specification for a clear
understanding of the art in ND-proxying and binding. understanding of the art in ND-proxying and binding.
Additionally, this document uses terminology from [RFC7102], Additionally, this document uses terminology from [RFC7102],
[I-D.ietf-6lo-rfc6775-update] and [I-D.ietf-6tisch-terminology], and [I-D.ietf-6lo-rfc6775-update] and [I-D.ietf-6tisch-terminology], and
introduces the following terminology: introduces the following terminology:
Sleeping Proxy A 6BBR acts as a Sleeping Proxy if it answers ND Sleeping Proxy
Neighbor Solicitation over the backbone on behalf of the
Registered Node whenever possible. This is the default mode
for this specification but it may be overridden, for instance
by configuration, into Unicasting Proxy.
Unicasting Proxy As a Unicasting Proxy, the 6BBR forwards NS A 6BBR acts as a Sleeping Proxy if it answers ND Neighbor
messages to the Registering Node, transforming Layer-2 Solicitation over the backbone on behalf of the Registered
multicast into unicast whenever possible. Node.
Routing proxy A 6BBR acts as a routing proxy if it advertises its Unicasting Proxy
own MAC address, as opposed to that of the node that performs
the registration, as the TLLA in the proxied NAs over the
backbone. In that case, the MAC address of the node is not
visible at Layer-2 over the backbone and the bridging fabric is
not aware of the addresses of the LLN devices and their
mobility. The 6BBR installs a connected host route towards the
registered node over the interface to the node, and acts as a
Layer-3 router for unicast packets to the node. The 6BBR
updates the ND Neighbor Cache Entries (NCE) in correspondent
nodes if the wireless node moves and registers to another 6BBR,
either with a single broadcast, or with a series of unicast
NA(O) messages, indicating the TLLA of the new router.
Bridging proxy A 6BBR acts as a bridging proxy if it advertises the A Unicasting Proxy forwards NS messages to the Registering
MAC address of the node that performs the registration as the Node, transforming Layer-2 multicast into unicast.
TLLA in the proxied NAs over the backbone. In that case, the
MAC address and the mobility of the node is still visible
across the bridged backbone fabric, as is traditionally the
case with Layer-2 APs. The 6BBR acts as a Layer-2 bridge for
unicast packets to the registered node. The MAC address
exposed in the S/TLLA is that of the Registering Node, which is
not necessarily the Registered Device. When a device moves
within a LLN mesh, it may end up attached to a different 6LBR
acting as Registering Node, and the LLA that is exposed over
the backbone will change.
Primary BBR The BBR that will defend a Registered Address for the Routing proxy
purpose of DAD over the backbone.
Secondary BBR A BBR to which the address is registered. A Secondary A routing proxy advertises its own MAC address, as opposed to
Router MAY advertise the address over the backbone and proxy that of the node that performs the registration, as the TLLA in
for it. the proxied NAs over the backbone.
Bridging proxy
A Bridging proxy advertises the MAC address of the node that
performs the registration as the TLLA in the proxied NAs over
the backbone. In that case, the MAC address and the mobility
of the node is still visible across the bridged backbone
fabric.
Primary BBR
The BBR that will defend a Registered Address for the purpose
of DAD over the backbone.
Secondary BBR
A BBR other than the Primary BBR to which an address is
registered. A Secondary Router MAY advertise the address over
the backbone and proxy for it.
4. Overview 4. Overview
An LLN node can move freely from an LLN anchored at a Backbone Router An LLN node can move freely from an LLN anchored at a Backbone Router
to an LLN anchored at another Backbone Router on the same backbone to an LLN anchored at another Backbone Router on the same backbone
and conserve any of the IPv6 addresses that it has formed, and keep any or all of the IPv6 addresses that it has formed.
transparently.
| |
+-----+ +-----+
| | Other (default) Router | | Gateway (default) Router
| | | |
+-----+ +-----+
| |
| Backbone Link | Backbone Link
+--------------------+------------------+ +--------------------+------------------+
| | | | | |
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| | Backbone | | Backbone | | Backbone | | Backbone | | Backbone | | Backbone
| | router | | router | | router | | router | | router | | router
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+
o o o o o o o o o o o o
o o o o o o o o o o o o o o o o o o o o o o o o o o o o
o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o
o o o o o o o o o o 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
The Backbone Routers maintain an abstract Binding Table of their Each Backbone Router (6BBR) maintains a Binding Table of its
Registered Nodes. The Binding Table operates as a distributed Registered Nodes. The Binding Table operates as a distributed
database of all the wireless Nodes whether they reside on the LLNs or database of wireless Nodes whether they reside on the LLNs or on the
on the backbone, and use an extension to the Neighbor Discovery backbone, and use an extension to the Neighbor Discovery Protocol to
Protocol to exchange that information across the Backbone in the exchange that information across the Backbone as with IPv6 ND.
classical ND reactive fashion.
The Extended Address Registration Option (EARO) defined in The Extended Address Registration Option (EARO) defined in
[I-D.ietf-6lo-rfc6775-update] is used to enable the registration for [I-D.ietf-6lo-rfc6775-update] is used to enable the registration for
routing and proxy option is included in the ND exchanges over the routing and proxy options in the ND exchanges over the backbone
backbone between the 6BBRs to sort out duplication from movement. between the 6BBRs to disambiguate duplication from movement.
Address duplication is sorted out with the Owner Unique-ID field in Address duplication is detected using the ROVR field in the EARO,
the EARO, which is a generalization of the EUI-64 that allows which is a generalization of the EUI-64 that allows different types
different types of unique IDs beyond the name space derived from the of unique IDs beyond the name space derived from the MAC addresses.
MAC addresses. First-Come First-Serve rules apply, whether the First-Come First-Serve rules apply, whether the duplication happens
duplication happens between LLN nodes as represented by their between LLN nodes as represented by their respective 6BBRs, or
respective 6BBRs, or between an LLN node and a classical node that between an LLN node and a node that defends its address over the
defends its address over the backbone with classical ND and does not backbone with IPv6 ND and does not include the EARO.
include the EARO option.
In case of conflicting registrations to multiple 6BBRs from a same In case of conflicting registrations to multiple 6BBRs from a same
node, a sequence counter called Transaction ID (TID) in the EARO node, a sequence counter called Transaction ID (TID) in the EARO
enables 6BBRs to sort out the latest anchor for that node. enables 6BBRs to determine the latest registration for that node.
Registrations with a same TID are compatible and maintained, but, in Registrations with a same TID are compatible and maintained, but, in
case of different TIDs, only the freshest registration is maintained case of different TIDs, only the freshest registration is maintained
and the stale state is eliminated. The EARO also transports a 'R' and the stale state is eliminated. The EARO also transports a 'R'
flag to be used by a 6LN when registering, to indicate that this 6LN flag to be used by a 6LN when registering, to indicate that this 6LN
is not a router and that it will not handle its own reachability. is not a router and that it will not handle its own reachability.
With this specification, Backbone Routers perform a ND proxy With this specification, Backbone Routers perform a ND proxy
operation over the Backbone Link on behalf of their Registered Nodes. operation over the Backbone Link on behalf of their Registered Nodes.
