wdiff draft-ietf-ipv6-link-scoped-mcast-03.txt draft-ietf-ipv6-link-scoped-mcast-04.txt

IPv6 WG
Internet Draft Jung-Soo Working Group J-S. Park
draft-ietf-ipv6-link-scoped-mcast-03.txt Myung-Ki
INTERNET DRAFT ETRI
Expires: January 2005 M-K. Shin
Hyoung-Jun
ETRI/NIST
H-J. Kim
ETRI
Expires: December 2003 June 2003
July 2004

Link Scoped IPv6 Multicast Addresses
<draft-ietf-ipv6-link-scoped-mcast-04.txt>

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Abstract

This document specifies an extension to the multicast addressing
architecture of the IPv6 protocol. The extension allows for the use
of interface-IDs to allocate multicast addresses. When the link-
local unicast address is configured at each interface of a host, an
interface ID is uniquely determined. By delegating multicast
addresses at the same time as the interface ID, each host can
identify their multicast addresses automatically at Layer 1 without
running an intra- or inter-domain allocation protocol in serverless
environments. Basically Basically, it is preferred to use this document updates the "Unicast-Prefix-
based IPv6 Multicast Addresses" method for the
link-local scope rather than Unicast-Prefix-based IPv6 Multicast
Addresses [RFC 3306].

Table of Contents Contents:

1. Introduction...................................................2 Introduction................................................2
2. Applicability..................................................2 Applicability...............................................3
3. Link scoped multicast address format...........................2 format........................3
4. Examples.......................................................4 Examples....................................................4
5. Considerations.................................................4 Considerations..............................................4
6. Security Considerations........................................4 Considerations.....................................5
7. References.....................................................4 Acknowledgments.............................................5
8. Acknowledgments................................................5
Author's Addresses................................................5 References..................................................5
Authors' Addresses.............................................6

1. Introduction

This specification defines an extension to the multicast portion of
the IPv6 addressing architecture [ADDRARCH]. [RFC 3513]. The current
architecture does not contain any built-in support for dynamic
address allocation. The extension allows for use of interface-IDs
to allocate multicast addresses. When the link-local unicast
address is configured at each interface of a host, an interface ID
is uniquely determined. By delegating multicast addresses at the
same time as the interface ID, each host can identify its multicast
addresses automatically without running an intra- or inter-domain
allocation protocol in serverless environments.

The current 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 and servers to get
dynamic multicast address allocation.

The use of interface ID-based multicast address allocation will, at
a minimum, remove the need to run the Multicast Address-Set Claim(MASC)
Protocol[RFC Claim
(MASC) Protocol [RFC 2909] and the Multicast Address Allocation
servers [RFC 2908].

Basically

Basically, it is preferred to use this document updates the "Unicast-Prefix-based IPv6
Multicast Addresses" method for the link-local
scope rather than Unicast-Prefix-based IPv6 Multicast Addresses
[RFC 3306]. This document changes and restricts the usage of defined fields
such as scope, plen and network prefix field in [RFC 3306].
Therefore, this document specifies encoded information for link-local link-
local scope in the multicast addresses.

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. [RFC 2119].

2. Applicability

The allocation technique in this document is designed to be used in
any environment in which link-local scope IPv6 multicast addresses
are assigned or selected. Especially, this method goes well with
nodes supplying multicast services in a zeroconf environment. For
example, multicast addresses less than or equal to link-local scope
are themselves generated by nodes supplying multicast services.

Consequently, this technique MIUST MUST be used for link scoped multicast
addresses. If you want to use multicast addresses greater than
link- local, you need other methods such as [RFC 3306].

3. Link scoped multicast address format

Section 2.7 of [ADDRARCH] [EFC 3513] defines the following operational format
of IPv6 multicast addresses:

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

Figure 1: Generic IPv6 multicast address format

This document introduces new formats that incorporate interface ID
information in the multicast address. The idea of delegating
multicast addresses at the same time as the interface ID can be
applicable to link-local.

Figure 2 illustrates the new format for link scoped multicast
addresses. That is, if the scope of the multicast address is link-
local scope, it is this format.

| 8 | 4 | 4 | 16 | 64 | 32 |
+--------+----+----+------------+----------------+---------------+
|11111111|flgs|scop| reserved | Interface ID | group ID |
+--------+----+----+------------+----------------+---------------+

Figure 2: link scoped multicast IPv6 address format

+-+-+-+-+
flgs is a set of 4 flags: |0|0|P|T|
+-+-+-+-+

o P = 0 indicates a multicast address that is not assigned
on the basis of the interface ID.
o P = 1 indicates a multicast address that is assigned
on the basis of the interface ID.
o If P = 1, T MUST be set to 1, otherwise the setting of
the T bit is defined in Section 2.7 of [RFC 2373].

flgs should use the same flag defined in section 4 of [RFC 3306].
That is, this document proposes the third bit of 'flgs' field to
indicate an Interface ID-based multicast addresses.

scop MUST be <= 2. The value of this multicast address It is necessary preferred to
distinguish between an Interface ID-based multicast address and a
unicast-prefix-based multicast address. If scop <= 2, the former MUST
be used. That is, use this document updates method for the link-
local scope rather than Unicast-Prefix-based IPv6 Multicast
Addresses [RFC 3306], which
describes the latter. 3306].

