Internet Engineering Task Force (IETF) P. Thubert, Ed.
Request for Comments: 9685 November 2024
Updates: 4861, 6550, 6553, 8505, 9010
Category: Standards Track
ISSN: 2070-1721
Listener Subscription for IPv6 Neighbor Discovery Multicast and Anycast
Addresses
Abstract
This document updates the 6LoWPAN extensions to IPv6 Neighbor
Discovery (specified in RFCs 4861 and 8505) to enable a listener to
subscribe to an IPv6 anycast or multicast address. This document
also updates the Routing Protocol for Low-Power and Lossy Networks
(RPL) (specified in RFCs 6550 and 6553) to add a new Non-Storing
multicast mode and new support for anycast addresses in Storing and
Non-Storing modes. This document extends RFC 9010 to enable a
6LoWPAN Router (6LR) to inject the anycast and multicast addresses in
RPL.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9685.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction
2. Terminology
2.1. Requirements Language
2.2. Terminology from Relevant RFCs
2.3. Abbreviations
2.4. New Terms
3. Overview
4. Amending RFC 4861
5. Extending RFC 7400
6. Amending RFC 6550
6.1. Mandating the ROVR Field
6.2. Updating MOP 3
6.3. New Non-Storing Multicast MOP
6.4. RPL Anycast Operation
6.5. New Registered Address Type Indicator P-Field
6.6. New RPL Target Option P-Field
7. Extending RFC 8505
7.1. Placing the New P-Field in the EARO
7.2. Placing the New P-Field in the EDAR Message
7.3. Registration Extensions
8. Extending RFC 9010
9. Leveraging RFC 8928
10. Consistent Uptime Option
11. Operational Considerations
12. Security Considerations
13. Backward Compatibility
14. IANA Considerations
14.1. New P-Field Values Registry
14.2. New EDAR Message Flags Registry
14.3. New Address Registration Option Flags
14.4. New RPL Target Option Flags
14.5. New RPL Mode of Operation
14.6. New 6LoWPAN Capability Bit
14.7. New Address Registration Option Status Values
14.8. New IPv6 Neighbor Discovery Option Format
15. References
15.1. Normative References
15.2. Informative References
Acknowledgments
Author's Address
1. Introduction
The design of Low-Power and Lossy Networks (LLNs) is generally
focused on saving energy, which is the most constrained resource of
all. Other design constraints, such as a limited memory capacity,
duty cycling of the LLN devices, and low-power lossy transmissions,
derive from that primary concern. The radio (when both transmitting
or simply listening) is a major energy drain, and the LLN protocols
must be adapted to allow the nodes to remain sleeping with the radio
turned off at most times.
"RPL: IPv6 Routing Protocol for Low-Power and Lossy Networks"
[RFC6550] provides IPv6 [RFC8200] routing services within such
constraints. To save signaling and routing state in constrained
networks, the RPL routing is only performed along a Destination-
Oriented Directed Acyclic Graph (DODAG) that is optimized to reach a
Root node, as opposed to along the shortest path between two peers,
which may be a fuzzy concept anyway in a radio LLN.
This stretches the routes between RPL nodes inside the DODAG for a
vastly reduced amount of control traffic and routing state that would
be required to operate an any-to-any shortest path protocol.
Additionally, broken routes may be fixed lazily and on-demand based
on data plane inconsistency discovery, which avoids wasting energy in
the proactive repair of unused paths.
RPL uses Destination Advertisement Object (DAO) messages to establish
Downward routes. DAO messages are an optional feature for
applications that require point-to-multipoint (P2MP) or point-to-
point (P2P) traffic. RPL supports two modes of Downward traffic:
Storing (fully stateful) or Non-Storing (fully source routed); see
Section 9 of [RFC6550]. The mode is signaled in the Mode of
Operation (MOP) field in the DODAG Information Object (DIO) messages
and applies to the whole RPL Instance.
Any given RPL Instance is either Storing or Non-Storing. In both
cases, P2P packets travel Up toward a DODAG root then Down to the
final destination (unless the destination is on the Upward route).
In the Non-Storing case, the packet will travel all the way to a
DODAG root before traveling Down. In the Storing case, the packet
may be directed Down towards the destination by a common ancestor of
the source and the destination prior to reaching a DODAG root.
Section 12 of [RFC6550] details the Storing Mode of Operation with
multicast support with source-independent multicast routing in RPL.
The classical Neighbor Discovery (ND) protocol [RFC4861] [RFC4862]
was defined for serial links and shared transit media such as
Ethernet at a time when broadcast on those media types was cheap,
while memory for neighbor cache was expensive. It was thus designed
as a reactive protocol that relies on caching and multicast
operations for the Address Discovery (aka lookup) and Duplicate
Address Detection (DAD) of IPv6 unicast addresses. Those multicast
operations typically impact every node on-link when at most one is
really targeted. This is a waste of energy and implies that all
nodes are awake to hear the request, which is inconsistent with
power-saving (sleeping) modes.
The original specification for 6LoWPAN ND, "Neighbor Discovery
Optimization for IPv6 over Low-Power Wireless Personal Area Networks
(6LoWPANs)" [RFC6775], was introduced to avoid the excessive use of
multicast messages and enable IPv6 ND for operations over energy-
constrained nodes. [RFC6775] changes the classical IPv6 ND model to
proactively establish the Neighbor Cache Entry (NCE) associated to
the unicast address of a 6LoWPAN Node (6LN) in one or more 6LoWPAN
Routers (6LRs) that serve it. To that effect, [RFC6775] defines a
new Address Registration Option (ARO) that is placed in unicast
Neighbor Solicitation (NS) and Neighbor Advertisement (NA) messages
between the 6LN and the 6LR.
"Registration Extensions for IPv6 over Low-Power Wireless Personal
Area Network (6LoWPAN) Neighbor Discovery" [RFC8505] updates
[RFC6775] so that a generic Address Registration mechanism can be
used to access services such as routing and ND proxy and introduces
the Extended Address Registration Option (EARO) for that purpose.
This provides a routing-agnostic interface for a host to request that
the router injects a unicast IPv6 address in the local routing
protocol and provides return reachability for that address.
"Routing for RPL (Routing Protocol for Low-Power and Lossy Networks)
Leaves" [RFC9010] provides the router counterpart of the mechanism
for a host that implements [RFC8505] to inject its unicast Unique
Local Addresses (ULAs) and Global Unicast Addresses (GUAs) in RPL.
Although RPL also provides multicast routing, 6LoWPAN ND supports
only the registration of unicast addresses, and there is no
equivalent of [RFC9010] to specify the 6LR behavior upon the
subscription of one or more multicast addresses.
"Multicast Listener Discovery Version 2 (MLDv2) for IPv6" [RFC3810]
enables the router to learn which node listens to which multicast
address, but as the classical IPv6 ND protocol, MLD relies on
multicasting queries to all nodes, which is unfit for low-power
operations. As for IPv6 ND, it makes sense to let the 6LNs control
when and how they maintain the state associated to their multicast
addresses in the 6LR, e.g., during their own wake time. In the case
of a constrained node that already implements [RFC8505] for unicast
reachability, it makes sense to extend that support to subscribe the
multicast addresses they listen to.
This specification Extends [RFC8505] and [RFC9010] by adding the
capability for the 6LN to subscribe anycast and multicast addresses
and for the 6LR to inject them in RPL when appropriate. Note that
due to the unreliable propagation of packets in the LLN, it cannot be
guaranteed that any given packet is delivered once and only once. If
a breakage happens along the preferred parent tree that is normally
used for multicast forwarding, the packet going Up may be rerouted to
an alternate parent, leading to potential failures and duplications,
whereas a packet going Down will not be delivered in the subtree. It
is up to the Upper Layer Protocols (ULPs) to cope with both
situations.
2. Terminology
2.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
In addition, "Extends" and "Amends" are used as more specific terms
for "Updates" per Section 3 of [UPDATES-TAG] as follows:
Amends/Amended by: This tag pair is used with an amending RFC that
changes the amended RFC. This could include bug fixes,
behavior changes, etc. This is intended to specify mandatory
changes to the protocol. The goal of this tag pair is to
signal to anyone looking to implement the amended RFC that
they MUST also implement the amending RFC.
Extends/Extended by: This tag pair is used with an extending RFC
that defines an optional addition to the extended RFC. This
can be used by documents that use existing extension points or
clarifications that do not change existing protocol behavior.
This signals to implementers and protocol designers that there
are changes to the extended RFC that they need to consider but
not necessarily implement.
2.2. Terminology from Relevant RFCs
This document uses terms and concepts that are discussed in:
* "Neighbor Discovery for IP version 6 (IPv6)" [RFC4861],
* "IPv6 Stateless Address Autoconfiguration" [RFC4862],
* "RPL: IPv6 Routing Protocol for Low-Power and Lossy Networks"
[RFC6550],
* "Neighbor Discovery Optimization for IPv6 over Low-Power Wireless
Personal Area Networks (6LoWPANs)" [RFC6775],
* "Registration Extensions for IPv6 over Low-Power Wireless Personal
Area Network (6LoWPAN) Neighbor Discovery" [RFC8505], and
* "Using RPI Option Type, Routing Header for Source Routes, and
IPv6-in-IPv6 Encapsulation in the RPL Data Plane" [RFC9008].
