Updates to the IPv6 Multicast Addressing Architecture
draft-ietf-6man-multicast-addr-arch-update-01
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 7371.
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|
|---|---|---|---|
| Authors | Mohamed Boucadair , Stig Venaas | ||
| Last updated | 2013-05-23 | ||
| Replaces | draft-boucadair-6man-multicast-addr-arch-update | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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draft-ietf-6man-multicast-addr-arch-update-01
6man Working Group M. Boucadair
Internet-Draft France Telecom
Updates: 3306,3956,4607,4291 (if approved) S. Venaas
Intended status: Standards Track Cisco
Expires: November 24, 2013 May 23, 2013
Updates to the IPv6 Multicast Addressing Architecture
draft-ietf-6man-multicast-addr-arch-update-01
Abstract
This document updates the IPv6 multicast addressing architecture by
defining the 17-20 reserved bits as generic flag bits. The document
provides also some clarifications related to the use of these flag
bits.
This document updates RFC 3956, RFC 3306, RFC 4607 and RFC 4291.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 24, 2013.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://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 Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Addressing Architecture Update . . . . . . . . . . . . . . . 2
3. Clarifications . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Flag Bits . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. IANA Assigned SSM Block . . . . . . . . . . . . . . . . . 4
4. RFC Updates . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. RFC3306 . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. RFC3956 . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.3. RFC4607 . . . . . . . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
8. Normative References . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
This document updates the IPv6 multicast addressing architecture
[RFC4291] by defining the 17-20 reserved bits as generic flag bits
(Section 2). The document provides also some clarifications related
to the use of these flag bits (Section 3.1) and also about IANA
assigned SSM blocks (Section 3.2).
This document updates [RFC3956], [RFC3306], [RFC4607] and [RFC4291].
2. Addressing Architecture Update
Bits 17-20 of a multicast address are defined in [RFC3956] and
[RFC3306] as reserved bits. This document defines these bits as
generic flag bits so that they apply to any multicast address.
Figure 1 and Figure 2 show the updated structure of the addressing
architecture. The first diagram shows the update of the base IPv6
addressing architecture, and the second shows the update of so-called
Embedded-RP.
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OLD:
| 8 | 4 | 4 | 112 bits |
+--------+----+----+----------------------------------------------+
|11111111|flgs|scop| group ID |
+--------+----+----+----------------------------------------------+
NEW:
| 8 | 4 | 4 | 4 | 108 bits |
+--------+----+----+----------------------------------------------+
|11111111|flgs|scop|flgs| group ID |
+--------+----+----+----+-----------------------------------------+
Figure 1: Updated IPv6 Multicast Addressing Architecture
OLD (RFC3956):
| 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 |
+--------+----+----+----+----+--------+----------------+----------+
|11111111|flgs|scop|rsvd|RIID| plen | network prefix | group ID |
+--------+----+----+----+----+--------+----------------+----------+
NEW:
| 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 |
+--------+----+----+----+----+--------+----------------+----------+
|11111111|flgs|scop|flgs|RIID| plen | network prefix | group ID |
+--------+----+----+----+----+--------+----------------+----------+
Figure 2: Embedded-RP with Updated IPv6 Multicast Address Arch.
Further specification documents may define a meaning for these flag
bits. Defining the bits 17-20 as flags for all IPv6 multicast
addresses allows addresses to be treated in a more uniform and
generic way, and allows for these bits to be defined in the future
for different purposes, irrespective of the specific type of
multicast address.
3. Clarifications
3.1. Flag Bits
Some implementations and specification documents do not treat the
flag bits as separate bits but tend to use their combined value as a
4-bit integer. This practice is a hurdle for assigning a meaning to
the remaining flag bits. Below are listed some examples for
illustration purposes:
o the reading of [RFC4607] may lead to conclude that ff3x::/32 is
the only allowed SSM IPv6 prefix block.
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o [RFC3956] states only ff70::/12 applies to Embedded-RP.
Particularly, implementations should not treat the fff0::/12 range
as Embedded-RP.
To avoid such confusion and to unambiguously associate a meaning with
the remaining flags, the following recommendation is made
Implementations MUST treat flag bits as separate bits.
3.2. IANA Assigned SSM Block
Another issue related to SSM is the IANA assigned SSM address block.
Per [RFC4607], ff3x::4000:0001 through ff3x::7fff:fff is the block
for IANA assignments (http://www.iana.org/assignments/ipv6-multicast-
addresses/ipv6-multicast-addresses.xml). However, IANA assignments
are permanent addresses and should not have the transient bit set.