The registration to the proxy service is done with a NS/NA(EARO) The registration to the proxy service is done with a NS/NA(EARO)
exchange. The EARO option with a 'R' flag is used in this exchange. The EARO with a 'R' flag is used in this specification to
specification to indicate to the 6BBR that it is expected to perform request the 6BBR to perform this proxy operation. The Backbone
this proxy operation. The Backbone Router operation is essentially Router operation is essentially similar to that of a Mobile IPv6
similar to that of a Mobile IPv6 (MIPv6) [RFC6275] Home Agent. This (MIPv6) [RFC6275] Home Agent. This enables mobility support for LLN
enables mobility support for LLN nodes that would move outside of the nodes that would move outside of the network delimited by the
network delimited by the Backbone link attach to a Home Agent from Backbone link attach to a Home Agent from that point on. This also
that point on. This also enables collocation of Home Agent enables collocation of Home Agent functionality within Backbone
functionality within Backbone Router functionality on the same Router functionality on the same backbone interface of a router.
backbone interface of a router. Further specification may extend Further specification may extend this be allowing the 6BBR to
this be allowing the 6BBR to redistribute host routes in routing redistribute host routes in routing protocols that would operate over
protocols that would operate over the backbone, or in MIPv6 or the the backbone, or in MIPv6 or the Locator/ID Separation Protocol
Locator/ID Separation Protocol (LISP) [RFC6830] to support mobility (LISP) [RFC6830] to support mobility on behalf of the nodes, etc...
on behalf of the nodes, etc...
The Optimistic Duplicate Address Detection [RFC4429] (ODAD) The Optimistic Duplicate Address Detection [RFC4429] (ODAD)
specification details how an address can be used before a Duplicate specification details how an address can be used before a Duplicate
Address Detection (DAD) is complete, and insists that an address that Address Detection (DAD) is complete, and insists that an address that
is TENTATIVE should not be associated to a Source Link-Layer Address is TENTATIVE should not be associated to a Source Link-Layer Address
Option in a Neighbor Solicitation message. This specification Option in a Neighbor Solicitation message. This specification makes
leverages ODAD to create a temporary proxy state in the 6BBR till DAD use of ODAD to create a temporary proxy state in the 6BBR till DAD is
is completed over the backbone. This way, the specification enables completed over the backbone. This way, the specification enables to
to distribute proxy states across multiple 6BBR and co-exist with distribute proxy states across multiple 6BBR and co-exist with IPv6
classical ND over the backbone. ND over the backbone.
5. Backbone Router Routing Operations 5. Backbone Router Routing Operations
| |
+-----+ +-----+
| | Other (default) Router | | Gateway (default) Router
| | | |
+-----+ +-----+
| /64 | /64
| Backbone Link | Backbone Link
+-------------------+-------------------+ +-------------------+-------------------+
| /64 | /64 | /64 | /64 | /64 | /64
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| | Backbone | | Backbone | | Backbone | | Backbone | | Backbone | | Backbone
| | router | | router | | router | | router | | router | | router
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+
o N*/128 o o o M*/128 o o P*/128 o N * /128 o M * /128 o P * /128
o o o o o o o o o o o o o o o o o o o o o o o o o o o o
o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o
o o o o o o o o o o o o o o o o o o o o
o o o o o o o o o o o o o o
LLN LLN LLN Figure 2: Example Routing Configuration for 3 LLNs in the ML Subnet
Figure 2: Routing Configuration in the ML Subnet
5.1. Over the Backbone Link 5.1. Over the Backbone Link
The Backbone Router is a specific kind of Border Router that performs A 6BBR is a specific kind of Border Router that performs proxy
proxy Neighbor Discovery on its backbone interface on behalf of the Neighbor Discovery on its backbone interface on behalf of the nodes
nodes that it has discovered on its LLN interfaces. that it has discovered on its LLN interfaces.
The backbone is expected to be a high speed, reliable Backbone link,
with affordable and reliable multicast capabilities, such as a
bridged Ethernet Network, and to allow a full support of classical ND
as specified in [RFC4861] and subsequent RFCs. In other words, the
backbone is not a LLN.
Still, some restrictions of the attached LLNs will apply to the Some restrictions of the attached LLNs will apply to the backbone.
backbone. In particular, it is expected that the MTU is set to the In particular, the MTU MUST be set to the same value on the backbone
same value on the backbone and all attached LLNs, and the scalability and all attached LLNs. The scalability of the whole subnet requires
of the whole subnet requires that broadcast operations are avoided as that broadcast operations are avoided as much as possible on the
much as possible on the backbone as well. Unless configured backbone as well. Unless configured otherwise, in the RAs that it
otherwise, the Backbone Router MUST echo the MTU that it learns in sends towards the LLN links, the Backbone Router MUST use the same
RAs over the backbone in the RAs that it sends towards the LLN links. MTU that it learns from RAs over the backbone.
As a router, the Backbone Router behaves like any other IPv6 router On the backbone side, the 6BBR behaves like any other IPv6 router.
on the backbone side. It has a connected route installed towards the It advertises on the backbone the prefixes of the LLNs for which it
backbone for the prefixes that are present on that backbone and that serves as a proxy.
it proxies for on the LLN interfaces.
As a proxy, the 6BBR uses an EARO option in the NS-DAD and the The 6BBR uses an EARO in the NS-DAD and the multicast NA messages
multicast NA messages that it generates over the Backbone Link on that it generates over the Backbone Link on behalf of a Registered
behalf of a Registered Node, and it places an EARO in its unicast NA Node, and it places an EARO in its unicast NA messages, if and only
messages, if and only if the NS/NA that stimulates it had an EARO in if the NS/NA that stimulates it had an EARO in it and the 'R' bit
it and the 'R' bit set. set.
When possible, the 6BBR SHOULD use unicast or solicited-node The 6BBR SHOULD use unicast or solicited-node multicast address
multicast address (SNMA) [RFC4291] to defend its Registered Addresses (SNMA) [RFC4291] to defend its Registered Addresses over the
over the backbone. In particular, the 6BBR MUST join the SNMA group backbone. In particular, the 6BBR MUST join the SNMA group that
that corresponds to a Registered Address as soon as it creates an corresponds to a Registered Address as soon as it creates an entry
entry for that address and as long as it maintains that entry, for that address, and as long as it maintains that entry.
whatever the state of the entry. The expectation is that it is
possible to get a message delivered to all the nodes on the backbone
that listen to a particular address and support this specification -
which includes all the 6BBRs in the MultiLink Subnet - by sending a
multicast message to the associated SNMA over the backbone.
The support of Optimistic DAD (ODAD) [RFC4429] is recommended for all Optimistic DAD (ODAD) [RFC4429] SHOULD be supported by the 6BBRs in
nodes in the backbone and followed by the 6BBRs in their proxy their proxy activity over the backbone. A node supporting ODAD MUST
activity over the backbone. With ODAD, any optimistic node MUST join join the SNMA of a Tentative address.
the SNMA of a Tentative address, which interacts better with this
specification.
This specification allows the 6BBR in Routing Proxy mode to advertise A 6BBR in Routing Proxy mode advertises the Registered IPv6 Address
the Registered IPv6 Address with the 6BBR Link Layer Address, and with the 6BBR Link Layer Address, and updates Neighbor Cache Entries
attempts to update Neighbor Cache Entries (NCE) in correspondent (NCE) in correspondent nodes over the backbone, using gratuitous
nodes over the backbone, using gratuitous NA(Override). This method NA(Override). This method may fail if the multicast message is not
may fail of the multicast message is not properly received, and properly received, and correspondent nodes may maintain an incorrect
correspondent nodes may maintain an incorrect neighbor state, which neighbor state, which they will eventually discover through Neighbor
they will eventually discover through Neighbor Unreachability Unreachability Detection (NUD). For slow movements, the NUD
Detection (NUD). Because mobility may be slow, the NUD procedure procedure defined in [RFC4861] may time out too quickly, and the
defined in [RFC4861] may be too impatient, and the support of support of [RFC7048] is recommended in all nodes in the network.
