Internet Engineering Task Force                                P. Savola
Internet-Draft                                                 CSC/FUNET
Obsoletes: 2908,2909 2776,2908,2909 (if approved)                     February 18, 2005
Expires:                             August 19, 8, 2005
approved)
Expires: February 9, 2006

       Overview of the Internet Multicast Addressing Architecture
                   draft-ietf-mboned-addrarch-01.txt
                   draft-ietf-mboned-addrarch-02.txt

Status of this Memo

   This document is an Internet-Draft and is subject to all provisions
   of Section 3 of RFC 3667.

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   The lack of up-to-date documentation on IP multicast address
   allocation and assignment procedures has caused a great deal of
   confusion.  To clarify the situation, this memo describes the
   allocation and assignment techniques and mechanisms currently (as of
   this writing) in use.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1   Terminology: Allocation or Assignment  . . . . . . . . . .  3
   2.  Multicast Address Allocation . . . . . . . . . . . . . . . . .  4  3
     2.1   Derived Allocation . . . . . . . . . . . . . . . . . . . .  4
       2.1.1   GLOP Allocation  . . . . . . . . . . . . . . . . . . .  4
       2.1.2   Unicast-prefix -based Allocation . . . . . . . . . . .  4
     2.2   Scope-relative Allocation  . . . . . . . . . . . . . . . .  5
     2.3   Static IANA Allocation . . . . . . . . . . . . . . . . . .  6
     2.4   Dynamic Allocation . . . . . . . . . . . . . . . . . . . .  6
   3.  Multicast Address Assignment . . . . . . . . . . . . . . . . .  6
     3.1   Derived Assignment . . . . . . . . . . . . . . . . . . . .  6
     3.2   SSM Assignment inside the Node . . . . . . . . . . . . . .  7
     3.3   Manually Configured Assignment . . . . . . . . . . . . . .  7
     3.4   Static IANA Assignment . . . . . . . . . . . . . . . . . .  7
     3.5   Dynamic Assignments  . . . . . . . . . . . . . . . . . . .  8
   4.  Summary and Future Directions  . . . . . . . . . . . . . . . .  9
     4.1   Prefix Allocation  . . . . . . . . . . . . . . . . . . . .  9
     4.2   Address Assignment . . . . . . . . . . . . . . . . . . . . 10
     4.3   Future Actions . . . . . . . . . . . . . . . . . . . . . . 10
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11 12
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     8.1   Normative References . . . . . . . . . . . . . . . . . . . 12
     8.2   Informative References . . . . . . . . . . . . . . . . . . 12 13
       Author's Address . . . . . . . . . . . . . . . . . . . . . . . 14
   A.  Open Issues  Changes  . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
   B.  Multicast Address Discovery
     A.1   Changes since -01  . . . . . . . . . . . . . . . . . . . 15 . 14
       Intellectual Property and Copyright Statements . . . . . . . . 16

1.  Introduction

   Good, up-to-date documentation of IP multicast is close to
   non-existent. non-
   existent.  Particularly, this is an issue with multicast address
   allocations (to networks and sites) and assignments (to hosts and
   applications).  This problem is stressed by the fact that there
   exists confusing or misleading documentation on the subject
   [RFC2908].  The consequence is that those who wish to learn of IP
   multicast and how the addressing works do not get a clear view of the
   current situation.

   The aim of this document is to provide a brief overview of multicast
   addressing and allocation techniques.  The term 'addressing
   architecture' refers to the set of addressing mechanisms and methods
   in an informal manner.

   It is important to note that Source-specific Multicast (SSM)
   [I-D.ietf-ssm-arch] does not have these addressing problems; hence,
   this document focuses on Any Source Multicast (ASM) model.  The
   applicability of SSM has been briefly discussed in
   [I-D.ietf-mboned-ipv6-multicast-issues].

   This memo obsoletes RFC 2908 RFCs 2776, 2908, and RFC 2909 and re-classifies them
   Historic.

1.1  Terminology: Allocation or Assignment

   Almost all multicast documents and many other RFCs (such as DHCPv4
   [RFC2131] and DHCPv6 [RFC3315]) have used the terms address
   "allocation" and "assignment" interchangeably.  However, the operator
   and address management communities use these for two conceptually
   different processes.

   In unicast operations, address allocations refer to leasing a large
   block of addresses from Internet Assigned Numbers Authority (IANA) to
   a Regional Internet Registry (RIR), (RIR) or from RIR to a Local Internet
   Registry (LIR) possibly through a National Internet Registry (NIR).
   Address assignments, on the other hand, are the leases of smaller
   address blocks or even single addresses to the end-user sites or
   end-users end-
   users themselves.

