draft-ietf-pim-igmp-mld-extension-02.txt   draft-ietf-pim-igmp-mld-extension-03.txt 
Network Working Group M. Sivakumar Network Working Group M. Sivakumar
Internet-Draft Juniper Networks Internet-Draft Juniper Networks
Updates: 3376, 3810 (if approved) S. Venaas Updates: 3376, 3810 (if approved) S. Venaas
Intended status: Standards Track Cisco Systems, Inc. Intended status: Standards Track Cisco Systems, Inc.
Expires: May 6, 2021 Z. Zhang Expires: July 19, 2021 Z. Zhang
ZTE Corporation ZTE Corporation
H. Asaeda H. Asaeda
NICT NICT
November 2, 2020 January 15, 2021
IGMPv3/MLDv2 Message Extension IGMPv3/MLDv2 Message Extension
draft-ietf-pim-igmp-mld-extension-02 draft-ietf-pim-igmp-mld-extension-03
Abstract Abstract
IGMP and MLD protocols are extensible, but no extensions have been IGMP and MLD protocols are extensible, but no extensions have been
defined so far. This document provides a well-defined way of defined so far. This document provides a well-defined way of
extending IGMP and MLD, using a list of TLVs (Type, Length and extending IGMP and MLD, using a list of TLVs (Type, Length and
Value). Value).
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 6, 2021. This Internet-Draft will expire on July 19, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 2 2. Conventions used in this document . . . . . . . . . . . . . . 3
3. Extension Format . . . . . . . . . . . . . . . . . . . . . . 3 3. Extension Format . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Multicast Listener Query Extension . . . . . . . . . . . 4 3.1. Multicast Listener Query Extension . . . . . . . . . . . 4
3.2. Version 2 Multicast Listener Report Extension . . . . . . 5 3.2. Version 2 Multicast Listener Report Extension . . . . . . 5
3.3. IGMP Membership Query Extension . . . . . . . . . . . . . 6 3.3. IGMP Membership Query Extension . . . . . . . . . . . . . 6
3.4. IGMP Version 3 Membership Report Extension . . . . . . . 7 3.4. IGMP Version 3 Membership Report Extension . . . . . . . 7
4. Applicability and backwards compatibility . . . . . . . . . . 8 4. Applicability and backwards compatibility . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Normative References . . . . . . . . . . . . . . . . . . 10 7.1. Normative References . . . . . . . . . . . . . . . . . . 10
7.2. Informative References . . . . . . . . . . . . . . . . . 10 7.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction 1. Introduction
In this document, we describe a generic method to extend IGMPv3 In this document, we describe a generic method to extend IGMPv3
[RFC3376] and MLDv2 [RFC3810] messages to accommodate information [RFC3376] and MLDv2 [RFC3810] messages to accommodate information
other than what is contained in the current message formats. This is other than what is contained in the current message formats. This is
done by allowing a list of TLVs (Type, Length and Value) to be used done by allowing a list of TLVs (Type, Length and Value) to be used
in the Additional Data part of IGMPv3 and MLDv2 messages. This in the Additional Data part of IGMPv3 and MLDv2 messages. This
document defines a registry for such TLVs, while other documents will document defines a registry for such TLVs, while other documents will
define the specific types and their values, and their semantics. The define the specific types and their values, and their semantics. The
extension would only be used when at least one TLV is to be added to 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 the message. This extension also applies to the lightweight versions
of IGMPv3 and MLDv2 as defined in [RFC5790]. of IGMPv3 and MLDv2 as defined in [RFC5790].
The extension will be part of additional data as mentioned in When this extension mechanism is used, it will make use of the entire
[RFC3810] Section 5.1.12 (resp. [RFC3376] Section 4.1.10) for query Additional Data section defined in IGMPv3/MLDv2 for TLVs. The TLV
messages and [RFC3810] Section 5.2.12 (resp. [RFC3376] scheme is flexible enough to provide for any future extensions.
Section 4.2.11) for report messages.
