draft-ietf-ipv6-link-scoped-mcast-09.txt   rfc4489.txt 
IPv6 Working Group J-S. Park Network Working Group J-S. Park
INTERNET DRAFT ETRI Request for Comments: 4489 M-K. Shin
Expires: January 18, 2006 M-K. Shin Updates: 3306 H-J. Kim
Updates: 3306 ETRI Category: Standards Track ETRI
H-J. Kim April 2006
ETRI
July 17, 2005
A Method for Generating Link Scoped IPv6 Multicast Addresses
<draft-ietf-ipv6-link-scoped-mcast-09.txt>
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). Copyright (C) The Internet Society (2006).
Abstract Abstract
This document specifies an extension to the multicast addressing This document specifies an extension to the multicast addressing
architecture of the IPv6 protocol. The extension allows for the use architecture of the IPv6 protocol. The extension allows the use of
of Interface Identifiers (IIDs) to allocate multicast addresses. Interface Identifiers (IIDs) to allocate multicast addresses. When a
When a link-local unicast address is configured at each interface link-local unicast address is configured at each interface of a node,
of a node, an IID is uniquely determined. After that, each node an IID is uniquely determined. After that, each node can generate
can generate their unique multicast addresses automatically without its unique multicast addresses automatically without conflicts. The
conflicts. Basically, this document proposes an alternative method alternative method for creating link-local multicast addresses
for creating link-local multicast addresses over a known method proposed in this document is better than known methods like unicast-
like unicast-prefix-based IPv6 multicast addresses. It is preferred prefix-based IPv6 multicast addresses. This memo updates RFC 3306.
to use this method for link-local scope rather than unicast-
prefix-based IPv6 multicast addresses. This memo update RFC3306.
Table of Contents: Table of Contents:
1. Introduction................................................2 1. Introduction ....................................................2
2. Applicability...............................................2 2. Applicability ...................................................2
3. Link Scoped Multicast Address Format........................3 3. Link-Scoped Multicast Address Format ............................3
4. Example ....................................................4 4. Example .........................................................3
5. Consideration of Lifetime ..................................4 5. Consideration of Lifetime .......................................4
6. Security Considerations.....................................4 6. Security Considerations .........................................4
7. Acknowledgments.............................................4 7. Acknowledgements ................................................4
8. References..................................................5 8. References ......................................................5
Author's Addresses.............................................5
1. Introduction 1. Introduction
This document defines an extension to the multicast portion of the This document defines an extension to the multicast portion of the
IPv6 addressing architecture [RFC 3513]. The current architecture IPv6 addressing architecture [RFC4291]. The current architecture
does not contain any built-in support for dynamic address does not contain any built-in support for dynamic address allocation.
allocation. The extension allows for use of IIDs to allocate The extension allows for use of IIDs to allocate multicast addresses.
multicast addresses. When a link-local unicast address is When a link-local unicast address is configured at each interface of
configured at each interface of a node, an IID is uniquely a node, an IID is uniquely determined. After that, each node can
determined. After that, each node can generate their unique generate its unique multicast addresses automatically without
multicast addresses automatically without conflicts. That is, conflicts. That is, these addresses could safely be configured at
these addresses could safely be configured at any time after DAD any time after Duplicate Address Detection (DAD) has completed.
(Duplicate Address Detection) has completed.
Basically, it is preferred to use this method for the link-local This method for the link-local scope is preferred over unicast-
scope rather than unicast-prefix-based IPv6 multicast addresses prefix-based IPv6 multicast addresses [RFC3306], since by delegating
[RFC 3306], since by delegating multicast addresses using the IID, multicast addresses using the IID, each node can generate its
each node can generate its multicast addresses automatically multicast addresses automatically without allocation servers. This
without allocation servers. This method goes well with method works better than the unicast-prefix-based method with
applications in serverless environment such as ad-hoc and network applications in serverless environments such as ad-hoc and network
mobility rather thant unicast-prefix-based method. This document mobility. This document restricts the usage of defined fields such
restricts the usage of defined fields such as scop, plen and as the scop, plen, and network prefix fields of [RFC3306].
network prefix fields of [RFC 3306]. Therefore, this document Therefore, this document specifies encoded information for link-local
specifies encoded information for link-local scope in multicast scope in multicast addresses.
addresses.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
this document are to be interpreted as described in [RFC 2119]. document are to be interpreted as described in [RFC2119].