   Therefore, in this memo, we will separate the two different
   functions: "allocation" describes how larger blocks of addresses are
   obtained by the network operators, and "assignment" describes how
   applications, nodes or sets of nodes obtain a multicast address for
   their use.

2.  Multicast Address Allocation

   Multicast address allocation, i.e., how a network operator might be
   able to obtain a larger block of addresses, can be handled in a
   number of ways as described below.

   Note that these are all only pertinent to ASM -- SSM requires no
   address block allocation because the group address has only local
   significance (however, we discuss the address assignment inside the
   node is
   still an issue discussed in Section 3.2).

2.1  Derived Allocation

   Derived allocations take the unicast prefix or some other properties
   of the network to determine unique multicast address allocations.

2.1.1  GLOP Allocation

   GLOP address allocation [RFC3180] inserts the 16-bit public
   Autonomous System (AS) number in the middle of the IPv4 multicast
   prefix 233.0.0.0/8, so that each AS number can get a /24 worth of
   multicast addresses.  While this is sufficient for multicast testing
   or small scale use, it might not be sufficient in all cases for
   extensive multicast use.

   A minor operational debugging issue with GLOP addresses is that the
   connection between the AS and the prefix is not apparent from the
   prefix, but has to be calculated (e.g., from [RFC3180], AS 5662 maps
   to 233.22.30.0/24).  A usage issue is that GLOP addresses are not
   tied to any prefix but to routing domains, so they cannot be used or
   calculated automatically.

2.1.2  Unicast-prefix -based Allocation

   RFC 3306 [RFC3306] describes a mechanism which embeds up to 64 first
   bits of an IPv6 unicast address in the prefix part of the IPv6
   multicast address, leaving at least 32 bits of group-id space
   available after the prefix mapping.

   A similar mapping has been proposed for IPv4
   [I-D.ietf-mboned-ipv4-uni-based-mcast], [I-D.ietf-mboned-ipv4-
   uni-based-mcast], but it provides a rather low amount of addresses
   (e.g., 1 per an IPv4 /24 block).  While there exist large networks
   without an AS number of their own, this has not been seen to add
   sufficient value compared to GLOP addressing.

   The IPv6 unicast-prefix -based allocations are an extremely useful
   way to allow each network operator, even each subnet, obtain
   multicast addresses easily, through an easy computation.  Further, as
   the IPv6 multicast header also includes the scope value [RFC3513],
   multicast groups of smaller scope can also be used with the same
   mapping.

   The IPv6 Embedded RP technique [RFC3956], used with Protocol
   Independent Multicast - Sparse Mode (PIM-SM), further leverages the
   unicast prefix based allocations, by embedding the unicast prefix and
   interface identifier of the PIM-SM Rendezvous Point (RP) in the
   prefix.  This provides all the necessary information needed to the
   routing systems to run the group in either inter- or intra-domain
   operation.  A difference to RFC 3306 is, however, that the hosts
   cannot calculate their "multicast prefix" automatically, as the
   prefix depends on the decisions of the operator setting up the RP but
   rather requires an assignment method.

   All the IPv6 unicast-prefix -based allocation techniques provide
   sufficient amount of multicast address space for the network
   operators.

2.2  Scope-relative Allocation

   Administratively scoped multicast [RFC2365] is provided by two
   different means: under 239.0.0.0/8 in IPv4 or by 4-bit encoding in
   the IPv6 multicast address prefix [RFC3513].

   As IPv6 scope-relative allocations can be handled with unicast-prefix
   -based multicast addressing as described in Section 2.1.2, and there
   is no need for separate scope-relative allocations, we'll just
   discuss IPv4 in this section.

   The IPv4 scope-relative prefix 239.0.0.0/8 is further divided to
   Local Scope (239.255.0.0/16) and Organization Local Scope
   (239.192.0.0/14); other parts of the administrative scopes are either
   reserved for expansion or undefined [RFC2365].  However, RFC 2365 is
   ambiguous as to whether it's the enterprises or the IETF who are
   allowed to expand the space.

   Topologies which act under a single administration can easily use the
   scoped multicast addresses for their internal groups.  Groups which
   need to be shared between multiple routing domains (but not
   propagated through Internet) are more problematic and typically need
   an assignment of a global multicast address because their scope is
   undefined.

   There is a large number of multicast applications (such as "Norton
   Ghost") which are restricted either to a link or a site, but it is
   extremely undesirable to propagate them further (either to the rest
   of the site, or beyond the site).  Typically many such applications
   have been given a static IANA address assignment; this makes it
   challenging to implement proper propagation limiting -- which could
   be easier if such applications could have been assigned specific
   scope-relative addresses instead.  This is an area of further future
   work.

