



Internet Engineering Task Force (IETF)                      M. Sivakumar
Request for Comments: 9279                              Juniper Networks
Category: Standards Track                                      S. Venaas
ISSN: 2070-1721                                      Cisco Systems, Inc.
                                                                Z. Zhang
                                                         ZTE Corporation
                                                               H. Asaeda
                                                                    NICT
                                                             August 2022


  Internet Group Management Protocol Version 3 (IGMPv3) and Multicast
         Listener Discovery Version 2 (MLDv2) Message Extension

Abstract

   This document specifies a generic mechanism to extend IGMPv3 and
   Multicast Listener Discovery Version 2 (MLDv2) by using a list of
   TLVs (Type, Length, and Value).

Status of This Memo

   This is an Internet Standards Track document.

   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
   Internet Standards 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/rfc9279.

Copyright Notice

   Copyright (c) 2022 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.

Table of Contents

   1.  Introduction
   2.  Conventions Used in This Document
   3.  Extension Format
     3.1.  Multicast Listener Query Extension
     3.2.  Version 2 Multicast Listener Report Extension
     3.3.  IGMP Membership Query Extension
     3.4.  IGMP Version 3 Membership Report Extension
   4.  No-op TLV
   5.  Processing the Extension
   6.  Applicability and Backwards Compatibility
   7.  Security Considerations
   8.  IANA Considerations
   9.  References
     9.1.  Normative References
     9.2.  Informative References
   Acknowledgements
   Authors' Addresses

1.  Introduction

   This document defines a generic method to extend IGMPv3 [RFC3376] and
   MLDv2 [RFC3810] messages to accommodate information other than what
   is contained in the current message formats.  This is done by
   allowing a list of TLVs to be used in the Additional Data section of
   IGMPv3 and MLDv2 messages.  This document defines a registry for such
   TLVs.  Other documents will define their specific types, and their
   values and semantics.  The extension would only be used when at least
   one TLV is to be added to the message.  This extension also applies
   to the lightweight versions of IGMPv3 and MLDv2 as defined in
   [RFC5790].

   When this extension mechanism is used, it replaces the Additional
   Data section defined in IGMPv3/MLDv2 with TLVs.

   Additional Data is defined for Query messages in IGMPv3
   (Section 4.1.10 of [RFC3376]) and MLDv2 (Section 5.1.12 of
   [RFC3810]), and for Report messages in IGMPv3 (Section 4.2.11 of
   [RFC3376]) and MLDv2 (Section 5.2.11 of [RFC3810]).

2.  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.

3.  Extension Format

   For each of the IGMPv3 and MLDv2 headers, a previously reserved bit
   is used to indicate the presence of this extension.  When this
   extension is used, the Additional Data of IGMPv3 and MLDv2 messages
   is formatted as follows.  Note that this format contains a variable
   number of TLVs.  It MUST contain at least one TLV.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Extension Type 1       |       Extension Length 1      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Extension Value 1                       |
   .                               .                               .
   .                               .                               .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Extension Type 2       |       Extension Length 2      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Extension Value 2                       |
   .                               .                               .
   .                               .                               .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Extension Type n       |       Extension Length n      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Extension Value n                       |
   .                               .                               .
   .                               .                               .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                         Figure 1: Extension Format

   Extension Type:  2 octets.  This identifies a particular Extension
      Type as defined in the "IGMP/MLD Extension Types" registry.  If
      this is not the first TLV, it will follow immediately after the
      end of the previous one.  There is no alignment or padding.

   Extension Length:  2 octets.  This specifies the length in octets of
      the following Extension Value field.  The length may be zero if no
      value is needed.

   Extension Value:  This field contains the value.  The specification
      defining the Extension Type describes the length and contents of
      this field.

   IGMPv3 and MLDv2 messages are defined so they can fit within the
   network MTU in order to avoid fragmentation.  An IGMPv3/MLDv2 Report
   message contains a number of records.  The records are called Group
   Records for IGMPv3 and Address Records for MLDv2.  When this
   extension mechanism is used, the number of records in each Report
   message SHOULD be kept small enough so that the entire message,
   including any extension TLVs, can fit within the network MTU.

3.1.  Multicast Listener Query Extension

   The MLDv2 Query message format [RFC3810] with extension is shown
   below.  The E-bit MUST be set to 1 to indicate that the extension is
   present.  Otherwise, it MUST be 0.