2.3. Abbreviations
This document uses the following abbreviations:
6CIO: Capability Indication Option
6LBR: 6LoWPAN Border Router
6LN: 6LoWPAN Node
6LR: 6LoWPAN Router
ARO: Address Registration Option
DAC: Duplicate Address Confirmation
DAD: Duplicate Address Detection
DAO: Destination Advertisement Object
DAR: Duplicate Address Request
DIO: DODAG Information Object
DMB: Direct MAC Broadcast
DODAG: Destination-Oriented Directed Acyclic Graph
EARO: Extended Address Registration Option
EDAC: Extended Duplicate Address Confirmation
EDAR: Extended Duplicate Address Request
IR: Ingress Replication
LLN: Low-Power and Lossy Network
MLD: Multicast Listener Discovery
MOP: Mode of Operation
NA: Neighbor Advertisement
NCE: Neighbor Cache Entry
ND: Neighbor Discovery
NS: Neighbor Solicitation
RA: Router Advertisement
RAN: RPL-Aware Node
ROVR: Registration Ownership Verifier (pronounced "rover")
RPL: Routing Protocol for Low-Power and Lossy Networks (pronounced
"ripple")
RS: Router Solicitation
RTO: RPL Target Option
RUL: RPL-Unaware Leaf
TID: Transaction ID
TIO: Transit Information Option
2.4. New Terms
This document introduces the following terms:
Origin: The node that issued an anycast or multicast advertisement,
in the form of either an NS(EARO) or a DAO(TIO, RTO) message.
Merge/merging: The action of receiving multiple anycast or multicast
advertisements, either internally from self, in the form of an
NS(EARO) message, or as a DAO(TIO, RTO) message, and
generating a single DAO(TIO, RTO). The RPL router maintains a
state per origin for each advertised address and merges the
advertisements for all subscriptions for the same address in a
single advertisement. A RPL router that merges multicast
advertisements from different origins becomes the origin of
the merged advertisement and uses its own values for the Path
Sequence and Registration Ownership Verifier (ROVR) fields.
Subscribe/subscription: The special form of registration that
leverages NS(EARO) to register (or subscribe to) a multicast
or an anycast address.
3. Overview
This specification Extends [RFC8505] to provide a registration method
(called "subscription" in this case) for anycast and multicast
addresses. The specification inherits the proof of ownership defined
in [RFC8928] that already protects the address registration in
[RFC8505] to also protect the new subscription mechanism. [RFC8505]
is agnostic to the routing protocol in which the address may be
redistributed.
As opposed to unicast addresses, there might be multiple
registrations from multiple parties for the same address. The router
retains one registration per party for each multicast or anycast
address but injects the route into the routing protocol only once for
each address. The injection happens asynchronously to the
registration. On the other hand, the validation exchange with the
registrar (6LBR) is still needed if the router checks the right for
the host to listen to the anycast or multicast address.
Figure 1 depicts the registration of an anycast or a multicast
address. As shown, the 6LBR receives and accepts multiple EDAR
messages for the same address, and the address being registered by
multiple nodes is not treated as a duplication.
6LoWPAN Node 6LR 6LBR
(host1) (router) (registrar)
| | |
| DMB link | |
| | |
| ND-Classic RS | |
|----------------->| |
|------------> | |
|------------------------> |
| ND-Classic RA | |
|<-----------------| |
| | |
| NS(EARO) | |
|----------------->| |
| | EDAR |
| |-------------->|
| | |
| | EDAC |
| |<--------------|
| NA(EARO) |
|<-----------------|<inject route> ->
| |
...
(host2) (router) 6LBR
| NS(EARO) | |
|----------------->| |
| | |
| | EDAR |
| |-------------->|
| | |
| | EDAC |
| |<--------------|
| NA(EARO) | |
|<-----------------| |
...
(host1) (router)
| NS(EARO) | |
|----------------->| |
| | |
| NA(EARO) | |
|<-----------------| |
...
| |<maintain route> ->
...
Figure 1: Registration Flow for an Anycast or Multicast Address
In classical networks, [RFC8505] may be used for an ND proxy
operation as specified in [RFC8929] or redistributed in a full-
fledged routing protocol such as what might be done in BGP for
Ethernet VPN [MAC-SIGNALING] or in the Routing in Fat Trees (RIFT)
protocol [RIFT]. The device mobility can be gracefully supported as
long as the routers can exchange and make sense of the sequence
counter in the TID field of the EARO.
In the case of LLNs, RPL [RFC6550] is the routing protocol of choice
and [RFC9010] specifies how the unicast address advertised with
[RFC8505] is redistributed in RPL. This specification also provides
RPL extensions for anycast and multicast address operation and
redistribution. In the RPL case, and unless specified otherwise, the
behavior is the same as it is for unicast for the 6LBR that acts as
RPL Root, the intermediate routers Down the RPL graph, the 6LRs that
act as access routers, and the 6LNs that are the RPL-unaware
destinations. In particular, forwarding a packet happens as
specified in Section 11 of [RFC6550], including loop avoidance and
detection, though in the multicast case, multiple copies might be
generated.
[RFC8505] is a prerequisite to this specification. A node that
implements this MUST also implement [RFC8505]. This specification
modifies existing options and updates the associated behaviors to
enable the registration for multicast addresses as an extension to
[RFC8505]. As with the registration of a unicast address, the
subscription to anycast and multicast addresses between a node and
its router(s) is agnostic (meaning it is independent) from the
routing protocol in which this information may be redistributed or
aggregated by the router to other routers. However, protocol
extensions would be needed in the protocol when multicast services
are not available.
This specification also Extends [RFC6550] and [RFC9010] to add
multicast ingress replication (IR) in Non-Storing mode and anycast
support in both Storing and Non-Storing modes in the case of a route-
over multilink subnet based on the RPL routing protocol. A 6LR that
implements the RPL extensions specified herein MUST also implement
[RFC9010].
Figure 2 illustrates the typical scenario of an LLN as a single IPv6
subnet, with a 6LBR that acts as Root for RPL operations and
maintains a registry of the active registrations as an abstract data
structure called an "Address Registrar" for 6LoWPAN ND.
The LLN may be a hub-and-spoke access link such as (Low-Power) Wi-Fi
[IEEE-802.11] and (Low-Energy) Bluetooth [IEEE-802.15.1] or a Route-
Over LLN such as the Wi-SUN [Wi-SUN] and IPv6 over the TSCH mode of
IEEE 802.15.4 (6TiSCH) [RFC9030] meshes that leverage 6LoWPAN
[RFC4919] [RFC6282] and RPL [RFC6550] over IEEE 802.15.4
[IEEE-802.15.4].
|
----+-------+------------
| Wire side
+------+
| 6LBR |
|(Root)|
+------+
o o o Wireless side
o o o o o o
o o o o o o o
o o o LLN o +---+
o o o o o |6LR|
o o o o o +---+
o o o o o o z
o o oo o o +---+
o |6LN|
+---+
Figure 2: Wireless Mesh
A leaf acting as a 6LN registers its unicast addresses to a RPL
router acting as a 6LR using a Layer 2 unicast NS message with an
EARO as specified in [RFC8505]. The registration state is
periodically renewed by the Registering Node before the lifetime
indicated in the EARO expires. As for unicast IPv6 addresses, the
6LR uses an EDAR and then an EDAC exchange with the 6LBR to notify
the 6LBR of the presence of the listeners.
This specification updates the EARO with a new 2-bit field, the
P-Field, as detailed in Section 7.1. The existing R flag that
requests reachability for the Registered Address gets new behavior.
With this extension, the 6LNs can now subscribe to the anycast and
multicast addresses they listen to, using a new P-Field in the EARO
to signal that the registration is for a multicast address. Multiple
6LNs may subscribe the same multicast address to the same 6LR. Note
the use of the term "subscribe": this means that when using the EARO
registration mechanism, a node registers the unicast addresses that
it owns but subscribes to the multicast addresses that it listens to.
With this specification, the 6LNs can also subscribe the anycast
addresses they accept using a new P-Field in the EARO to signal that
the registration is for an anycast address. For multicast addresses,
multiple 6LNs may subscribe the same anycast address to the same 6LR.
If the R flag is set in the subscription of one or more 6LNs for the
same address, the 6LR injects the anycast addresses and multicast
addresses of a scope larger than the link-scope in RPL, based on the
longest subscription lifetime across the active subscriptions for the
address.
