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.
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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