[RFC7048] is recommended in all nodes in the network.
Since the MultiLink Subnet may grow very large in terms of individual Since the MultiLink Subnet may grow to contain many nodes, multicast
IPv6 addresses, multicasts should be avoided as much as possible even should be avoided as much as possible even on the backbone. Though
on the backbone. Though it is possible for plain hosts to hosts can participate using legacy IPv6 ND, all nodes connected to
participate with legacy IPv6 ND support, the support by all nodes the backbone SHOULD support [I-D.ietf-6man-rs-refresh], which also
connected to the backbone of [I-D.ietf-6man-rs-refresh] is requires the support of [RFC7559].
recommended, and this implies the support of [RFC7559] as well.
5.2. Over the LLN Link 5.2. Over the LLN Link
As a router, the Nodes and Backbone Router operation on the LLN BBRs and LLN hosts on the LLN follow [RFC6775] and do not depend on
follows [RFC6775]. Per that specification, LLN Hosts generally do multicast RAs to discover routers. LLN nodes SHOULD accept multicast
not depend on multicast RAs to discover routers. It is still RAs [RFC7772], but those are rare on the LLN link. Nodes SHOULD
generally required for LLN nodes to accept multicast RAs [RFC7772], follow the Simple Procedures for Detecting Network Attachment in IPv6
but those are rare on the LLN link. Nodes are expected to follow the [RFC6059] (DNA procedures) to assert movements, and to support the
Simple Procedures for Detecting Network Attachment in IPv6 [RFC6059] Packet-Loss Resiliency for Router Solicitations [RFC7559] to make the
(DNA procedures) to assert movements, and to support the Packet-Loss unicast RS more reliable.
Resiliency for Router Solicitations [RFC7559] to make the unicast RS
more reliable.
An LLN node signals that it requires IPv6 ND proxy services from a LLN node signals that it requires IPv6 ND proxy services from a 6BBR
6BBR by registering the corresponding IPv6 Address with an NS(EARO) by registering the corresponding IPv6 Address with an NS(EARO)
message with the 'R' flag set. The LLN node that performs the message with the 'R' flag set. The LLN node that performs the
registration (the Registering Node) may be the owner of the IPv6 registration (the Registering Node) may be the owner of the IPv6
Address (the Registered Node) or a 6LBR that performs the Address (the Registered Node) or a 6LBR that performs the
registration on its behalf. registration on its behalf.
When operating as a Routing Proxy, the router installs hosts routes When operating as a Routing Proxy, the BBR installs host routes
(/128) to the Registered Addresses over the LLN links, via the (/128) to the Registered Addresses over the LLN links, via the
Registering Node as identified by the Source Address and the SLLAO Registering Node as identified by the Source Address and the SLLA
option in the NS(EARO) messages. option in the NS(EARO) messages. In that case, the MAC address of
the node is not visible at Layer-2 over the backbone and the bridging
fabric is not aware of the addresses of the LLN devices and their
mobility. The 6BBR installs a connected host route towards the
registered node over the interface to the node, and acts as a Layer-3
router for unicast packets to the node.
In that mode, the 6BBR handles the ND protocol over the backbone on In that mode, the 6BBR handles the ND protocol over the backbone on
behalf of the Registered Nodes, using its own MAC address in the TLLA behalf of the Registered Nodes, using its own MAC address in the TLLA
and SLLA options in proxyed NS and NA messages. It results that for and SLLA options in proxied NS and NA messages. For each Registered
each Registered Address, a number of peer Nodes on the backbone have Address, multiple peer Nodes on the backbone may have resolved the
resolved the address with the 6BBR MAC address and keep that mapping address with the 6BBR MAC address and store that mapping in their
stored in their Neighbor cache. Neighbor cache.
The 6BBR SHOULD maintain, per Registered Address, the list of the For each Registered Address, the 6BBR SHOULD maintain a list of the
peers on the backbone to which it answered with it MAC address, and peers on the backbone which have associated its MAC address with the
when a binding moves to a different 6BBR, it SHOULD send a unicast Registered Address. If that Registered Address moves to a different
gratuitous NA(O) individually to each of them to inform them that the 6BBR, the first 6BBR SHOULD unicast a gratuitous NA(Override) to each
address has moved and pass the MAC address of the new 6BBR in the such peer, to supply the MAC address of the new 6BBR in the TLLA
TLLAO option. If the 6BBR can not maintain that list, then it SHOULD option for the Address.
remember whether that list is empty or not and if not, send a
multicast NA(O) to all nodes to update the impacted Neighbor Caches
with the information from the new 6BBR.
The Bridging Proxy is a variation where the BBR function is A Bridging Proxy can be implemented in a Layer-3 switch, or in a
implemented in a Layer-3 switch or an wireless Access Point that acts wireless Access Point that acts as an IPv6 Host. In the latter case,
as a Host from the IPv6 standpoint, and, in particular, does not the SLLA option in the proxied NA messages is that of the Registering
operate the routing of IPv6 packets. In that case, the SLLAO in the Node, and the 6BBR acts as a Layer-2 bridge for unicast packets to
proxied NA messages is that of the Registering Node and classical the Registered Address. The MAC address in the S/TLLA is that of the
bridging operations take place on data frames. Registering Node, which is not necessarily the Registered Node. When
a device moves within a LLN mesh, it may attach to a different 6LBR
acting as Registering Node, and the MAC address advertised over the
backbone will change.
If a registration moves from one 6BBR to the next, but the If a registration moves from one 6BBR to the next, but the
Registering Node does not change, as indicated by the S/TLLAO option Registering Node does not change, as indicated by the S/TLLA option
in the ND exchanges, there is no need to update the Neighbor Caches in the ND exchanges, there is no need to update the Neighbor Caches
in the peers Nodes on the backbone. On the other hand, if the LLAO in the peers Nodes on the backbone. On the other hand, if the LLA
changes, the 6BBR SHOULD inform all the relevant peers as described changes, the 6BBR SHOULD inform all the relevant peers as described
above, to update the impacted Neighbor Caches. In the same fashion, above, to update the impacted Neighbor Caches. In the same fashion,
if the Registering Node changes with a new registration, the 6BBR if the Registering Node changes with a new registration, the 6BBR
SHOULD also update the impacted Neighbor Caches over the backbone. SHOULD also update the impacted Neighbor Caches over the backbone.
6. BackBone Router Proxy Operations 6. Backbone Router Proxy Operations
This specification enables a Backbone Router to proxy Neighbor This specification enables a Backbone Router to proxy Neighbor
Discovery operations over the backbone on behalf of the nodes that Discovery operations over the backbone on behalf of the nodes that
are registered to it, allowing any node on the backbone to reach a are registered to it, allowing any node on the backbone to reach a
Registered Node as if it was on-link. The backbone and the LLNs are Registered Node as if it was on-link. The backbone and the LLNs are
considered different Links in a MultiLink subnet but the prefix that considered different Links in a MultiLink subnet but the prefix that
is used may still be advertised as on-link on the backbone to support is used may still be advertised as on-link on the backbone to support
legacy nodes; multicast ND messages are link-scoped and not forwarded legacy nodes; multicast ND messages are link-scoped and not forwarded
across the backbone routers. across the backbone routers.
