< draft-thubert-6man-ipv6-over-wireless-00.txt   draft-thubert-6man-ipv6-over-wireless-01.txt >
6MAN P. Thubert, Ed. 6MAN P. Thubert, Ed.
Internet-Draft Cisco Systems Internet-Draft Cisco Systems
Intended status: Informational April 26, 2019 Intended status: Informational April 30, 2019
Expires: October 28, 2019 Expires: November 1, 2019
IPv6 Neighbor Discovery on Wireless Networks IPv6 Neighbor Discovery on Wireless Networks
draft-thubert-6man-ipv6-over-wireless-00 draft-thubert-6man-ipv6-over-wireless-01
Abstract Abstract
This document describes how the original IPv6 Neighbor Discovery and This document describes how the original IPv6 Neighbor Discovery and
Wireless ND (WiND) can be applied on various abstractions of wireless Wireless ND (WiND) can be applied on various abstractions of wireless
media. media.
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
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 28, 2019. This Internet-Draft will expire on November 1, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. IP Models . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. IP Models . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.1. Physical Broadcast Domain . . . . . . . . . . . . . . . . 2 2.1. Physical Broadcast Domain . . . . . . . . . . . . . . . . 2
2.2. MAC-Layer Broadcast Emulations . . . . . . . . . . . . . 3 2.2. MAC-Layer Broadcast Emulations . . . . . . . . . . . . . 3
2.3. Mapping the IPv6 Link Abstraction . . . . . . . . . . . . 4 2.3. Mapping the IPv6 Link Abstraction . . . . . . . . . . . . 5
2.4. Mapping the IPv6 Subnet Abstraction . . . . . . . . . . . 6 2.4. Mapping the IPv6 Subnet Abstraction . . . . . . . . . . . 6
3. IPv6 Over Wireless . . . . . . . . . . . . . . . . . . . . . 7 3. Wireless ND . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Case of LPWANs . . . . . . . . . . . . . . . . . . . . . 7 3.1. Introduction to WiND . . . . . . . . . . . . . . . . . . 6
3.2. Case of Infrastructure BSS and ESS . . . . . . . . . . . 7 3.2. Links and Link-Local Addresses . . . . . . . . . . . . . 7
3.3. Case of Mesh Under Technologies . . . . . . . . . . . . . 8 3.3. Subnets and Global Addresses . . . . . . . . . . . . . . 8
3.4. Case of DMC radios . . . . . . . . . . . . . . . . . . . 8 4. WiND Applicability . . . . . . . . . . . . . . . . . . . . . 9
3.4.1. Using IPv6 ND only . . . . . . . . . . . . . . . . . 9 4.1. Case of LPWANs . . . . . . . . . . . . . . . . . . . . . 10
3.4.2. Using Wireless ND . . . . . . . . . . . . . . . . . . 9 4.2. Case of Infrastructure BSS and ESS . . . . . . . . . . . 10
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 4.3. Case of Mesh Under Technologies . . . . . . . . . . . . . 11
5. Security Considerations . . . . . . . . . . . . . . . . . . . 12 4.4. Case of DMC radios . . . . . . . . . . . . . . . . . . . 11
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12 4.4.1. Using IPv6 ND only . . . . . . . . . . . . . . . . . 11
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.4.2. Using Wireless ND . . . . . . . . . . . . . . . . . . 11
7.1. Normative References . . . . . . . . . . . . . . . . . . 12 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
7.2. Informative References . . . . . . . . . . . . . . . . . 13 6. Security Considerations . . . . . . . . . . . . . . . . . . . 14
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 14 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.1. Normative References . . . . . . . . . . . . . . . . . . 14
8.2. Informative References . . . . . . . . . . . . . . . . . 15
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
2. IP Models 2. IP Models
2.1. Physical Broadcast Domain 2.1. Physical Broadcast Domain
At the physical (PHY) Layer, a broadcast domain is the set of all At the physical (PHY) Layer, a broadcast domain is the set of all
peers that may receive a datagram that one sends over an interface. peers that may receive a datagram that one sends over an interface.
