[Docs] [txt|pdf|xml|html] [Tracker] [Email] [Diff1] [Diff2] [Nits]
Versions: 00 01 02 03 04
6MAN P. Thubert, Ed.
Internet-Draft Cisco Systems
Intended status: Informational April 30, 2019
Expires: November 1, 2019
IPv6 Neighbor Discovery on Wireless Networks
draft-thubert-6man-ipv6-over-wireless-01
Abstract
This document describes how the original IPv6 Neighbor Discovery and
Wireless ND (WiND) can be applied on various abstractions of wireless
media.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 1, 2019.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Thubert Expires November 1, 2019 [Page 1]
Internet-Draft Applying Wireless ND April 2019
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. IP Models . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.1. Physical Broadcast Domain . . . . . . . . . . . . . . . . 2
2.2. MAC-Layer Broadcast Emulations . . . . . . . . . . . . . 3
2.3. Mapping the IPv6 Link Abstraction . . . . . . . . . . . . 5
2.4. Mapping the IPv6 Subnet Abstraction . . . . . . . . . . . 6
3. Wireless ND . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Introduction to WiND . . . . . . . . . . . . . . . . . . 6
3.2. Links and Link-Local Addresses . . . . . . . . . . . . . 7
3.3. Subnets and Global Addresses . . . . . . . . . . . . . . 8
4. WiND Applicability . . . . . . . . . . . . . . . . . . . . . 9
4.1. Case of LPWANs . . . . . . . . . . . . . . . . . . . . . 10
4.2. Case of Infrastructure BSS and ESS . . . . . . . . . . . 10
4.3. Case of Mesh Under Technologies . . . . . . . . . . . . . 11
4.4. Case of DMC radios . . . . . . . . . . . . . . . . . . . 11
4.4.1. Using IPv6 ND only . . . . . . . . . . . . . . . . . 11
4.4.2. Using Wireless ND . . . . . . . . . . . . . . . . . . 11
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
6. Security Considerations . . . . . . . . . . . . . . . . . . . 14
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.1. Normative References . . . . . . . . . . . . . . . . . . 14
8.2. Informative References . . . . . . . . . . . . . . . . . 15
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
2. IP Models
2.1. Physical Broadcast Domain
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.
This set can comprise a single peer on a serial cable used as point-
to-point (P2P) link. It may also comprise multiple peer nodes on a
broadcast radio or a shared physical resource such as the legacy
Ethernet shared wire.
On WLAN and WPAN radios, the physical broadcast domain is defined by
a particular transmitter, as the set of nodes that can receive what
this transmitter is sending. Litterally every datagram defines its
own broadcast domain since the chances of reception of a given
datagram are statistical. In average and in stable conditions, the
broadcast domain of a particular node can be still be seen as mostly
constant and can be used to define a closure of nodes on which an
upper-layer abstraction can be built.
Thubert Expires November 1, 2019 [Page 2]
Internet-Draft Applying Wireless ND April 2019
A PHY-layer communication can be established between 2 nodes if their
physical broadcast domains overlap.
On WLAN and WPAN radios, this property is usually reflexive, meaning
that if B can receive a datagram from A, then A can receive a
datagram from B. But there can be asymmetries due to power levels,
interferers near one of the receivers, or differences in the quality
of the hardware (e.g., cristals, PAs and antennas) that may affect
the balance to the point that the connectivity becomes mostly uni-
directional, e.g., A to B but not practically not B to A. It takes a
particular effort to place a set of devices in a fashion that all
their physical broadcast domains fully overlap, and it can not be
assumed in the general case. In other words, the property of radio
connectivity is generally not transitive, meaning that A may talk to
B and B may talk to C does not necessarily imply that A can talk to
C.
We define MAC-Layer Direct Broadcast (DMC) a transmission mode where
the broadcast domain that is usable at the MAC layer is directly the
physical broadcast domain. IEEE 802.15.4 [IEEE802154] and IEEE
802.11 [IEEE80211] OCB (for Out of the Context of a BSS) are examples
of DMC radios. This constrasts with a number of MAC-layer Broadcast
Emulation schemes that are described in the next section.
2.2. MAC-Layer Broadcast Emulations
While a physical broadcast domain is constrained to a single shared
wire, Ethernet Briging emulates the broadcast properties of that wire
over a whole physical mesh of Ethernet links. For the upper layer,
the qualities of the shared wire are essentially conserved, with a
reliable and cheap broadcast operation over a closure of nodes
defined by their connectivity to the emulated wire.
