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IPv6 Neighbor Discovery Multicast Address Registration
draft-thubert-6lo-multicast-registration-00

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This is an older version of an Internet-Draft whose latest revision state is "Replaced".
Author Pascal Thubert
Last updated 2021-09-30
Replaced by draft-ietf-6lo-multicast-registration, draft-ietf-6lo-multicast-registration, draft-ietf-6lo-multicast-registration, draft-ietf-6lo-multicast-registration
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draft-thubert-6lo-multicast-registration-00
6lo                                                      P. Thubert, Ed.
Internet-Draft                                             Cisco Systems
Updates: 6550, 8505, 9010 (if approved)                30 September 2021
Intended status: Standards Track                                        
Expires: 3 April 2022

         IPv6 Neighbor Discovery Multicast Address Registration
              draft-thubert-6lo-multicast-registration-00

Abstract

   This document updates RFC 8505 in order to enable the registration by
   a 6LN of an IPv6 multicast address to a 6LR.  This document also
   extends RFC 9010 to enable the 6LR to inject the address in the RPL
   multicast support.

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 3 April 2022.

Copyright Notice

   Copyright (c) 2021 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.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   4
     2.2.  References  . . . . . . . . . . . . . . . . . . . . . . .   4
     2.3.  Glossary  . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Extending RFC 7400  . . . . . . . . . . . . . . . . . . . . .   7
   5.  Updating RFC 6550 . . . . . . . . . . . . . . . . . . . . . .   7
   6.  Updating RFC 8505 . . . . . . . . . . . . . . . . . . . . . .   8
     6.1.  New EARO flag . . . . . . . . . . . . . . . . . . . . . .   8
     6.2.  Multicast Registration  . . . . . . . . . . . . . . . . .   8
   7.  Updating RFC 9010 . . . . . . . . . . . . . . . . . . . . . .   9
   8.  Backward Compatibility  . . . . . . . . . . . . . . . . . . .   9
   9.  Deployment considerations . . . . . . . . . . . . . . . . . .  10
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  10
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
     11.1.  New ARO flag . . . . . . . . . . . . . . . . . . . . . .  11
     11.2.  New 6LoWPAN Capability Bits  . . . . . . . . . . . . . .  11
   12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  11
   13. Normative References  . . . . . . . . . . . . . . . . . . . .  11
   14. Informative References  . . . . . . . . . . . . . . . . . . .  13
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  14

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 is a major energy drain
   and the protocol signaling must be adapted to optimize their
   transmissions and avoid any waste.

   The "Routing Protocol for Low Power and Lossy Networks" [RFC6550]
   (RPL) to provide 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 2 peers,
   whatever that would mean in a given LLN.

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   This trades the quality of peer-to-peer (P2P) paths 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 dataplane inconsistency discovery, which avoids wasting energy in
   the proactive repair of unused paths.

   Section 12 of [RFC6550] details the "Storing Mode of Operation with
   multicast support" with source-independent multicast routing in RPL.

   The classical "IPv6 Neighbor Discovery (IPv6 ND) Protocol" [RFC4861]
   [RFC4862] was defined for serial links and shared transit media such
   as Ethernet at a time when broadcast was cheap on those media while
   memory for neighbor cache was expensive.  It was thus designed as a
   reactive protocol that relies on caching and multicast operations for
   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, which
   is a waste of energy, and imply that all nodes are awake to hear the
   request, which is inconsistent with power saving (sleeping) modes.

   The original 6LoWPAN ND, "Neighbor Discovery Optimizations for
   6LoWPAN networks" [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 the a
   6LoWPAN Router(s) (6LR) that serves 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 6LoWPAN Neighbor Discovery" [RFC8505]
   updates [RFC6775] into a generic Address Registration mechanism that
   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 provide return reachability for that address.