ND Messages on the backbone side that do not match to a registration By default, a 6BBR operates as a Sleeping Proxy, as follows:
on the LLN side are not acted upon on the LLN side, which stands
protected. 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.
The default operation in this specification is Sleeping proxy which
means:
o creating a new entry in an abstract Binding Table for a new o Create a new entry in a Binding Table for a new Registered Address
Registered Address and validating that the address is not a and ensure that the address is not a duplicate over the backbone
duplicate over the backbone
o defending a Registered Address over the backbone using NA messages o Defend a Registered Address over the backbone using NA messages
with the Override bit set on behalf of the sleeping node whenever with the Override bit set on behalf of the sleeping node
possible
o advertising a Registered Address over the backbone using NA o Advertise a Registered Address over the backbone using NA
messages, asynchronously or as a response to a Neighbor messages, asynchronously or as a response to a Neighbor
Solicitation messages. Solicitation messages.
o Looking up a destination over the backbone in order to deliver o To deliver packets arriving from the LLN, use Neighbor
packets arriving from the LLN using Neighbor Solicitation Solicitation messages to look up the destination over the
messages. backbone.
o Forwarding packets from the LLN over the backbone, and the other o Forward packets between the LLN and the backbone.
way around.
o Eventually triggering a liveliness verification of a stale o Verify liveliness when needed for a stale registration.
registration.
A 6BBR may act as a Sleeping Proxy only if the state of the binding A 6BBR may act as a Sleeping Proxy only for a Registered Address that
entry is REACHABLE, or TENTATIVE in which case the answer is delayed. is REACHABLE, or TENTATIVE in which case the answer is delayed. In
any other state, the Sleeping Proxy operates as a Unicasting Proxy.
In any other state, the Sleeping Proxy operates as a Unicasting The 6BBR does not act on ND Messages over the backbone unless they
Proxy. 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 As a Unicasting Proxy, the 6BBR forwards NS lookup messages to the
Registering Node, transforming Layer-2 multicast into unicast Registering Node, transforming Layer-2 multicast into unicast. This
whenever possible. This is not possible in UNREACHABLE state, so the is not possible in UNREACHABLE state, so the NS messages are
NS messages are multicasted, and rate-limited to protect the medium multicasted, and rate-limited with an exponential back-off to protect
with an exponential back-off. In other states, The messages are the medium. In other states, the messages are forwarded to the
forwarded to the Registering Node as unicast Layer-2 messages. In Registering Node as unicast Layer-2 messages. In TENTATIVE state,
TENTATIVE state, the NS message is either held till DAD completes, or the NS message is either held till DAD completes, or dropped.
dropped.
The draft introduces the optional concept of primary and secondary The draft introduces the optional concept of primary and secondary
BBRs. The primary is the backbone router that has the highest EUI-64 BBRs. The primary is the backbone router that has the highest EUI-64
address of all the 6BBRs that share a registration for a same address of all the 6BBRs that share a registration for a same
Registered Address, with the same Owner Unique ID and same Registered Address, with the same ROVR and same Transaction ID, the
Transaction ID, the EUI-64 address being considered as an unsigned EUI-64 address being considered as an unsigned 64bit integer. A
64bit integer. The concept is defined with the granularity of an given 6BBR can be primary for a given address and secondary for
address, that is a given 6BBR can be primary for a given address and another address, regardless on whether or not the addresses belong to
secondary or another one, regardless on whether the addresses belong the same node. The primary Backbone Router is in charge of
to the same node or not. The primary Backbone Router is in charge of
protecting the address for DAD over the Backbone. Any of the Primary protecting the address for DAD over the Backbone. Any of the Primary
and Secondary 6BBR may claim the address over the backbone, since and Secondary 6BBR may claim the address over the backbone, since
they are all capable to route from the backbone to the LLN node, and they are all capable to route from the backbone to the LLN node; the
the address appears on the backbone as an anycast address. address appears on the backbone as an anycast address.
The Backbone Routers maintain a distributed binding table, using The Backbone Routers maintain a distributed binding table, using IPv6
classical ND over the backbone to detect duplication. This ND over the backbone to detect duplication. This specification
specification requires that: requires that:
1. All addresses that can be reachable from the backbone, including 1. Addresses in a LLN that can be reachable from the backbone by way
IPv6 addresses based on burn-in EUI64 addresses MUST be of a 6BBR MUST be registered to that 6BBR.
registered to the 6BBR.
2. A Registered Node MUST include the EARO option in an NS message 2. A Registered Node MUST include the EARO in the NS message when
that used to register an addresses to a 6LR; the 6LR MUST registering its addresses to a 6LR. The 6LR MUST forward the
propagate that option unchanged to the 6LBR in the DAR/DAC EARO unchanged to the 6LBR in the DAR/DAC exchange. The 6LBR
exchange, and the 6LBR MUST propagate that option unchanged in MUST propagate the EARO unchanged to 6BBR.
proxy registrations.
3. The 6LR MUST echo the same EARO option in the NA that it uses to 3. The 6LR MUST respond with the same EARO in the NA, except for the
respond, but for the status filed which is not used in NS status field.
messages, and significant in NA.
A false positive duplicate detection may arise over the backbone, for A false positive duplicate detection may arise over the backbone, for
instance if the Registered Address is registered to more than one instance if the Registered Address is registered to more than one
LBR, or if the node has moved. Both situations are handled LBR, or if the node has moved. Both situations are handled by the
gracefully unbeknownst to the node. In the former case, one LBR 6BBR transparently to the node. In the former case, one LBR becomes
becomes primary to defend the address over the backbone while the primary to defend the address over the backbone while the others
others become secondary and may still forward packets back and forth. become secondary and may still forward packets. In the latter case
In the latter case the LBR that receives the newest registration wins the LBR that receives the newest registration becomes primary.
and becomes primary.
The expectation in this specification is that there is a single
Registering Node at a time per Backbone Router for a given Registered
Address, but that a Registered Address may be registered to Multiple
6BBRs for higher availability.
Over the LLN, and for any given Registered Address, it is REQUIRED Only one node may register a given Address at a particular 6BBR.
that: However, that Registered Address may be registered to Multiple 6BBRs
for higher availability.
de-registrations (newer TID, same OUID, null Lifetime) are Over the LLN, Binding Table management is as follows:
accepted and responded immediately with a status of 4; the entry
is deleted;
newer registrations (newer TID, same OUID, non-null Lifetime) are De-registrations (newer TID, same ROVR, null Lifetime) are
accepted and responded with a status of 0 (success); the entry is accepted and acknowledged with a status of 4; the entry is
updated with the new TID, the new Registration Lifetime and the deleted;
new Registering Node, if any has changed; in TENTATIVE state the
response 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 OUID) from a same Newer registrations (newer TID, same ROVR, non-null Lifetime) are
Registering Node are not processed but responded with a status of acknowledged with a status of 0 (success); the binding is updated
0 (success); they are expected to be identical and an error may be with the new TID, the Registration Lifetime and the Registering
logged if not; in TENTATIVE state, the response is held and may be Node; in TENTATIVE state the acknowledgement is held and may be
overwritten, but it MUST be eventually produced and it carries the overwritten; in other states the Registration-Lifetime timer is
result of the DAD process; restarted and the entry is placed in REACHABLE state.
older registrations (not(newer or equal) TID, same OUID) from a Identical registrations (same TID, same ROVR) from a same
same Registering Node are ignored; Registering Node are acknowledged with a status of 0 (success).