In the RPL Storing Mode of Operation with multicast support
(Section 12 of [RFC6550]), the DAO messages for the multicast address
percolate along the RPL-preferred parent tree and mark a subtree that
becomes the multicast tree for that multicast address, with 6LNs that
subscribed to the address as the leaves. As prescribed in Section 12
of [RFC6550], the 6LR forwards a multicast packet as an individual
unicast Medium Access Control (MAC) frame to each peer along the
multicast tree, except to the node it received the packet from.
In the new RPL Non-Storing Mode of Operation with ingress replication
multicast support that is introduced here, the DAO messages announce
the multicast addresses as Targets, and never as Transits. The
multicast distribution is an IR whereby the Root encapsulates the
multicast packets to all the 6LRs that are transit for the multicast
address, using the same source-routing header as for unicast targets
attached to the respective 6LRs.
LLN links are typically Direct MAC Broadcast (DMB) (see more in
[IPv6-OVER-WIRELESS]) with no emulation to increase range (over
multiple radio hops) or reliability. In such links, broadcasting is
unreliable and asynchronous transmissions force a listener to remain
awake, so asynchronous broadcasting is generally inefficient. Thus,
the expectation is that whenever possible, the 6LRs deliver the
multicast packets as individual unicast MAC frames to each of the
6LNs that subscribed to the multicast address. On the other hand, in
a network where nodes do not sleep, asynchronous broadcasting may
still help recovering faster when state is lost.
With this specification, anycast addresses can be injected in RPL in
both Storing and Non-Storing modes. In Storing mode, the RPL router
accepts DAO messages from multiple children for the same anycast
address, but it only forwards a packet to one of the children. In
Non-Storing mode, the Root maintains the list of all the RPL nodes
that announced the anycast address as Target, but it forwards a given
packet to only one of them.
Operationally speaking, deploying a new MOP means that one cannot
update a live network. The network administrator must create a new
instance with MOP 5 and migrate nodes to that instance by allowing
them to join it.
For backward compatibility, this specification allows building a
single DODAG signaled as MOP 1 that conveys anycast, unicast, and
multicast packets using the same source-routing mechanism; see more
in Section 11.
It is also possible to leverage this specification between the 6LN
and the 6LR for the registration of unicast, anycast, and multicast
IPv6 addresses in networks that are not necessarily LLNs and/or where
the routing protocol between the 6LR and its peer routers is not
necessarily RPL. In that case, the distribution of packets between
the 6LR and the 6LNs may effectively rely on a broadcast or multicast
support at the lower layer (e.g., using this specification as a
replacement to MLD in an Ethernet-bridged domain and still using
either a plain MAC-layer broadcast or snooping of this protocol to
control the flooding). It may also rely on overlay services to
optimize the impact of Broadcast, Unknown, and Multicast (BUM)
traffic over a fabric, e.g., registering with [MAC-SIGNALING] and
forwarding with [RFC9574].
For instance, it is possible to operate a RPL Instance in the new
Non-Storing Mode of Operation with ingress replication multicast
support (while possibly signaling a MOP of 1) and use "Multicast
Protocol for Low-Power and Lossy Networks (MPL)" [RFC7731] for the
multicast operation. MPL floods the DODAG with the multicast
messages independently of the RPL DODAG topologies. Two variations
are possible:
* In one possible variation, all the 6LNs set the R flag in the EARO
for a multicast target, upon which the 6LRs send a unicast DAO
message to the Root; the Root filters out the multicast messages
for which there is no listener and only floods when a listener
exists.
* In a simpler variation, the 6LNs do not set the R flag and the
Root floods all the multicast packets over the whole DODAG. Using
a configuration mechanism, it is also possible to control the
behavior of the 6LR to ignore the R flag. It can be configured to
either always or never send the DAO message and/or to control the
Root and specify which groups it should flood or not flood.
Note that if the configuration instructs the 6LR not to send the DAO
message, then MPL can be used in conjunction with the RPL Storing
mode as well.
4. Amending RFC 4861
Section 7.1 of [RFC4861] requires silently discarding NS and NA
packets when the Target Address is a multicast address. This
specification Amends [RFC4861] by allowing the advertisement of
multicast and anycast addresses in the Target Address field when the
NS message is used for a registration, per Section 5.5 of [RFC8505].
5. Extending RFC 7400
This specification Extends "6LoWPAN-GHC: Generic Header Compression
for IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs)"
[RFC7400] by defining a new capability bit for use in the 6CIO.
[RFC7400] was already extended by [RFC8505] for use in IPv6 ND
messages.
The new "Registration for Unicast, Multicast, and Anycast Addresses
Supported" X flag indicates to the 6LN that the 6LR accepts unicast,
multicast, and anycast address registrations as specified in this
document and will ensure that packets for the Registered Address will
be routed to the 6LNs that registered with the R flag set
appropriately.
Figure 3 illustrates the X flag in its position (8, counting 0 to 15
in network order in the 16-bit array); see Section 14.6 for the IANA
registration of capability bits.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length = 1 | Reserved |X|A|D|L|B|P|E|G|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: New Capability Bits in the 6CIO
New Option Field:
X: This is a 1-bit flag for "Registration for Unicast, Multicast,
and Anycast Addresses Supported".
6. Amending RFC 6550
This specification Amends [RFC6550] to mandate the use of the ROVR
field as the indication of the origin of a Target advertisement in
RPL DAO messages, as specified as an option in Section 6.1 of
[RFC9010].
This specification Extends [RFC6550] with a new P-Field in the RPL
Target Option (RTO).
The specification also Amends the behaviors of the Modes of Operation
MOP 1 and MOP 3 and Extends [RFC6550] with a new MOP 5.
6.1. Mandating the ROVR Field
For anycast and multicast advertisements (in NS or DAO messages),
multiple origins may subscribe to the same address, in which case the
multiple advertisements from the different or unknown origins are
merged by the common parent; in that case, the common parent becomes
the origin of the merged advertisements and uses its own ROVR value.
On the other hand, a parent that propagates an advertisement from a
single origin uses the original ROVR in the propagated RTO, as it
does for unicast address advertisements, so the origin is recognized
across multiple hops.
[RFC6550] uses the Path Sequence in the Transit Information Option
(TIO) to retain only the freshest unicast route and remove the stale
ones, e.g., in the case of mobility. [RFC9010] copies the
Transaction ID (TID) from the EARO into the Path Sequence and the
ROVR field into the associated RTO. This way, it is possible to
identify both the Registering Node and the order of registration in
RPL for each individual advertisement, so the most recent path and
lifetime values are used.
This specification Extends [RFC6550] for anycast and multicast
advertisements to require that the Path Sequence be used between, and
only between, advertisements for the same Target and from the same
origin (i.e., with the same ROVR value). In that case, only the
freshest advertisement is retained, but the freshness comparison
cannot apply if the origin is not determined (i.e., the origin did
not support this specification).
[RFC6550] uses the Path Lifetime in the TIO to indicate the remaining
time for which the advertisement is valid for unicast route
determination, and a Path Lifetime value of 0 invalidates that route.
[RFC9010] maps the Address Registration lifetime in the EARO and the
Path Lifetime in the TIO so they are comparable when both forms of
advertisements are received.
The RPL router that merges multiple advertisements for the same
anycast or multicast addresses MUST use and advertise the longest
remaining lifetime across all the origins of the advertisements for
that address. When the lifetime expires, the router sends a no-path
DAO message (i.e., the lifetime is 0) using the same value for the
ROVR value as for the previous advertisements. This value refers to
either the single descendant that advertised the Target if there is
only one or the router itself if there is more than one.
Note that the Registration Lifetime, TID, and ROVR fields are also
placed in the EDAR message so the state created by the EDAR is also
comparable with that created upon an NS(EARO) or a DAO message. For
simplicity, the text below mentions only NS(EARO) but it also applies
to EDAR.
6.2. Updating MOP 3
RPL supports multicast operations in the Storing Mode of Operation
with multicast support (MOP 3), which provides source-independent
multicast routing in RPL, as prescribed in Section 12 of [RFC6550].
MOP 3 is a Storing Mode of Operation. This operation builds a
multicast tree within the RPL DODAG for each multicast address. This
specification provides additional details for the MOP 3.
The expectation in MOP 3 is that the unicast traffic also follows the
Storing Mode of Operation. However, this is rarely the case in LLN
deployments of RPL where the Non-Storing Mode of Operation (MOP 1) is
the norm. Though it is preferred to build separate RPL Instances,
one in MOP 1 and one in MOP 3, this specification allows hybrid use
of the Storing mode for multicast and the Non-Storing mode for
unicast in the same RPL Instance, as is elaborated in more detail in
Section 11.
For anycast and multicast advertisements, including MOP 3, the ROVR
field is placed in the RTO as specified in [RFC9010] for both MOP 3
and MOP 5 as it is for unicast advertisements.
Though it was implicit with [RFC6550], this specification clarifies
that the freshness comparison based on the Path Sequence is not used
when the origin cannot be determined, which occurs in the case of
multiple subscriptions of a multicast or unicast address. The
comparison is to be used only between advertisements from the same
origin, which is either an individual subscriber or a descendant that
merged multiple advertisements.