Quoting from [RFC4607]:
"T = 1 indicates a non-permanently-assigned ("transient")
multicast address.".
4. RFC Updates
4.1. RFC3306
This document changes Section 4 of [RFC3306] as follows:
OLD:
| 8 | 4 | 4 | 8 | 8 | 64 | 32 |
+--------+----+----+--------+--------+----------------+----------+
|11111111|flgs|scop|reserved| plen | network prefix | group ID |
+--------+----+----+--------+--------+----------------+----------+
+-+-+-+-+
flgs is a set of 4 flags: |0|0|P|T|
+-+-+-+-+
o P = 0 indicates a multicast address that is not assigned
based on the network prefix. This indicates a multicast
address as defined in [ADDRARCH].
o P = 1 indicates a multicast address that is assigned based
on the network prefix.
o If P = 1, T MUST be set to 1, otherwise the setting of the T
bit is defined in Section 2.7 of [ADDRARCH].
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The reserved field MUST be zero.
NEW:
| 8 | 4 | 4 | 8 | 8 | 64 | 32 |
+--------+----+----+--------+--------+----------------+----------+
|11111111|flgs|scop|reserved| plen | network prefix | group ID |
+--------+----+----+--------+--------+----------------+----------+
+-+-+-+-+
flgs is a set of 4 flags: |X|Y|P|T|
+-+-+-+-+
X and Y may each be set to 0 or 1.
o P = 0 indicates a multicast address that is not assigned
based on the network prefix. This indicates a multicast
address as defined in [ADDRARCH].
o P = 1 indicates a multicast address that is assigned based
on the network prefix.
o T is set according to the definition in Section 2.7
of [ADDRARCH]. Unicast-Prefix-based addresses would
typically not be IANA assigned, so in most cases T would
be set to 1.
This document changes Section 6 of [RFC3306] as follows:
OLD:
These settings create an SSM range of FF3x::/32 (where 'x' is any
valid scope value). The source address field in the IPv6 header
identifies the owner of the multicast address.
NEW:
T flag is set according to whether the addresses are assigned by
IANA.
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If the flag bits are to 0011, these settings create an SSM range
of ff3x::/32 (where 'x' is any valid scope value). The source
address field in the IPv6 header identifies the owner of the
multicast address. ff3x::/32 is not the only allowed SSM prefix
range. For example, ff2x::/32 would be IANA assigned SSM
addresses.
4.2. RFC3956
This document changes Section 2 of [RFC3956] as follows:
OLD:
As described in [RFC3306], the multicast address format is as
follows:
| 8 | 4 | 4 | 8 | 8 | 64 | 32 |
+--------+----+----+--------+----+----------------+----------+
|11111111|flgs|scop|reserved|plen| network prefix | group ID |
+--------+----+----+--------+----+----------------+----------+
Where flgs are "0011". (The first two bits are as yet undefined,
sent as zero and ignored on receipt.)
NEW:
As described in [RFC3306], the multicast address format is as
follows:
| 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 |
+--------+----+----+---------+----+----------------+----------+
|11111111|flgs|scop|flgs|rsvd|plen| network prefix | group ID |
+--------+----+----+---------+----+----------------+----------+
+-+-+-+-+
flgs is a set of four flags: |X|R|P|T|
+-+-+-+-+
X may be set to 0 or 1.
This document changes Section 3 of [RFC3956] as follows:
OLD:
| 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 |
+--------+----+----+----+----+----+----------------+----------+
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|11111111|flgs|scop|rsvd|RIID|plen| network prefix | group ID |
+--------+----+----+----+----+----+----------------+----------+
+-+-+-+-+
flgs is a set of four flags: |0|R|P|T|
+-+-+-+-+
When the highest-order bit is 0, R = 1 indicates a multicast address
that embeds the address on the RP. Then P MUST be set to 1, and
consequently T MUST be set to 1, as specified in [RFC3306]. In
effect, this implies the prefix FF70::/12. In this case, the last 4
bits of the previously reserved field are interpreted as embedding
the RP interface ID, as specified in this memo.
The behavior is unspecified if P or T is not set to 1, as then the
prefix would not be FF70::/12. Likewise, the encoding and the
protocol mode used when the two high-order bits in "flgs" are set to
11 ("FFF0::/12") is intentionally unspecified until such time that
the highest-order bit is defined. Without further IETF
specification, implementations SHOULD NOT treat the FFF0::/12 range
as Embedded-RP.