   "Routing for RPL Leaves" [RFC9010] provides the router counterpart of
   the mechanism for a host that implements [RFC8505] to inject its
   unicast Unique Local Addresses (ULAs) and Glocal Unicast Addresses
   (GUAs) in RPL.  But though 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 registration of a multicast address.

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   The "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
   address 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 specify a simple extension to that
   code to register the multicast addresses they listen to.

   This specification extends [RFC8505] and [RFC9010] to add the
   capability for the 6LN to register multicast addresses and for the
   6LR to inject them in the RPL multicast support.

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.

2.2.  References

   This document uses terms and concepts that are discussed in:

   *  "Neighbor Discovery for IP version 6" [RFC4861] and "IPv6
      Stateless address Autoconfiguration" [RFC4862],

   *  Neighbor Discovery Optimization for Low-Power and Lossy Networks
      [RFC6775], as well as

   *  "Registration Extensions for 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.  Glossary

   This document uses the following acronyms:

   6BBR   6LoWPAN Backbone Router
   6BBR   6LoWPAN Border Router
   6LN    6LoWPAN Node

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   6LR    6LoWPAN Router
   6CIO   Capability Indication Option
   AMC    Address Mapping Confirmation
   AMR    Address Mapping Request
   ARO    Address Registration Option
   DAC    Duplicate Address Confirmation
   DAD    Duplicate Address Detection
   DAR    Duplicate Address Request
   EARO   Extended Address Registration Option
   EDAC   Extended Duplicate Address Confirmation
   EDAR   Extended Duplicate Address Request
   DODAG  Destination-Oriented Directed Acyclic Graph
   LLN    Low-Power and Lossy Network
   NA     Neighbor Advertisement
   NCE    Neighbor Cache Entry
   ND     Neighbor Discovery
   NS     Neighbor Solicitation
   ROVR   Registration Ownership Verifier
   RA     Router Advertisement
   RS     Router Solicitation
   TID    Transaction ID

3.  Overview

   [RFC8505] is a pre-requisite to this specification.  A node that
   implement this MUST also implement [RFC8505].  This specification
   does not introduce a new option; it modifies existing options and
   updates the associated behaviors to enable the registration of
   multicast addresses with [RFC8505].

   This specification also extends [RFC6550] and [RFC9010] in the case
   of a route-over multilink subnet based on the RPL routing protocol.
   A 6LR that implements the RPL extensions specified therein MUST also
   implement [RFC9010].

   Figure 1 illustrates the classical situation of an LLN as a single
   IPv6 Subnet, with a 6LoWPAN Border Router (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 Std 802.11] and Bluetooth (Low Energy) [IEEE Std 802.15.1], or
   a Route-Over LLN such as the Wi-SUN mesh [Wi-SUN] that leverages
   6LoWPAN [RFC4919][RFC6282] and RPL [RFC6550] over [IEEE Std
   802.15.4].

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                     |
         ----+-------+------------
             |     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  o   6LR
      o o  o o   o  o  z
       o   o   o o       z
             o            6LN

                          Figure 1: Wireless Mesh

   A leaf acting as a 6LN registers its unicast addresses to a RPL
   router acting as a 6LR, using a 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.

   With this specification, the 6LNs can now register for the multicast
   addresses they listen to, using a new M flag in the EARO to signal a
   registration for a multicast address.  Multiple 6LN can register for
   the same multicast address to the samme 6LR.  Note the use of the
   term "for", the nodes registers the unicast addresses it owns, but
   registers for multicast addresses that it listens to.

   If the R flag is set in the registration of one or more 6LNs for the
   same multicast address, the 6LR injects the multicast address in the
   RPL multicast support, based on the longest registration lifetime
   across those 6LNs.  The DAO messages for the multicast address
   percolate along the RPL preferred parent tree in storing mode of
   operation and form a subtree for that multicast address with 6LNs
   that registered for it as the leaves.

