RFC 9279
Internet Group Management Protocol Version 3 (IGMPv3) and Multicast Listener Discovery Version 2 (MLDv2) Message Extension
Pages: ~12
IETF/rtg/pim/draft-ietf-pim-igmp-mld-extension-08
Proposed Standard
M. Sivakumar
Juniper Networks
S. Venaas
Cisco Systems, Inc.
Z. Zhang
ZTE Corporation
H. Asaeda
National Institute of Information and Communications Technology
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.
1. Introduction
This document defines a generic method to extend IGMPv3 [RFC 3376] and MLDv2 [RFC 3810] 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 [RFC 5790].
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 RFC 3376) and MLDv2 (Section 5.1.12 of RFC 3810), and for Report messages in IGMPv3 (Section 4.2.11 of RFC 3376) and MLDv2 (Section 5.2.11 of RFC 3810).
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 | . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- 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.
3.1. Multicast Listener Query Extension
The MLDv2 Query message format [RFC 3810] 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 |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.2. Version 2 Multicast Listener Report Extension
The MLDv2 Report message format [RFC 3810] 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 |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.3. IGMP Membership Query Extension
The IGMPv3 Query message format [RFC 3376] 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 |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.4. IGMP Version 3 Membership Report Extension
The IGMPv3 Report message format [RFC 3376] 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 |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 |
. . .
. . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- 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 [RFC 3376] and MLDv2 [RFC 3810]. 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.
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 [RFC 3376] and [RFC 3810]. 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 [RFC 3376] and [RFC 3810] 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" [RFC 8126]. The registry is common for IGMP and MLD.
Two Extension Types (65534 and 65535) are provided for "Experimental Use" [RFC 8126]. Any experiments should be confined to closed environments where it is unlikely that they may conflict with other experiments; see [RFC 3692].
IANA has initially populated the registry as shown in Table 1
Table 1: IGMP/MLD Extension Types
| Extension Type | Length | Name | Reference |
|---|---|---|---|
| 0 | variable | No-op | RFC 9279 |
| 1-65533 | Unassigned | ||
| 65534-65535 | variable | Reserved for Experimental Use |
9. References
9.1. Normative References
- [RFC2119]
-
S. Bradner, "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]
-
B. Cain, S. Deering, I. Kouvelas, B. Fenner, 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]
-
R. Vida, and L. Costa, "Multicast Listener Discovery Version 2 (MLDv2) for IPv6", RFC 3810, DOI 10.17487/RFC3810, June 2004,
<https://www.rfc-editor.org/info/ >.rfc3810 - [RFC8126]
-
M. Cotton, B. Leiba, 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]
-
B. Leiba, "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]
-
T. Narten, "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]
-
H. Liu, W. Cao, 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