If they are not identical, an error SHOULD be logged. In
TENTATIVE state, the response is held and may be overwritten, but
it MUST be eventually produced and it carries the result of the
DAD process;
Older registrations (older TID, same ROVR) from a Registering Node
are ignored;
identical and older registrations (not-newer TID, same OUID) from Identical and older registrations (not-newer TID, same ROVR) from
a different Registering Node are responded immediately with a a different Registering Node are acknowledged with a status of 3
status of 3 (moved); this may be rate limited to protect the (moved); this may be rate limited to protect the medium;
medium;
and any registration for a different Registered Node (different Any registration for a different Registered Node (different ROVR)
OUID) are responded immediately with a status of 1 (duplicate). are acknowledged with a status of 1 (duplicate).
6.1. Registration and Binding State Creation 6.1. Registration and Binding State Creation
Upon a registration for a new address with an NS(EARO) with the 'R' Upon receiving a registration for a new address with an NS(EARO) with
bit set, the 6BBR performs a DAD operation over the backbone placing the 'R' bit set, the 6BBR performs DAD over the backbone, placing the
the new address as target in the NS-DAD message. The EARO from the new address as target in the NS-DAD message. The EARO from the
registration MUST be placed unchanged in the NS-DAD message, and an registration MUST be placed unchanged in the NS-DAD message, and an
entry is created in TENTATIVE state for a duration of Neighbor Cache entry created in TENTATIVE state for a duration of
TENTATIVE_DURATION. The NS-DAD message is sent multicast over the TENTATIVE_DURATION. The NS-DAD message is sent multicast over the
backbone to the SNMA address associated with the registered address. backbone to the SNMA associated with the registered address, unless
If that operation is known to be costly, and the 6BBR has an that operation is known to be costly, and the 6BBR has an indication
indication from another source (such as a NCE) that the Registered from another source (such as a Neighbor Cache entry) that the
Address was present on the backbone, that information may be Registered Address was known on the backbone; in the latter case, an
leveraged to send the NS-DAD message as a Layer-2 unicast to the MAC NS-DAD message may be sent as a Layer-2 unicast to the MAC Address
that was associated with the Registered Address. that was associated with the Registered Address.
In TENTATIVE state: In TENTATIVE state after EARO with 'R' bit set:
o the entry is removed if an NA is received over the backbone for 1. The entry is removed if an NA is received over the backbone for
the Registered Address with no EARO option, or with an EARO option the Registered Address with no EARO, or with an EARO with a
with a status of 1 (duplicate) that indicates an existing status of 1 (duplicate) that indicates an existing registration
registration for another LLN node. The OUID and TID fields in the for another LLN node. The ROVR and TID fields in the EARO
EARO option received over the backbone are ignored. A status of 1 received over the backbone are ignored. A status of 1 is
is returned in the EARO option of the NA back to the Registering returned in the EARO of the NA back to the Registering Node;
Node;
o the entry is also removed if an NA with an ARO option with a 2. The entry is also removed if an NA with an ARO option with a
status of 3 (moved), or a NS-DAD with an ARO option that indicates status of 3 (moved), or a NS-DAD with an ARO option that
a newer registration for the same Registered Node, is received indicates a newer registration for the same Registered Node, is
over the backbone for the Registered Address. A status of 3 is received over the backbone for the Registered Address. A status
returned in the NA(EARO) back to the Registering Node; of 3 is returned in the NA(EARO) back to the Registering Node;
o when a registration is updated but not deleted, e.g. from a newer 3. When a registration is updated but not deleted, e.g. from a newer
registration, the DAD process on the backbone continues and the registration, the DAD process on the backbone continues and the
running timers are not restarted; running timers are not restarted;
o Other NS (including DAD with no EARO option) and NA from the 4. Other NS (including DAD with no EARO) and NA from the backbone
backbone are not responded in TENTATIVE state, but the list of are not acknowledged in TENTATIVE state. To cover legacy nodes
their origins may be kept in memory and if so, the 6BBR may send that do not support ODAD, the list of their origins MAY be stored
them each a unicast NA with eventually an EARO option when the and then, if the TENTATIVE_DURATION timer elapses, the 6BBR MAY
TENTATIVE_DURATION timer elapses, so as to cover legacy nodes that send each such legacy node a unicast NA.
do not support ODAD.
o When the TENTATIVE_DURATION timer elapses, a status 0 (success) is 5. When the TENTATIVE_DURATION timer elapses, a status 0 (success)
returned in a NA(EARO) back to the Registering Node(s), and the is returned in a NA(EARO) back to the Registering Node(s), and
entry goes to REACHABLE state for the Registration Lifetime; the the entry goes to REACHABLE state for the Registration Lifetime.
DAD process is successful and the 6BBR MUST send a multicast The 6BBR MUST send a multicast NA(EARO) to the SNMA associated to
NA(EARO) to the SNMA associated to the Registered Address over the the Registered Address over the backbone with the Override bit
backbone with the Override bit set so as to take over the binding set so as to take over the binding from other 6BBRs.
from other 6BBRs.
6.2. Defending Addresses 6.2. Defending Addresses
If a 6BBR has an entry in REACHABLE state for a Registered Address: If a 6BBR has an entry in REACHABLE state for a Registered Address:
o If the 6BBR is primary, or does not support the function of o If the 6BBR is primary, or does not support the function of
primary, it MUST defend that address over the backbone upon an primary, it MUST defend that address over the backbone upon
incoming NS-DAD, either if the NS does not carry an EARO, or if an receiving NS-DAD, either if the NS does not carry an EARO, or if
EARO is present that indicates a different Registering Node an EARO is present that indicates a different Registering Node
(different OUID). The 6BBR sends a NA message with the Override (different ROVR). The 6BBR sends a NA message with the Override
bit set and the NA carries an EARO option if and only if the NS- bit set and the NA carries an EARO if and only if the NS-DAD did
DAD did so. When present, the EARO in the NA(O) that is sent in so. When present, the EARO in the NA(Override) that is sent in
response to the NS-DAD(EARO) carries a status of 1 (duplicate), response to the NS-DAD(EARO) carries a status of 1 (duplicate),
and the OUID and TID fields in the EARO option are obfuscated with and the ROVR and TID fields in the EARO are obfuscated with null
null or random values to avoid network scanning and impersonation or random values to avoid network scanning and impersonation
attacks. attacks.
o If the 6BBR receives an NS-DAD(EARO) that reflect a newer o If the 6BBR receives an NS-DAD(EARO) for a newer registration, the
registration, the 6BBR updates the entry and the routing state to 6BBR updates the entry and the routing state to forward packets to
forward packets to the new 6BBR, but keeps the entry REACHABLE. the new 6BBR, but keeps the entry REACHABLE. Afterwards, the 6BBR
In that phase, it MAY use REDIRECT messages to reroute traffic for MAY use REDIRECT messages to reroute traffic for the Registered
the Registered Address to the new 6BBR. Address to the new 6BBR.