One such TLV is being defined in [I-D.ietf-bier-mld] Additional Data is defined for query messages in IGMPv3 [RFC3376]
Section 4.1.10 and MLDv2 [RFC3810] Section 5.1.12, and for report
messages in IGMPv3 [RFC3376] Section 4.2.11 and MLDv2 [RFC3810]
Section 5.2.11.
One such TLV is being defined for use in BIER IGMP/MLD overlays
[I-D.ietf-bier-mld]. This TLV provides BIER specific information
that only will be processed by BIER routers.
2. Conventions used in this document 2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. Extension Format 3. Extension Format
A previously reserved bit in the IGMPv2 and MLDv2 headers is used to A previously reserved bit in the IGMPv3 and MLDv2 headers is used to
indicate whether this extension is used. It is set to 1 if it is indicate whether this extension is used. When this extension is
used, otherwise 0. When this extension is used, the Additional Data used, the Additional Data of IGMPv3 and MLDv2 messages would be
of IGMPv3 and MLDv2 messages would be formatted as follows. Note formatted as follows. Note that this format contains a variable
that this format contains a variable number of TLVs. It MUST contain number of TLVs. It MUST contain at least one TLV.
at least one TLV.
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Total Extension Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extension Type 1 | Extension Length 1 | | Extension Type 1 | Extension Length 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extension Value 1 | | Extension Value 1 |
. . . . . .
. . . . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extension Type 2 | Extension Length 2 | | Extension Type 2 | Extension Length 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extension Value 2 | | Extension Value 2 |
. . . . . .
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extension Type n | Extension Length n | | Extension Type n | Extension Length n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extension Value n | | Extension Value n |
. . . . . .
. . . . . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Extension Format Figure 1: Extension Format
Reserved: 2 octets. Reserved. MUST be set to 0. MUST be ignored
when received.
Total Extension Length: 2 octets. The remaining length of the
extension. This value MUST be equal to ((2 + 2) * n) + Extension
Length 1 + Extension Length 2 + ... Extension Length n. That is,
it is the sum of the lenghts of all the TLVs, including the type
field (2 octets), and the length field (2 octets) of each TLV.
The total number of octets used by the extension is the value of
this field plus 4 (including the 2 octets Reserved field and the 2
octets of this field).
Extension Type: 2 octets. This identifies a particular Extension Extension Type: 2 octets. This identifies a particular Extension
Type as defined in the IGMP/MLD Extension Type Registry. Type as defined in the IGMP/MLD Extension Type Registry.
Extension Length: 2 octets. This specifies the length in octets Extension Length: 2 octets. This specifies the length in octets
of the following Extension Value field. of the following Extension Value field. Note that this value may
be zero, in which case there is no Extension Value field present.
The next type field, if any, will come immediately after this
length field.
Extension Value: This field contains the value. The length and Extension Value: This field contains the value. The length and
the contents of this field is according to the specification of the contents of this field is according to the specification of
the Extension Type as defined in the IGMP/MLD Extension Type the Extension Type as defined in the IGMP/MLD Extension Type
Registry. The length MUST be as specified in the Extension Length Registry. The length MUST be as specified in the Extension Length
field. field.
Note that there may be additional data following this extension. The There MUST be no data in the message after the last TLV. The TLVs
Total Extension Length field would indicate where this extension are processed until the end of the message is reached. When
ends, and the additional data starts. Also, there is a possibility processing the TLVs an implementation MUST keep track of how many
that an implementation uses the Additional Data part of IGMP/MLD octets are remaining in the message and stop TLV processing when
messages, but not according to this extension scheme. When a message there is no room for any further TLVs. That is, TLV processing stops
is received, it MUST be verified that the Total Extension Length is if there are less than 4 octets remaining in the message after a TLV
equal to ((2 + 2) * n) + Extension Length 1 + Extension Length 2 + is processed since there is not enough room for an additional minimal
... Extension Length n, where n is the number of TLVs. Note that the TLV. Also if a TLV has a length exceeding the remainder of the
value of n is not known ahead of time. An implementation would walk message, that TLV is ignored, and further TLV processing stops.
