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Generic Address Assignment Option for 6LowPAN Neighbor Discovery
draft-ietf-6lo-nd-gaao-01

Document Type Active Internet-Draft (6lo WG)
Authors Luigi Iannone , Zhe Lou , Adnan Rashid
Last updated 2024-11-25
Replaces draft-iannone-6lo-nd-gaao
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draft-ietf-6lo-nd-gaao-01
6lo Working Group                                             L. Iannone
Internet-Draft                                                    D. Lou
Intended status: Standards Track                                  Huawei
Expires: 29 May 2025                                           A. Rashid
                                                     Politecnico di Bari
                                                        25 November 2024

    Generic Address Assignment Option for 6LowPAN Neighbor Discovery
                       draft-ietf-6lo-nd-gaao-01

Abstract

   This document specifies a new extension to the IPv6 Neighbor
   Discovery in Low Power and Lossy Networks, enabling a node to request
   to be assigned an address or a prefix from neighbor routers.  Such
   mechanism allows to algorithmically assign addresses and prefixes to
   nodes in a 6LowPAN deployment.

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 29 May 2025.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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 Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Notation . . . . . . . . . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Definition of Terms . . . . . . . . . . . . . . . . . . . . .   4
   5.  Algorithmically Assigned Addresses and Prefixes . . . . . . .   5
   6.  Generic Address Assignment Option . . . . . . . . . . . . . .   6
   7.  Messages Sequence and Processing  . . . . . . . . . . . . . .   8
     7.1.  Request Phase . . . . . . . . . . . . . . . . . . . . . .   8
     7.2.  Optional Confirmation Phase . . . . . . . . . . . . . . .   9
     7.3.  Message exchange optimization . . . . . . . . . . . . . .  10
   8.  GAAO Error Conditions . . . . . . . . . . . . . . . . . . . .  11
   9.  Signaling GAAO Support  . . . . . . . . . . . . . . . . . . .  12
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
     10.1.  IPv6 ND Option Types . . . . . . . . . . . . . . . . . .  12
     10.2.  6LoWPAN Capability Bits  . . . . . . . . . . . . . . . .  13
     10.3.  GAAO Error code  . . . . . . . . . . . . . . . . . . . .  13
     10.4.  Address Assignment Function Registry . . . . . . . . . .  13
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  14
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  14
   References  . . . . . . . . . . . . . . . . . . . . . . . . . . .  14
     Normative References  . . . . . . . . . . . . . . . . . . . . .  14
     Informative References  . . . . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   Low Power and Lossy Networks (LLNs) have adapted the design of
   Internet protocols to more constrained environments, by taking into
   consideration of energy saving, limited memory capacity, and duty
   cycling of the LLN devices, as well as low-power lossy transmissions.
   Since the wireless interface is a major energy drain, protocols
   aiming at being deployed over LLN must be designed in such a way to
   reduce as much as possible transmissions, allowing to turn off the
   radio interface or put the interface or the whole node in the
   sleeping mode.

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   IPv6 Neighbor Discovery has been also adapted to the LLN environment
   in [RFC6775], later updated by [RFC8505], [RFC8929], and [RFC9010].
   In particular, interface address assignment relies on address auto-
   configuration [RFC4862], since the use of Dynamic Host Configuration
   Protocol (DHCP [RFC8415]) is not adapted to LLN deployments.  Hence,
   mechanisms to register these self-generated addresses have been
   designed ([RFC6775], [I-D.ietf-6lo-prefix-registration], [RFC8505],
   [I-D.ietf-6lo-multicast-registration]).

   Recent use cases show, however, that there are some advantages in
   assigning addresses in an algorithmically managed way.  In
   particular, in some scenarios, routing and forwarding can be
   simplified ([RFC9453], [I-D.ietf-6lo-path-aware-semantic-addressing],
   [SHENOY21], [BLESS22], [RIDOUX05]), hence reducing the power
   consumption and memory footprint.  Algorithmic address assignment has
   its own pros and cons, as well as deployment requirements.  However,
   they have the common benefit of being easily distributed.  In other
   words, it is not necessary to have a centralized approach, like DHCP,
   rather a node can obtain an address generated by one of its neighbors
   who simply runs an algorithm.