A RPL router maintains a remaining Path Lifetime for each DAO message
that it receives for a multicast target and sends its own DAO message
for that target with the longest remaining lifetime across its
listening children. If the router has only one descendant listening,
it propagates the TID and ROVR as received. Conversely, if the
router merges multiple advertisements (possibly including one for
itself as a listener), the router uses its own ROVR and TID values.
This implies a possible transition of ROVR and TID values when the
number of listening children changes from one to more or back to one,
which should not be considered as an error or a change of ownership
by the parents above.
6.3. New Non-Storing Multicast MOP
This specification adds a Non-Storing Mode of Operation with ingress
replication multicast support RPL (as assigned by IANA; see
Section 14.5) whereby the Non-Storing Mode DAO to the Root may
advertise a multicast address in the RTO, whereas the TIO cannot.
In that mode, the RPL Root performs an IR operation on the multicast
packets. This means that it transmits one copy of each multicast
packet to each 6LR that is a transit for the multicast target, using
the same source-routing header and encapsulation as it would for a
unicast packet for a RPL-Unaware Leaf (RUL) attached to that 6LR.
For the intermediate routers, the packet appears as any source-routed
unicast packet. The difference shows only at the 6LR, which
terminates the source-routed path and forwards the multicast packet
to all 6LNs that registered for the multicast address.
For a packet that is generated by the Root, the Root builds a source-
routing header as shown in Section 8.1.3 of [RFC9008], but for which
the last and only the last address is multicast. For a packet that
is not generated by the Root, the Root encapsulates the multicast
packet as per Section 8.2.4 of [RFC9008]. In that case, the outer
header is purely unicast, and the encapsulated packet is purely
multicast.
For anycast and multicast advertisements in NA messages (at the 6LR)
and DAO messages (at the Root), as discussed in Section 6.2, the
freshness comparison based on the TID field is applied only between
messages from the same origin, as determined by the same value in the
ROVR field.
The Root maintains a remaining Path Lifetime for each advertisement
it receives, and a 6LR generates the DAO message for multicast
addresses with the longest remaining lifetime across its registered
6LNs, using its own ROVR and TID when multiple 6LNs have subscribed
or when the 6LR is a subscriber.
This specification allows enabling the operation in a MOP 1 brown
field for this new mode as well; see more in Section 11.
6.4. RPL Anycast Operation
With multicast, the address has a recognizable format, and a
multicast packet is to be delivered to all the active subscribers.
In contrast, the format of an anycast address is not distinguishable
from that of a unicast address. A legacy node may issue a DAO
message without setting the P-Field to 2; the unicast behavior may
apply to anycast traffic within a portion of the network, but the
packets will still be delivered. That message will be
undistinguishable from a unicast advertisement, and the anycast
behavior in the data plane can only happen if all the nodes that
advertise the same anycast address are synchronized with the same
TID. That way, the multiple paths can remain in the RPL DODAG.
With the P-Field set to 2, this specification alleviates the issue of
synchronizing the TIDs and ROVR fields. As for multicast, the
freshness comparison based on the TID (in the EARO) and the Path
Sequence (in the TIO) is ignored unless the messages have the same
origin; this is inferred by the same ROVR in the RTO and/or the EARO,
and the latest value of the lifetime is retained for each origin.
A RPL router that propagates an advertisement from a single origin
uses the ROVR and Path Sequence from that origin, whereas a router
that merges multiple subscriptions uses its own ROVR and Path
Sequence and the longest lifetime over the different advertisements.
A target is routed as anycast by a parent (or the Root) that received
at least one DAO message for that target with the P-Field set to 2.
As opposed to multicast, the anycast operation described herein
applies to both addresses and prefixes, and the P-Field can be set to
2 for both. An external destination (such as an address or prefix)
that may be injected as a RPL Target from multiple border routers
should be injected as anycast in RPL to enable load balancing. In
contrast, a mobile target that is multihomed should be advertised as
unicast over the multiple interfaces to favor the TID comparison
instead of multipath load balancing.
For either multicast or anycast, there can be multiple subscriptions
from multiple origins, each using a different value of the ROVR field
that identifies the individual subscription. The 6LR maintains a
subscription state per value of the ROVR for each multicast or
anycast address, but it injects the route into RPL only once for each
address. In the case of a multicast address, this occurs only if its
scope is larger than the link-scope (three or more). Since the
subscriptions are considered separate, the check on the TID that acts
as the subscription sequence only applies to the subscription with
the same ROVR.
Like the 6LR, a RPL router in Storing mode propagates the merged
advertisement to its parent(s) in DAO messages once and only once for
each address, but it retains a routing table entry for each of the
children that advertised the address.
When forwarding multicast packets Down the DODAG, the RPL router
copies all the children that advertised the address in their DAO
messages. In contrast, when forwarding anycast packets Down the
DODAG, the RPL router MUST copy one and only one of the children that
advertised the address in their DAO messages and forward it to one
parent if there is no such child.
6.5. New Registered Address Type Indicator P-Field
The new Registered Address Type Indicator (RATInd) is created for use
in the RTO, the EARO, and the header of EDAR messages. The RATInd
indicates whether an address is unicast, multicast, or anycast. The
new 2-bit P-Field is defined to transport the RATInd in different
protocols.
The P-Field can take the values shown in Table 2.
The intent for the value of 3 is a prefix registration (see
[REGISTRATION]), which is expected to be published after this
specification. At the time of this writing, RPL already advertises
prefixes, and treats unicast addresses as prefixes with a length of
128, so it does not need that new value. On the other hand, 6LoWPAN
ND does not, so the value of 3 (meaning prefix registration) will not
be processed adequately. As a result:
* When the value of 3 is received in an RTO (see Section 6.6), this
value MUST be ignored by the receiver (meaning it is treated as a
value of 0) but the message is processed normally (as per
[RFC6550] and [RFC9010]).
* In the case of an EARO (see Section 7.1) or an EDAR (see
Section 7.2), the message MUST be dropped, and the receiving node
MAY either reply with a status of 12 "Invalid Registration" or
remain silent.
6.6. New RPL Target Option P-Field
[RFC6550] recognizes a multicast address by its format (as specified
in Section 2.7 of [RFC4291]) and applies the specified multicast
operation if the address is recognized as multicast. This
specification updates [RFC6550] to add the 2-bit P-Field (see
Section 6.5) to the RTO to indicate that the Target Address is to be
processed as unicast, multicast, or anycast.
* An RTO that has the P-Field set to 0 is called a unicast RTO.
* An RTO that has the P-Field set to 1 is called a multicast RTO.
* An RTO that has the P-Field set to 2 is called an anycast RTO.
The suggested position for the P-Field is 2 counting from 0 to 7 in
network order as shown in Figure 4, based on Figure 4 of [RFC9010],
which defines the flags in positions 0 and 1:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0x05 | Option Length |F|X| P |ROVRsz | Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Target Prefix (Variable Length) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
... Registration Ownership Verifier (ROVR) ...
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Format of the RPL Target Option (RTO)
New and updated Option Field:
P: This is a 2-bit field; see Section 6.5.
7. Extending RFC 8505
This specification Extends [RFC8505] by adding the concept of a
subscription for anycast and multicast addresses and creating a new
field called the P-Field in the EARO and in the EDAR and EDAC
messages to signal the type of registration.
7.1. Placing the New P-Field in the EARO
Section 4.1 of [RFC8505] defines the EARO as an extension to the ARO
defined in [RFC6775]. This specification adds a new P-Field that is
placed in the EARO flags and is set as follows:
* The P-Field is set to 1 to signal that the Registered Address is a
multicast address. When the P-Field is 1 and the R flag is set to
1 as well, the 6LR that conforms to this specification joins the
multicast stream (e.g., by injecting the address in the RPL
multicast support that is extended in this specification for the
Non-Storing mode).
* The P-Field is set to 2 to signal that the Registered Address is
an anycast address. When the P-Field is 2 and the R flag is 1,
the 6LR that conforms to this specification injects the anycast
address in the routing protocol(s) that it participates in (e.g.,
in the RPL anycast support that is introduced in this
specification for both the Storing and Non-Storing modes).
Figure 5 illustrates the P-Field in its position (2, counting 0 to 7
in network order in the 8-bit array); see Section 14.1 for the IANA
registration of P-Field values.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Status | Opaque |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Rsv| P | I |R|T| TID | Registration Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
... Registration Ownership Verifier (ROVR) ...
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Extended Address Registration Option (EARO) Format
New and updated Option Fields:
Rsv: This is a 2-bit field. It is reserved and MUST be set to 0 and
ignored by the receiver.
P: This is a 2-bit P-Field; see Section 6.5.