This set can comprise a single peer on a serial cable used as point- This set can comprise a single peer on a serial cable used as point-
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duration that can be 100 times that of a unicast. For that reason, duration that can be 100 times that of a unicast. For that reason,
upper layer protocols should tend to avoid the use of broadcast when upper layer protocols should tend to avoid the use of broadcast when
operating over Wi-Fi. operating over Wi-Fi.
In an IEEE Std 802.11 Infrastructure Extended Service Set (ESS), the In an IEEE Std 802.11 Infrastructure Extended Service Set (ESS), the
process of the association also prepares a bridging state proactively process of the association also prepares a bridging state proactively
at the AP, so as to avoid the reactive broadcast lookup that takes at the AP, so as to avoid the reactive broadcast lookup that takes
place in the process of transparent bridging over a spanning tree. place in the process of transparent bridging over a spanning tree.
This model provides a more reliable operation than the reactive This model provides a more reliable operation than the reactive
transparent bridging and avoid the need of multicast, and it is only transparent bridging and avoid the need of multicast, and it is only
logical that IPv6 ND evolved towards proposes similar methods at logical that IPv6 [RFC8200] Neighbor Discovery (ND)
[RFC4861][RFC4862] evolved towards proposes similar methods at
Layer-3 for its operation. Layer-3 for its operation.
in some cases of WLAN and WPAN radios, a mesh-under technology (e.g., in some cases of WLAN and WPAN radios, a mesh-under technology (e.g.,
a IEEE 802.11s or IEEE 802.15.10) provides meshing services that are a IEEE 802.11s or IEEE 802.15.10) provides meshing services that are
similar to bridgeing, and the broadcast domain is well defined by the similar to bridgeing, and the broadcast domain is well defined by the
membership of the mesh. Mesh-Under emulates a broadcast domain by membership of the mesh. Mesh-Under emulates a broadcast domain by
flooding the broadcast packets at Layer-2. When operating on a flooding the broadcast packets at Layer-2. When operating on a
single frequency, this operation is known to interfere with itself, single frequency, this operation is known to interfere with itself,
forcing deployment to introduce delays that dampen the collisions. forcing deployment to introduce delays that dampen the collisions.
All in all, the mechanism is slow, inefficient and expensive. All in all, the mechanism is slow, inefficient and expensive.
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DAD operation cannot provide once and for all guarantees on the DAD operation cannot provide once and for all guarantees on the
broadcast domain defined by one radio transmitter if that transmitter broadcast domain defined by one radio transmitter if that transmitter
keeps meeting new peers on the go. The nodes may need to form new keeps meeting new peers on the go. The nodes may need to form new
LLAs to talk to one another and the scope where LLA uniqueness can be LLAs to talk to one another and the scope where LLA uniqueness can be
dynamically checked is that pair of nodes. As long as there's no dynamically checked is that pair of nodes. As long as there's no
conflict a node may use the same LLA with multiple peers but it has conflict a node may use the same LLA with multiple peers but it has
to revalidate DAD with every new peer node. In practice, each pair to revalidate DAD with every new peer node. In practice, each pair
of nodes defines a temporary P2P link, which can be modeled as a sub- of nodes defines a temporary P2P link, which can be modeled as a sub-
interface of the radio interface. interface of the radio interface.
Wireless Neighbor Discovery (WiND)
[RFC6775][RFC8505][I-D.ietf-6lo-backbone-router][I-D.ietf-6lo-ap-nd]
defines a new ND operation that derives from the IEEE 802.11
Infrastructure mode. For LLAs, DAD is performed between
communicating pairs of nodes. It is carried out as part of a
registration process that is based on a NS/NA exchange that
transports an Extended Address Registration Option (EARO). During
that process, the DAD is validated and a Neighbor Cache Entry (NCE)
is populated with a single unicast exchange.
