RFC 9778

IANA Considerations for Internet Group Management Protocols

📅 published March 2025, from ietf

RFC 9778: IANA Considerations for Internet Group Management Protocols ✨

Request for Comments: 9778 💖
Title: IANA Considerations for Internet Group Management Protocols 🦋
Author: B. Haberman, Ed. (JHU APL) 🎀
Category: Best Current Practice 👑
BCP: 57
Date: March 2025 🌸
Obsoletes: 3228
Stream: Internet Engineering Task Force (IETF)
ISSN: 2070-1721

Abstract 🫶

okay so this doc gives revised IANA considerations for IGMP (the Internet Group Management Protocol) and MLD (Multicast Listener Discovery). it's basically the instructions IANA follows when it manages the values for the different fields in those protocol headers. 💅

it obsoletes RFC 3228 and unifies the guidelines for IPv4 and IPv6 group management protocols. iconic unification energy 🔥

Status of This Memo 📜

this memo documents an Internet Best Current Practice ✨

this is an IETF product and it reflects the consensus of the IETF community. it went through public review and got approved for publication by the Internet Engineering Steering Group (IESG). if you want more on BCPs, check out Section 2 of RFC 7841.

info about the current status of this doc, any errata, and how to send feedback lives at https://www.rfc-editor.org/info/rfc9778 💜

Copyright Notice 🌈

this doc is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) as they stand on the publication date. please actually read those, bestie, because they spell out your rights and restrictions for this doc. 🙈 code components pulled out of this doc must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions, and they come without warranty, as the Revised BSD License describes.

some of this doc may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. the people controlling the copyright in some of that older material may not have granted the IETF Trust the right to allow modifications outside the IETF Standards Process. so unless you get an adequate license from those copyright holders, this doc may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process. the only exceptions are formatting it for publication as an RFC or translating it into languages other than English. 🫶

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 🧚

okay so the sections coming up explain the allocation guidelines for the specified fields in the IGMP [STD100] and MLD [STD101] headers. some of these registries were already around, and this doc creates the others. 🍓

this doc obsoletes [RFC3228] and unifies the guidelines for IPv4 and IPv6 group management protocols. the vibe is consistent across both now ✨

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 doc are defined in [RFC8126] 🔥

2.1. Type and Code Fields 🎀

2.1.1. Internet Group Management Protocol 🦋

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

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

the registration procedure has changed to Standards Action.
the references to [RFC3228], including the reference for the registry, have changed to this doc.

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

the registration procedure has changed to Standards Action.
the reference for the registry has changed to this doc.

quick note: the policy for assigning Code values for new IGMP Types MUST be defined in the document that defines the new Type value. 🫶

2.1.2. Multicast Listener Discovery 🌈

same deal as IGMP, the MLD header also has Type and Code fields. assignment of those fields in the MLD header is defined in [RFC4443], with a registration policy of IETF Review. check https://www.iana.org/assignments/icmpv6-parameters for the details ✨

2.2. IGMP/MLD Query Message Flags 🧚

IANA 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's populated like this:

+===========+============+=============+===========+
| 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 lines up with 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]. 🍓

assigning new bit flags within the Flags field requires Standards Action. 🔥

2.3. IGMP/MLD Report Message Flags 💖

IANA 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's populated like this:

+===========+============+=============+===========+
| 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 this registry lines up with the column header in the packet format diagrams in [STD101] and [STD100] 🦋

again, assigning new bit flags within the Flags field requires Standards Action. ✨

3. Security Considerations 🚨

okay, serious moment, bestie 😭 security analyzers like firewalls and network intrusion detection monitors often rely on unambiguous interpretations of the fields described in this memo. when new values get assigned, existing analyzers that don't understand them may fail. that can mean losing connectivity if the analyzer refuses to forward the unrecognized traffic, or losing security if it forwards the traffic and the new values get used in an attack. 💀

this is why high visibility matters so much. the Standards Action process gives the assignments that visibility whenever possible, so please keep that in mind 🔥

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 🦋

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ietf: rfc9778 2025-03
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