IPv6 Working Group J-S. Park
INTERNET DRAFT ETRI
Expires: January 2005 M-K. Shin
ETRI/NIST
H-J. Kim
ETRI
July 2004
Link Scoped IPv6 Multicast Addresses
<draft-ietf-ipv6-link-scoped-mcast-04.txt>
Status of this Memo
By submitting this Internet-Draft, I certify that any applicable
patent or other IPR claims of which I am aware have been disclosed,
and any of which I become aware will be disclosed, in accordance
with RFC 3668.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other docu-
ments 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 of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on January 2005.
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, it is preferred to use this method for the
link-local scope rather than Unicast-Prefix-based IPv6 Multicast
Addresses [RFC 3306].
Park et al. Expires January 2005 [Page 1]
INTERNET-DRAFT Link Scoped IPv6 Multicast Addresses July 2004
Table of Contents:
1. Introduction................................................2
2. Applicability...............................................3
3. Link scoped multicast address format........................3
4. Examples....................................................4
5. Considerations..............................................4
6. Security Considerations.....................................5
7. Acknowledgments.............................................5
8. References..................................................5
Authors' Addresses.............................................6
1. Introduction
This specification defines an extension to the multicast portion of
the IPv6 addressing architecture [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 2909] and the Multicast Address Allocation
servers [RFC 2908].
Basically, it is preferred to use this method for the link-local
scope rather than Unicast-Prefix-based IPv6 Multicast Addresses
[RFC 3306]. This document 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 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].
Park et al. Expires January 2005 [Page 2]
INTERNET-DRAFT Link Scoped IPv6 Multicast Addresses July 2004
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 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 [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
Park et al. Expires January 2005 [Page 3]
INTERNET-DRAFT Link Scoped IPv6 Multicast Addresses July 2004
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. It is preferred to use this method for the link-
local scope rather than Unicast-Prefix-based IPv6 Multicast
Addresses [RFC 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::a12:34ff:fe56:7890, the
multicast prefix of the host is FF32:0:a12:34ff:fe56:7890::/96.
5. Considerations
It is preferred to use this method for scop <= 2 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].
Note that if an SSM implementation checks for FF3x::/32, not
FF3x::/96, the other nodes not implementing this specification will
Park et al. Expires January 2005 [Page 4]
INTERNET-DRAFT Link Scoped IPv6 Multicast Addresses July 2004
interpret the link-local 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 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 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.
[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", RFC 3513, April 2003.
Informative
Park et al. Expires January 2005 [Page 5]
INTERNET-DRAFT Link Scoped IPv6 Multicast Addresses July 2004
[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," 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.
[SSM ARCH] H. Holbrook and B. Cain, "Source-Specific Multicast for
IP", Work In Progress, October 2003.
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/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
Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed
to pertain to the implementation or use of the technology described
in this document or the extent to which any license under such
rights might or might not be available; nor does it represent that
it has made any independent effort to identify any such rights.
Information on the procedures with respect to rights in RFC
documents can be found in BCP 78 and BCP 79.
Park et al. Expires January 2005 [Page 6]
INTERNET-DRAFT Link Scoped IPv6 Multicast Addresses July 2004
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use
of such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository
at http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at ietf-
ipr@ietf.org.
Disclaimer of Validity
This document and the information contained herein are provided on
an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT
THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR
ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2004). This document is
subject to the rights, licenses and restrictions contained in BCP
78, and except as set forth therein, the authors retain all their
rights.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Park et al. Expires January 2005 [Page 7]