In large switched fabrics, overlay techniques enable a limited
connectivity between nodes that are known to a mapping server. The
emulated broadcast domain is configured to the system, e.g., with a
VXLAN network identifier (VNID). Broadcast operations on the overlay
can be emulated but can become very expensive, and it makes sense to
proactively install the relevant state in the mapping server as
opposed to rely on reactive broadcast lookups.
An IEEE Std 802.11 Infrastructure Basic Service Set (BSS) also
provides a closure of nodes as defined by the broadcast domain of a
central Access Point (AP). The AP relays both unicast and broadcast
packets and ensures a reflexive and transitive emulation of the
shared wire between the associated nodes, with the capability to
signal link-up/link-down to the upper layer. Within an
Infrastructure BSS, the physical broadcast domain of the AP serves as
Thubert Expires November 1, 2019 [Page 3]
Internet-Draft Applying Wireless ND April 2019
emulated broadcast domain for all the nodes that are associated to
the AP. Broadcast packets are relayed by the AP and are not
acknowledged. For that reason, special efforts are made to ensure
that all nodes in the BSS receive the broadcast transmission. To
achieve this, the transmission is sent at the highest power and
slowest PHY speed. This translates into maximum co-channel
interferences for others and longest occupancy of the medium, for a
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
operating over Wi-Fi.
In an IEEE Std 802.11 Infrastructure Extended Service Set (ESS), the
process of the association also prepares a bridging state proactively
at the AP, so as to avoid the reactive broadcast lookup that takes
place in the process of transparent bridging over a spanning tree.
This model provides a more reliable operation than the reactive
transparent bridging and avoid the need of multicast, and it is only
logical that IPv6 [RFC8200] Neighbor Discovery (ND)
[RFC4861][RFC4862] evolved towards proposes similar methods at
Layer-3 for its operation.
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
similar to bridgeing, and the broadcast domain is well defined by the
membership of the mesh. Mesh-Under emulates a broadcast domain by
flooding the broadcast packets at Layer-2. When operating on a
single frequency, this operation is known to interfere with itself,
forcing deployment to introduce delays that dampen the collisions.
All in all, the mechanism is slow, inefficient and expensive.
Going down the list of cases above, the cost of a broadcast
transmissions becomes increasingly expensive, and there is a push to
rethink the upper-layer protocols so as to reduce the depency on
broadcast operations.
There again, a MAC-layer communication can be established between 2
nodes if their MAC-layer broadcast domains overlap. In the absence
of a MAC-layer emulation such as a mesh-under or an Infrastructure
BSS, the MAC-layer broadcast domain is congruent with that of the
PHY-layer and inherits its properties for reflexivity and
transitivity. IEEE 802.11p, which operates Out of the Context of a
BSS (DMC radios) is an example of a network that does not have a MAC-
Layer broadcast domain emulation, which means that it will exhibit
mostly reflexive and mostly non-transitive transmission properties.
Thubert Expires November 1, 2019 [Page 4]
Internet-Draft Applying Wireless ND April 2019
2.3. Mapping the IPv6 Link Abstraction
IPv6 defines a concept of Link, Link Scope and Link-Local Addresses
(LLA), an LLA being unique and usable only within the Scope of a
Link. The IPv6 Neighbor Discovery (ND) [RFC4861][RFC4862] Duplicate
Adress Detection (DAD) process leverages a multicast transmission to
ensure that an IPv6 address is unique as long as the owner of the
address is connected to the broadcast domain. It must be noted that
in all the cases in this specification, the Layer-3 multicast
operation is always a MAC_Layer broadcast for the lack of a Layer-2
multicast operation that could handle a possibly very large number of
groups in order to make the unicast efficient. This means that for
every multicast packet regardless of the destination group, all nodes
will receive the packet and process it all the way to Layer-3.
On wired media, the Link is often confused with the physical
broadcast domain because both are determined by the serial cable or
the Ethernet shared wire. Ethernet Bridging reinforces that illusion
by provising a MAC-Layer broadcast domain that emulates a physical
broadcast domain over the mesh of wires. But the difference shows on
legacy Non-Broadcast Multi-Access (NBMA) such as ATM and Frame-Relay,
on shared links and on newer types of NBMA networks such as radio and
composite radio-wires networks. It also shows when private VLANs or
Layer-2 cryptography restrict the capability to read a frame to a
subset of the connected nodes.
In mesh-under and Infrastructure BSS, the IP Link extends beyond the
physical broadcast domain to the emulated MAC-Layer broadcast domain.