   This situation highlights an existing gap that this document tries to
   fill: 6LowPAN nodes have no means to directly request an address (or
   address prefix) from routers that are their direct neighbors.
   Currently, either auto-configuration is used, or DHCP has to be
   deployed.  The former is energy efficient, but makes it hard to
   implement solutions like
   [I-D.ietf-6lo-path-aware-semantic-addressing], [SHENOY21], [BLESS22],
   and [RIDOUX05].  The latter, on the opposite, allows the use of
   sophisticated assignment algorithms, but remains inefficient from an
   energy consumption viewpoint.

   This document proposes a new Neighbor Discovery Option, namely the
   Generic Address Assignment Option (GAAO), in order for a node to
   issue an address or prefix request to neighboring routers.  This new
   GAA Option complements the Extended Address Registration Option,
   defined in [RFC8505], further extended in
   [I-D.ietf-6lo-prefix-registration] and
   [I-D.ietf-6lo-multicast-registration].

2.  Requirements Notation

   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.

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3.  Terminology

   This document assumes familiarity with the terminology defined in
   [RFC6775] and [RFC8505].  In particular for the following acronyms:

   6CIO: Capability Indication Option

   6LBR: 6LoWPAN Border Router

   6LN: 6LoWPAN Node

   6LoWPAN: IPv6 over Low-Power Wireless Personal Area Network

   6LR: 6LoWPAN Router

   ARO: Address Registration Option

   EARO: Extended Address Registration Option

   LLN: Low-Power and Lossy Network

   NA: Neighbor Advertisement

   ND: Neighbor Discovery

   NS: Neighbor Solicitation

   RA: Router Advertisement

   RS: Router Solicitation

   SLLAO: Source Link-Layer Address Option

   TLLAO: Target Link-Layer Address Option

4.  Definition of Terms

   Address Assignment Function (AAF):  The Address Assignment Function
      (AAF) is an implementation of the algorithm used by 6LRs to assign
      an address/prefix to requesting nodes.  In order to avoid
      addressing issues, only one single AAF is used in a deployment.

   GAAO: Generic Address Assignment Option defined in the present
   document ({Sec:GAAO}).

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5.  Algorithmically Assigned Addresses and Prefixes

   The IPv6 address assignment model inside a local domain is based on
   randomly assigned Interface IDentifier (IID), either done in a
   centralized way using DHCP, which can guarantee no address collision,
   or by decentralized State-Less Address Auto-Configuration (SLAAC
   [RFC4862]), which needs additional mechanisms to ensure the
   uniqueness of addresses.  However, there is a third approach for
   address assignment, which is distributed and collision-free:
   algorithmically generated addresses (e.g., [SHENOY21], [BLESS22],
   [RIDOUX05], [ERIKSSON04]).

   The main idea is to use an Address Assignment Function (AAF) to
   assign addresses and prefixes to nodes joining a network.  All nodes,
   6LNs, 6LRs, and 6LBRs, MUST use the same AAF in the same network
   instance.  Each node acquiring an address firstly needs to select a
   neighbor 6LR by choosing among the nodes that replied with a Router
   Advertisement (RA) after an initial Router Solicitation (RS), as
   defined in [RFC6775].  Then, the node explicitly requests an address
   (or prefix) to the selected 6LR.  Depending on the underlying
   technology and algorithm used, the node may optionally confirm its
   usage.  The high-level sequence of actions is depicted in Figure 1.

    6LN                      6LR
    |                         |
    | 1. Address Request      | \
    |------------------------>|  |
    |                         |   > Request Phase
    | 2. Address Offer        |  |
    |<------------------------| /
    |                         |
    | 3. Address Acceptation  | \
    |------------------------>|  |
    |                         |   > Optional Confirmation Phase
    | 4. Address Confirmation |  |
    |<------------------------| /

               Figure 1: Address/Prefix assignment sequence.

   The optional confirmation phase (namely step 3 and 4), is implemented
   by using the address registration procedure defined in [RFC8505],
   {!I-D.ietf-6lo-multicast-registration}, or {I-D.ietf-6lo-prefix-
   registration}. Basically, it uses an EARO and SLLAO messages to
   register an address, which in this case is not a self-generated
   address.  However, in order to issue the initial request, namely
   steps 1 and 2, a new Generic Address Assignment Option (GAAO) is
   required and proposed, since no existing mechanism can be readily
   used for this purpose.  In the remaining of this document, the format

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   of this option is firstly defined (Section 6), followed by a revised
   Address/Prefix assignment messages sequence and processing
   (Section 7).

6.  Generic Address Assignment Option

   In order for a node to request the assignment of an address or
   prefix, the Generic Address Assignment Option (GAAO) message is used.
   The format of the GAAO message is shown in Figure 2.