        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Type = 130   |      Code     |           Checksum            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Maximum Response Code      |           Reserved            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       *                                                               *
       |                                                               |
       *                       Multicast Address                       *
       |                                                               |
       *                                                               *
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |E| Resv|S| QRV |     QQIC      |     Number of Sources (N)     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       *                                                               *
       |                                                               |
       *                       Source Address [1]                      *
       |                                                               |
       *                                                               *
       |                                                               |
       +-                                                             -+
       |                                                               |
       *                                                               *
       |                                                               |
       *                       Source Address [2]                      *
       |                                                               |
       *                                                               *
       |                                                               |
       +-                              .                              -+
       .                               .                               .
       .                               .                               .
       +-                                                             -+
       |                                                               |
       *                                                               *
       |                                                               |
       *                       Source Address [N]                      *
       |                                                               |
       *                                                               *
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                            Extension                          |
       ~                                                               ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 2: MLD Query Extension

3.2.  Version 2 Multicast Listener Report Extension

   The MLDv2 Report message format [RFC3810] with extension is shown
   below.  The E-bit MUST be set to 1 to indicate that the extension is
   present.  Otherwise, it MUST be 0.

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Type = 143   |    Reserved   |           Checksum            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |E|         Reserved            |Nr of Mcast Address Records (M)|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       .                                                               .
       .                  Multicast Address Record [1]                 .
       .                                                               .
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       .                                                               .
       .                  Multicast Address Record [2]                 .
       .                                                               .
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                               .                               |
       .                               .                               .
       |                               .                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       .                                                               .
       .                  Multicast Address Record [M]                 .
       .                                                               .
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                            Extension                          |
       ~                                                               ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 3: MLD Report Extension

3.3.  IGMP Membership Query Extension

   The IGMPv3 Query message format [RFC3376] with the extension is shown
   below.  The E-bit MUST be set to 1 to indicate that the extension is
   present.  Otherwise, it MUST be 0.


        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Type = 0x11  | Max Resp Code |           Checksum            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Group Address                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |E| Resv|S| QRV |     QQIC      |     Number of Sources (N)     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       Source Address [1]                      |
       +-                                                             -+
       |                       Source Address [2]                      |
       +-                              .                              -+
       .                               .                               .
       .                               .                               .
       +-                                                             -+
       |                       Source Address [N]                      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                            Extension                          |
       ~                                                               ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 4: IGMP Query Extension

3.4.  IGMP Version 3 Membership Report Extension

   The IGMPv3 Report message format [RFC3376] with the extension is
   shown below.  The E-bit MUST be set to 1 to indicate that the
   extension is present.  Otherwise, it MUST be 0.

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Type = 0x22  |    Reserved   |           Checksum            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |E|         Reserved            |  Number of Group Records (M)  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       .                                                               .
       .                        Group Record [1]                       .
       .                                                               .
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       .                                                               .
       .                        Group Record [2]                       .
       .                                                               .
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                               .                               |
       .                               .                               .
       |                               .                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       .                                                               .
       .                        Group Record [M]                       .
       .                                                               .
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                            Extension                          |
       ~                                                               ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 5: IGMP Report Extension

4.  No-op TLV

   The No-op TLV is a No-Operation TLV that MUST be ignored during
   processing.  This TLV may be used to verify that the extension
   mechanism has been implemented correctly.  Note that there is no
   alignment requirement, so there is no need to use this Extension Type
   to provide alignment.

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |        No-op Type = 0         |          No-op Length         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                             Value                             |
       .                               .                               .
       .                               .                               .
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                         Figure 6: No-op TLV Format

   No-op Type:  2 octets.  The type of the No-op TLV extension is 0.

   Extension Length:  2 octets.  This specifies the length in octets of
      the following Value field.  The length may be zero if no value is
      needed.

   Value:  This field contains the value.  As this Extension Type is
      always ignored, the value can be arbitrary data.  The number of
      octets used MUST match the specified length.

5.  Processing the Extension

   The procedure specified in this document only applies when the E-bit
   is set.

   If the validation of the TLVs fails, the entire Additional Data field
   MUST be ignored as specified in IGMPv3 [RFC3376] and MLDv2 [RFC3810].
   The following checks must pass for the validation of the TLVs not to
   fail:

   *  At least one TLV MUST be present.

   *  There MUST NOT be any data in the IP payload after the last TLV.
      To check this, the parser needs to walk through each of the TLVs
      until there are less than four octets left in the IP payload.  If
      there are any octets left, validation fails.

   *  The total length of the Extension MUST NOT exceed the remainder of
      the IP payload length.  For this validation, only the content of
      the Extension Length fields is examined.

   Future documents defining a new Extension Type MUST specify any
   additional processing and validation.  These rules, if any, will be
   examined only after the general validation succeeds.

   TLVs with unsupported Extension Types MUST be ignored.

6.  Applicability and Backwards Compatibility

   IGMP and MLD implementations, particularly implementations on hosts,
   rarely change.  The adoption process of this extension mechanism is
   expected to be slow.  As new extension TLVs are defined, it may take
   a long time for them to be supported.  Due to this, defining new
   extension TLVs should not be taken lightly, and it is crucial to
   consider backwards compatibility.