7.2. Placing the New P-Field in the EDAR Message
Section 4 of [RFC6775] provides the same format for DAR and DAC
messages but the Status field is only used in DAC messages and has to
be set to 0 in DAR messages. [RFC8505] extends the DAC message as an
EDAC but does not change the Status field in the EDAR.
This specification repurposes the Status field in the EDAR as a Flags
field. It adds a new P-Field to the EDAR flags field to match the
P-Field in the EARO and signal the new types of registration. The
EDAC message is not modified.
Figure 6 illustrates the P-Field in its position (0, counting 0 to 7
in network order in the 8-bit array); see Section 14.2 for the IANA
registration of EDAR message flags.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type |CodePfx|CodeSfx| Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| P | Reserved | TID | Registration Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
... Registration Ownership Verifier (ROVR) ...
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Registered Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Extended Duplicate Address Request (EDAR) Message Format
New and updated Option Fields:
Reserved: This is a 6-bit field. It is reserved and MUST be set to
0 and ignored by the receiver.
P: This is a 2-bit field; see Section 6.5.
7.3. Registration Extensions
[RFC8505] specifies the following behaviors:
* A router that expects to reboot may send a final RA message, upon
which nodes should subscribe elsewhere or redo the subscription to
the same router upon reboot. In all other cases, a node reboot is
silent. When the node comes back to life, existing registration
state might be lost if it was not persisted, e.g., in persistent
memory.
* The registration method is specified only for unicast addresses.
* The 6LN must register all its ULAs and GUAs with an NS(EARO)
message.
* The 6LN may set the R flag in the EARO to obtain return
reachability services by the 6LR, e.g., through ND proxy
operations or by injecting the route in a route-over subnet.
* the 6LR maintains a registration state per Registered Address,
including an NCE with the Link-Layer Address (LLA) of the
Registered Node (the 6LN here).
This specification Amends the above behaviors and Extends them with
the following behaviors:
* The concept of subscription is introduced for anycast and
multicast addresses as an extension to the registration of a
unicast address. The respective operations are similar from the
perspective of the 6LN, but they show important differences on the
router side, which maintains a separate state for each origin and
merges them in its own advertisements.
* New ARO Statuses are introduced to indicate a "Registration
Refresh Request" and an "Invalid Registration" (see Table 8).
The former status is used in asynchronous NA(EARO) messages to
indicate to peer 6LNs that they are requested to reregister all
addresses that were previously registered to the originating node.
The NA message may be sent to a unicast or a multicast link-scope
address and should be contained within the L2 range where nodes
may have effectively registered or, respectively, subscribed to
this router (e.g., a radio broadcast domain). The latter is
generic to any error in the EARO and is used, for example, to
report that the P-Field is not consistent with the Registered
Address in NS(EARO) and EDAR messages.
A router that wishes to refresh its state (e.g., upon reboot or in
any situation where it may have missed a registration or lost a
registration state) SHOULD send an asynchronous NA(EARO) with this
new status value. Failure to do so will delay the recovery of the
network until the next periodic registration by the attached 6LNs
and packets may be lost until then. That asynchronous multicast
NA(EARO) MUST be sent to the all-nodes link-scope multicast
address (ff02::1), and the Target MUST be set to the link-local
address that was exposed previously by this node to accept
registrations.
The TID field in the multicast NA(EARO) message is the one
associated to the Target and follows the same rules as the TID in
the NS(EARO) message for the same Target; see Section 5.2 of
[RFC8505], which points to Section 7.2 of [RFC6550] for the
lollipop mechanism used in the TID operation. It is incremented
by the sender each time it sends a new series of NS and/or NA
messages with the EARO about the Target. The TID indicates a
reboot when it is in the "straight" part of the lollipop, between
the initial value and 255. After that, the TID remains below 128
as long as the device is alive. An asynchronous multicast
NA(EARO) with a TID below 128 MUST NOT be considered as indicating
a reboot.
The asynchronous multicast NA(EARO) indicating a "Registration
Refresh Request" MAY be reissued a few times within a short
period, to increase the chances that the message is received by
all registered nodes despite the unreliable transmissions within
the LLN; the TID MUST be incremented each time. The receiver 6LN
MUST consider that multiple NA(EARO) messages indicating a
"Registration Refresh Request" from the same 6LR received within
that short period with comparable and increasing TID values (i.e.,
their absolute difference is less than the SEQUENCE_WINDOW; see
Section 7.2 of [RFC6550]) are in fact indicative of the same
request. The 6LN MUST process one and only one of the series of
messages. If the TIDs are desynchronized (not comparable) or
decreased, then the NA(EARO) is considered as a new request and it
MUST be processed.
The multicast NA(EARO) SHOULD be resent enough times for the TID
to be issued with the value of 255 so the next NA(EARO) after the
initial series is outside the lollipop and is not confused with a
reboot. By default, the TID initial setting after boot is 252,
the SEQUENCE_WINDOW is 4, the duration of the short period is 10
seconds, the interval between retries is 1 second, and the number
of retries is 3. To reach 255 at boot time, the sender MAY either
issue at least 4 NA messages, skip a TID value, or start with a
value that is more than 252. The best values for the short
period, the number of retries, and the TID initial setting depend
on the environment and SHOULD be configurable.
* A new IPv6 ND Consistent Uptime Option (CUO) is introduced to be
placed in IPv6 ND messages. The CUO allows figuring out the state
consistency between the sender and the receiver. For instance, a
node that rebooted needs to reset its uptime to 0. A router that
changed information like a prefix information option has to
advertise an incremented state sequence. To that effect, the CUO
carries a Node State Sequence Information (NSSI) and a Consistent
Uptime. See Section 10 for the option details.
A node that receives the CUO checks whether it is indicative of a
desynchronization between peers. A peer that discovers that a
router has changed should reassess which addresses it formed based
on the new PIOs from that router and resync the state that it
installed in the router (e.g., the registration state for its
addresses). In the process, the peer may attempt to:
- form new addresses and register them,
- deprecate old addresses and deregister them using a Lifetime of
0, and
- reform any potentially lost state (e.g., by registering again
an existing address that it will keep using).
A loss of state is inferred if the Consistent Uptime of the peer
is less than the time since the state was installed, or if the
NSSI is incremented for a Consistent Uptime.
* Registration for multicast and anycast addresses is now supported.
The P-Field is added to the EARO to signal when the Registered
Address is anycast or multicast. The value of the P-Field is not
consistent with the Registered Address if:
- the Registered Address is a multicast address (Section 2.4 of
[RFC4291]) and the P-Field indicates a value that is not 1, or
- the Registered Address is not a multicast address and the
P-Field indicates a value that is 1.
If this occurs, then the message, NS(EARO) or EDAR, MUST be
dropped, and the receiving node MAY either reply with a status of
12 "Invalid Registration" or remain silent.
* The Status field in the EDAR message that was reserved and not
used in [RFC8505] is repurposed to transport the flags to signal
multicast and anycast.
* The 6LN MUST also subscribe all the IPv6 multicast addresses that
it listens to, and it MUST set the P-Field to 1 in the EARO for
those addresses. The one exception is the all-nodes link-scope
multicast address ff02::1 [RFC4291], which is implicitly
registered by all nodes, meaning that all nodes are expected to
accept messages sent to ff02::1 but are not expected to register
it.
* The 6LN MAY set the R flag in the EARO to obtain the delivery of
the multicast packets by the 6LR (e.g., by MLD proxy operations,
or by injecting the address in a route-over subnet or in the
Protocol Independent Multicast [RFC7761] protocol).
* The 6LN MUST also subscribe all the IPv6 anycast addresses that it
supports, and it MUST set the P-Field in the EARO to 2 for those
addresses.
* The 6LR and the 6LBR are extended to accept more than one
subscription for the same address when it is anycast or multicast,
since multiple 6LNs may subscribe to the same address of these
types. In both cases, the ROVR in the EARO uniquely identifies a
registration within the namespace of the Registered Address.
* The 6LR MUST also consider that all the nodes that registered an
address to it (as known by the Source Link-Layer Address Option
(SLLAO)) also registered ff02::1 [RFC4291] to the all-nodes link-
scope multicast address.
* The 6LR MUST maintain a subscription state per tuple (IPv6
address, ROVR) for both anycast and multicast types of addresses.
It SHOULD notify the 6LBR with an EDAR message, unless it
determined that the 6LBR is legacy and does not support this
specification. In turn, the 6LBR MUST maintain a subscription
state per tuple (IPv6 address, ROVR) for both anycast and
multicast types of address.
8. Extending RFC 9010
[RFC9010] specifies the following behaviors:
* The 6LR has no specified procedure to inject multicast and anycast
routes in RPL even though RPL supports multicast.
* Upon a registration with the R flag set to 1 in the EARO, the 6LR
injects the address in the RPL unicast support.
* Upon receiving a packet directed to a unicast address for which it
has an active registration, the 6LR delivers the packet as a
unicast Layer 2 frame to the LLA of the node that registered the
unicast address.