     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/PfxLen |    Opaque     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |C|      Reserved       |  AAF  |     Assignment   Lifetime     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
   ...            Registration Ownership Verifier (ROVR)           ...
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |                        Address/Prefix                         |
    |                          (128 bits)                           |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 2: Generic Address Assignment Option format.

   Generic Address Assignment Option Fields:

   Type:  TBD

   Length:  8-bit unsigned integer.  The length of the option in units
      of 8 bytes.  This field is set to 1 plus the size of the ROVR
      field when the option is used in NS messages.  It is augmented by
      2 (16 bytes) when this option is used in NA messages because the
      assigned address/prefix is appended to the option.

   Status/PfxLen:  8-bits unsigned integer.  This field has two
      purposes.  It indicates the Prefix Length of the assigned address
      if the assignment is successful.  On success, the returned GAAO
      message will have 16 bytes of the assigned address/prefix appended
      to it, which means that the Length field will increased by 2 (cf.
      Length field).  In case of failure, when no address/prefix is
      returned, this field indicates an error code (See table 1 in
      [RFC8505] and Section 8 for error codes).  In this case, the
      returned GAAO message will not have any address/prefix appended to

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      it and the Length field has not been increased.  A returning GAA
      Option with the same length as the one sent indicates error
      condition, whose code is indicated in this field.  This field MUST
      be set to 0 on transmission and ignored on reception in NS
      messages.

   Opaque:  As defined in [RFC8505], where values different from 0 are
      interpreted as an abstract index that is used to decide from which
      routing topology the address is expected to be assigned.

   C:  Confirmation requested.  It MUST be initialized to 0 by in NS
      messages by the requester and MUST be ignored by the receiver.
      The 6LR replying to the request with an NA message MAY set this
      bit to indicate that it requests a confirmation that the address/
      prefix is accepted and will be used.  When the requester receives
      an NA message with this bit set, it MUST explicitly register the
      received address/prefix to the same 6LR using the procedures
      defined in [RFC8505], [I-D.ietf-6lo-prefix-registration], and
      [I-D.ietf-6lo-multicast-registration], according to the type of
      the assigned address/prefix.

   Reserved:  This field is reserved for future use.  It MUST be
      initialized to 0 by the sender and MUST be ignored by the
      receiver.

   Address Assignment Function(AAF):  4-bits unsigned integer.  Describe
      the Address Assignment Function (AAF), i.e. the algorithm, used to
      assign the address/prefix. 0 is a special value indicating that
      the field is not used.  On request in an NS message, this field
      MAY be set to 0 to indicate there is no preference on how the
      address is assigned.  If different from 0 it means that it is
      requested to use a specific known AAF to assign the address/prefix
      (see Section 8).  Section 10.4 describes possible values of this
      field.

   Assignment Lifetime:  16-bit unsigned integer, expressed in minutes.
      In an NS message, the field expresses the minimum desired
      lifetime.  It MAY be set to zero in the NS message, indicating no
      particular desired lifetime.  In NA messages it expresses the
      granted maximum lifetime.

   ROVR: As defined in [RFC8505].

   Address/Prefix:  128 bits address or prefix returned in a GAA Option
      in an NA message.  This field is not present in GAAO requests in
      NS messages and in NA messages when an error occurs.

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7.  Messages Sequence and Processing

   When a node bootstraps, it typically does multicast a Routing
   Solicitation (RS) and receives one or more unicast Routing
   Advertisements (RA) messages from neighbor 6LRs.  The node can choose
   one or more 6LRs from which to request address(es) or prefix(es).  A
   node can perform an address request at any time, not necessarily at
   boot time using Neighbor Solicitation (NS) and Neighbor Advertisement
   (NA) messages.

7.1.  Request Phase

   When the node requests an address, the node will go through the
   following steps:

   1.  The node will issue an NS message with the GAA Option to request
       an address assignment.  This initial GAA Option has a length
       equal to ROVR's length as a multiple of 8 bytes plus one (no
       address appended), Status/PfxLen set to 0.  Opaque, as well as
       the F-bit and I-bits will be set according to local
       configuration.  The C-bit is set to zero.  The P-bits are set
       according to the type of address it is requesting.  The AAF is
       set to zero if the node has no preference for the assignment
       algorithm, otherwise it is set to the selected AAF code.  The
       lifetime field is set to the minimum desired lifetime, or zero
       otherwise.

