WDIFF

draft-ietf-ipngwg-uni-based-mcast-03.txt-13623.txt --> rfc3306.txt

IPNGWG

Network Working Group B. Haberman
Internet Draft Nortel Networks
draft-ietf-ipngwg-uni-based-mcast-03.txt
Request for Comments: 3306 Consultant
Category: Standards Track D. Thaler
October 2001
Microsoft
Expires April
August 2002

Unicast-Prefix-based IPv6 Multicast Addresses

Status of this Memo

This document is specifies an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026 [RFC 2026].

Internet-Drafts are working documents of Internet standards track protocol for the
Internet Engineering
Task Force (IETF), its areas, community, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts. Internet-Drafts are draft documents valid requests discussion and suggestions for a maximum
improvements. Please refer to the current edition of
six months the "Internet
Official Protocol Standards" (STD 1) for the standardization state
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."

The list status of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.

The list this protocol. Distribution of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. this memo is unlimited.

Abstract

This specification defines an extension to the multicast addressing
architecture of the IP Version 6 protocol. The extension presented
in this document allows for unicast-prefix-based allocation of
multicast addresses. By delegating multicast addresses at the same
time as unicast prefixes, network operators will be able to identify
their multicast addresses without needing to run an inter-domain
allocation protocol.

Table of Contents

Status of this Memo................................................1
Abstract...........................................................1

1. Introduction....................................................2
2. Motivation......................................................2
3. Terminology.....................................................2
4. Multicast Address Format........................................2
5. Address Lifetime................................................3 Lifetime................................................4
6. Source-Specific Multicast Addresses.............................4
7. Examples........................................................4
8. Security Considerations.........................................4

Haberman, Thaler 1

Internet Draft Unicast Prefix-based IPv6 Multicast October 2001 Considerations.........................................5
9. References......................................................5
AuthorÆs
Author's Address...................................................6
Full Copyright Statement...........................................6 Statement...........................................7

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RFC 3306 Unicast-Prefix-based IPv6 Multicast August 2002

1. Introduction

This document specifies an extension to the multicast portion of the
IPv6 addressing architecture [ADDRARCH]. The current architecture
does not contain any built-in support for dynamic address allocation.
This proposal introduces encoded information in the multicast address
to allow for dynamic allocation of IPv6 multicast addresses and IPv6
source-specific multicast addresses.

2. Motivation

The current IPv4 multicast address allocation architecture [RFC 2908]
is based on a multi-layered, multi-protocol system. The goal of this
proposal is to reduce the number of protocols that need to be
deployed in order to get dynamic multicast address allocation.

The use of unicast prefix-based multicast address allocation will, at
a minimum, remove the need to run the Multicast Address Allocation
Protocol (AAP) [AAP WORK] and the Multicast Address-Set Claim (MASC)
Protocol [RFC 2909].

3. Terminology

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].

4. Multicast Address Format

Section 2.7 of [ADDRARCH] defines the following operational format of
IPv6 multicast addresses:

| 8 | 4 | 4 | 112 |
+--------+----+----+---------------------------------------------+
|11111111|flgs|scop| group ID |
+--------+----+----+---------------------------------------------+

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RFC 3306 Unicast-Prefix-based IPv6 Multicast August 2002

This document introduces a new format that incorporates unicast
prefix information in the multicast address. The following
illustrates the new format:

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Internet Draft Unicast Prefix-based IPv6 Multicast October 2001

| 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].

The reserved field MUST be zero.

plen indicates the actual number of bits in the network prefix field
that identify the subnet when P = 1.

network prefix identifies the network prefix of the unicast subnet
owning the multicast address. If P = 1, this field contains the
unicast network prefix assigned to the domain owning, or allocating,
the multicast address. All non-significant bits of the network
prefix field SHOULD be zero.

It should be noted that the Interface Identifier requirements in
Section 2.5.1 of [ADDRARCH] effectively restricts restrict the length of the
unicast prefix to 64 bits, hence the network prefix portion of the
multicast address will be at most 64 bits.

Group ID is set based on the guidelines outlined in [IPV6 GID].

The scope of the unicast-prefix based multicast address MUST NOT
exceed the scope of the unicast prefix embedded in the multicast
address.

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RFC 3306 Unicast-Prefix-based IPv6 Multicast August 2002

5. Address Lifetime

The lifetime of a unicast prefix-based multicast addresses address SHOULD NOT
exceed the Valid Lifetime field in the Prefix Information option,
corresponding to the unicast prefix being used, contained in the
Neighbor Discovery Router Advertisement message [RFC 2461]. The
lifetime of the multicast address is needed to support the Abstract
API for Multicast Address Allocation [RFC 2771].

