draft-ietf-ipv6-link-scoped-mcast-06.txt   draft-ietf-ipv6-link-scoped-mcast-07.txt 
IPv6 Working Group J-S. Park IPv6 Working Group J-S. Park
INTERNET DRAFT ETRI INTERNET DRAFT ETRI
Expires: April 2005 M-K. Shin Expires: June 2005 M-K. Shin
ETRI/NIST ETRI/NIST
H-J. Kim H-J. Kim
ETRI ETRI
October 2004 December 2004
Link Scoped IPv6 Multicast Addresses Link Scoped IPv6 Multicast Addresses
<draft-ietf-ipv6-link-scoped-mcast-06.txt> <draft-ietf-ipv6-link-scoped-mcast-07.txt>
Status of this Memo Status of this Memo
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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 for the use
of Interface Identifiers (IIDs) to allocate multicast addresses. of Interface Identifiers (IIDs) to allocate multicast addresses.
When a link-local unicast address is configured at each interface When a link-local unicast address is configured at each interface
of a node, an IID is uniquely determined. After then, each node of a node, an IID is uniquely determined. After that, each node
can generate their unique multicast addresses automatically without can generate their unique multicast addresses automatically without
conflicts. Basically, it is preferred to use this method for the conflicts. Basically, this document proposes an alternative method
link-local scope rather than unicast-prefix-based IPv6 multicast for creating link-local multicast addresses over a known method
addresses [RFC 3306]. like unicast-prefix-based IPv6 multicast addresses. It is preferred
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 ....................................................4
5. Considerations..............................................4 5. Consideration of Lifetime ..................................4
6. Security Considerations.....................................4 6. Security Considerations.....................................4
7. References..................................................4 7. Acknowledgments.............................................4
8. Acknowledgments.............................................5 8. References..................................................5
Author's Addresses.............................................5 Author's Addresses.............................................5
1. Introduction 1. Introduction
This specification defines an extension to the multicast portion of This document defines an extension to the multicast portion of the
the IPv6 addressing architecture [RFC 3513]. The current IPv6 addressing architecture [RFC 3513]. The current architecture
architecture does not contain any built-in support for dynamic does not contain any built-in support for dynamic address
address allocation. The extension allows for use of IIDs to allocation. The extension allows for use of IIDs to allocate
allocate multicast addresses. When a link-local unicast address is multicast addresses. When a link-local unicast address is
configured at each interface of a node, an IID is uniquely configured at each interface of a node, an IID is uniquely
determined. After then, each node can generate their unique determined. After that, each node can generate their unique
multicast addresses automatically without conflicts. That is, multicast addresses automatically without conflicts. That is,
these addresses could safely be configured at any time after DAD these addresses could safely be configured at any time after DAD
(Duplicate Address Detection) is completed. (Duplicate Address Detection) has completed.
Basically, it is preferred to use this method for the link-local Basically, it is preferred to use this method for the link-local
scope rather than unicast-prefix-based IPv6 multicast addresses scope rather than unicast-prefix-based IPv6 multicast addresses
[RFC 3306]. This document restricts the usage of defined fields [RFC 3306]. This document restricts the usage of defined fields
such as scop, plen and network prefix fields of [RFC 3306]. such as scop, plen and network prefix fields of [RFC 3306].
Therefore, this document specifies encoded information for link- Therefore, this document specifies encoded information for link-
local scope in multicast addresses. local scope in multicast 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", "June", and "OPTIONAL" in
this document are to be interpreted as described in [RFC 2119]. this document are to be interpreted as described in [RFC 2119].
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. Especially, this method goes 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 link-local scope are themselves generated by nodes supplying to link-local scope are themselves generated by nodes supplying
multicast services without conflicts. Also, nodes which are multicast services without conflicts. Also, hosts which are
supplied multicast services, easily consist of multicast addresses supplied multicast services from multicast servers then make
of multicast servers using NDP (address resolution) and well-known multicast addresses of multicast servers using ND (address
group IDs. resolution) and well-known group IDs.