This specification Extends [RFC9010] by adding the following
behavior:
* Upon a subscription with the R flag and the P-Field both set to 1
in the EARO, if the scope of the multicast address is above link-
scope [RFC7346], then the 6LR injects the address in the RPL
multicast support and sets the P-Field in the RTO to 1 as well.
* Upon a subscription with the R flag set to 1 and the P-Field set
to 2 in the EARO, the 6LR injects the address in the new RPL
anycast support and sets the P-Field to 2 in the RTO.
* Upon receiving a packet directed to a multicast address for which
it has at least one subscription, the 6LR delivers a copy of the
packet as a unicast Layer 2 frame to the LLA of each of the nodes
that registered to that multicast address.
* Upon receiving a packet directed to an anycast address for which
it has at least one subscription, the 6LR delivers a copy of the
packet as a unicast Layer 2 frame to the LLA of exactly one of the
nodes that registered to that multicast address.
9. Leveraging RFC 8928
"Address-Protected Neighbor Discovery for Low-Power and Lossy
Networks" [RFC8928] was defined to protect the ownership of unicast
IPv6 addresses that are registered with [RFC8505].
With [RFC8928], it is possible for a node to autoconfigure a pair of
public and private keys and use them to sign the registration of
addresses that are either autoconfigured or obtained through other
methods.
The first hop router (the 6LR) may then validate a registration and
perform source address validation on packets coming from the sender
node (the 6LN).
Anycast and multicast addresses are not owned by one node. Multiple
nodes may subscribe to the same address. In that context, the method
specified in [RFC8928] cannot be used with autoconfigured key pairs
to protect a single ownership.
For an anycast or a multicast address, it is still possible to
leverage [RFC8928] to enforce the right to subscribe. If [RFC8928]
is used, a key pair MUST be associated with the address before it is
deployed, and a ROVR MUST be generated from that key pair as
specified in [RFC8928]. The address and the ROVR MUST then be
installed in the 6LBR so it can recognize the address and compare the
ROVR on the first subscription.
The key pair MUST then be provisioned in each node that needs to
subscribe to the anycast or multicast address, so the node can follow
the steps in [RFC8928] to subscribe to the address.
10. Consistent Uptime Option
This specification introduces a new option that characterizes the
uptime of the sender. The option may be used by routers in RA
messages and by any node in NS, NA, and RS messages. It is used by
the receiver to infer whether some state synchronization might be
lost (e.g., due to reboot).
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Exponent | Uptime Mantissa |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S|U| flags | NSSI | Peer NSSI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Consistent Uptime Option (CUO) Format
Type: Assigned by IANA; see Table 9.
Length: 1
Uptime Exponent: A 6-bit unsigned integer and the Exponent to the
base 2 of the uptime unit.
Uptime Mantissa: A 10-bit unsigned integer and the mantissa of the
uptime value.
S: A 1-bit flag set to 1 to indicate that the sender is low-power
and may sleep.
U: A 1-bit flag set to 1 to indicate that the Peer NSSI field is
valid; it MUST be set to 0 when the message is not unicast and
MUST be set to 1 when the message is unicast and the sender has an
NSSI state for the intended receiver.
flags: 6-bit flags that are reserved and that MUST be set to 0 by
the sender and ignored by the receiver.
NSSI: A 12-bit unsigned integer that represents the Node State
Sequence Information (NSSI). It MUST be stored by the receiver if
it has a dependency on information advertised or stored at the
sender.
Peer NSSI: A 12-bit unsigned integer that echoes the last known NSSI
from the peer.
The Consistent Uptime indicates how long the sender has been
continuously up and running (though possibly sleeping) without loss
of state. It is expressed by the Uptime Mantissa in units of 2 to
the power of the Uptime Exponent in milliseconds. The receiver
derives the boot time of the sender as the current time minus the
sender's Consistent Uptime.
If the boot time of the sender is updated to a newer time, any state
that the receiver installed in the sender before the reboot is
probably lost. The receiver MUST reassess all the state it installed
in the server (e.g., any registration) and reinstall if it is still
needed.
The U flag not set in a unicast message indicates that the sender has
lost all state from this node. If the U flag is set, then the Peer
NSSI field can be used to assess which changes the sender missed.
For the other way around, any state that was installed in the
receiver from information by the sender before it rebooted MUST be
removed and may or may not be reinstalled later.
The value of the uptime is reset to 0 at some point of the sender's
reboot sequence, but it may not still be 0 when the first message is
sent, so the receiver must not expect a value of 0 as the signal of a
reboot.
+----------+----------+------------+--------+
| Mantissa | Exponent | Resolution | Uptime |
+----------+----------+------------+--------+
| 1 | 0 | 1 ms | 1 ms |
+----------+----------+------------+--------+
| 5 | 10 | 1 s | 5 s |
+----------+----------+------------+--------+
| 2 | 15 | 30 s | 1 min |
+----------+----------+------------+--------+
| 2 | 21 | 33 min | 1 hour |
+----------+----------+------------+--------+
Table 1: Consistent Uptime Rough Values
The NSSI SHOULD be stored in persistent memory by the sender and
incremented when it may have missed or lost state about a peer, or
when it has updated some state in a fashion that will impact a peer
(e.g., a host formed a new address or a router advertises a new
prefix). When persisting is not possible, then the NSSI is randomly
generated.
As long as the NSSI remains constant, the cross-dependent state (such
as addresses in a host that depend on a prefix in a router) can
remain stable, meaning less checks in the receiver. Any change in
the value of the NSSI is an indication that the sender updated some
state and that the dependent state in the receiver should be
reassessed (e.g., addresses that were formed based on an RA with a
previous NSSI should be checked, or new addresses may be formed and
registered).
11. Operational Considerations
With this specification, a RPL DODAG forms a realm, and multiple RPL
DODAGs may be federated in a single RPL Instance administratively.
This means that a multicast address that needs to span a RPL DODAG
MUST use a scope of Realm-Local whereas a multicast address that
needs to span a RPL Instance MUST use a scope of Admin-Local as
discussed in Section 3 of [RFC7346], "IPv6 Multicast Address Scopes".
"IPv6 Addressing of IPv4/IPv6 Translators" [RFC6052] enables
embedding IPv4 addresses in IPv6 addresses. The Root of a DODAG may
leverage that technique to translate IPv4 traffic in IPv6 and route
along the RPL domain. When encapsulating a packet with an IPv4
multicast Destination Address, it MUST use a multicast address with
the appropriate scope, Realm-Local or Admin-Local.
"Unicast-Prefix-based IPv6 Multicast Addresses" [RFC3306] enables
forming 2^32 multicast addresses from a single /64 prefix. If an
IPv6 prefix is associated to an Instance or a RPL DODAG, this
provides a namespace that can be used in any desired fashion. For
instance, it is possible for a standard defining organization to form
its own registry and allocate 32-bit values from that namespace to
network functions or device types. When used within a RPL deployment
that is associated with a /64 prefix, the IPv6 multicast addresses
can be automatically derived from the prefix and the 32-bit value for
either a Realm-Local or an Admin-Local multicast address as needed in
the configuration.
This specification introduces the new RPL MOP 5. Operationally
speaking, deploying a new RPL MOP means that one cannot update a live
network. The network administrator must create a new instance with
MOP 5 and migrate nodes to that instance by allowing them to join it.
In a "green field" deployment where all nodes support this
specification, it is possible to deploy a single RPL Instance using a
multicast MOP for unicast, multicast, and anycast addresses.
In a "brown field" where legacy devices that do not support this
specification coexist with upgraded devices, it is RECOMMENDED to
deploy one RPL Instance in any MOP (typically MOP 1) for unicast that
legacy nodes can join and a separate RPL Instance dedicated to
multicast and anycast operations using a multicast MOP.
To deploy a Storing mode multicast operation using MOP 3 in a RPL
domain, it is required that the RPL routers that support MOP 3 have
enough density to build a DODAG that covers all the potential
listeners and includes the spanning multicast trees that are needed
to distribute the multicast flows. This might not be the case when
extending the capabilities of an existing network.
In the case of the new Non-Storing multicast MOP, arguably the new
support is only needed at the 6LRs that will accept multicast
listeners. It is still required that each listener be able to reach
at least one such 6LR, so the upgraded 6LRs must be deployed to cover
all the 6LNs that need multicast services.
Using separate RPL Instances for unicast traffic on the one hand and
for anycast and multicast traffic on the other hand allows for the
use of different objective functions; one favors the link quality Up
for unicast collection and the other favors Downwards link quality
for multicast distribution.
However, this might be impractical in some use cases where the
signaling and the state to be installed in the devices are very
constrained, the upgraded devices are too sparse, or the devices do
not support more multiple instances.