2. Applicability 2. Applicability
The allocation technique in this document is designed to be used in The allocation technique in this document is designed to be used in
any environment in which link-local scope IPv6 multicast addresses any environment in which link-local scope IPv6 multicast addresses
are assigned or selected. Especially, this method goes well with are assigned or selected. This method goes especially well with
nodes supplying multicast services in a zeroconf/serverless nodes supplying multicast services in a zeroconf/serverless
environment. For example, multicast addresses less than or equal environment. For example, multicast addresses less than or equal to
to link-local scope are themselves generated by nodes supplying link-local scope are themselves generated by nodes supplying
multicast services without conflicts. Also, hosts which are multicast services without conflicts. Also, hosts that are supplied
supplied multicast services from multicast servers then make multicast services from multicast servers then make multicast
multicast addresses of multicast servers using ND (address addresses of multicast servers using ND (address resolution) and
resolution) and well-known group IDs. well-known group IDs [RFC2461].
Consequently, this technique MUST only be used for link scoped Consequently, this technique MUST only be used for link scoped
multicast addresses. If you want to use multicast addresses multicast addresses. If you want to use multicast addresses greater
greater than link-local scope, you need to use other methods as than link-local scope, you need to use other methods as described in
described in [RFC 3306]. [RFC3306].
3. Link Scoped Multicast Address Format 3. Link-Scoped Multicast Address Format
This document specifies a new format that incorporates IID in the This document specifies a new format that incorporates IID in the
link-local scope multicast addresses. link-local scope multicast addresses.
Figure 1 illustrates the new format for link scoped multicast Figure 1 illustrates the new format for link-scoped multicast
addresses. addresses.
| 8 | 4 | 4 | 8 | 8 | 64 | 32 | | 8 | 4 | 4 | 8 | 8 | 64 | 32 |
+--------+----+----+--------+--------+----------------+----------+ +--------+----+----+--------+--------+----------------+----------+
|11111111|flgs|scop|reserved| plen | IID | group ID | |11111111|flgs|scop|reserved| plen | IID | group ID |
+--------+----+----+--------+--------+----------------+----------+ +--------+----+----+--------+--------+----------------+----------+
Figure 1: Link scoped multicast IPv6 address format Figure 1. Link-Scoped Multicast IPv6 Address Format
The flgs, scop, and plen fields are used to identify whether an
address is a multicast address, as follows:
Flgs, scop, and plen fields are used to identify whether an address
is a multicast address as specified in this document as follows:
1. flgs MUST be "0011". 1. flgs MUST be "0011".
2. scop MUST be <= 2. 2. scop MUST be <= 2.
3. The reserved field MUST be zero. 3. The reserved field MUST be zero.
4. "plen" field is a special value "1111 1111" (decimal 255).
The IID field (replacing the 64-bit prefix field from [RFC 3306]) 4. The "plen" field is a special value, "1111 1111" (decimal 255).
is used to distinguish each node from others. Given the use of
this method for link-local scope, the IID embedded in the multicast
address MUST only come from the IID of the link-local unicast
address on the interface after DAD has completed. That is, the
creation of the multicast address MUST only occur after DAD has
completed as part of the auto-configuration process.
Group ID is generated to indicate a multicast application and is The IID field (replacing the 64-bit prefix field from [RFC3306]) is
used to guarantee its uniqueness only in the host. It may also be used to distinguish each node from others. Given the use of this
set on the basis of the guidelines outlined in [RFC 3307]. method for link-local scope, the IID embedded in the multicast
address MUST only come from the IID of the link-local unicast address
on the interface after DAD has completed. That is, the creation of
the multicast address MUST only occur after DAD has completed as part
of the auto-configuration process.
Group ID is generated to indicate a 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 [RFC3307].
4. Example 4. Example
This is an example of link scoped IPv6 multicast addresses. For In an Ethernet environment, if the link-local unicast address is
example in an ethernet environment, if the link-local unicast FE80::A12:34FF:FE56:7890, the link-scoped multicast prefix of the
address is FE80::A12:34FF:FE56:7890, the link scoped multicast node is FF32:00FF:A12:34FF:FE56:7890::/96.
prefix of the node is FF32:00FF:A12:34FF:FE56:7890::/96.
5. Consideration of Lifetime 5. Consideration of Lifetime
Generally, Link scoped multicast addresses have no lifetime because Generally, link-scoped multicast addresses have no lifetime, because
link-local unicast addresses also have no lifetime. But, it is not link-local unicast addresses also have no lifetime. However, this is
true in environment of mobile. Even though multicast addresses are not true in the mobile environment. Even though multicast addresses
created from the unique IID of unicast address, their useful are created from the unique IIDs of unicast addresses, their useful
lifetime is linked to the period during which the IID is known to lifetime is linked to the period during which the IID is known to be
be unique. Thus, it is possible to conflict between IIDs, due to a unique. Thus, conflict is possible between IIDs, due to a new node
new node in merged network that uses the same IID as a powered in merged network that uses the same IID as a powered node.
node.
