



Internet Engineering Task Force (IETF)                  B. Haberman, Ed.
Request for Comments: 9778                                       JHU APL
BCP: 57                                                       March 2025
Obsoletes: 3228                                                         
Category: Best Current Practice                                         
ISSN: 2070-1721


      IANA Considerations for Internet Group Management Protocols

Abstract

   This document specifies revised IANA considerations for the Internet
   Group Management Protocol (IGMP) and the Multicast Listener Discovery
   (MLD) protocol.  This document specifies the guidance provided to
   IANA to manage values associated with various fields within the
   protocol headers of the group management protocols.

   This document obsoletes RFC 3228 and unifies guidelines for IPv4 and
   IPv6 group management protocols.

Status of This Memo

   This memo documents an Internet Best Current Practice.

   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
   BCPs 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/rfc9778.

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Table of Contents

   1.  Introduction
     1.1.  Conventions Used in This Document
   2.  IANA Considerations
     2.1.  Type and Code Fields
       2.1.1.  Internet Group Management Protocol
       2.1.2.  Multicast Listener Discovery
     2.2.  IGMP/MLD Query Message Flags
     2.3.  IGMP/MLD Report Message Flags
   3.  Security Considerations
   4.  References
     4.1.  Normative References
     4.2.  Informative References
   Contributors
   Author's Address

1.  Introduction

   The sections that follow describe the allocation guidelines
   associated with the specified fields within the Internet Group
   Management Protocol (IGMP) [STD100] and the Multicast Listener
   Discovery (MLD) [STD101] headers.  Some of these registries were
   created previously, while others are created by this document.

   This document obsoletes [RFC3228] and unifies guidelines for IPv4 and
   IPv6 group management protocols.

1.1.  Conventions Used in This Document

   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.  IANA Considerations

   The registration procedures used in this document are defined in
   [RFC8126].

2.1.  Type and Code Fields

2.1.1.  Internet Group Management Protocol

   The IGMP header contains the following fields that carry values
   assigned from IANA-managed name spaces: Type and Code.  Code field
   values are defined relative to a specific Type value.

   [RFC3228] created the "IGMP Type Numbers" registry for the IGMP Type
   field.  This document updates that registry in two ways:

   *  The registration procedure has been changed to Standards Action.

   *  The references to [RFC3228], including the reference for the
      registry, have been changed to this document.

   [RFC3228] created the '"Code" Fields' registry for Code values for
   existing IGMP Type fields.  This document updates that registry in
   two ways:

   *  The registration procedure has been changed to Standards Action.

   *  The reference for the registry has been changed to this document.

   Note that the policy for assigning Code values for new IGMP Types
   MUST be defined in the document defining the new Type value.

2.1.2.  Multicast Listener Discovery

   As with IGMP, the MLD header also contains Type and Code fields.
   Assignment of those fields within the MLD header is defined in
   [RFC4443] with a registration policy of IETF Review; see
   <https://www.iana.org/assignments/icmpv6-parameters>.

2.2.  IGMP/MLD Query Message Flags

   IANA has created the "IGMP/MLD Query Message Flags" registry for the
   bits in the Flags field of the MLDv2 Query Message [STD101] and the
   IGMPv3 Query Message [STD100].  It has been populated as follows:

   +===========+============+=============+===========+
   | Flags Bit | Short Name | Description | Reference |
   +===========+============+=============+===========+
   | 0         | E          | Extension   | [RFC9279] |
   +-----------+------------+-------------+-----------+
   | 1-3       | Unassigned                           |
   +-----------+--------------------------------------+

      Table 1: IGMP/MLD Query Message Flags Registry

   The Flags Bit value in the registry above corresponds to the column
   header in the packet format diagrams in Sections 4.1 and 4.2 of
   [STD100] and Sections 5.1 and 5.2 of [STD101].

   The assignment of new bit flags within the Flags field requires
   Standards Action.

2.3.  IGMP/MLD Report Message Flags

   IANA has created the "IGMP/MLD Report Message Flags" registry for the
   bits in the Flags field of the MLDv2 Report Message and the IGMPv3
   Report Message.  It has been populated as follows:

   +===========+============+=============+===========+
   | Flags Bit | Short Name | Description | Reference |
   +===========+============+=============+===========+
   | 0         | E          | Extension   | [RFC9279] |
   +-----------+------------+-------------+-----------+
   | 1-15      | Unassigned                           |
   +-----------+--------------------------------------+

     Table 2: IGMP/MLD Report Message Flags Registry

   The Flags Bit value in the registry above corresponds to the column
   header in the packet format diagrams in [STD101] and [STD100].

   The assignment of new bit flags within the Flags field requires
   Standards Action.

3.  Security Considerations

   Security analyzers such as firewalls and network intrusion detection
   monitors often rely on unambiguous interpretations of the fields
   described in this memo.  As new values for the fields are assigned,
   existing security analyzers that do not understand the new values may
   fail, resulting in either loss of connectivity if the analyzer
   declines to forward the unrecognized traffic or loss of security if
   it does forward the traffic and the new values are used as part of an
   attack.  This vulnerability argues for high visibility (which the
   Standards Action process ensures) for the assignments whenever
   possible.

4.  References

4.1.  Normative References

   [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>.

   [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>.

   [STD100]   Internet Standard 100,
              <https://www.rfc-editor.org/info/std100>.
              At the time of writing, this STD comprises the following:

              Haberman, B., Ed., "Internet Group Management Protocol,
              Version 3", STD 100, RFC 9776, DOI 10.17487/RFC9776, March
              2025, <https://www.rfc-editor.org/info/rfc9776>.

   [STD101]   Internet Standard 101,
              <https://www.rfc-editor.org/info/std101>.
              At the time of writing, this STD comprises the following:

              Haberman, B., Ed., "Multicast Listener Discovery Version 2
              (MLDv2) for IPv6", STD 101, RFC 9777,
              DOI 10.17487/RFC9777, March 2025,
              <https://www.rfc-editor.org/info/rfc9777>.

4.2.  Informative References

   [RFC3228]  Fenner, B., "IANA Considerations for IPv4 Internet Group
              Management Protocol (IGMP)", BCP 57, RFC 3228,
              DOI 10.17487/RFC3228, February 2002,
              <https://www.rfc-editor.org/info/rfc3228>.

   [RFC4443]  Conta, A., Deering, S., and M. Gupta, Ed., "Internet
              Control Message Protocol (ICMPv6) for the Internet
              Protocol Version 6 (IPv6) Specification", STD 89,
              RFC 4443, DOI 10.17487/RFC4443, March 2006,
              <https://www.rfc-editor.org/info/rfc4443>.

   [RFC9279]  Sivakumar, M., Venaas, S., Zhang, Z., and H. Asaeda,
              "Internet Group Management Protocol Version 3 (IGMPv3) and
              Multicast Listener Discovery Version 2 (MLDv2) Message
              Extension", RFC 9279, DOI 10.17487/RFC9279, August 2022,
              <https://www.rfc-editor.org/info/rfc9279>.

Contributors

   Bill Fenner is the author of [RFC3228], which provided a portion of
   the content contained herein.

Author's Address

   Brian Haberman (editor)
   Johns Hopkins University Applied Physics Lab
   Email: brian@innovationslab.net