   As prescribed in section 12 of [RFC6550], the RPL routers forward the
   multicast packets as individual unicast MAC frames to each child that
   advertised the multicast address in its DAO message . The same way,
   the 6LR delivers the multicast packet as individual unicast MAC
   frames to each of the 6LNs that registered for the multicast address.

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4.  Extending RFC 7400

   This specification defines a new capability bit for use in the 6CIO
   as defined by "6LoWPAN-GHC: Generic Header Compression for IPv6 over
   Low-Power Wireless Personal Area Networks (6LoWPANs)" [RFC7400] and
   extended in [RFC8505] for use in IPv6 ND messages.

   The new "Registration of Multicast Address Supported" (M) flag
   indicates to the 6LN that the 6LR accepts multicast address
   registrations as specified in this document and will ensure that
   packets for the multicast Registered Address will be routed to the
   6LNs that registered with the R flag set.

   Figure 2 illustrates the M flag in its suggested position (8,
   counting 0 to 15 in network order in the 16-bit array), to be
   confirmed by IANA.

       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   |M|A|D|L|B|P|E|G|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Reserved                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Figure 2: New Capability Bits in the 6CIO

   New Option Field:

   M  1-bit flag: "Registration of Multicast Address Supported"

5.  Updating RFC 6550

   RPL supports multicast operation 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 is needed to build a
   multicast tree within the RPL DODAG for each multicast Address.

   The expectation is that the unicast traffic also follows the Storing
   Mode of Operation.  But this is rarely the case in current 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 to hybrid
   the Storing Mode for multicast and Non-Storing Mode for unicast in
   the same RPL Instance, more in Section 9 .

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6.  Updating RFC 8505

6.1.  New EARO flag

   Section 4.1 of [RFC8505] defines the EARO as an extension to the ARO
   option defined in [RFC6775].  This specification adds a new M flag to
   the EARO flags field to signal that the Registered Address is a
   multicast address.  When both the M and the R flags are set, the 6LR
   that conforms this specification joins the multicast stream, e.g., by
   injecting the address in the RPL multicast support.

   Figure 3 illustrates the M flag in its suggested position (4,
   counting 0 to 8 in network order in the 8-bit array), to be confirmed
   by IANA.

      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     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |Rsvd |M| I |R|T|     TID       |     Registration Lifetime     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
    ...             Registration Ownership Verifier                 ...
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                        Figure 3: EARO Option Format

   New Option Field:

   M  1-bit flag: "Registration of Multicast Address Supported"

6.2.  Multicast Registration

   With [RFC8505]:

   *  Only unicast addresses can be registered.

   *  The 6LN must register all its ULA and GUA with a NS(EARO).

   *  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).

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   This specification adds the following behaviour:

   *  Registration of multicast addresses is now supported.

   *  The 6LN MUST also register all the IPv6 multicast addresses that
      it listens to and it MUST set the M flag in the EARO for those
      addresses.

   *  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 6LR maintains a registration state per tuple (IPv6 address,
      LLA) since multiple 6LNs may listen to the same multicast address.

7.  Updating RFC 9010

   With [RFC9010]:

   *  The 6LR injects only unicast routes in RPL

   *  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 the nodes that registered the
      unicast address.

   This specification adds the following behaviour:

   *  Upon a registration with the R and the M flags set to 1 in the
      EARO, the 6LR injects the address in the RPL multicast support.

   *  Upon receiving a packet directed to a multicast address for which
      it has at least one registration, 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.

8.  Backward Compatibility

   A legacy 6LN will not register multicast address and the service will
   be the same when the network is upgraded.  A legacy 6LR will not set
   the M flag in the 6CIO and an upgraded 6LN will not register
   multicast addresses.

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9.  Deployment considerations

   To deploy this specification in a RPL domain, it is REQUIRED that
   there is enough density of RPL routers that support MOP 3 to build
   the spanning multicast trees that are needed to distribute the
   multicast flows.