This is a scenario where DAD also fails to guarantee the uniqueness In this scenario, DAD also fails to guarantee uniqueness of the
of the unicast address, so this document does not try to address unicast address, but this document does not try to address this
this issue. issue.
6. Security Considerations 6. Security Considerations
The uniqueness of multicast addresses using this method is The uniqueness of multicast addresses using this method is guaranteed
guaranteed by the DAD process. So, it is needed to get a secure by the DAD process. So, a secure DAD process is needed for stability
DAD process for stability of this method. This document proposes of this method. This document proposes the mechanism in [RFC3041]
the mechanism in [RFC 3041] for this purpose. for this purpose.
[RFC 3041] describes the privacy extension to IPv6 stateless [RFC3041] describes the privacy extension to IPv6 stateless address
address autoconfiguration to how to configure the IID of non-link- autoconfiguration to configure the IID of non-link-local scope
local scope unicast addresses. [RFC 3041] can not be used for unicast addresses. [RFC3041] cannot be used for making a link-local
making a link-local unicast address, and hence it cannot be used to unicast address, and hence it cannot be used to create an IID for
create an IID for link-scoped multicast address. However, as [RFC link-scoped multicast address. However, as [RFC3041] does not
3041] does not protect the privacy of link-local unicast addresses, protect the privacy of link-local unicast addresses, it does not seem
it does not protect the privacy of link-local unicast addresses, it to be required to protect the privacy of IID-based link-local
does not seem to be required to protect the privacy of IID-based multicast addresses.
link-local multicast addresses.
7. Acknowledgements 7. Acknowledgements
We would like to thank Dave Thaler and Brian Haberman for his We would like to thank Dave Thaler and Brian Haberman for their
comments related to the consistency between the unicast prefix- comments related to the consistency between the unicast prefix-based
based multicast draft and this one. Special thanks are due to Erik multicast document and this one. Special thanks are due to Erik
Nordmark and Pekka Savola for valuable comments. Nordmark and Pekka Savola for valuable comments.
8. References 8. References
Normative 8.1. Normative References
[RFC 2119] S. Bradner, "Key words for use in RFCs to indicate
Requirement Levels", RFC 2119, March 1997.
[RFC 2461] T. Narten, E. Nordmark and W. Simpson, "Neighbor
Discovery for IP Version 6 (IPv6)", RFC 2461,
December 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 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Multicast Addresses," RFC 3306, August 2002. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 3307] B. Haberman, "Allocation Guidelines for IPv6 Multicast [RFC2461] Narten, T., Nordmark, E., and W. Simpson, "Neighbor
Addresses," RFC 3307, August 2002. Discovery for IP Version 6 (IPv6)", RFC 2461, December
1998..ti 3
[RFC 3513] R. Hinden and S. Deering, "IP Version 6 Addressing [RFC3041] Narten, T. and R. Draves, "Privacy Extensions for
Architecture", RFC 3513, April 2003. Stateless Address Autoconfiguration in IPv6", RFC 3041,
January 2001.
Informative [RFC3306] Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6
Multicast Addresses", RFC 3306, August 2002.
[RFC 3956] P. Savola and B. Haberman, "Embedding the Rendezvous [RFC3307] Haberman, B., "Allocation Guidelines for IPv6 Multicast
Point (RP) Address in an IPv6 Multicast Address Addresses", RFC 3307, August 2002.
[SSM ARCH] H. Holbrook and B. Cain, "Source-Specific Multicast [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
for IP", Work In Progress, September 2004. Architecture", RFC 4291, February 2006.
Authors' Addresses Authors' Addresses
Jung-Soo Park Jung-Soo Park
ETRI PEC ETRI PEC
161 Gajeong-Dong, Yuseong-Gu, Daejeon 305-350, Korea 161 Gajeong-Dong, Yuseong-Gu, Daejeon 305-350, Korea
Phone: +82 42 860 6514 Phone: +82 42 860 6514
Email: jspark@pec.etri.re.kr EMail: pjs@etri.re.kr
Myung-Ki Shin Myung-Ki Shin
ETRI/NIST ETRI PEC
820 West Diamond Avenue 161 Gajeong-Dong, Yuseong-Gu, Daejeon 305-350, Korea
Gaithersburg, MD 20899, USA
Tel : +1 301 975-3613 Phone: +82 42 860 4847
Fax : +1 301 590-0932 EMail: myungki.shin@gmail.com
E-mail : mshin@nist.gov
Hyoung-Jun Kim Hyoung-Jun Kim
ETRI PEC ETRI PEC
161 Gajeong-Dong, Yuseong-Gu, Daejeon 305-350, Korea 161 Gajeong-Dong, Yuseong-Gu, Daejeon 305-350, Korea
Phone: +82 42 860 6576 Phone: +82 42 860 6576
Email: khj@etri.re.kr EMail: khj@etri.re.kr
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