2.4. Mapping the IPv6 Subnet Abstraction 2.4. Mapping the IPv6 Subnet Abstraction
IPv6 also defines a concept of Subnet for Glocal and Unique Local IPv6 also defines a concept of Subnet for Glocal and Unique Local
Addresses. Addresses in a same Subnet share a same prefix and by Addresses. Addresses in a same Subnet share a same prefix and by
extension, a node belongs to a Subnet if it has an interface with an extension, a node belongs to a Subnet if it has an interface with an
address on that Subnet. A Subnet prefix is Globally Unique so it is address on that Subnet. A Subnet prefix is Globally Unique so it is
sufficient to validate that an address that is formed from a Subnet sufficient to validate that an address that is formed from a Subnet
prefix is unique within that Subnet to guarantee that it is globally prefix is unique within that Subnet to guarantee that it is globally
unique. IPv6 aggregation relies on the property that a packet from unique. IPv6 aggregation relies on the property that a packet from
the outside of a Subnet can be routed to any router that belongs to the outside of a Subnet can be routed to any router that belongs to
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On IEEE Std. 802.3, a Subnet is often congruent with an IP Link On IEEE Std. 802.3, a Subnet is often congruent with an IP Link
because both are determined by the physical attachment to an Ethernet because both are determined by the physical attachment to an Ethernet
shared wire or an IEEE Std. 802.1 bridged broadcast domain. In that shared wire or an IEEE Std. 802.1 bridged broadcast domain. In that
case, the connectivity over the Link is transitive, the Subnet can case, the connectivity over the Link is transitive, the Subnet can
appear as onlink, and any node can resolve a destination MAC address appear as onlink, and any node can resolve a destination MAC address
of any other node directly using IPv6 Neighbor Discovery. of any other node directly using IPv6 Neighbor Discovery.
But an IP Link and an IP Subnet are not always congruent. In a But an IP Link and an IP Subnet are not always congruent. In a
shared Link situation, a Subnet may encompass only a subset of the shared Link situation, a Subnet may encompass only a subset of the
nodes connected to the Link. In Route-Over Multi-Link Subnets nodes connected to the Link. In Route-Over Multi-Link Subnets (MLSN)
(MLSN), routers federate the Links between nodes that belong to the [RFC4903], routers federate the Links between nodes that belong to
Subnet, the Subnet is not onlink and it extends beyond any of the the Subnet, the Subnet is not onlink and it extends beyond any of the
federated Links. federated Links.
The DAD and lookup procedures in IPv6 ND expects that a node in a The DAD and lookup procedures in IPv6 ND expects that a node in a
Subnet is reachable within the broadcast domain of any other node in Subnet is reachable within the broadcast domain of any other node in
the Subnet when that other node attempts to form an address that the Subnet when that other node attempts to form an address that
would be a duplicate or attempts to resolve the MAC address of this would be a duplicate or attempts to resolve the MAC address of this
node. This is why ND is only applicable for P2P and transit links, node. This is why ND is only applicable for P2P and transit links,
and requires extensions for other topologies. and requires extensions for other topologies.
WiND extends IPv6 ND for Hub-and-Spoke MLSN (e.g., a central and some 3. Wireless ND
peripheral nodes in Bluetooth low energy (BTLE)[RFC7668]) and Route-
Over MLSN (e.g., [I-D.ietf-6tisch-architecture] leveraging [RFC6550]) 3.1. Introduction to WiND
topologies.
Wireless Neighbor Discovery (WiND)
[RFC6775][RFC8505][I-D.ietf-6lo-backbone-router][I-D.ietf-6lo-ap-nd]
defines a new ND operation that is based on 2 major paradigm changes,
proactive address registration by hosts to their attachment routers
and routing to host routes (/128) within the subnet. This allows
WiND to avoid the classical ND expectations of transit links and
Subnet-wide broadcast domains.
The proactive address registration is performed with a new option in
NS/NA messages, the Extended Address Registration Option (EARO)
defiend in [RFC8505]. This method allows to prepare and maintain the
host routes in the routers and avoids the reactive NS(Lookup) found
in IPv6 ND. This is a direct benefit for wireless Links since it
avoids the MAC level broadcasts that are associated to NS(Lookup).