When using a single RPL Instance, MOP 3 expects the Storing Mode of
Operation for both unicast and multicast, which is an issue in
constrained networks that typically use MOP 1 for unicast. This
specification allows a mixed mode that is signaled as MOP 1 in the
DIO messages for backward compatibility, where limited multicast and/
or anycast is available, under the following conditions:
* There MUST be enough density of the 6LRs that support the mixed
mode to cover all the 6LNs that require multicast or anycast
services. In Storing mode, there MUST be enough density of the
6LRs that support the mixed mode to also form a DODAG to the Root.
* The RPL routers that support the mixed mode are configured to
operate in accordance with the desired operation in the network.
* The MOP signaled in the RPL DIO messages is MOP 1 to enable the
legacy nodes to operate as leaves.
* The support of multicast and/or anycast in the RPL Instance SHOULD
be signaled by the 6LRs to the 6LN using a 6CIO; see Section 5.
* Alternatively, the support of multicast in the RPL domain can be
globally known by other means including configuration or external
information such as support of a version of an industry standard
that mandates it. In that case, all the routers MUST support the
mixed mode.
12. Security Considerations
This specification Extends [RFC8505] and [RFC9010] and leverages
[RFC9008]. The security sections in these documents also apply to
this document. In particular, the link layer SHOULD be sufficiently
protected to prevent rogue access.
RPL [RFC6550] already supports routing on multicast addresses,
whereby the endpoint that subscribes to the group by injecting the
multicast address participates as a RPL-Aware Node (RAN) in the RPL.
Using an extension of [RFC8505] as opposed to RPL to subscribe the
address allows a RPL-Unaware Leaf (RUL) to subscribe as well. As
noted in [RFC9010], this provides a better security posture for the
RPL network, since the nodes that do not really need to speak RPL, or
are not trusted enough to inject RPL messages, can be forbidden from
doing so, which bars a number of attack vectors from within RPL.
Acting as an RUL, those nodes may still leverage the RPL network
through the capabilities that are opened via ND operations. With
this specification, a node that needs multicast delivery can now
obtain the service in a RPL domain while not being allowed to inject
RPL messages.
Compared to [RFC6550], this specification enables tracking the origin
of the multicast subscription inside the RPL network. This is a
first step to enable a form of Route Ownership Validation (ROV) (see
[RFC6811]) in RPL using the ROVR field in the EARO as proof of
ownership.
Section 9 leverages [RFC8928] to prevent a rogue node from
registering a unicast address that it does not own. The mechanism
could be extended to anycast and multicast addresses if the values of
the ROVR they use are known in advance, but how this is done is not
in scope for this specification. One way would be to authorize the
ROVR of the valid users in advance. A less preferred way would be to
synchronize the ROVR and TID values across the valid subscribers as
preshared key material.
In the latter case, it could be possible to update the keys
associated to an address in all the 6LNs, but the flow is not clearly
documented and may not complete in due time for all nodes in LLN use
cases. It may be simpler to install an all-new address with new keys
over a period of time, and switch the traffic to that address when
the migration is complete.
13. Backward Compatibility
A legacy 6LN will not subscribe multicast addresses, and the service
will be the same when the network is upgraded. A legacy 6LR will not
set the X flag in the 6CIO, and an upgraded 6LN will not subscribe
multicast addresses.
Upon receiving an EDAR message, a legacy 6LBR may not realize that
the address being registered is anycast or multicast and will return
that it is a duplicate in the EDAC status. The 6LR MUST ignore a
duplicate status in the EDAC for anycast and multicast addresses.
As detailed in Section 11, it is possible to add multicast on an
existing MOP 1 deployment.
The combination of a multicast address and the P-Field set to 0 in an
RTO in a MOP 3 RPL Instance is an indication to the receiver that
supports this specification (the parent) that the sender (child) does
not support this specification. However, the RTO is accepted and
processed as if the P-Field was set to 1 for backward compatibility.
When the DODAG is operated in MOP 3, a legacy node will not set the
P-Field and still expect multicast service as specified in Section 12
of [RFC6550]. In MOP 3, an RTO that is received with a target that
is multicast and the P-Field set to 0 MUST be considered as multicast
and MUST be processed as if the P-Field is set to 1.
14. IANA Considerations
IANA has made changes under the "Internet Control Message Protocol
version 6 (ICMPv6) Parameters" [IANA.ICMP] and "Routing Protocol for
Low Power and Lossy Networks (RPL)" [IANA.RPL] registry groupings;
see details in the subsections that follow.
14.1. New P-Field Values Registry
IANA has created a new "P-Field Values" registry under the "Internet
Control Message Protocol version 6 (ICMPv6) Parameters" registry
group to store the expression of the RATInd as a P-Field.
The registration procedure is Standards Action [RFC8126]. The
initial allocations are as indicated in Table 2:
+-------+--------------------------------------+-----------+
| Value | Registered Address Type Indicator | Reference |
+-------+--------------------------------------+-----------+
| 0 | Registration for a Unicast Address | RFC 9685 |
+-------+--------------------------------------+-----------+
| 1 | Registration for a Multicast Address | RFC 9685 |
+-------+--------------------------------------+-----------+
| 2 | Registration for an Anycast Address | RFC 9685 |
+-------+--------------------------------------+-----------+
| 3 | Unassigned | RFC 9685 |
+-------+--------------------------------------+-----------+
Table 2: P-Field Values Registry
14.2. New EDAR Message Flags Registry
IANA has created a new "EDAR Message Flags" registry under the
"Internet Control Message Protocol version 6 (ICMPv6) Parameters"
registry group.
The registration procedure is IETF Review or IESG Approval [RFC8126].
The initial allocations are as indicated in Table 3:
+------------+------------------+------------------------+
| Bit Number | Meaning | Reference |
+------------+------------------+------------------------+
| 0-1 | P-Field (2 bits) | RFC 9685, Section 14.1 |
+------------+------------------+------------------------+
| 2-7 | Unassigned | |
+------------+------------------+------------------------+
Table 3: EDAR Message Flags Registry
14.3. New Address Registration Option Flags
IANA has made an addition to the "Address Registration Option Flags"
registry [IANA.ICMP.ARO.FLG] under the "Internet Control Message
Protocol version 6 (ICMPv6) Parameters" registry group as indicated
in Table 4:
+------------+------------------+------------------------+
| Bit Number | Description | Reference |
+------------+------------------+------------------------+
| 2-3 | P-Field (2 bits) | RFC 9685, Section 14.1 |
+------------+------------------+------------------------+
Table 4: New Address Registration Option Flags
14.4. New RPL Target Option Flags
IANA has made an addition to the "RPL Target Option Flags" registry
[IANA.RPL.RTO.FLG] under the "Routing Protocol for Low Power and
Lossy Networks (RPL)" registry group as indicated in Table 5:
+------------+------------------------+------------------------+
| Bit Number | Capability Description | Reference |
+------------+------------------------+------------------------+
| 2-3 | P-Field (2 bits) | RFC 9685, Section 14.1 |
+------------+------------------------+------------------------+
Table 5: New RPL Target Option Flags
14.5. New RPL Mode of Operation
IANA has made an addition to the "Mode of Operation" registry
[IANA.RPL.MOP] under the "Routing Protocol for Low Power and Lossy
Networks (RPL)" registry group as indicated in Table 6:
+-------+---------------------------------------+-----------+
| Value | Description | Reference |
+-------+---------------------------------------+-----------+
| 5 | Non-Storing Mode of Operation with | RFC 9685 |
| | ingress replication multicast support | |
+-------+---------------------------------------+-----------+
Table 6: New RPL Mode of Operation
14.6. New 6LoWPAN Capability Bit
IANA has made an addition to the "6LoWPAN Capability Bits" registry
[IANA.ICMP.6CIO] under the "Internet Control Message Protocol version
6 (ICMPv6) Parameters" registry group as indicated in Table 7:
+-----+--------------------------------------------+-----------+
| Bit | Description | Reference |
+-----+--------------------------------------------+-----------+
| 8 | X flag: Registration for Unicast, | RFC 9685 |
| | Multicast, and Anycast Addresses Supported | |
+-----+--------------------------------------------+-----------+
Table 7: New 6LoWPAN Capability Bit
14.7. New Address Registration Option Status Values
IANA has made additions to the "Address Registration Option Status
Values" registry [IANA.ICMP.ARO.STAT] under the "Internet Control
Message Protocol version 6 (ICMPv6) Parameters" registry group as
indicated in Table 8:
+-------+------------------------------+-----------+
| Value | Description | Reference |
+-------+------------------------------+-----------+
| 11 | Registration Refresh Request | RFC 9685 |
+-------+------------------------------+-----------+
| 12 | Invalid Registration | RFC 9685 |
+-------+------------------------------+-----------+
Table 8: New Address Registration Option Status
Values
14.8. New IPv6 Neighbor Discovery Option Format
IANA has made an addition to the "IPv6 Neighbor Discovery Option
Formats" registry under the "Internet Control Message Protocol
version 6 (ICMPv6) Parameters" registry group as indicated in
Table 9:
+------+--------------------------+-----------+
| Type | Description | Reference |
+------+--------------------------+-----------+
| 42 | Consistent Uptime Option | RFC 9685 |
+------+--------------------------+-----------+
Table 9: New IPv6 Neighbor Discovery Option
Format
15. References
15.1. Normative References
[IANA.ICMP]
IANA, "Internet Control Message Protocol version 6
(ICMPv6) Parameters",
<https://www.iana.org/assignments/icmpv6-parameters>.