o If the 6BBR receives an NA(EARO) that reflect a newer o If the 6BBR receives an NA(EARO) for a newer registration, the
registration, the 6BBR removes its entry and sends a NA(AERO) with 6BBR removes its entry and sends a NA(EARO) with a status of 3
a status of 3 (moved) to the Registering Node, if the Registering (MOVED) to the Registering Node, if the Registering Node is
Node is different from the Registered Node. If necessary, the different from the Registered Node. The 6BBR cleans up existing
6BBR cleans up ND cache in peers nodes as discussed in Neighbor Cache Entries in peer nodes as discussed in Section 5.1,
Section 5.1, by sending a series of unicast to the impacted nodes, by unicasting to each such peer, or one broadcast NA(Override).
or one broadcast NA(O) to all-nodes.
o If the 6BBR received a NS(LOOKUP) for a Registered Address, it o If the 6BBR receives a NS(LOOKUP) for a Registered Address, it
answers immediately with an NA on behalf of the Registered Node, answers immediately with an NA on behalf of the Registered Node,
without polling it. There is no need of an EARO in that exchange. without polling it. There is no need of an EARO in that exchange.
o When the Registration-Lifetime timer elapses, the entry goes to o When the Registration-Lifetime timer elapses, the entry goes to
STALE state for a duration of STABLE_STALE_DURATION in LLNs that STALE state for a duration of STABLE_STALE_DURATION in LLNs that
keep stable addresses such as LWPANs, and UNSTABLE_STALE_DURATION keep stable addresses such as LWPANs, and UNSTABLE_STALE_DURATION
in LLNs where addresses are renewed rapidly, e.g. for privacy in LLNs where addresses are renewed rapidly, e.g. for privacy
reasons. reasons.
The STALE state is a chance to keep track of the backbone peers that The STALE state enables tracking of the backbone peers that have a
may have an ND cache pointing on this 6BBR in case the Registered Neighbor Cache entry pointing to this 6BBR in case the Registered
Address shows back up on this or a different 6BBR at a later time. Address shows up later. If the Registered Address is claimed by
In STALE state: another node on the backbone, with an NS-DAD or an NA, the 6BBR does
not defend the address. In STALE state:
o If the Registered Address is claimed by another node on the o If STALE_DURATION elapses, the 6BBR removes the entry.
backbone, with an NS-DAD or an NA, the 6BBR does not defend the
address. Upon an NA(O), or the stale time elapses, the 6BBR
removes its entry and sends a NA(AERO) with a status of 4
(removed) to the Registering Node.
o If the 6BBR received a NS(LOOKUP) for a Registered Address, the o Upon receiving an NA(Override) the 6BBR removes its entry and
sends a NA(EARO) with a status of 4 (removed) to the Registering
Node.
o If the 6BBR receives a NS(LOOKUP) for a Registered Address, the
6BBR MUST send an NS(NUD) following rules in [RFC7048] to the 6BBR MUST send an NS(NUD) following rules in [RFC7048] to the
Registering Node targeting the Registered Address prior to Registering Node targeting the Registered Address prior to
answering. If the NUD succeeds, the operation in REACHABLE state answering. If the NUD succeeds, the operation in REACHABLE state
applies. If the NUD fails, the 6BBR refrains from answering the applies. If the NUD fails, the 6BBR refrains from answering the
lookup. The NUD expected to be mapped by the Registering Node lookup. The NUD SHOULD be used by the Registering Node to
into a liveliness validation of the Registered Node if they are in indicate liveness of the Registered Node, if they are different
fact different nodes. nodes.
7. Security Considerations 7. Security Considerations
This specification expects that the link layer is sufficiently 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, it is Backbone Link or MAC sublayer cryptography. In particular, the LLN
expected that the LLN MAC provides secure unicast to/from the MAC is required to provide secure unicast to/from the Backbone Router
Backbone Router and secure Broadcast from the Backbone Router in a and secure Broadcast from the Backbone Router in a way that prevents
way that prevents tempering with or replaying the RA messages. tempering with or replaying the RA messages.
The use of EUI-64 for forming the Interface ID in the link local The use of EUI-64 for forming the Interface ID in the link local
address prevents the usage of Secure ND ([RFC3971] and [RFC3972]) and address prevents the usage of Secure ND ([RFC3971] and [RFC3972]) and
address privacy techniques. This specification RECOMMENDS the use of address privacy techniques. This specification RECOMMENDS the use of
additional protection against address theft such as provided by additional protection against address theft such as provided by
[I-D.ietf-6lo-ap-nd], which guarantees the ownership of the OUID. [I-D.ietf-6lo-ap-nd], which guarantees the ownership of the ROVR.
When the ownership of the OUID cannot be assessed, this specification When the ownership of the ROVR cannot be assessed, this specification
limits the cases where the OUID and the TID are multicasted, and limits the cases where the ROVR and the TID are multicasted, and
obfuscates them in responses to attempts to take over an address. obfuscates them in responses to attempts to take over an address.
8. Protocol Constants 8. Protocol Constants
This Specification uses the following constants: This Specification uses the following constants:
TENTATIVE_DURATION: 800 milliseconds TENTATIVE_DURATION: 800 milliseconds
STABLE_STALE_DURATION: 24 hours STABLE_STALE_DURATION: 24 hours
UNSTABLE_STALE_DURATION: 5 minutes UNSTABLE_STALE_DURATION: 5 minutes
DEFAULT_NS_POLLING: 3 times DEFAULT_NS_POLLING: 3 times
9. IANA Considerations 9. IANA Considerations
This document has no request to IANA. This document has no request to IANA.
10. Acknowledgments 10. Acknowledgments
skipping to change at page 19, line 16 skipping to change at page 17, line 23
Kudos to Eric Levy-Abegnoli who designed the First Hop Security Kudos to Eric Levy-Abegnoli who designed the First Hop Security
infrastructure at Cisco. infrastructure at Cisco.
11. References 11. References
11.1. Normative References 11.1. Normative References
[I-D.ietf-6lo-rfc6775-update] [I-D.ietf-6lo-rfc6775-update]
Thubert, P., Nordmark, E., Chakrabarti, S., and C. Thubert, P., Nordmark, E., Chakrabarti, S., and C.
Perkins, "An Update to 6LoWPAN ND", draft-ietf-6lo- Perkins, "Registration Extensions for 6LoWPAN Neighbor
rfc6775-update-13 (work in progress), February 2018. Discovery", draft-ietf-6lo-rfc6775-update-21 (work in
progress), June 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>. 2006, <https://www.rfc-editor.org/info/rfc4291>.
skipping to change at page 20, line 32 skipping to change at page 18, line 44
6man-efficient-nd-07 (work in progress), February 2015. 6man-efficient-nd-07 (work in progress), February 2015.
[I-D.delcarpio-6lo-wlanah] [I-D.delcarpio-6lo-wlanah]
Vega, L., Robles, I., and R. Morabito, "IPv6 over Vega, L., Robles, I., and R. Morabito, "IPv6 over
802.11ah", draft-delcarpio-6lo-wlanah-01 (work in 802.11ah", draft-delcarpio-6lo-wlanah-01 (work in
progress), October 2015. progress), October 2015.
