Updates to Dynamic IPv6 Multicast Address Group IDs
draft-ietf-pim-updt-ipv6-dyn-mcast-addr-grp-id-07

Network Working Group                                        N. Karstens
Internet-Draft                                                    Garmin
Updates: 3307 (if approved)                                 D. Farinacci
Intended status: Standards Track                             lispers.net
Expires: 26 February 2026                                     M. McBride
                                                               Futurewei
                                                          25 August 2025

          Updates to Dynamic IPv6 Multicast Address Group IDs
           draft-ietf-pim-updt-ipv6-dyn-mcast-addr-grp-id-07

Abstract

   Describes limitations of the existing range of dynamic IPv6 multicast
   addresses specified in RFC3307.  Recommends replacing these
   allocations with a new registry in the IPv6 Multicast Address Space
   Registry registry group.  Suggests initial contents of the new
   registry: a reduced allocation for MADCAP (RFC2730), a Private Use
   range, and Solicited-Node multicast addresses (which were not
   previously noted in RFC3307).

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 26 February 2026.

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   Please review these documents carefully, as they describe your rights

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   and restrictions with respect to this document.  Code Components
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  Updated Dynamic Multicast Group IDs . . . . . . . . . . . . .   3
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   For IPv6 multicast addresses, Section 2 of [RFC3307] defines the
   lower 32 bits of the IPv6 address, which are mapped directly to the
   link-layer, as the group ID, and then assigns ranges of group ID
   values based on how they are allocated.  Section 4.3 describes
   dynamic assignment of group ID values and lists two different
   approaches (server allocation and host allocation).  However, both
   approaches are assigned the same range of group ID values, which
   means they cannot coexist without risking an address collision.  Also
   concerning is that the range for dynamic assignment overlaps with the
   range used for Solicited-Node multicast addresses (see Section 2.7.1
   of [RFC4291]).

   Only one server allocation protocol has been defined so far (see
   [RFC2730]), but [I-D.ietf-pim-zeroconf-mcast-addr-alloc-ps] advocates
   developing a decentralized, zero-configuration host allocation
   protocol.  This document updates the dynamic IPv6 multicast group ID
   ranges to better align with current practices for protocol number
   assignment and to support development of additional dynamic
   allocation protocols.

1.1.  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.

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2.  Updated Dynamic Multicast Group IDs

   Existing group ID allocations specified in [RFC3307], Section 4.3 and
   [RFC4291], Section 2.7.1 are summarized in the following table:

   +-----------------------+----------------+------------+------------+
   |                       |                |            |            |
   |                       |                |            |            |
   | 0x80000000-0xFEFFFFFF |                | Server     | Host       |
   |                       |                | allocation | allocation |
   |                       |                | (MADCAP)   |            |
   +-----------------------+----------------+            |            |
   | 0xFF000000-0xFFFFFFFF | Solicited-Node |            |            |
   +-----------------------+----------------+------------+------------+

                      Table 1: Existing Allocations

   This document updates the allocations in [RFC3307], Section 4.3 and
   moves them into a new registry in the IPv6 Multicast Address Space
   Registry registry group.  The registry shall be populated with the
   following entries:

     +=======================+=====================+=================+
     | Range                 | Description         | Reference       |
     +=======================+=====================+=================+
     | 0x80000000-0x8FFFFFFF | MADCAP              | [RFC2730]       |
     +-----------------------+---------------------+-----------------+
     | 0x90000000-0xFDFFFFFF | Unassigned          |                 |
     +-----------------------+---------------------+-----------------+
     | 0xFE000000-0xFEFFFFFF | Private Use         | [This document] |
     +-----------------------+---------------------+-----------------+
     | 0xFF000000-0xFFFFFFFF | Solicited-Node      | [RFC4291],      |
     |                       | multicast addresses | Section 2.7.1   |
     +-----------------------+---------------------+-----------------+

                        Table 2: Updated Allocations

   This reduces the range previously available for MADCAP, while still
   providing a sizable allocation.  It also allocates a Private Use
   range, which can be used in isolated deployments for purposes such as
   manual address allocation or experimentation with new dynamic
   allocation protocols.  Finally, this documents the range used for
   Solicited-Node multicast addresses.  All remaining entries are
   reserved for future assignment as new protocols are developed.

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3.  Security Considerations

   This document does not expand on any security considerations beyond
   what is discussed in [RFC3307].

4.  IANA Considerations

   IANA should create a new registry named "Dynamic Multicast Group IDs"
   in the "IPv6 Multicast Address Space Registry" registry group.  This
   registry shall initially contain the entries listed in Table 2.  The
   "Standards Action" registration policy is required to update the
   registry.

   IANA should also update the references to
   "FF3X:0:0:0:0:0:8000:0-FF3X:0:0:0:0:0:FFFF:FFFF" in the "Unicast-
   based (Including SSM) Multicast Group IDs" registry in the "IPv6
   Multicast Address Space Registry" registry group.  The registration
   procedure should indicate that this range uses dynamic assignment
   according to the protocols listed in the new "Dynamic Multicast Group
   IDs" registry and include a reference to this document.  The
   description in the registry entry should indicate that this range
   uses dynamic assignment according to the protocols listed in the new
   "Dynamic Multicast Group IDs" registry and the reference should be
   changed to this document.

5.  Acknowledgement

   Special thanks to the National Marine Electronics Association for
   their contributions in developing marine industry standards and their
   support for this research.

   The authors are grateful to the members of the PIM working group for
   their early brainstorming sessions and review of this draft, and to
   the following individuals specifically:

   *  Dave Thaler for discussing MADCAP deployment in Microsoft products
      and the impact of changing the range of group IDs used by MADCAP

   *  Stig Venaas for recognizing the need for a range of addresses that
      can be allocated manually

6.  References

6.1.  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>.

   [RFC3307]  Haberman, B., "Allocation Guidelines for IPv6 Multicast
              Addresses", RFC 3307, DOI 10.17487/RFC3307, August 2002,
              <https://www.rfc-editor.org/info/rfc3307>.

   [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>.

6.2.  Informative References

   [I-D.ietf-pim-zeroconf-mcast-addr-alloc-ps]
              Karstens, N., Farinacci, D., and M. McBride, "Zeroconf
              Multicast Address Allocation Problem Statement and
              Requirements", Work in Progress, Internet-Draft, draft-
              ietf-pim-zeroconf-mcast-addr-alloc-ps-06, 3 July 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-pim-
              zeroconf-mcast-addr-alloc-ps-06>.

   [RFC2730]  Hanna, S., Patel, B., and M. Shah, "Multicast Address
              Dynamic Client Allocation Protocol (MADCAP)", RFC 2730,
              DOI 10.17487/RFC2730, December 1999,
              <https://www.rfc-editor.org/info/rfc2730>.

   [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>.

Authors' Addresses

   Nate Karstens
   Garmin International, Inc.
   1200 E. 151st St.
   Olathe, KS 66062-3426
   United States of America
   Email: nate.karstens@gmail.com

   Dino Farinacci
   lispers.net
   San Jose, CA
   United States of America
   Email: farinacci@gmail.com

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   Mike McBride
   Futurewei
   United States of America
   Email: michael.mcbride@futurewei.com

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