NEW:
| 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 |
+--------+----+----+----+----+----+----------------+----------+
|11111111|flgs|scop|flgs|RIID|plen| network prefix | group ID |
+--------+----+----+----+----+----+----------------+----------+
+-+-+-+-+
flgs is a set of four flags: |X|R|P|T|
+-+-+-+-+
X may be set to 0 or 1.
R = 1 indicates a multicast address that embeds the address of the RP.
P MUST be set to 1 according to [RFC3306], as this is a special case of
unicast-prefix based addresses. This implies that for instance prefixes
ff70::/12 and fff0::/12 are embedded RP prefixes, but all multicast
addresses with the R-bit set to 1 MUST be treated as Embedded RP
addresses. The behavior is unspecified if P is not set to 1. When the
R-bit is set, the last 4 bits of the previously reserved field are
interpreted as embedding the RP interface ID, as specified in this memo.
This document changes Section 4 of [RFC3956] as follows:
OLD:
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It MUST be a multicast address with "flgs" set to 0111, that is,
to be of the prefix FF70::/12,
NEW:
It MUST be a multicast address with R-bit set to 1.
It MUST have P-bit set to 1 when using the embedding in this
document as it is a prefix-based address.
This document changes Section 7.1 of [RFC3956] as follows:
OLD:
To avoid loops and inconsistencies, for addresses in the range
FF70::/12, the Embedded-RP mapping MUST be considered the longest
possible match and higher priority than any other mechanism.
NEW:
To avoid loops and inconsistencies, for addresses with R-bit set
to 1, the Embedded-RP mapping MUST be considered the longest
possible match and higher priority than any other mechanism.
4.3. RFC4607
This document changes the abstract of [RFC4607] as follows:
OLD:
IP version 4 (IPv4) addresses in the 232/8 (232.0.0.0 to
232.255.255.255) range are designated as source-specific multicast
(SSM) destination addresses and are reserved for use by source-
specific applications and protocols. For IP version 6 (IPv6), the
address prefix FF3x::/32 is currently reserved for source-specific
multicast use but others may be reserved in the future. This
document defines an extension to the Internet network service that
applies to datagrams sent to SSM addresses and defines the host
and router requirements to support this extension.
NEW:
IP version 4 (IPv4) addresses in the 232/8 (232.0.0.0 to
232.255.255.255) range are designated as source-specific multicast
(SSM) destination addresses and are reserved for use by source-
specific applications and protocols. For IP version 6 (IPv6), the
address prefix ff3x::/32 is currently reserved for source-specific
multicast use but others may be reserved in the future. This
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document defines an extension to the Internet network service that
applies to datagrams sent to SSM addresses and defines the host
and router requirements to support this extension.
This document changes Section 1 of [RFC4607] as follows:
OLD:
For IPv6, the address prefix FF3x::/32 is reserved for source-
specific multicast use, where 'x' is any valid scope identifier,
by [IPv6-UBM]. Using the terminology of [IPv6-UBM], all SSM
addresses must have P=1, T=1, and plen=0. [IPv6-MALLOC] mandates
that the network prefix field of an SSM address also be set to
zero, hence all SSM addresses fall in the FF3x::/96 range. Future
documents may allow a non-zero network prefix field if, for
instance, a new IP- address-to-MAC-address mapping is defined.
Thus, address allocation should occur within the FF3x::/96 range,
but a system should treat all of FF3x::/32 as SSM addresses, to
allow for compatibility with possible future uses of the network
prefix field.
NEW:
For IPv6, all SSM addresses must have P=1 and plen=0 while T-bit
is set according to whether the addresses are assigned by IANA
[I-D.ietf-6man-multicast-addr-arch-update]. In particular, a
system should treat all of ff3x::/32 and ff2x::/32 as SSM
addresses, to allow for compatibility with possible future uses of
the network prefix field. Other SSM prefixes can be defined in
the future.
5. IANA Considerations
This document may require IANA updates. However, at this point it is
not clear exactly what these updates may be.
6. Security Considerations
Security considerations discussed in [RFC3956], [RFC3306], [RFC4607]
and [RFC4291] MUST be taken into account.
7. Acknowledgements
Many thanks to B. Haberman for the discussions prior to the
publication of this document.
8. Normative References
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3306] Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6
Multicast Addresses", RFC 3306, August 2002.
[RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous
Point (RP) Address in an IPv6 Multicast Address", RFC
3956, November 2004.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for
IP", RFC 4607, August 2006.
Authors' Addresses
Mohamed Boucadair
France Telecom
Rennes 35000
France
Email: mohamed.boucadair@orange.com
Stig Venaas
Cisco
USA
Email: stig@cisco.com
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