The EARO provides information to the router that is independent to
the routing protocol and routing can take multiple forms, from a
traditional IGP to a collapsed ub-and-Spoke model where only one
router owns and advertises the prefix. [RFC8505] is already
referenced for RIFT [I-D.ietf-rift-rift], RPL [RFC6550] with
[I-D.thubert-roll-unaware-leaves] and IPv6 ND proxy
[I-D.ietf-6lo-backbone-router].
WiND does not change IPv6 addressing [RFC4291] or the current
practices of assigning prefixes to subnets. It is still typical to
assign a /64 to a subnet and to use interface IDs of 64 bits.
Duplicate Address detection within the Subnet is performed with a
central registrar, using new ND Extended Duplicate Address messages
(EDAR and EDAC) [RFC8505]. This operation modernizes ND for
application in overlays with Map Resolvers and enables unicast
lookups [I-D.thubert-6lo-unicast-lookup] for addresses registered to
the resolver.
WiND also enables to extend a legacy /64 on Ethernet with ND proxy
over the wireless. This way nodes can form any address the want and
move freely from an L3-AP (that is really a backbone router in
bridging mode, more in [I-D.ietf-6lo-backbone-router]) to another,
without renumbering.
WiND is also compatible with DHCPv6 and other forms of address
assignment in which case it can still be used for DAD.
3.2. Links and Link-Local Addresses
For Link-Local Addresses, DAD is performed between communicating
pairs of nodes. It is carried out as part of a registration process
that is based on a NS/NA exchange that transports an EARO. During
that process, the DAD is validated and a Neighbor Cache Entry (NCE)
is populated with a single unicast exchange.
Ior instance, in the case of a Bluetooth Low Energy (BLE) [RFC7668]
Hub-and Spoke configuration, Uniqueness of Link local Addresses need
only to be verified between the pairs of communicating nodes, a
central router and a peripheral host. In that example, 2 peripheral
hosts connected to the same central router can not have the same Link
Local Address because the Binding Cache Entries (BCEs) would collide
at the central router which could not talk to both over the same
interface. The WiND operation is appropriate for that DAD operation,
but the one from ND is not, because peripheral hosts are not on the
same broadcast domain. On the other hand, Global and ULA DAD is
validated at the Subnet Level, using a registrar hosted by the
central router.
3.3. Subnets and Global Addresses
WiND extends IPv6 ND for Hub-and-Spoke (e.g., BLE) and Route-Over
(e.g., RPL) Multi-Link Subnets (MLSNs).
In the Hub-and-Spoke case, each Hub-Spoke pair is a distinct IP Link, In the Hub-and-Spoke case, each Hub-Spoke pair is a distinct IP Link,
and a Subnet can be mapped on a collection of Links that are and a Subnet can be mapped on a collection of Links that are
connected to the Hub. The Subnet prefix is associated to the Hub. connected to the Hub. The Subnet prefix is associated to the Hub.
Acting as 6LR, the Hub advertises the prefix as not-onlink to the Acting as 6LR, the Hub advertises the prefix as not-onlink to the
spokes in RA messages Prefix Information Options (PIO). Acting as spokes in RA messages Prefix Information Options (PIO). Acting as
6LNs, the Spokes autoconfigure addresses from that prefix and 6LNs, the Spokes autoconfigure addresses from that prefix and
register them to the Hub with a corresponding lifetime. Acting as a register them to the Hub with a corresponding lifetime. Acting as a
6LBR, the Hub maintains a binding table of all the registered IP 6LBR, the Hub maintains a binding table of all the registered IP
addresses and rejects duplicate registrations, thus ensuring a DAD addresses and rejects duplicate registrations, thus ensuring a DAD
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The registration in [RFC8505] is abstract to the routing protocol and The registration in [RFC8505] is abstract to the routing protocol and
provides enough information to feed a routing protocol such as RPL provides enough information to feed a routing protocol such as RPL
[draft unaware leaf]. In a degraded mode, all the Hubs are connected [draft unaware leaf]. In a degraded mode, all the Hubs are connected
to a same high speed backbone such as an Ethernet bridging domain to a same high speed backbone such as an Ethernet bridging domain
where IPv6 ND is operated. In that case, it is possible to federate where IPv6 ND is operated. In that case, it is possible to federate
the Hub, Spoke and Backbone nodes as a single Subnet, operating IPv6 the Hub, Spoke and Backbone nodes as a single Subnet, operating IPv6
ND proxy operations [I-D.ietf-6lo-backbone-router] at the Hubs, ND proxy operations [I-D.ietf-6lo-backbone-router] at the Hubs,
acting as 6BBRs. It can be observed that this latter design builds a acting as 6BBRs. It can be observed that this latter design builds a
form of Layer-3 Infrastructure ESS. form of Layer-3 Infrastructure ESS.