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 than link-local scope, you need to use other methods as greater than link-local scope, you need to use other methods as
described in [RFC 3306]. described in [RFC 3306].
3. Link Scoped Multicast Address Format 3. Link Scoped Multicast Address Format
[RFC 3306] defines the following format of unicast-prefix-based
IPv6 multicast addresses:
| 8 | 4 | 4 | 8 | 8 | 64 | 32 |
+--------+----+----+--------+--------+----------------+----------+
|11111111|flgs|scop|reserved| plen | network prefix | group ID |
+--------+----+----+--------+--------+----------------+----------+
Figure 1: Unicast-Prefix-based IPv6 multicast address format
This document specifies a new format that incorporates IID This document specifies a new format that incorporates IID
information in the multicast addresses. The idea of delegating information in the multicast addresses. The idea of delegating
multicast addresses can be applicable to link-local scope. multicast addresses can be applicable to link-local scope.
Figure 2 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| LSM | IID | group ID | |11111111|flgs|scop|reserved| LSM | IID | group ID |
+--------+----+----+--------+--------+----------------+----------+ +--------+----+----+--------+--------+----------------+----------+
Figure 2: Link scoped multicast IPv6 address format Figure 1: Link scoped multicast IPv6 address format
flgs MUST be "0011". (The first two bits have been yet undefined, flgs MUST be "0011". (The first two bits set to zero by the
sent as zero and ignored on receipt) flgs MUST use the same flag sending node and ignored on receipt). "flgs" MUST use the same
defined in section 4 of [RFC 3306]. flag defined in section 4 of [RFC 3306].
scop MUST be <= 2. It is preferred to use this method for the scop MUST be <= 2. It is preferred to use this method for the
link-local scope rather than unicast-prefix-based IPv6 multicast link-local scope rather than unicast-prefix-based IPv6 multicast
addresses [RFC 3306]. addresses [RFC 3306]. But, the users can choose whichever they
wish and deem appropriate.
The reserved field MUST be zero. The reserved field MUST be zero.
LSM (Link Scoped Multicast) field MUST be "1111 1111" which maps to LSM field MUST be "1111 1111" which maps to the plen field in [RFC
the plen field in [RFC 3306], whereas the plen field in [RFC 3306] 3306], whereas the plen field in [RFC 3306] MUST NOT be greater
MUST NOT be greater than 64. than 64.
That is, flgs, scop, and LSM fields are used to identify whether an That is, flgs, scop, and plen fields are used to identify whether
address is a multicast address as specified in this document. an address is a multicast address as specified in this document.
The IID field is used to distinguish each node from others. And The IID field is used to distinguish each node from others. And
this value is obtained from the IEEE EUI-64 based interface this value is obtained from the IEEE EUI-64 based interface
identifier of the link-local unicast IPv6 address. Given the use identifier of the link-local unicast IPv6 address. Given the use
of this method for link-local scope, the IID embedded in the of this method for link-local scope, the IID embedded in the
multicast address MUST only come from the IID of the link-local multicast address MUST only come from the IID of the link-local
unicast address on the interface after DAD has completed. That is, unicast address on the interface after DAD has completed. That is,
the creation of the multicast address MUST only occur after DAD has the creation of the multicast address MUST only occur after DAD has
completed as part of the auto-configuration process. completed as part of the auto-configuration process.
Group ID is generated to indicate multicast application and is used Group ID is generated to indicate a multicast application and is
to guarantee its uniqueness only in the host. It may also be set used to guarantee its uniqueness only in the host. It June also be
on the basis of the guidelines outlined in [RFC 3307]. set on the basis of the guidelines outlined in [RFC 3307].