Relying on Multicast for the ND operation remains feasible but
becomes detrimental to unicast traffic, energy-inefficient and
unreliable, and its use is discouraged.
On DMC radios, IP Links between peers come and go as the individual
physical broadcast domains of the transmitters meet and overlap. The
DAD operation cannot provide once and for all guarantees on the
broadcast domain defined by one radio transmitter if that transmitter
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
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
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-
interface of the radio interface.
Thubert Expires November 1, 2019 [Page 5]
Internet-Draft Applying Wireless ND April 2019
2.4. Mapping the IPv6 Subnet Abstraction
IPv6 also defines a concept of Subnet for Glocal and Unique Local
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
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
prefix is unique within that Subnet to guarantee that it is globally
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 Subnet, and that this router will be able to either resolve the
destination MAC address and deliver the packet, or route the packet
to the destination within the Subnet. If the Subnet is known as
onlink, then any node may also resolve the destination MAC address
and deliver the packet, but if the Subnet is not onlink, then a host
that does not have an NCE for the destination will need to pass the
packet to a router.
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
shared wire or an IEEE Std. 802.1 bridged broadcast domain. In that
case, the connectivity over the Link is transitive, the Subnet can
appear as onlink, and any node can resolve a destination MAC address
of any other node directly using IPv6 Neighbor Discovery.
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
nodes connected to the Link. In Route-Over Multi-Link Subnets (MLSN)
[RFC4903], routers federate the Links between nodes that belong to
the Subnet, the Subnet is not onlink and it extends beyond any of the
federated Links.
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
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
node. This is why ND is only applicable for P2P and transit links,
and requires extensions for other topologies.
3. Wireless ND
3.1. Introduction to WiND
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
Thubert Expires November 1, 2019 [Page 6]
Internet-Draft Applying Wireless ND April 2019
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
Thubert Expires November 1, 2019 [Page 7]
Internet-Draft Applying Wireless ND April 2019
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,
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.
Acting as 6LR, the Hub advertises the prefix as not-onlink to the
spokes in RA messages Prefix Information Options (PIO). Acting as
6LNs, the Spokes autoconfigure addresses from that prefix and
register them to the Hub with a corresponding lifetime. Acting as a
6LBR, the Hub maintains a binding table of all the registered IP
addresses and rejects duplicate registrations, thus ensuring a DAD
protection for a registered address even if the registering node is
sleeping. Acting as 6LR, the Hub also maintains an NCE for the
registered addresses and can deliver a packet to any of them for
their respective lifetimes. It can be observed that this design
builds a form of Layer-3 Infrastructure BSS.
A Route-Over MLSN is considered as a collection of Hub-and-Spoke
where the Hubs form a connected dominating set of the member nodes of
the Subnet, and IPv6 routing takes place between the Hubs within the
Subnet. A single logical 6LBR is deployed to serve the whole mesh.
The registration in [RFC8505] is abstract to the routing protocol and
provides enough information to feed a routing protocol such as RPL
[draft unaware leaf]. In a degraded mode, all the Hubs are connected
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
the Hub, Spoke and Backbone nodes as a single Subnet, operating IPv6
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
form of Layer-3 Infrastructure ESS.
Thubert Expires November 1, 2019 [Page 8]
Internet-Draft Applying Wireless ND April 2019
4. WiND Applicability
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.
Thubert Expires November 1, 2019 [Page 9]
Internet-Draft Applying Wireless ND April 2019
4.1. Case of LPWANs
LPWANs are by nature so constrained that the addresses and Subnets
are fully pre-configured and operate as P2P or Hub-and-Spoke. This
saves the steps of neighbor Discovery and enables a very efficient
stateful compression of the IPv6 header.
4.2. Case of Infrastructure BSS and ESS
In contrast to IPv4, IPv6 enables a node to form multiple addresses,
some of them temporary to elusive, and with a particular attention
paid to privacy. Addresses may be formed and deprecated
asynchronously to the association. Even if the knowledge of IPv6
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,
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
IPv6 addresses, in particular for addresses rarely used and in a
situation of mobility. This may also result in undesirable remanent
state in the AP when a STA ceases to use an IPv6 address. It results
that snooping protocols is not a recommended technique and that it
should only be used as last resort.
The recommended alternate is to use the IPv6 Registration method
speficied in p. By that method, the AP exposes its capability to
proxy ND to the STA in Router Advertisement messages. In turn, the
STA may request proxy ND services from the AP for one or more IPv6
addresses, using an Address Registration Option. The Registration
state has a lifetime that limits unwanted state remanence in the
network. The registration is optionally secured using
[I-D.ietf-6lo-ap-nd] to prevent address theft and impersonation. The
registration carries a sequence number, which enables a fast mobility
without a loss of connectivity.