3. IPv6 Over Wireless 4. WiND Applicability
3.1. Case of LPWANs WiND allows P2P, P2MP hub-and spoke, MAC-level broadcast domain
emulation such as mesh-under and Wi-Fi BSS, and route over meshes.^
There is an intersection where Link and Subnet are congruent and
where both ND and WiND could apply. These includes P2P, the MAC
emulation of a PHY broadcast domain, and the particular case of
always on, fully overlapping physical radio broadcast domain. But
even in those cases where both are possible, WiND is preferable vs.
ND because it reduces the need of broadcast ( this is discussed in
the introduction of [I-D.ietf-6lo-backbone-router]).
There are also numerous practical use cases in the wireless world
where Links and Subnets are not P2P and not congruent:
o IEEE std 802.11 infrastructure BSS enables one subnet per AP, and
emulates a broadcast domain at L2. Infra ESS extends that and
recommends to use an IPv6 ND proxy [IEEE80211] to coexist with
Ethernet connected nodes. WiND incorporates an ND proxy to serve
that need and that was missing so far.
o BlueTooth is Hub-and-Spoke at the MAC layer. It would make little
sense to configure a different subnet between the central and each
individual peripheral node (e.g., sensor). Rather, [RFC7668]
allocates a prefix to the central node acting as router (6LR), and
each peripheral host (acting as a host (6LR) forms one or more
address(es) from that same prefix and registers it.
o A typical Smartgrid networks puts together Route-Over MLSNs that
comprise thousands of IPv6 nodes. The 6TiSCH architecture
[I-D.ietf-6tisch-architecture] reflects the Route-Over model, and
generalizes it for multiple other applications. Each node in a
Smartgrid network may have tens to a hundred others nodes in
range. A key problem for the routing protocol is which other
node(s) should this node peer with, because most of the possible
peers do not provide added routing value. When both energy and
bandwidth are constrained,talking to them is a bad idea and most
of the possible P2P links are not even used. Peerings that are
actually used come and go with the dynamics of radio signal
propagation. It results that allocating prefixes to all the
possible P2P Links and maintain as many addresses in all nodes is
not even considered.
4.1. Case of LPWANs
LPWANs are by nature so constrained that the addresses and Subnets LPWANs are by nature so constrained that the addresses and Subnets
are fully pre-configured and operate as P2P or Hub-and-Spoke. This are fully pre-configured and operate as P2P or Hub-and-Spoke. This
saves the steps of neighbor Discovery and enables a very efficient saves the steps of neighbor Discovery and enables a very efficient
stateful compression of the IPv6 header. stateful compression of the IPv6 header.