through the TLVs and add the 4 octet overhead and the length of each
TLV, until the sum is larger or equal to the Total Extension Length, IGMPv3 and MLDv2 messages are defined so that they can fit within the
or until the end of the IGMP/MLD message, whichever happens first. network MTU, in order to avoid fragmentation. When this extension
Any additional data after this MUST be ignored, except the data MUST mechanism is used, the number of Group Records in each Report message
be included in checksum computations. If the sum is not equal to the should be kept small enough that the entire message, including any
Total Extension Length, then it is assumed that this extension is not extension TLVs can fit within the network MTU.
being used, and this specification does not apply.
3.1. Multicast Listener Query Extension 3.1. Multicast Listener Query Extension
The MLD query format with extension is shown below. The E-bit is set The MLD query format with extension is shown below. The E-bit MUST
to 1 to indicate that the extension is present. be set to 1 to indicate that the extension is present. Otherwise it
MUST be 0.
0 1 2 3 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 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 | | Type = 130 | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Response Code | Reserved | | Maximum Response Code | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
* * * *
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| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extension | | Extension |
~ ~ ~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: MLD Query Extension Figure 2: MLD Query Extension
3.2. Version 2 Multicast Listener Report Extension 3.2. Version 2 Multicast Listener Report Extension
The MLD report format with extension is shown below. The E-bit is The MLD report format with extension is shown below. The E-bit MUST
set to 1 to indicate that the extension is present. be set to 1 to indicate that the extension is present. Otherwise it
MUST be 0.
0 1 2 3 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 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 | | Type = 143 | Reserved | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|E| Reserved |Nr of Mcast Address Records (M)| |E| Reserved |Nr of Mcast Address Records (M)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
. . . .
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extension | | Extension |
~ ~ ~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: MLD Report Extension Figure 3: MLD Report Extension
3.3. IGMP Membership Query Extension 3.3. IGMP Membership Query Extension
The IGMP query format with the extension is shown below. The E-bit The IGMP query format with the extension is shown below. The E-bit
is set to 1 to indicate that the extension is present. 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
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 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 | | Type = 0x11 | Max Resp Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Address | | Group Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|E| Resv|S| QRV | QQIC | Number of Sources (N) | |E| Resv|S| QRV | QQIC | Number of Sources (N) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extension | | Extension |
~ ~ ~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: IGMP Query Extension Figure 4: IGMP Query Extension
3.4. IGMP Version 3 Membership Report Extension 3.4. IGMP Version 3 Membership Report Extension
The IGMP report format with the extension is shown below. The E-bit The IGMP report format with the extension is shown below. The E-bit
is set to 1 to indicate that the extension is present. 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
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 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 | | Type = 0x22 | Reserved | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|E| Reserved | Number of Group Records (M) | |E| Reserved | Number of Group Records (M) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
. . . .
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extension | | Extension |
~ ~ ~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: IGMP Report Extension Figure 5: IGMP Report Extension
4. Applicability and backwards compatibility 4. Applicability and backwards compatibility
IGMP and MLD implementations, host implementations in particular, IGMP and MLD implementations, host implementations in particular,
rarely change, and it expected to take a long time for them to rarely change, and it is expected to take a long time for them to
support this extension mechanism. Also as new extensions are support this extension mechanism. Also as new extensions are
defined, it may take a long time before they are supported. defined, it may take a long time before they are supported. Due to
this, defining extensions should not be taken lightly, and it is
crucial to consider backwards compatibility.
Implementations that do not support this extension mechanism will Implementations that do not support this extension mechanism will
simply ignore the extension, provided they are compliant with IGMPv3 simply ignore the extension, provided they are compliant with IGMPv3
and MLDv2 RFCs, and behave as if the extension is not present. and MLDv2 RFCs, which specify that additional data must be ignored,
Implementations that support this extension MUST behave as if it is and behave as if the extension is not present. Implementations that
not present if they support non of the extension types in an IGMP/MLD support this extension MUST behave as if it is not present if they
message. If they support at least one of the types, they will support none of the extension types in an IGMP/MLD message. If they
process the supported types according to the respective type support at least one of the types, they will process the supported
specifications, and ignore any unsupported types. types according to the respective type specifications, and ignore any
unsupported types.
