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Versions: 00 01 02 03 04 05 06 07 08 09 RFC 4489

  IPv6 WG
  Internet Draft                                         Jung-Soo Park
  draft-ietf-ipv6-link-scoped-mcast-03.txt               Myung-Ki Shin
                                                        Hyoung-Jun Kim
                                                                  ETRI
  Expires: December 2003                                     June 2003


                  Link Scoped IPv6 Multicast Addresses


Status of this Memo

  This document is an Internet-Draft and is in full conformance with
  all provisions of Section 10 of RFC2026.

  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 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 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.

  For potential updates to the above required-text see:
  http://www.ietf.org/ietf/1id-guidelines.txt


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 this document updates the "Unicast-Prefix-
  based IPv6 Multicast Addresses" for the link-local scope [RFC 3306].


Table of Contents

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



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1. Introduction

  This specification defines 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.  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 this document updates the "Unicast-Prefix-based IPv6
  Multicast Addresses" for the link-local scope [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 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.


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 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] 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


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  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 <= 2.  The value of this multicast address is necessary 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, this document updates the [RFC 3306], which
  describes the latter.

  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].




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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, the multicast
  prefix of the host is FF32:0:1234:56FF:FE78:90AB::/96.  For SSM,
  multicast address will be FF32::/96.


5. Considerations

  This document updates [RFC 3306] for the scope <= 2 case.

  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 SSM address.  To resolve this,
  the usage of this format is restricted within link-local scope.


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. 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] R. Hinden and S. Deering, "IP Version 6 Addressing
             Architecture", Work In Progress, October 2002.


  Informative

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


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             1998.

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

  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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