3.2. Case of Infrastructure BSS and ESS 4.2. Case of Infrastructure BSS and ESS
In contrast to IPv4, IPv6 enables a node to form multiple addresses, In contrast to IPv4, IPv6 enables a node to form multiple addresses,
some of them temporary to elusive, and with a particular attention some of them temporary to elusive, and with a particular attention
paid to privacy. Addresses may be formed and deprecated paid to privacy. Addresses may be formed and deprecated
asynchronously to the association. Even if the knowledge of IPv6 asynchronously to the association. Even if the knowledge of IPv6
addresses used by a STA can be obtained by snooping protocols such as addresses used by a STA can be obtained by snooping protocols such as
IPv6 ND and DHCPv6, or by observing data traffic sourced at the STA, IPv6 ND and DHCPv6, or by observing data traffic sourced at the STA,
such methods provide only an imperfect knowledge of the state of the such methods provide only an imperfect knowledge of the state of the
STA at the AP. This may result in a loss of connectivity for some STA at the AP. This may result in a loss of connectivity for some
IPv6 addresses, in particular for addresses rarely used and in a IPv6 addresses, in particular for addresses rarely used and in a
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[I-D.ietf-6lo-backbone-router]. With that specification, the AP [I-D.ietf-6lo-backbone-router]. With that specification, the AP
participates to the protocol as a Backbone Router, typically participates to the protocol as a Backbone Router, typically
operating as a bridging proxy though the routing proxy operation is operating as a bridging proxy though the routing proxy operation is
also possible. As a bridging proxy, the proxy replies to NS lookups also possible. As a bridging proxy, the proxy replies to NS lookups
with the MAC address of the STA, and then bridges packets to the STA with the MAC address of the STA, and then bridges packets to the STA
normally; as a routing proxy, it replies with its own MAC address and normally; as a routing proxy, it replies with its own MAC address and
then routes to the STA at the IP layer. The routing proxy reduces then routes to the STA at the IP layer. The routing proxy reduces
the need to expose the MAC address of the STA on the wired side, for the need to expose the MAC address of the STA on the wired side, for
a better stability and scalability of the bridged fabric. a better stability and scalability of the bridged fabric.
3.3. Case of Mesh Under Technologies 4.3. Case of Mesh Under Technologies
The Mesh-Under provides a broadcast domain emulation with reflexive The Mesh-Under provides a broadcast domain emulation with reflexive
and Transitive properties and defines a transit Link for IPv6 and Transitive properties and defines a transit Link for IPv6
operations. It results that the model for IPv6 operation is similar operations. It results that the model for IPv6 operation is similar
to that of a BSS, with the root of the mesh operating an Access Point to that of a BSS, with the root of the mesh operating an Access Point
does in a BSS/ESS. While it is still possible to operate IPv6 ND, does in a BSS/ESS. While it is still possible to operate IPv6 ND,
the inefficiencies of the flooding operation make the IPv6 ND the inefficiencies of the flooding operation make the IPv6 ND
operations even less desirable than in a BSS, and the use of WiND is operations even less desirable than in a BSS, and the use of WiND is
highly recommended. highly recommended.
3.4. Case of DMC radios 4.4. Case of DMC radios
IPv6 over DMC radios uses P2P Links that can be formed and maintained IPv6 over DMC radios uses P2P Links that can be formed and maintained
when a pair of DMC radios transmitters are in range from one another. when a pair of DMC radios transmitters are in range from one another.
3.4.1. Using IPv6 ND only 4.4.1. Using IPv6 ND only
By definition, DMC radios uses IEEE Std. 802.11 transmissions but DMC radios do not provide MAC level broadcast emulation. An example
does not provide the BSS functions. of that is OCB (outside the context of a BSS), which uses IEEE Std.
802.11 transmissions but does not provide the BSS functions.
It is possible to form P2P IP Links between each individual pairs of It is possible to form P2P IP Links between each individual pairs of
nodes and operate IPv6 ND over those Links with Link Local addresses. nodes and operate IPv6 ND over those Links with Link Local addresses.
DAD must be performed for all addresses on all P2P IP Links. DAD must be performed for all addresses on all P2P IP Links.
If special deployment care is taken so that the physical broadcast If special deployment care is taken so that the physical broadcast
domains of a collection of the nodes fully overlap, then it is also domains of a collection of the nodes fully overlap, then it is also
possible to build an IP Subnet within that collection of nodes and possible to build an IP Subnet within that collection of nodes and
operate IPv6 ND. operate IPv6 ND.