The ESS mode requires a proxy ND operation at the AP. The proxy ND
operation must cover Duplicate Address Detection, Neighbor
Unreachability Detection, Address Resolution and Address Mobility to
transfer a role of ND proxy to the AP where a STA is associated
following the mobility of the STA. The proxy ND specification
associated to the address registration is
[I-D.ietf-6lo-backbone-router]. With that specification, the AP
participates to the protocol as a Backbone Router, typically
operating as a bridging proxy though the routing proxy operation is
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
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
Thubert Expires November 1, 2019 [Page 10]
Internet-Draft Applying Wireless ND April 2019
the need to expose the MAC address of the STA on the wired side, for
a better stability and scalability of the bridged fabric.
4.3. Case of Mesh Under Technologies
The Mesh-Under provides a broadcast domain emulation with reflexive
and Transitive properties and defines a transit Link for IPv6
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
does in a BSS/ESS. While it is still possible to operate 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
highly recommended.
4.4. Case of DMC radios
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.
4.4.1. Using IPv6 ND only
DMC radios do not provide MAC level broadcast emulation. An example
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
nodes and operate IPv6 ND over those Links with Link Local addresses.
DAD must be performed for all addresses on all P2P IP Links.
If special deployment care is taken so that the physical broadcast
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
operate IPv6 ND.
The model can be stretched beyond the scope of IPv6 ND if an external
mechanism avoids duplicate addresses and if the deployment ensures
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
Subnet and the Prefix is advertised as not onlink.
4.4.2. Using Wireless ND
Though this can be achieved with IPv6 ND, WiND is the recommended
approach since it uses more unicast communications which are more
reliable and less impacting for other users of the medium.
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-
Thubert Expires November 1, 2019 [Page 11]
Internet-Draft Applying Wireless ND April 2019
Interval Option [RFC6275]. If available, the message can be
transported in a compressed form in a beacon, e.g., in OCB Basic
Safety Messages (BSM) that are nominally sent every 100ms. An active
beaconing mode is possible whereby the Host sends broadcast RS
messages to which a router can answer with a unicast RA.
A router that has Internet connectivity and is willing to serve as an
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
conflict to anyone, so DAD is not necessary at that stage.
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
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
address from the advertised prefix and register it.
6LoWPAN Node 6LR
(RPL leaf) (router)
| |
| LLN link |
| |
| IPv6 ND RS |
|-------------->|
|-----------> |
|------------------>
| IPv6 ND RA |
|<--------------|
| |
| NS(EARO) |
|-------------->|
| |
| NA(EARO) |
|<--------------|
| |
Figure 1: Initial Registration Flow
The lifetime in the registration should start with a small value
(X=RMin, TBD), and exponentially grow with each reregistration to a
mlarger value (X=Rmax, TBD). The IP Link is considered down when
(X=NbBeacons, TDB) expected messages are not received in a row. It
must be noted that the Link flapping does not affect the state of the
registration and when a Link comes back up, the active -lifetime not
elapsed- registrations are still usable. Packets should be held or
destroyed when the Link is down.
Thubert Expires November 1, 2019 [Page 12]
Internet-Draft Applying Wireless ND April 2019
P2P Links may be federated in Hub-and-Spoke and then in Route-Over
MLSNs as described above. More details on the operation of WiND and
RPL over the MLSN can be found in section 3.1, 3.2, 4.1 and 4.2.2 of
[I-D.ietf-6tisch-architecture].
6LoWPAN Node 6LR 6LBR 6BBR
(RPL leaf) (router) (root)
| | | |
| 6LoWPAN ND |6LoWPAN ND+RPL | 6LoWPAN ND | IPv6 ND
| LLN link |Route-Over mesh|Ethernet/serial| Backbone
| | | |
| IPv6 ND RS | | |
|-------------->| | |
|-----------> | | |
|------------------> | |
| IPv6 ND RA | | |
|<--------------| | |
| | <once> | |
| NS(EARO) | | |
|-------------->| | |
| 6LoWPAN ND | Extended DAR | |
| |-------------->| |
| | | NS(EARO) |
| | |-------------->|
| | | | NS-DAD
| | | |------>
| | | | (EARO)
| | | |
| | | NA(EARO) |<timeout>
| | |<--------------|
| | Extended DAC | |
| |<--------------| |
| NA(EARO) | | |
|<--------------| | |
| | | |
Figure 2: Initial Registration Flow over Multi-Link Subnet
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
Units (OBUs) within its physical broadcast domain. An example of
Route-Over MLSN is a collection of cars in a parking lot operating
RPL to extend the connectivity provided by the RSU beyond its
physical broadcast domain. Cars may then operate NEMO [RFC3963] for
their own prefix using their address derived from the prefix of the
RSU as CareOf Address.