The lifetime of link scoped multicast addresses 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. Example 4. Example
This is an example of link scoped IPv6 multicast addresses. For This is an example of link scoped IPv6 multicast addresses. For
example in an ethernet environment, if the link-local unicast example in an ethernet environment, if the link-local unicast
address is FE80::A12:34FF:FE56:7890, the link scoped multicast address is FE80::A12:34FF:FE56:7890, the link scoped multicast
prefix of the node is FF32:00FF:A12:34FF:FE56:7890::/96. prefix of the node is FF32:00FF:A12:34FF:FE56:7890::/96.
5. Considerations 5. Consideration of Lifetime
Since multicast addresses are created from the unique IID, their
useful lifetime is linked to the period during which the IID is
known to be unique. Thus, it is possible to conflict between IIDs,
due to a new node joining the network that uses the same IID. The
document does not consider this case at this phase. It is another
challenging issue and out of scope of this document.
The link scoped multicast address format supports source-specific Generally, Link scoped multicast addresses have no lifetime because
multicast addresses by the same method, as defined by [RFC 3306]. link-local unicast addresses also have no lifetime. But, it is not
true in environment of mobile. Even though multicast addresses are
created from the unique IID of unicast address, their useful
lifetime is linked to the period during which the IID is known to
be unique. Thus, it is possible to conflict between IIDs, due to a
new node in merged network that uses the same IID and a powered
node. The document does not consider this case at this phase. It
is another challenging issue and out of scope of this document.
6. Security Considerations 6. Security Considerations
The uniqueness of multicast addresses using this method is
guaranteed by the DAD process. So, it is needed to get a secure
DAD process for stability of this method. This document proposes
the mechanism in [RFC 3041] for this purpose.
[RFC 3041] describes the privacy extension to IPv6 stateless [RFC 3041] describes the privacy extension to IPv6 stateless
address autoconfiguration for an IID. The secure IID, generated by address autoconfiguration for an IID and how to configure the
[RFC 3041], can be used for consisting of a link scoped multicast global-scope unicast addresses. The privacy extension method in
address since the uniqueness is verified by the DAD procedure as [RFC 3041] is triggered when a host receives a router advertisement
part of the secure auto-configuration process. with a prefix information option carrying a global-scope prefix for
the purpose of address auto-configuration. That is, [RFC 3041] can
not be used for making a link-local unicast address. Since the IID
embedded in the link scoped multicast address MUST only come from
the IID of the link-local unicast address on the interface after
DAD has completed, the secure IID, generated by [RFC 3041], can not
be used for consisting of a link scoped multicast address. But, it
is possible to use secure IID for expanding the intensity of
security regardless of a difficulty of acquisition of multicast
server 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 his
comments related to the consistency between the unicast prefix- comments related to the consistency between the unicast prefix-
based multicast draft and this one. Special thanks are due to Erik based multicast draft 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 Normative
[RFC 2119] S. Bradner, "Key words for use in RFCs to indicate [RFC 2119] S. Bradner, "Key words for use in RFCs to indicate
skipping to change at page 5, line 31 skipping to change at page 5, line 35
Multicast Addresses," RFC 3306, August 2002. Multicast Addresses," RFC 3306, August 2002.
[RFC 3307] B. Haberman, "Allocation Guidelines for IPv6 Multicast [RFC 3307] B. Haberman, "Allocation Guidelines for IPv6 Multicast
Addresses," RFC 3307, August 2002. Addresses," RFC 3307, August 2002.
[RFC 3513] R. Hinden and S. Deering, "IP Version 6 Addressing [RFC 3513] R. Hinden and S. Deering, "IP Version 6 Addressing
Architecture", RFC 3513, April 2003. Architecture", RFC 3513, April 2003.
Informative Informative
[RFC 3956] P. Savola and B. Haberman, "Embedding the Rendezvous
Point (RP) Address in an IPv6 Multicast Address
[SSM ARCH] H. Holbrook and B. Cain, "Source-Specific Multicast [SSM ARCH] H. Holbrook and B. Cain, "Source-Specific Multicast
for IP", Work In Progress, September 2004. for IP", Work In Progress, September 2004.
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: jspark@pec.etri.re.kr
skipping to change at page 6, line 25 skipping to change at page 6, line 34
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