Internet Engineering Task Force (IETF)                  B. Haberman, Ed.Request for Comments: 9778                                       JHU APLBCP: 57                                                       March 2025Obsoletes: 3228                                                         Category: Best Current Practice                                         ISSN: 2070-1721      IANA Considerations for Internet Group Management ProtocolsAbstract   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.   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.   This document may contain material from IETF Documents or IETF   Contributions published or made publicly available before November   10, 2008.  The person(s) controlling the copyright in some of this   material may not have granted the IETF Trust the right to allow   modifications of such material outside the IETF Standards Process.   Without obtaining an adequate license from the person(s) controlling   the copyright in such materials, this document may not be modified   outside the IETF Standards Process, and derivative works of it may   not be created outside the IETF Standards Process, except to format   it for publication as an RFC or to translate 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 Address1.  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 Fields2.1.1.  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.  References4.1.  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