The reserved field MUST be zero which maps to a plen of zero in RFC
3306.

Interface ID field is used to distinguish each host from others.
And this value is obtained from the IEEE EUI-64 based interface
identifier of the link-local unicast IPv6 address. Given the use
of this method for link-local scope, the interface ID embedded in
the multicast address SHOULD come from the interface ID of the
link-local unicast address on the interface after DAD has
completed. That is, the creation of the multicast address MUST
occur after DAD has completed as part of the auto-config process.

Group ID is generated to indicate multicast application and is used
to guarantee its uniqueness only in the host. It may also be set
on the basis of the guidelines outlined in [RFC 3307].

The lifetime of an Interface ID-based multicast address has no
dependency on the Valid Lifetime field in the Prefix Information
option, corresponding to the unicast address being used, contained
in the Router Advertisement message [RFC 2461].

4. Examples

This is an example of an interface ID-based multicast address with
link-local scope. For example in an Ethernet environment, if the
link-local unicast address is FE80::12:34:56:78:90:AB, FE80::a12:34ff:fe56:7890, the
multicast prefix of the host is FF32:0:1234:56FF:FE78:90AB::/96. For SSM,
multicast address will be FF32::/96. FF32:0:a12:34ff:fe56:7890::/96.

5. Considerations

This document updates [RFC 3306]

It is preferred to use this method for the scope scop <= 2 case. rather than
Unicast-Prefix-based IPv6 Multicast Addresses [RFC 3306]. This
document considers only link scoped multicast addresses. For this
purpose, scop field is used shown in figure 2.

The link scoped multicast address format supports source-specific
multicast addresses by the same method, as defined by [RFC 3306]. So,
it could be confused with a RFC 3306

Note that if an SSM address. To resolve this, implementation checks for FF3x::/32, not
FF3x::/96, the usage of other nodes not implementing this format is restricted within specification will
interpret the link-local scope. multicast addresses generated using this
specification as SSM addresses, since the document uses the
reserved field in such a fashion that plen=0 [RFC 3306]. In order
to avoid this conflict, we recommend SSM implementations must check
for FF3x::/96, as described in Allocation Guidelines for IPv6
Multicast Addresses [RFC 3307] section 3.

6. Security Considerations

[RFC 3041] describes the privacy extension to IPv6 stateless
address autoconfiguration for an interface ID. The interface ID,
generated by [RFC 3041], is also used in this method since the
uniqueness is verified by DAD procedure as part of the secure auto-config auto-
config process.

Using source-specific multicast addresses can sometimes aid in the
prevention of denial-of-service attacks by arbitrary sources,
although no guarantee is provided. A more in-depth discussion of
the security considerations for SSM can be found in [SSM ARCH].

7. Acknowledgements

We would like to thank Dave Thaler and Brian Haberman for his
comments related to the consistency between the unicast prefix-
based multicast draft and this one. Special thanks are due to Erik
Nordmark and Pekka Savola for valuable comments.

8. References

Normative

[RFC 2119] S. Bradner, "Key words for use in RFCs to indicate
Requirement Levels", RFC 2119, March 1997.

[RFC 2373] R. Hinden and S. Deering, "IP Version 6 Addressing
Architecture", RFC 2373, October 1998.

[RFC 3041] T. Narten and R. Draves, "Privacy Extensions for
Stateless Address Autoconfiguration in IPv6," RFC 3041,
April 2001.

[RFC 3306] B. Haberman and D. Thaler, "Unicast-Prefix-based IPv6
Multicast Addresses," RFC 3306, August 2002.

[ADDRARCH]

[RFC 3307] B. Haberman, "Allocation Guidelines for IPv6 Multicast
Addresses," RFC 3307, August 2002.

[RFC 3513] R. Hinden and S. Deering, "IP Version 6 Addressing
Architecture", Work In Progress, October 2002. RFC 3513, April 2003.

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

[RFC 2908] D. Thaler, M. Handley and D. Estrin, "The Internet
Multicast Address Allocation Architecture," RFC2908, RFC 2908,
September 2000.

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

[RFC 3307] B. Haberman, "Dynamic Allocation Guidelines for IPv6
Multicast Addresses," Work In Progress, October 2001.

[SSM ARCH] H. Holbrook and B. Cain, "Source-Specific Multicast for
IP", Work In Progress, March October 2003.

8. Acknowledgments

We would like to thank Dave Thaler and Brian Haberman for his
comments related to the consistency between the unicast prefix-based
multicast draft and this one.

Author's

Authors' Addresses

Jung-Soo Park
ETRI PEC
161 Gajeong-Dong, Yuseong-Gu, Daejon 305-600, Korea
Phone: +82 42 860 6514
Email: jspark@pec.etri.re.kr

Myung-Ki Shin
ETRI PEC
161 Gajeong-Dong, Yuseong-Gu, Daejon 305-600, Korea
Phone: +82 42 860 4847
Email: mkshin@pec.etri.re.kr
ETRI/NIST
820 West Diamond Avenue
Gaithersburg, MD 20899, USA
Tel : +1 301 975-3613
Fax : +1 301 590-0932
E-mail : mshin@nist.gov

Hyoung-Jun Kim
ETRI PEC
161 Gajeong-Dong, Yuseong-Gu, Daejon 305-600, Korea
Phone: +82 42 860 6576
Email: khj@etri.re.kr

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