It should be noted that the unicast prefix's Valid Lifetime in the
Router Advertisement message does not indicate that the prefix will

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Internet Draft Unicast Prefix-based IPv6 Multicast October 2001
become invalid at the end of the lifetime. Rather, that value is
typically a constant until a renumbering event is scheduled after
which, the prefix does become invalid.

The use of unicast prefix-based multicast addresses after the unicast
prefix has become invalid may lead to operational problems. For
example, routers that perform policy checks comparing the multicast
prefix against the unicast prefix assigned to an AS may discard the
packet.

6. Source-Specific Multicast Addresses

The unicast prefix-based IPv6 multicast address format supports
Source-specific multicast addresses, as defined by [SSM ARCH]. To
accomplish is, this, a node MUST:

o Set P = 1.
o Set plen = 0.
o Set network prefix = 0.

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.

7. Examples

The following are a few examples of the structure of unicast prefix-
based multicast addresses.

- Global prefixes - A network with a unicast prefix of
3FFE:FFFF:1::/48 would also have a unicast prefix-based
multicast prefix of FF3x:0030:3FFE:FFFF:0001::/96 (where 'x'
is any valid scope).

- Link-local prefix - A network segment (e.g. a 10baseT
Ethernet) using the link-local prefix would also be able
to use the multicast prefix FF32:000A:FE80::/96.
- SSM - All IPv6 SSM multicast addresses will have the format
FF3x::/96.

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RFC 3306 Unicast-Prefix-based IPv6 Multicast August 2002

8. Security Considerations

It is possible that the embedded unicast prefix can aid in
identifying the allocation domain of a given multicast address,
though an allocation domain choosing to avoid being traced has no
obstacles currently to creating addresses using a prefix not assigned
to it, or using a smaller scope embedded prefix.

Using source-specific multicast addresses can sometimes aid in the
prevention of denial-of-service attacks by arbitrary sources,

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Internet Draft Unicast Prefix-based IPv6 Multicast October 2001
although no guarantee is provided. A more in-depth discussion of the
security considerations for SSM can be found in [SSM ARCH].

9. References

[RFC 2026] S. Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026, October 1996.

[RFC 2460] Deering, S. Deering and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.

[ADDRARCH] Hinden, R. Hinden and S. Deering, "IP Version 6 Addressing
Architecture", Work In Progress, RFC 2373, July 2001. 1998.

[RFC 2908] Thaler, D., Handley, M., M. and D. Estrin, D., "The Internet
Multicast Address Allocation Architecture", RFC 2908,
September 2000.

[AAP WORK] Handley, M. Handley and S. Hanna, "Multicast Address Allocation
Protocol (AAP)", Work In Progress.

[RFC 2909] P. Radoslavov, et al, " The P., Estrin, D., Govindan, R., Handley, M.,
Kumar, S. and D. Thaler, "The Multicast Address-Set Claim
(MASC) Protocol", RFC 2909, September 2000.

[RFC 2119] S. Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, BCP14, March 1999.

[IPV6 GID] B. Haberman, B., "Dynamic Allocation Guidelines for IPv6
Multicast Addresses", Work In Progress, September 2001. RFC 3307, June 2002.

[RFC 2461] Narten, T., Nordmark, E., E. and W. Simpson, W., "Neighbor
Discovery for IP Version 6 (IPv6)", RFC 2461, December
1998.

[RFC 2771] R. Finlayson, " An R., "An Abstract API for Multicast Address
Allocation", RFC 2771, February 2000.

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RFC 3306 Unicast-Prefix-based IPv6 Multicast August 2002

[SSM ARCH] Holbrook, H. Holbrook and B. Cain, "Source-Specific Multicast for
IP", Work In Progress, March 2001.

Haberman, Thaler 5

AuthorÆs Progress.

Author's Address

Brian Haberman
Nortel Networks
300 Perimeter Park
Morrisville, NC 27560
1-919-905-7484
haberman@nortelnetworks.com
Consultant
Phone: 1-919-949-4828
EMail: bkhabs@nc.rr.com

Dave Thaler
Microsoft Corporation
One Microsoft Way
Redmond, WA 48105-6399
Phone: 1-425-703-8835
EMail: dthaler@microsoft.com

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RFC 3306 Unicast-Prefix-based IPv6 Multicast August 2002

Full Copyright Statement

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HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Haberman,

Acknowledgement

Funding for the RFC Editor function is currently provided by the
Internet Society.

Haberman & Thaler 6 Standards Track [Page 7]

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