   2.  Assuming no errors occur, the node will receive an NA message
       with a GAA Option with a length increased by two, compared to the
       corresponding NS message, because of the presence of the address/
       prefix field.  All fields have been copied back except for:

       *  Pfxlen: now indicating the length of the prefix.

       *  C: The C bit is set if the 6LR requests a confirmation via a
          registration procedure.

       *  AAF: It is the algorithm, used to assign the address/prefix.
          If the node is a 6LR it will use the same AAF to generate
          addresses/prefixes to requesting neighbor nodes.

       *  Assignment lifetime: The maximum lifetime of the assigned
          address/prefix.

   The message sequence is depicted in Figure 3.

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    6LN                     6LR
     |                       |
     |  NS(GAAO)             |
     |---------------------->|
     |                       |
     |  NA(GAAO)             |
     |<----------------------|
     |                       |

   Figure 3: Address/Prefix assignment with GAAO message sequence and no
                           confirmation request.

7.2.  Optional Confirmation Phase

   Depending on the algorithm in use and the underlying technology the
   address assignment procedure terminates after these two messages.
   This may be sufficient for instance in deployments where the link
   layer offers reliable packet delivery.  The use of this option is
   done by configuration.  Documents defining Address Allocation
   Function MUST explicitly state whether this phase remains optional or
   is mandatory due to factors specific to the proposed algorithm.

   If the C bit is set, to confirm the acceptance and usage of the
   proposed address/prefix received in the NA message, the 6LN MUST
   register with the obtained address by following the procedures in
   [RFC8505], [I-D.ietf-6lo-multicast-registration], or
   [I-D.ietf-6lo-prefix-registration] depending on the type of address.

   In this case, the complete sequence of actions is depicted in
   Figure 4.

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    6LN                     6LR
     |                       |
     |  NS(GAAO)             |
     |---------------------->|
     |                       |
     |  NA(GAAO)             |
     |<----------------------|
     |                       |
     |  NS(EARO+TLLAO)       |
     |---------------------->|
     |                       |
         ...
   Procedure According to [RFC8505],
   [I-D.ietf-6lo-multicast-registration], or
   [I-D.ietf-6lo-prefix-registration]
   depending on the type of address.
         ...
     |                       |
     |  NA(EARO+TLLAO)       |
     |<----------------------|

      Figure 4: Address/Prefix assignment with GAAO message sequence.

   The specifications in [RFC8505],
   [I-D.ietf-6lo-multicast-registration], and
   [I-D.ietf-6lo-prefix-registration], define how nodes can keep
   address/prefix registering state so to maintain addressing in case of
   reboot.  When needed, in order to use this feature with GAAO, after
   reboot the optional confirmation phase MUST be used to perform an
   explicit registration.  However, when using GAAO, and when preforming
   the re-registering, if a "Registration Refresh Request" or "Invalid
   Registration" status value is returned, the node MUST restart from
   the top with the initial request phase.

7.3.  Message exchange optimization

   The request of a prefix/address uses a NS/NA transaction likewise
   prefix/address registration.  In order to reduce the number fo
   transactions the GAA Option MAY be used at the same time like the
   EARO+SLLAO options.  In other words the GAA Option can be picky-
   bagged on other transactions.  For instance, it can be picky-bagged
   in an link-layer address registration, as shown in Figure 5.  In this
   case the returning NA will contain two addresses, one in the TLLA
   Option, namely the registered link-layer-address, and one directly
   appended in the GAA Option, namely the offered prefix/address.

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    6LN                    6LR
     |                       |
     |  NS(EARO+TLLAO+GAAO)  |
     |---------------------->|
     |                       |
     |  NA(EARO+TLLAO+GAAO)  |
     |<----------------------|
     |                       |

      Figure 5: Message sequence when GAA Option is picky-bagged on a
                    link-layer registration transaction.

   When prefix/address request is performed at boot time, the GAAO
   request MAY be appended as an option of the first RS message,
   implicitly signaling that the node sending the RS message supports
   the specifications in the present document.  In the same way, the
   responding routers that support this document send back a prefix/
   address offer in a GAA Option appended to the returning RA message,
   as depicted in Figure 6.

    6LN                    6LR
     |                       |
     |  RS(SLLAO+GAAO)       |
     |---------------------->|
     |                       |
     |  RA(SLLAO+GAAO)       |
     |<----------------------|
     |                       |

     Figure 6: Message sequence when GAA Option is used with the RS/RA
                                transaction.

   6LRs that do not support GAAO will simply ignore the option, and the
   corresponding RA, which will not include the GAA Option, implicitly
   signaling that the feature is not supported.