Thubert Expires November 1, 2019 [Page 13]
Internet-Draft Applying Wireless ND April 2019
5. IANA Considerations
This specification does not require IANA action.
6. Security Considerations
This specification refers to the security sections of IPv6 ND and
WiND, respectively.
7. Acknowledgments
Many thanks to the participants of the 6lo WG where a lot of the work
discussed here happened. Also ROLL, 6TiSCH, and 6LoWPAN.
8. References
8.1. Normative References
[I-D.ietf-6lo-ap-nd]
Thubert, P., Sarikaya, B., Sethi, M., and R. Struik,
"Address Protected Neighbor Discovery for Low-power and
Lossy Networks", draft-ietf-6lo-ap-nd-12 (work in
progress), April 2019.
[I-D.ietf-6lo-backbone-router]
Thubert, P., Perkins, C., and E. Levy-Abegnoli, "IPv6
Backbone Router", draft-ietf-6lo-backbone-router-11 (work
in progress), February 2019.
[RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
Thubert, "Network Mobility (NEMO) Basic Support Protocol",
RFC 3963, DOI 10.17487/RFC3963, January 2005,
<https://www.rfc-editor.org/info/rfc3963>.
[RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and
More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191,
November 2005, <https://www.rfc-editor.org/info/rfc4191>.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007,
<https://www.rfc-editor.org/info/rfc4861>.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862,
DOI 10.17487/RFC4862, September 2007,
<https://www.rfc-editor.org/info/rfc4862>.
Thubert Expires November 1, 2019 [Page 14]
Internet-Draft Applying Wireless ND April 2019
[RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
2011, <https://www.rfc-editor.org/info/rfc6275>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
[RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C.
Perkins, "Registration Extensions for IPv6 over Low-Power
Wireless Personal Area Network (6LoWPAN) Neighbor
Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018,
<https://www.rfc-editor.org/info/rfc8505>.
8.2. Informative References
[I-D.ietf-6tisch-architecture]
Thubert, P., "An Architecture for IPv6 over the TSCH mode
of IEEE 802.15.4", draft-ietf-6tisch-architecture-20 (work
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]
"IEEE Standard 802.11 - IEEE Standard for Information
Technology - Telecommunications and information exchange
between systems Local and metropolitan area networks -
Specific requirements - Part 11: Wireless LAN Medium
Access Control (MAC) and Physical Layer (PHY)
Specifications.".
[IEEE802154]
IEEE standard for Information Technology, "IEEE Std.
802.15.4, Part. 15.4: Wireless Medium Access Control (MAC)
and Physical Layer (PHY) Specifications for Low-Rate
Wireless Personal Area Networks".
Thubert Expires November 1, 2019 [Page 15]
Internet-Draft Applying Wireless ND April 2019
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>.
[RFC4903] Thaler, D., "Multi-Link Subnet Issues", RFC 4903,
DOI 10.17487/RFC4903, June 2007,
<https://www.rfc-editor.org/info/rfc4903>.
[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012,
<https://www.rfc-editor.org/info/rfc6550>.
[RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
Bormann, "Neighbor Discovery Optimization for IPv6 over
Low-Power Wireless Personal Area Networks (6LoWPANs)",
RFC 6775, DOI 10.17487/RFC6775, November 2012,
<https://www.rfc-editor.org/info/rfc6775>.
[RFC7668] Nieminen, J., Savolainen, T., Isomaki, M., Patil, B.,
Shelby, Z., and C. Gomez, "IPv6 over BLUETOOTH(R) Low
Energy", RFC 7668, DOI 10.17487/RFC7668, October 2015,
<https://www.rfc-editor.org/info/rfc7668>.
Author's Address
Pascal Thubert (editor)
Cisco Systems, Inc
Building D
45 Allee des Ormes - BP1200
MOUGINS - Sophia Antipolis 06254
FRANCE
Phone: +33 497 23 26 34
Email: pthubert@cisco.com
Thubert Expires November 1, 2019 [Page 16]
Html markup produced by rfcmarkup 1.129d, available from
https://tools.ietf.org/tools/rfcmarkup/