[IANA.ICMP.6CIO]
IANA, "6LoWPAN Capability Bits",
<https://www.iana.org/assignments/icmpv6-parameters>.
[IANA.ICMP.ARO.FLG]
IANA, "Address Registration Option Flags",
<https://www.iana.org/assignments/icmpv6-parameters>.
[IANA.ICMP.ARO.STAT]
IANA, "Address Registration Option Status Values",
<https://www.iana.org/assignments/icmpv6-parameters>.
[IANA.RPL] IANA, "Routing Protocol for Low Power and Lossy Networks
(RPL)", <https://www.iana.org/assignments/rpl>.
[IANA.RPL.MOP]
IANA, "Mode of Operation",
<https://www.iana.org/assignments/rpl>.
[IANA.RPL.RTO.FLG]
IANA, "RPL Target Option Flags",
<https://www.iana.org/assignments/rpl>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3306] Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6
Multicast Addresses", RFC 3306, DOI 10.17487/RFC3306,
August 2002, <https://www.rfc-editor.org/info/rfc3306>.
[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>.
[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>.
[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>.
[RFC7346] Droms, R., "IPv6 Multicast Address Scopes", RFC 7346,
DOI 10.17487/RFC7346, August 2014,
<https://www.rfc-editor.org/info/rfc7346>.
[RFC7400] Bormann, C., "6LoWPAN-GHC: Generic Header Compression for
IPv6 over Low-Power Wireless Personal Area Networks
(6LoWPANs)", RFC 7400, DOI 10.17487/RFC7400, November
2014, <https://www.rfc-editor.org/info/rfc7400>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[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>.
[RFC8928] Thubert, P., Ed., Sarikaya, B., Sethi, M., and R. Struik,
"Address-Protected Neighbor Discovery for Low-Power and
Lossy Networks", RFC 8928, DOI 10.17487/RFC8928, November
2020, <https://www.rfc-editor.org/info/rfc8928>.
[RFC9010] Thubert, P., Ed. and M. Richardson, "Routing for RPL
(Routing Protocol for Low-Power and Lossy Networks)
Leaves", RFC 9010, DOI 10.17487/RFC9010, April 2021,
<https://www.rfc-editor.org/info/rfc9010>.
[RFC9030] Thubert, P., Ed., "An Architecture for IPv6 over the Time-
Slotted Channel Hopping Mode of IEEE 802.15.4 (6TiSCH)",
RFC 9030, DOI 10.17487/RFC9030, May 2021,
<https://www.rfc-editor.org/info/rfc9030>.
15.2. Informative References
[IEEE-802.11]
IEEE, "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",
DOI 10.1109/IEEESTD.2021.9363693, IEEE Std 802.11-2020,
<https://ieeexplore.ieee.org/document/9363693>.
[IEEE-802.15.1]
IEEE, "IEEE Standard for Information technology - Local
and metropolitan area networks - Specific requirements -
Part 15.1a: Wireless Medium Access Control (MAC) and
Physical Layer (PHY) specifications for Wireless Personal
Area Networks (WPAN)", IEEE Std 802.15.1-2005,
DOI 10.1109/IEEESTD.2005.96290,
<https://ieeexplore.ieee.org/document/1490827>.
[IEEE-802.15.4]
IEEE, "IEEE Standard for Low-Rate Wireless Networks",
DOI 10.1109/IEEESTD.2020.9144691, IEEE Std 802.15.4-2020,
<https://ieeexplore.ieee.org/document/9144691>.
[IPv6-OVER-WIRELESS]
Thubert, P., Ed. and M. Richardson, "Architecture and
Framework for IPv6 over Non-Broadcast Access", Work in
Progress, Internet-Draft, draft-ietf-6man-ipv6-over-
wireless-06, 23 May 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-6man-
ipv6-over-wireless-06>.
[MAC-SIGNALING]
Thubert, P., Ed., Przygienda, T., and J. Tantsura, "Secure
EVPN MAC Signaling", Work in Progress, Internet-Draft,
draft-thubert-bess-secure-evpn-mac-signaling-04, 13
September 2023, <https://datatracker.ietf.org/doc/html/
draft-thubert-bess-secure-evpn-mac-signaling-04>.
[REGISTRATION]
Thubert, P., Ed., "IPv6 Neighbor Discovery Prefix
Registration", Work in Progress, Internet-Draft, draft-
ietf-6lo-prefix-registration-06, 9 November 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-6lo-
prefix-registration-06>.
[RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener
Discovery Version 2 (MLDv2) for IPv6", RFC 3810,
DOI 10.17487/RFC3810, June 2004,
<https://www.rfc-editor.org/info/rfc3810>.
[RFC4919] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6
over Low-Power Wireless Personal Area Networks (6LoWPANs):
Overview, Assumptions, Problem Statement, and Goals",
RFC 4919, DOI 10.17487/RFC4919, August 2007,
<https://www.rfc-editor.org/info/rfc4919>.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
DOI 10.17487/RFC6052, October 2010,
<https://www.rfc-editor.org/info/rfc6052>.
[RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
DOI 10.17487/RFC6282, September 2011,
<https://www.rfc-editor.org/info/rfc6282>.
[RFC6811] Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R.
Austein, "BGP Prefix Origin Validation", RFC 6811,
DOI 10.17487/RFC6811, January 2013,
<https://www.rfc-editor.org/info/rfc6811>.
[RFC7731] Hui, J. and R. Kelsey, "Multicast Protocol for Low-Power
and Lossy Networks (MPL)", RFC 7731, DOI 10.17487/RFC7731,
February 2016, <https://www.rfc-editor.org/info/rfc7731>.
[RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
Multicast - Sparse Mode (PIM-SM): Protocol Specification
(Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
2016, <https://www.rfc-editor.org/info/rfc7761>.
[RFC8929] Thubert, P., Ed., Perkins, C.E., and E. Levy-Abegnoli,
"IPv6 Backbone Router", RFC 8929, DOI 10.17487/RFC8929,
November 2020, <https://www.rfc-editor.org/info/rfc8929>.
[RFC9008] Robles, M.I., Richardson, M., and P. Thubert, "Using RPI
Option Type, Routing Header for Source Routes, and IPv6-
in-IPv6 Encapsulation in the RPL Data Plane", RFC 9008,
DOI 10.17487/RFC9008, April 2021,
<https://www.rfc-editor.org/info/rfc9008>.
[RFC9574] Rabadan, J., Ed., Sathappan, S., Lin, W., Katiyar, M., and
A. Sajassi, "Optimized Ingress Replication Solution for
Ethernet VPNs (EVPNs)", RFC 9574, DOI 10.17487/RFC9574,
May 2024, <https://www.rfc-editor.org/info/rfc9574>.
[RIFT] Przygienda, A., Ed., Head, J., Ed., Sharma, A., Thubert,
P., Rijsman, B., and D. Afanasiev, "RIFT: Routing in Fat
Trees", Work in Progress, Internet-Draft, draft-ietf-rift-
rift-24, 23 May 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-rift-
rift-24>.
[UPDATES-TAG]
Kühlewind, M. and S. Krishnan, "Definition of new tags for
relations between RFCs", Work in Progress, Internet-Draft,
draft-kuehlewind-rswg-updates-tag-02, 8 July 2024,
<https://datatracker.ietf.org/doc/html/draft-kuehlewind-
rswg-updates-tag-02>.
[Wi-SUN] Robert, H., Liu, B., Zhang, M., and C. Perkins, "Wi-SUN
FAN Overview", Work in Progress, Internet-Draft, draft-
heile-lpwan-wisun-overview-00, 3 July 2017,
<https://datatracker.ietf.org/doc/html/draft-heile-lpwan-
wisun-overview-00>.
Acknowledgments
This work is a production of an effective collaboration between the
IETF 6lo WG and the Wi-Sun FAN WG. Thanks to all in both WGs who
contributed reviews and productive suggestions, in particular:
Carsten Bormann, Paul Duffy, Klaus Hueske, Adnan Rashid, Rahul
Jadhav, Gene Falendysz, Don Sturek, Dario Tedeschi, Saurabh Jain, and
Chris Hett, with special thanks to Esko Dijk for his useful WGLC
reviews and proposed changes. Also many thanks to Éric Vyncke, Sandy
Ginoza, Zaheduzzaman Sarker, Paul Wouters, Roman Danyliw, John
Scudder, Dirk Von Hugo, Murray Kucherawy, Kyle Rose, Scott Kelly, and
Dan Romascanu for their suggestions and comments during the IETF last
call and IESG review cycle.
Author's Address