It is possible that a new extension type only applies to queries, or It is possible that a new extension type only applies to queries, or
only reports, or there may be other specific conditions for when it only to reports, or there may be other specific conditions for when
is to be used. A document defining a new type MUST specify clearly it is to be used. A document defining a new type MUST specify
under what conditions the new type should be used, including for clearly under what conditions the new type should be used, including
which message types. It MUST also be considered what the behavior for which message types. It MUST also be considered what the
should be if a message is not used in the defined manner, e.g., if it behavior should be if a message is not used in the defined manner,
is present in a query message, when it was only expected to be used e.g., if it is present in a query message, when it was only expected
in reports. to be used in reports.
When defining new types, care must be taken to ensure that nodes that When defining new types, care must be taken to ensure that nodes that
support the type can co-exist with nodes that don't, on the same support the type can co-exist with nodes that don't, on the same
subnet. There could be multiple routers where only some support the subnet. There could be multiple routers where only some support the
extension, or multiple hosts where only some support the extension. extension, or multiple hosts where only some support the extension.
Or a router may support it and none of the hosts, or all hosts may Or a router may support it and none of the hosts, or all hosts may
support it, but none of the routers. With multiple types being used, support it, but none of the routers. With multiple types being used,
it must also be considered that some hosts or routers may only it must also be considered that some hosts or routers may only
support some of the types, and potentially one node might support support some of the types, and potentially one node might support
only one type, and another node only another type. only one type, and another node only another type.
Documents defining new types MUST have security considerations Documents defining new types MUST have security considerations
relevant to the new types. They MUST also in addition to defining relevant to the new types. They MUST also in addition to defining
the behavior of host and routers supporting the new types, consider the behavior of hosts and routers supporting the new types, consider
compatibility with hosts and routers on the same subnet that do not compatibility with hosts and routers on the same subnet that do not
support the new types. Further, they MUST consider whether there are support the new types. Further, they MUST consider whether there are
any dependencies or restrictions on combinations between the new any dependencies or restrictions on combinations between the new
types and any pre-existing types. types and any pre-existing types.
The extension mechanism do not support IGMPv1, IGMPv2 and MLDv1. As This document defines an extension mechanism only for IGMPv3 and
nodes may send older version message, they would also not be able to MLDv2. Hence this mechanism would not apply if hosts or routers send
send messages using this extension. older version message.
5. Security Considerations 5. Security Considerations
This document extends MLD (resp. IGMP) message formats. As such, This document extends IGMP and MLD message formats, allowing for a
there is no impact on security or changes to the considerations in variable number of TLVs. Implementations must take care when parsing
[RFC3810] and [RFC3376]. The respective types defined using this the TLVs to not exceed the packet boundary, an attacker could
extension may impact security and MUST be considered as part of the intentionally specify a TLV with a length exceeding the boundary.
respective specifications.
An implementation could add a large number of minimal TLVs in a
message to increase the cost of processing the message to magnify a
Denial of Service attack.
The respective types defined using this extension may impact security
and this MUST be considered as part of the respective specifications.
6. IANA Considerations 6. IANA Considerations
A new registry called "IGMP/MLD Extension Types" should be created A new registry called "IGMP/MLD Extension Types" should be created
with registration procedure "IETF Review" as defined in [RFC8126] with registration procedure "IETF Review" as defined in [RFC8126]
with this document as a reference. The registry should be common for with this document as a reference. The registry should be common for
IGMP and MLD and can perhaps be added to the "Internet Group IGMP and MLD and can perhaps be added to the "Internet Group
Management Protocol (IGMP) Type Numbers" section. The initial Management Protocol (IGMP) Type Numbers" section. The initial
content of the registry should be as below. content of the registry should be as below.
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