8.  GAAO Error Conditions

   The GAA Option uses error codes defined in [RFC6775] and [RFC8505],
   and revised in [RFC9010].  This specification introduces a new status
   code when the AAF in the GAA Option in an NS message is not supported
   by 6LR, as follows (see also Section 10):

   AAF Not Supported:  The AAF in the GAA Option in the NS message is
      not supported by 6LR that received the message.

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   This status MUST be used when a node requesting an address/prefix did
   put an AAF value, in the corresponding field, which is not supported
   by the 6LR receiving the request.  When the node receives this status
   back it can perform one of the following actions:

   *  Re-issue the same request without specifying an AAF.  Meaning set
      the AAF Field to 0.

   *  Re-issue the same request with a different AAF.

   *  Do nothing.

   The action to be used is selected by configuration.

9.  Signaling GAAO Support

   This specification defines five new capability bits for use in the
   6CIO as defined by [RFC7400] ("6LoWPAN-GHC: Generic Header
   Compression for IPv6 over Low-Power Wireless Personal Area Networks
   (6LoWPANs)"), for use in IPv6 ND messages.  A 6LowPAN node that
   supports this specification MUST set the M flag.

    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|F|X|A|D|L|B|P|E|G|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Reserved                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 7: New GAAO Capability Bit in the 6CIO.

   M:  The node supports managed addresses via the Generic Address
      Assignment Capability.

10.  IANA Considerations

   This section provides guidance to the Internet Assigned Numbers
   Authority (IANA) regarding registration of values related to the GAAO
   specification, in accordance with BCP 26 [RFC8126].

10.1.  IPv6 ND Option Types

   IANA is requested to make an addition to the "IPv6 Neighbor Discovery
   Option Formats" registry under the heading "Internet Control Message
   Protocol version 6 (ICMPv6) Parameters" as indicated in Table 1:

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    +================+===================================+===========+
    | Type           | Description                       | Reference |
    +================+===================================+===========+
    | 42 (Suggested) | Generic Address Assignment Option | [This     |
    |                |                                   | Document] |
    +----------------+-----------------------------------+-----------+

             Table 1: New Generic Address Assignment Option.

10.2.  6LoWPAN Capability Bits

   IANA is requested to make an addition to the "6LoWPAN Capability
   Bits" registry under the registry group "Internet Control Message
   Protocol version 6 (ICMPv6) Parameters" as indicated in Table 2:

        +================+============================+===========+
        | Bit            | Description                | Reference |
        +================+============================+===========+
        | 16 (Suggested) | Generic Address Assignment | [This     |
        |                | Capability (M) Flag        | Document] |
        +----------------+----------------------------+-----------+

                    Table 2: New 6LoWPAN Capability Bit.

10.3.  GAAO Error code

   IANA is requested to make an addition to the "Address Registration
   Option Status Values" registry under the registry group "Internet
   Control Message Protocol version 6 (ICMPv6) Parameters" as indicated
   in Table 3:

         +================+===================+=================+
         | Value          | Description       | Reference       |
         +================+===================+=================+
         | 13 (Suggested) | AAF Not Supported | [This Document] |
         +----------------+-------------------+-----------------+

             Table 3: New address registration option value.

10.4.  Address Assignment Function Registry

   IANA is asked to create a registry group named "Generic Address
   Assignment Option".

   Such registry group should be populated with a one-octet registry
   named "Address Assignment Function" and used to identify the used AAF
   used.  The registry is populated as shown in Table 4:

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         +=========+================================+===========+
         | Value   | AAF Name                       | Reference |
         +=========+================================+===========+
         | 0x0     | No AAF.  This can be used only | [This     |
         |         | in NS message to indicate that | Document] |
         |         | no specific AAF is demanded.   |           |
         +---------+--------------------------------+-----------+
         | 0x1-0xE | Un-assigned                    |           |
         +---------+--------------------------------+-----------+
         | 0xF     | Experimental Use. Used for     | [This     |
         |         | experimental purposes during   | Document] |
         |         | implementation of new AAFs.    |           |
         +---------+--------------------------------+-----------+

                Table 4: Allocation Function sub-registry

   Values can be assigned by IANA on a "First Come, First Served" basis
   according to [RFC8126].

11.  Security Considerations

   This document extends [RFC8505], which already extended [RFC6775], as
   such the security considerations of both documents apply to this
   specification.  In particular, the link layer SHOULD provide
   sufficient protection to prevent potential attacks.  Recommendations
   listed in Section 7 of [RFC8505] SHOULD be applied as well to this
   specification.