[I-D.ietf-6lo-ap-nd] [I-D.ietf-6lo-ap-nd]
Thubert, P., Sarikaya, B., and M. Sethi, "Address Thubert, P., Sarikaya, B., and M. Sethi, "Address
Protected Neighbor Discovery for Low-power and Lossy Protected Neighbor Discovery for Low-power and Lossy
Networks", draft-ietf-6lo-ap-nd-06 (work in progress), Networks", draft-ietf-6lo-ap-nd-07 (work in progress),
February 2018. September 2018.
[I-D.ietf-6lo-nfc] [I-D.ietf-6lo-nfc]
Choi, Y., Hong, Y., Youn, J., Kim, D., and J. Choi, Choi, Y., Hong, Y., Youn, J., Kim, D., and J. Choi,
"Transmission of IPv6 Packets over Near Field "Transmission of IPv6 Packets over Near Field
Communication", draft-ietf-6lo-nfc-09 (work in progress), Communication", draft-ietf-6lo-nfc-10 (work in progress),
January 2018. July 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-13 (work of IEEE 802.15.4", draft-ietf-6tisch-architecture-14 (work
in progress), November 2017. in progress), April 2018.
[I-D.ietf-6tisch-terminology] [I-D.ietf-6tisch-terminology]
Palattella, M., Thubert, P., Watteyne, T., and Q. Wang, Palattella, M., Thubert, P., Watteyne, T., and Q. Wang,
"Terminology in IPv6 over the TSCH mode of IEEE "Terms Used in IPv6 over the TSCH mode of IEEE 802.15.4e",
802.15.4e", draft-ietf-6tisch-terminology-09 (work in draft-ietf-6tisch-terminology-10 (work in progress), March
progress), June 2017. 2018.
[I-D.ietf-bier-architecture] [I-D.ietf-bier-architecture]
Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and
S. Aldrin, "Multicast using Bit Index Explicit S. Aldrin, "Multicast using Bit Index Explicit
Replication", draft-ietf-bier-architecture-08 (work in Replication", draft-ietf-bier-architecture-08 (work in
progress), September 2017. progress), September 2017.
[I-D.ietf-ipv6-multilink-subnets] [I-D.ietf-ipv6-multilink-subnets]
Thaler, D. and C. Huitema, "Multi-link Subnet Support in Thaler, D. and C. Huitema, "Multi-link Subnet Support in
IPv6", draft-ietf-ipv6-multilink-subnets-00 (work in IPv6", draft-ietf-ipv6-multilink-subnets-00 (work in
skipping to change at page 24, line 7 skipping to change at page 22, line 14
[RFC8163] Lynn, K., Ed., Martocci, J., Neilson, C., and S. [RFC8163] Lynn, K., Ed., Martocci, J., Neilson, C., and S.
Donaldson, "Transmission of IPv6 over Master-Slave/Token- Donaldson, "Transmission of IPv6 over Master-Slave/Token-
Passing (MS/TP) Networks", RFC 8163, DOI 10.17487/RFC8163, Passing (MS/TP) Networks", RFC 8163, DOI 10.17487/RFC8163,
May 2017, <https://www.rfc-editor.org/info/rfc8163>. May 2017, <https://www.rfc-editor.org/info/rfc8163>.
11.3. External Informative References 11.3. External Informative References
[IEEEstd8021] [IEEEstd8021]
IEEE standard for Information Technology, "IEEE Standard IEEE standard for Information Technology, "IEEE Standard
for Information technology-- Telecommunications and for Information technology -- Telecommunications and
information exchange between systems Local and information exchange between systems Local and
metropolitan area networks Part 1: Bridging and metropolitan area networks Part 1: Bridging and
Architecture". Architecture".
[IEEEstd80211] [IEEEstd80211]
IEEE standard for Information Technology, "IEEE Standard IEEE standard for Information Technology, "IEEE Standard
for Information technology-- Telecommunications and for Information technology -- Telecommunications and
information exchange between systems Local and information exchange between systems Local and
metropolitan area networks-- Specific requirements Part metropolitan area networks-- Specific requirements Part
11: Wireless LAN Medium Access Control (MAC) and Physical 11: Wireless LAN Medium Access Control (MAC) and Physical
Layer (PHY) Specifications". Layer (PHY) Specifications".
[IEEEstd802151] [IEEEstd802151]
IEEE standard for Information Technology, "IEEE Standard IEEE standard for Information Technology, "IEEE Standard
for Information Technology - Telecommunications and for Information Technology - Telecommunications and
Information Exchange Between Systems - Local and Information Exchange Between Systems - Local and
Metropolitan Area Networks - Specific Requirements. - Part Metropolitan Area Networks - Specific Requirements. - Part
15.1: Wireless Medium Access Control (MAC) and Physical 15.1: Wireless Medium Access Control (MAC) and Physical
Layer (PHY) Specifications for Wireless Personal Area Layer (PHY) Specifications for Wireless Personal Area
Networks (WPANs)". Networks (WPANs)".
[IEEEstd802154] [IEEEstd802154]
IEEE standard for Information Technology, "IEEE Standard IEEE standard for Information Technology, "IEEE Standard
for Local and metropolitan area networks-- Part 15.4: Low- for Local and metropolitan area networks -- Part 15.4:
Rate Wireless Personal Area Networks (LR-WPANs)". Low-Rate Wireless Personal Area Networks (LR-WPANs)".
Appendix A. Requirements
This section lists requirements that were discussed at 6lo for an
update to 6LoWPAN ND. This specification meets most of them, but
those listed in Appendix A.5 which are deferred to a different
specification such as [I-D.ietf-6lo-ap-nd].
A.1. Requirements Related to Mobility
Due to the unstable nature of LLN links, even in a LLN of immobile
nodes a 6LoWPAN Node may change its point of attachment to a 6LR, say
6LR-a, and may not be able to notify 6LR-a. Consequently, 6LR-a may
still attract traffic that it cannot deliver any more. When links to
a 6LR change state, there is thus a need to identify stale states in
a 6LR and restore reachability in a timely fashion.
Req1.1: Upon a change of point of attachment, connectivity via a new
6LR MUST be restored timely without the need to de-register from the
previous 6LR.
Req1.2: For that purpose, the protocol MUST enable to differentiate
between multiple registrations from one 6LoWPAN Node and
registrations from different 6LoWPAN Nodes claiming the same address.
Req1.3: Stale states MUST be cleaned up in 6LRs.
Req1.4: A 6LoWPAN Node SHOULD also be capable to register its Address
to multiple 6LRs, and this, concurrently.
A.2. Requirements Related to Routing Protocols
The point of attachment of a 6LoWPAN Node may be a 6LR in an LLN
mesh. IPv6 routing in a LLN can be based on RPL, which is the
routing protocol that was defined at the IETF for this particular
purpose. Other routing protocols than RPL are also considered by
Standard Defining Organizations (SDO) on the basis of the expected
network characteristics. It is required that a 6LoWPAN Node attached
via ND to a 6LR would need to participate in the selected routing
protocol to obtain reachability via the 6LR.
Next to the 6LBR unicast address registered by ND, other addresses
including multicast addresses are needed as well. For example a
routing protocol often uses a multicast address to register changes
to established paths. ND needs to register such a multicast address
to enable routing concurrently with discovery.
Multicast is needed for groups. Groups MAY be formed by device type
(e.g. routers, street lamps), location (Geography, RPL sub-tree), or
both.