   It is generally RECOMMENDED to deploy one RPL Instance in any Mode of
   Operation (typically MOP 1) for unicast that legacy nodes can join,
   and a separate RPL Instance dedicated to multicast operations and
   operating in MOP 3.  This allows to use a different objective
   function for both direction, favouring the link quality up for
   unicast collection and down for multicast distribution.

   But this might be impractical in some use cases where the signaling
   and the state to be installed in the devices are very constrained.
   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 (MOP 1 fo runicast and MOP 3 for
   multicast) under the following conditions:

   *  All the RPL routers support the mixed mode and are configured to
      operate in that mode/

   *  The MOP signaled in the RPL DODAG Information Object (DIO)
      messages is MOP 1 to enable the legacy nodes to operate as leaves.

   *  T The support of multicast in the RPL Instance SHOULD be signaled
      by the 6LR to the 6LN using a 6CIO, see Section 4.

   *  Altrenatively, the support of multicast in the RPL domain can be
      known by other means such as configuration or external information
      such as support of a version of an industry standard that mandates
      it.

10.  Security Considerations

   This specification extends [RFC8505], and the security section of
   that document also applies to this document.  In particular, the link
   layer SHOULD be sufficiently protected to prevent rogue access.

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11.  IANA Considerations

   Note to RFC Editor, to be removed: please replace "This RFC"
   throughout this document by the RFC number for this specification
   once it is allocated.  Also, the I Field is defined in RFC 9010 but
   we failed to insert it in the subregistry and the flags appear as
   unspecified though they are.

   IANA is requested to make a number of changes under the "Internet
   Control Message Protocol version 6 (ICMPv6) Parameters" registry, as
   follows.

11.1.  New ARO flag

   IANA is requested to make additions to the Address Registration
   Option flags subregistry as follows:

           +---------------+----------------------+-----------+
           | ARO flag      | Meaning              | Reference |
           +---------------+----------------------+-----------+
           | 4 and 5       | "I" Field            | RFC 8505  |
           +---------------+----------------------+-----------+
           | 3 (suggested) | M flag: Registration | This RFC  |
           |               | of Multicast Address |           |
           +---------------+----------------------+-----------+

                          Table 1: New ARO flag

11.2.  New 6LoWPAN Capability Bits

   IANA is requested to make an addition to the Subregistry for "6LoWPAN
   Capability Bits" subregistry as follows:

       +----------------+-----------------------------+-----------+
       | Capability Bit | Meaning                     | Reference |
       +----------------+-----------------------------+-----------+
       | 8 (suggested)  | M flag: Registration of     | This RFC  |
       |                | Multicast Address Supported |           |
       +----------------+-----------------------------+-----------+

                   Table 2: New 6LoWPAN Capability Bits

12.  Acknowledgments

13.  Normative References

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   [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>.

   [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>.

   [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>.

   [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>.

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   [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>.

14.  Informative References

   [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>.

   [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>.

   [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>.

   [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>.

   [Wi-SUN]   Heile, B., (Remy), B. L., Zhang, M., and C. E. 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>.

   [IEEE Std 802.15.4]
              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".

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   [IEEE Std 802.11]
              IEEE standard for Information Technology, "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.",
              <https://ieeexplore.ieee.org/document/9363693>.

   [IEEE Std 802.15.1]
              IEEE standard for Information Technology, "IEEE Standard
              for Information Technology - Telecommunications and
              Information Exchange Between Systems - Local and
              Metropolitan Area Networks - Specific Requirements. - Part
              15.1: Wireless Medium Access Control (MAC) and Physical
              Layer (PHY) Specifications for Wireless Personal Area
              Networks (WPANs)".

Author's Address

   Pascal Thubert (editor)
   Cisco Systems, Inc
   Building D
   45 Allee des Ormes - BP1200
   06254 Mougins - Sophia Antipolis
   France

   Phone: +33 497 23 26 34
   Email: pthubert@cisco.com

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