IANA Considerations for Internet Group Management Protocols
RFC 9778 also known as BCP 57


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.
Copyright Notice
 Copyright (c) 2025 IETF Trust and the persons identified as the
 document authors. All rights reserved.
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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