The model can be stretched beyond the scope of IPv6 ND if an external The model can be stretched beyond the scope of IPv6 ND if an external
mechanism avoids duplicate addresses and if the deployment ensures mechanism avoids duplicate addresses and if the deployment ensures
the connectivity between peers. This can be achieved for instance in the connectivity between peers. This can be achieved for instance in
a Hub-and-Spoke deployment if the Hub is the only router in the a Hub-and-Spoke deployment if the Hub is the only router in the
Subnet and the Prefix is advertised as not onlink. Subnet and the Prefix is advertised as not onlink.
3.4.2. Using Wireless ND 4.4.2. Using Wireless ND
Though this can be achieved with IPv6 ND, WiND is the recommended Though this can be achieved with IPv6 ND, WiND is the recommended
approach since it uses more unicast communications which are more approach since it uses more unicast communications which are more
reliable and less impacting for other users of the medium. reliable and less impacting for other users of the medium.
Router and Hosts respectively send a compressed RA/NA with a SLLAO at Router and Hosts respectively send a compressed RA/NA with a SLLAO at
a regular period. The period can be indicated in a RA as in an RA- a regular period. The period can be indicated in a RA as in an RA-
Interval Option [RFC6275]. If available, the message can be Interval Option [RFC6275]. If available, the message can be
transported in a compressed form in a beacon, e.g., in OCB Basic transported in a compressed form in a beacon, e.g., in OCB Basic
Safety Messages (BSM) that are nominally sent every 100ms. An active Safety Messages (BSM) that are nominally sent every 100ms. An active
beaconing mode is possible whereby the Host sends broadcast RS beaconing mode is possible whereby the Host sends broadcast RS
messages to which a router can answer with a unicast RA. messages to which a router can answer with a unicast RA.
A router that has Internet connectivity and is willing to serve as an A router that has Internet connectivity and is willing to serve as an
Internet Access may advertise itself as a default router [RFC4191] in Internet Access may advertise itself as a default router [RFC4191] in
its RA. The NA/RA is sent over an Unspecified Link where it does not its RA. The NA/RA is sent over an Unspecified Link where it does not
conflict to anyone, so DAD is not necessary at that stage. conflict to anyone, so DAD is not necessary at that stage.
The receiver instantiates a Link where the sender's address is not a The receiver instantiates a Link where the sender's address is not a
duplicate. To achieve this, it forms an LLA that does not conflict duplicate. To achieve this, it forms an LLA that does not conflict
with that of the sender and registers to the sender using [RFC 8505]. with that of the sender and registers to the sender using [RFC8505].
If the sender sent an RA(PIO) the receiver can also autoconfigure an If the sender sent an RA(PIO) the receiver can also autoconfigure an
address from the advertised prefix and register it. address from the advertised prefix and register it.
6LoWPAN Node 6LR 6LoWPAN Node 6LR
(RPL leaf) (router) (RPL leaf) (router)
| | | |
| LLN link | | LLN link |
| | | |
| IPv6 ND RS | | IPv6 ND RS |
|-------------->| |-------------->|
skipping to change at page 11, line 38 skipping to change at page 13, line 43
| | | NA(EARO) |<timeout> | | | NA(EARO) |<timeout>
| | |<--------------| | | |<--------------|
| | Extended DAC | | | | Extended DAC | |
| |<--------------| | | |<--------------| |
| NA(EARO) | | | | NA(EARO) | | |
|<--------------| | | |<--------------| | |
| | | | | | | |
Figure 2: Initial Registration Flow over Multi-Link Subnet Figure 2: Initial Registration Flow over Multi-Link Subnet
An example Hub-And-Spoke is an OCB Road-Side Unit (RSU) that owns a An example Hub-and-Spoke is an OCB Road-Side Unit (RSU) that owns a
prefix, provides Internet connectivity using that prefix to On-Board prefix, provides Internet connectivity using that prefix to On-Board
Units (OBUs) within its physical broadcast domain. An example of Units (OBUs) within its physical broadcast domain. An example of
Route-Over MLSN is a collection of cars in a parking lot operating Route-Over MLSN is a collection of cars in a parking lot operating
RPL to extend the connectivity provided by the RSU beyond its RPL to extend the connectivity provided by the RSU beyond its
physical broadcast domain. Cars may then operate NEMO [RFC3963] for physical broadcast domain. Cars may then operate NEMO [RFC3963] for
their own prefix using their address derived from the prefix of the their own prefix using their address derived from the prefix of the
RSU as CareOf Address. RSU as CareOf Address.
