Internet DRAFT - draft-boucadair-6man-multicast-addr-arch-update
draft-boucadair-6man-multicast-addr-arch-update
6man Working Group M. Boucadair
Internet-Draft France Telecom
Updates: 3306,3956,4607,4291 S. Venaas
(if approved) Cisco
Intended status: Standards Track January 16, 2013
Expires: July 20, 2013
Updates to the IPv6 Multicast Addressing Architecture
draft-boucadair-6man-multicast-addr-arch-update-00
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
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and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 20, 2013.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Addressing Architecture Update . . . . . . . . . . . . . . . . 3
3. Clarifications . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Flag Bits . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. IANA Assigned SSM Block . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5
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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.
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.
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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.
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. IANA Considerations
This document may require IANA updates. However, at this point it is
not clear exactly what these updates may be.
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5. Security Considerations
Security considerations discussed in [RFC3956], [RFC3306], [RFC4607]
and [RFC4291] MUST be taken into account.
6. Acknowledgements
Many thanks to B. Haberman for the discussions prior to the
publication of this document.
7. Normative References
[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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