   Implementations that do not support this extension mechanism will
   ignore it, as specified in [RFC3376] and [RFC3810].  As mentioned in
   the previous section, unsupported extension TLVs are ignored.

   It is possible that a new extension TLV will only apply to queries or
   only to reports, or that there may be other specific conditions for
   when it is to be used.  A document defining a new Extension Type MUST
   specify the conditions under which the new Extension Type should be
   used, including which message types.  It MUST also be specified what
   the behavior should be if a message is not used in the defined
   manner, e.g., if it is present in a Query message, when it was only
   expected to be used in reports.

   When defining new Extension Types, the effect of partial support for
   the new TLV, by either the hosts or routers, on the same link should
   be carefully considered.  Further, whether there are any dependencies
   or restrictions on combinations between the new Extension Types and
   any preexisting Extension Types must be considered.

   This document defines an extension mechanism only for IGMPv3 and
   MLDv2.  Hence, this mechanism does not apply if hosts or routers send
   older version messages.

7.  Security Considerations

   The Security Considerations of [RFC3376] and [RFC3810] also apply
   here.

   This document extends the IGMP and MLD message formats, allowing for
   a variable number of TLVs.  Implementations must take care not to
   exceed the packet boundary when parsing the TLVs, because an attacker
   could intentionally specify a TLV with a length exceeding the
   boundary.

   An implementation could add a large number of minimal TLVs in a
   message to increase the cost of processing the message.  This would
   magnify a denial-of-service attack.

8.  IANA Considerations

   IANA has created a new registry called "IGMP/MLD Extension Types" in
   the "Internet Group Management Protocol (IGMP) Type Numbers" section
   and lists this document as the reference.  The registration procedure
   is "IETF Review" [RFC8126].  The registry is common for IGMP and MLD.

   Two Extension Types (65534 and 65535) are provided for "Experimental
   Use" [RFC8126].  Any experiments should be confined to closed
   environments where it is unlikely that they may conflict with other
   experiments; see [RFC3692].

   IANA has initially populated the registry as shown in Table 1

       +================+==========+==================+===========+
       | Extension Type | Length   | Name             | Reference |
       +================+==========+==================+===========+
       | 0              | variable | No-op            | RFC 9279  |
       +----------------+----------+------------------+-----------+
       | 1-65533        |          | Unassigned       |           |
       +----------------+----------+------------------+-----------+
       | 65534-65535    | variable | Reserved for     |           |
       |                |          | Experimental Use |           |
       +----------------+----------+------------------+-----------+

                    Table 1: IGMP/MLD Extension Types

9.  References

9.1.  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>.

   [RFC3376]  Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
              Thyagarajan, "Internet Group Management Protocol, Version
              3", RFC 3376, DOI 10.17487/RFC3376, October 2002,
              <https://www.rfc-editor.org/info/rfc3376>.

   [RFC3810]  Vida, R., Ed. and L. Costa, Ed., "Multicast Listener
              Discovery Version 2 (MLDv2) for IPv6", RFC 3810,
              DOI 10.17487/RFC3810, June 2004,
              <https://www.rfc-editor.org/info/rfc3810>.

   [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>.

9.2.  Informative References

   [RFC3692]  Narten, T., "Assigning Experimental and Testing Numbers
              Considered Useful", BCP 82, RFC 3692,
              DOI 10.17487/RFC3692, January 2004,
              <https://www.rfc-editor.org/info/rfc3692>.

   [RFC5790]  Liu, H., Cao, W., and H. Asaeda, "Lightweight Internet
              Group Management Protocol Version 3 (IGMPv3) and Multicast
              Listener Discovery Version 2 (MLDv2) Protocols", RFC 5790,
              DOI 10.17487/RFC5790, February 2010,
              <https://www.rfc-editor.org/info/rfc5790>.

Acknowledgements

   The authors thank Ron Bonica, Ian Duncan, Wesley Eddy, Leonard
   Giuliano, Jake Holland, Tommy Pauly, Pete Resnick, Alvaro Retana, and
   Zhaohui Zhang for reviewing the document and providing valuable
   feedback.

Authors' Addresses

   Mahesh Sivakumar
   Juniper Networks
   64 Butler St
   Milpitas, CA 95035
   United States of America
   Email: sivakumar.mahesh@gmail.com


   Stig Venaas
   Cisco Systems, Inc.
   Tasman Drive
   San Jose, CA 95134
   United States of America
   Email: stig@cisco.com


   Zheng(Sandy) Zhang
   ZTE Corporation
   No. 50 Software Ave, Yuhuatai District
   Nanjing
   210000
   China
   Email: zhang.zheng@zte.com.cn


   Hitoshi Asaeda
   National Institute of Information and Communications Technology
   4-2-1 Nukui-Kitamachi, Koganei, Tokyo
   184-8795
   Japan
   Email: asaeda@nict.go.jp