4. IANA Considerations 5. IANA Considerations
This specification does not require IANA action. This specification does not require IANA action.
5. Security Considerations 6. Security Considerations
This specification refers to the security sections of IPv6 ND and This specification refers to the security sections of IPv6 ND and
WiND, respectively. WiND, respectively.
6. Acknowledgments 7. Acknowledgments
Many thanks to the participants of the 6lo WG where a lot of the work Many thanks to the participants of the 6lo WG where a lot of the work
discussed here happened. Also ROLL, 6TiSCH, and 6LoWPAN. discussed here happened. Also ROLL, 6TiSCH, and 6LoWPAN.
7. References 8. References
7.1. Normative References 8.1. Normative References
[I-D.ietf-6lo-ap-nd] [I-D.ietf-6lo-ap-nd]
Thubert, P., Sarikaya, B., Sethi, M., and R. Struik, Thubert, P., Sarikaya, B., Sethi, M., and R. Struik,
"Address Protected Neighbor Discovery for Low-power and "Address Protected Neighbor Discovery for Low-power and
Lossy Networks", draft-ietf-6lo-ap-nd-12 (work in Lossy Networks", draft-ietf-6lo-ap-nd-12 (work in
progress), April 2019. progress), April 2019.
[I-D.ietf-6lo-backbone-router] [I-D.ietf-6lo-backbone-router]
Thubert, P., Perkins, C., and E. Levy-Abegnoli, "IPv6 Thubert, P., Perkins, C., and E. Levy-Abegnoli, "IPv6
Backbone Router", draft-ietf-6lo-backbone-router-11 (work Backbone Router", draft-ietf-6lo-backbone-router-11 (work
skipping to change at page 13, line 16 skipping to change at page 15, line 20
(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>.
[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>.
7.2. Informative References 8.2. Informative References
[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-20 (work of IEEE 802.15.4", draft-ietf-6tisch-architecture-20 (work
in progress), March 2019. in progress), March 2019.
[I-D.ietf-rift-rift]
Team, T., "RIFT: Routing in Fat Trees", draft-ietf-rift-
rift-05 (work in progress), April 2019.
[I-D.thubert-6lo-unicast-lookup]
Thubert, P. and E. Levy-Abegnoli, "IPv6 Neighbor Discovery
Unicast Lookup", draft-thubert-6lo-unicast-lookup-00 (work
in progress), January 2019.
[I-D.thubert-roll-unaware-leaves]
Thubert, P., "Routing for RPL Leaves", draft-thubert-roll-
unaware-leaves-07 (work in progress), April 2019.
[IEEE80211] [IEEE80211]
"IEEE Standard 802.11 - IEEE Standard for Information "IEEE Standard 802.11 - IEEE Standard for Information
Technology - Telecommunications and information exchange Technology - Telecommunications and information exchange
between systems Local and metropolitan area networks - between systems Local and metropolitan area networks -
Specific requirements - Part 11: Wireless LAN Medium Specific requirements - Part 11: Wireless LAN Medium
Access Control (MAC) and Physical Layer (PHY) Access Control (MAC) and Physical Layer (PHY)
Specifications.". Specifications.".
[IEEE802154] [IEEE802154]
IEEE standard for Information Technology, "IEEE Std. IEEE standard for Information Technology, "IEEE Std.
802.15.4, Part. 15.4: Wireless Medium Access Control (MAC) 802.15.4, Part. 15.4: Wireless Medium Access Control (MAC)
and Physical Layer (PHY) Specifications for Low-Rate and Physical Layer (PHY) Specifications for Low-Rate
Wireless Personal Area Networks". Wireless Personal Area Networks".
[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>.
[RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery
Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April
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>.
[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J., [RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
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>.
 End of changes. 27 change blocks. 
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