   Depending on the Assignment Function in use, the number of available
   addresses may encounter limitations.  A rouge node may leverage on
   this knowledge to carry out address exhaustion attacks by
   impersonating different nodes and performing multiple requests.

Acknowledgements

   This document received many comments and help from community people.
   The authors would like to thank all of them.

References

Normative References

   [I-D.ietf-6lo-multicast-registration]
              Thubert, P., "IPv6 Neighbor Discovery Multicast and
              Anycast Address Listener Subscription", Work in Progress,
              Internet-Draft, draft-ietf-6lo-multicast-registration-19,
              16 May 2024, <https://datatracker.ietf.org/doc/html/draft-
              ietf-6lo-multicast-registration-19>.

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   [I-D.ietf-6lo-prefix-registration]
              Thubert, P., "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>.

   [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/rfc/rfc2119>.

   [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/rfc/rfc4862>.

   [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/rfc/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/rfc/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/rfc/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/rfc/rfc8174>.

   [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/rfc/rfc8505>.

   [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/rfc/rfc9010>.

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Informative References

   [BLESS22]  Bless, R., Zitterbart, M., Despotovic, Z., and A. Hecker,
              "KIRA: Distributed Scalable ID-based Routing with Fast
              Forwarding", 2022 IFIP Networking Conference (IFIP
              Networking) pp. 1-9,
              DOI 10.23919/ifipnetworking55013.2022.9829816, June 2022,
              <https://doi.org/10.23919/
              ifipnetworking55013.2022.9829816>.

   [ERIKSSON04]
              Eriksson, J., Faloutsos, M., and S. Krishnamurthy,
              "Scalable ad hoc routing: the case for dynamic
              addressing", IEEE INFOCOM 2004 vol. 2, pp. 1108-1119,
              DOI 10.1109/infcom.2004.1356997, February 2005,
              <https://doi.org/10.1109/infcom.2004.1356997>.

   [I-D.ietf-6lo-path-aware-semantic-addressing]
              Iannone, L., Li, G., Lou, Z., Liu, P., Long, R.,
              Makhijani, K., and P. Thubert, "Path-Aware Semantic
              Addressing (PASA) for Low power and Lossy Networks", Work
              in Progress, Internet-Draft, draft-ietf-6lo-path-aware-
              semantic-addressing-08, 18 September 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-6lo-
              path-aware-semantic-addressing-08>.

   [RFC8415]  Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
              Richardson, M., Jiang, S., Lemon, T., and T. Winters,
              "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
              RFC 8415, DOI 10.17487/RFC8415, November 2018,
              <https://www.rfc-editor.org/rfc/rfc8415>.

   [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/rfc/rfc8929>.

   [RFC9453]  Hong, Y., Gomez, C., Choi, Y., Sangi, A., and S.
              Chakrabarti, "Applicability and Use Cases for IPv6 over
              Networks of Resource-constrained Nodes (6lo)", RFC 9453,
              DOI 10.17487/RFC9453, September 2023,
              <https://www.rfc-editor.org/rfc/rfc9453>.

   [RIDOUX05] Ridoux, J., Fladenmuller, A., Viniotis, Y., and K.
              Salamatian, "Trellis-Based Virtual Regular Addressing
              Structures in Self-organized Networks", Lecture Notes in
              Computer Science pp. 511-522, DOI 10.1007/11422778_41,
              2005, <https://doi.org/10.1007/11422778_41>.

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   [SHENOY21] Shenoy, N., Chandraiah, S., and P. Willis, "A Structured
              Approach to Routing in the Internet", 2021 IEEE 22nd
              International Conference on High Performance Switching and
              Routing (HPSR) pp. 1-6,
              DOI 10.1109/hpsr52026.2021.9481818, June 2021,
              <https://doi.org/10.1109/hpsr52026.2021.9481818>.

Authors' Addresses

   Luigi Iannone
   Huawei Technologies France S.A.S.U.
   18, Quai du Point du Jour
   92100 Boulogne-Billancourt
   France
   Email: luigi.iannone@huawei.com

   David Lou
   Huawei Technologies Duesseldorf GmbH
   Riesstrasse 25
   80992 Munich
   Germany
   Email: zhe.lou@huawei.com

   Adnan Rashid
   Politecnico di Bari
   Via Edoardo Orabona 4
   70126 Bari
   Italy
   Email: adnan.rashid@poliba.it

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