The Bit Index Explicit Replication (BIER) Architecture
[I-D.ietf-bier-architecture] proposes an optimized technique to
enable multicast in a LLN with a very limited requirement for routing
state in the nodes.
Related requirements are:
Req2.1: The ND registration method SHOULD be extended in such a
fashion that the 6LR MAY advertise the Address of a 6LoWPAN Node over
the selected routing protocol and obtain reachability to that Address
using the selected routing protocol.
Req2.2: Considering RPL, the Address Registration Option that is used
in the ND registration SHOULD be extended to carry enough information
to generate a DAO message as specified in [RFC6550] section 6.4, in
particular the capability to compute a Path Sequence and, as an
option, a RPLInstanceID.
Req2.3: Multicast operations SHOULD be supported and optimized, for
instance using BIER or MPL. Whether ND is appropriate for the
registration to the 6BBR is to be defined, considering the additional
burden of supporting the Multicast Listener Discovery Version 2
[RFC3810] (MLDv2) for IPv6.
A.3. Requirements Related to the Variety of Low-Power Link types
6LoWPAN ND [RFC6775] was defined with a focus on IEEE std. 802.15.4
and in particular the capability to derive a unique Identifier from a
globally unique MAC-64 address. At this point, the 6lo Working Group
is extending the 6LoWPAN Header Compression (HC) [RFC6282] technique
to other link types ITU-T G.9959 [RFC7428], Master-Slave/Token-
Passing [RFC8163], DECT Ultra Low Energy [RFC8105], Near Field
Communication [I-D.ietf-6lo-nfc], IEEE std. 802.11ah
[I-D.delcarpio-6lo-wlanah], as well as IEEE1901.2 Narrowband
Powerline Communication Networks
[I-D.popa-6lo-6loplc-ipv6-over-ieee19012-networks] and BLUETOOTH(R)
Low Energy [RFC7668].
Related requirements are:
Req3.1: The support of the registration mechanism SHOULD be extended
to more LLN links than IEEE 802.15.4, matching at least the LLN links
for which an "IPv6 over foo" specification exists, as well as Low-
Power Wi-Fi.
Req3.2: As part of this extension, a mechanism to compute a unique
Identifier should be provided, with the capability to form a Link-
Local Address that SHOULD be unique at least within the LLN connected
to a 6LBR discovered by ND in each node within the LLN.
Req3.3: The Address Registration Option used in the ND registration
SHOULD be extended to carry the relevant forms of unique Identifier.
Req3.4: The Neighbour Discovery should specify the formation of a
site-local address that follows the security recommendations from
[RFC7217].
A.4. Requirements Related to Proxy Operations
Duty-cycled devices may not be able to answer themselves to a lookup
from a node that uses classical ND on a backbone and may need a
proxy. Additionally, the duty-cycled device may need to rely on the
6LBR to perform registration to the 6BBR.
The ND registration method SHOULD defend the addresses of duty-cycled
devices that are sleeping most of the time and not capable to defend
their own Addresses.
Related requirements are:
Req4.1: The registration mechanism SHOULD enable a third party to
proxy register an Address on behalf of a 6LoWPAN node that may be
sleeping or located deeper in an LLN mesh.
Req4.2: The registration mechanism SHOULD be applicable to a duty-
cycled device regardless of the link type, and enable a 6BBR to
operate as a proxy to defend the registered Addresses on its behalf.
Req4.3: The registration mechanism SHOULD enable long sleep
durations, in the order of multiple days to a month.
A.5. Requirements Related to Security
In order to guarantee the operations of the 6LoWPAN ND flows, the
spoofing of the 6LR, 6LBR and 6BBRs roles should be avoided. Once a
node successfully registers an address, 6LoWPAN ND should provide
energy-efficient means for the 6LBR to protect that ownership even
when the node that registered the address is sleeping.
In particular, the 6LR and the 6LBR then should be able to verify
whether a subsequent registration for a given Address comes from the
original node.
In a LLN it makes sense to base security on layer-2 security. During
bootstrap of the LLN, nodes join the network after authorization by a
Joining Assistant (JA) or a Commissioning Tool (CT). After joining
nodes communicate with each other via secured links. The keys for
the layer-2 security are distributed by the JA/CT. The JA/CT can be
part of the LLN or be outside the LLN. In both cases it is needed
that packets are routed between JA/CT and the joining node.
Related requirements are:
Req5.1: 6LoWPAN ND security mechanisms SHOULD provide a mechanism for
the 6LR, 6LBR and 6BBR to authenticate and authorize one another for
their respective roles, as well as with the 6LoWPAN Node for the role
of 6LR.
Req5.2: 6LoWPAN ND security mechanisms SHOULD provide a mechanism for
the 6LR and the 6LBR to validate new registration of authorized
nodes. Joining of unauthorized nodes MUST be impossible.
Req5.3: 6LoWPAN ND security mechanisms SHOULD lead to small packet
sizes. In particular, the NS, NA, DAR and DAC messages for a re-
registration flow SHOULD NOT exceed 80 octets so as to fit in a
secured IEEE std. 802.15.4 frame.
Req5.4: Recurrent 6LoWPAN ND security operations MUST NOT be
computationally intensive on the LoWPAN Node CPU. When a Key hash
calculation is employed, a mechanism lighter than SHA-1 SHOULD be
preferred.
Req5.5: The number of Keys that the 6LoWPAN Node needs to manipulate
SHOULD be minimized.
Req5.6: The 6LoWPAN ND security mechanisms SHOULD enable CCM* for use
at both Layer 2 and Layer 3, and SHOULD enable the reuse of security
code that has to be present on the device for upper layer security
such as TLS.
Req5.7: Public key and signature sizes SHOULD be minimized while
maintaining adequate confidentiality and data origin authentication
for multiple types of applications with various degrees of
criticality.
Req5.8: Routing of packets should continue when links pass from the
unsecured to the secured state.
Req5.9: 6LoWPAN ND security mechanisms SHOULD provide a mechanism for
the 6LR and the 6LBR to validate whether a new registration for a
given address corresponds to the same 6LoWPAN Node that registered it
initially, and, if not, determine the rightful owner, and deny or
clean-up the registration that is duplicate.
A.6. Requirements Related to Scalability
Use cases from Automatic Meter Reading (AMR, collection tree
operations) and Advanced Metering Infrastructure (AMI, bi-directional
communication to the meters) indicate the needs for a large number of
LLN nodes pertaining to a single RPL DODAG (e.g. 5000) and connected
to the 6LBR over a large number of LLN hops (e.g. 15).
Related requirements are:
Req6.1: The registration mechanism SHOULD enable a single 6LBR to
register multiple thousands of devices.
Req6.2: The timing of the registration operation should allow for a
large latency such as found in LLNs with ten and more hops.
Author's Address Authors' Addresses
Pascal Thubert (editor) Pascal Thubert (editor)
Cisco Systems, Inc Cisco Systems, Inc
Building D Building D
45 Allee des Ormes - BP1200 45 Allee des Ormes - BP1200
MOUGINS - Sophia Antipolis 06254 MOUGINS - Sophia Antipolis 06254
FRANCE FRANCE
Phone: +33 497 23 26 34 Phone: +33 497 23 26 34
Email: pthubert@cisco.com Email: pthubert@cisco.com
Charles E. Perkins
Futurewei
2330 Central Expressway
Santa Clara 95050
United States of America
Email: charliep@computer.org
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