   There has also been work -- it might be able on protocol to mitigate this issue if there was more
   coordination inside the scope-relative allocation block. automatically discover
   multicast scope zones [RFC2776], but it has never been seriously
   implemented or deployed.

2.3  Static IANA Allocation

   In some rare cases, some organizations may have been able to obtain
   static multicast address allocations (of up to 256 addresses)
   directly from IANA.  Typically these have been meant as a block of
   static assignments to multicast applications, as described in
   Section 3.4.  In principle, IANA does not allocate multicast address
   blocks to the operators but GLOP or Unicast-prefix -based allocations
   should be used instead.

2.4  Dynamic Allocation

   RFC 2908 [RFC2908] proposed three different layers of multicast
   address allocation and assignment, where layers 3 (inter-domain
   allocation) and layer 2 (intra-domain allocation) could be applicable
   here.  Multicast Address-Set Claim Protocol (MASC) [RFC2909] is an
   example of the former, and Multicast Address Allocation Protocol
   (AAP) [I-D.ietf-malloc-aap] (abandoned in 2000 due lack of interest
   and technical problems) is an example of the latter.

   Both of the proposed allocation protocols were quite complex, and
   have never been deployed or seriously implemented.

   It can be concluded that there are no dynamic multicast address
   allocation protocols, and other methods such as GLOP or
   unicast-prefix unicast-
   prefix -based addressing should be used instead.

3.  Multicast Address Assignment

   For multicast address assignment, i.e., how an application learns the
   address it can use, or a node (or a set of nodes) learns an address
   it could use for an application, has a number of options as described
   below.

   Any IPv6 address assignment method should be aware of the guidelines
   for the assignment of the group-IDs for IPv6 multicast addresses
   [RFC3307].

3.1  Derived Assignment

   There are significantly fewer options for derived address assignment
   compared to derived allocation.  Derived multicast assignment is has
   only
   being been specified for IPv6 link-scoped multicast
   [I-D.ietf-ipv6-link-scoped-mcast], [I-D.ietf-ipv6-
   link-scoped-mcast], where the EUI64 is embedded in the multicast
   address, providing a node with unique multicast addresses for link-local link-
   local ASM communications.

3.2  SSM Assignment inside the Node

   While the SSM multicast addresses have only local (to the node)
   significance, there is still a minor issue on how to assign the
   addresses between the applications running on the same node (or more
   precisely, an IP address).

   This assignment is not considered to be a problem because typically
   the addresses for the applications are selected manually or
   statically, but if done using an API, Application Programming Interface
   (API), the API could check that the addresses do not conflict prior
   to assigning one.

3.3  Manually Configured Assignment

   With manually configured assignment, the network operator which who has a
   multicast address prefix assigns the multicast group addresses to the
   requesting nodes using a manual process.

   Typically the user or administrator which wants to use a multicast
   address for particular application requests an address from the
   network operator using phone, email, or similar means, and the
   network operator provides the user with a multicast address.  Then
   the user/administrator of the node or application manually configures
   the application to use the assigned multicast address.

   This is a relatively simple process; it has been sufficient for
   certain applications which require manual configuration in any case,
   or which cannot or do not want to justify a static IANA assignment.
   The manual assignment works when the number of participants in a
   group is small, as each participant has to be manually configured.

   This is the most commonly used technique when the multicast
   application does not have a static IANA assignment.

3.4  Static IANA Assignment

   In contrast to manually configured assignment, as described above,
   static IANA assignment refers to getting a globally unique assignment
   for the particular application directly from IANA.  Guidelines for
   IANA are described in [I-D.ietf-mboned-rfc3171bis]. [RFC3171][I-D.ietf-mboned-rfc3171bis].

   This is seen as lucrative because it's the simplest approach for
   application developers because they can then hard-code the multicast
   address, requiring
   address.  Hard-coding requires no lease of the usable multicast
   address, and likewise the client applications do not need to perform
   any kind of service discovery (but depending on hard-coded
   addresses).  However, this is a bad approach architecturally, as we
   should focus on enhancing and deploying service discovery and address
   assignment (as needed) instead of encouraging a "land-grab" of
   multicast addresses.

   [RFC3138] describes how to handle those GLOP assignments (called
   "eGLOP") which use the private-use AS number space (233.252.0.0/14).
   It was envisioned that IANA would delegate the responsibility of
   these to RIRs, which would assign or allocate addresses as best
   seemed fit.  However, this was never carried out as IANA did not make
   these allocations to RIRs due to procedural reasons.

   In summary, there are applications which have obtained a static IANA
   assignment, some of which are really needed, and some of which
   probably should not have been granted.

3.5  Dynamic Assignments

   The layer 1 of RFC 2908 [RFC2908] described dynamic assignment from
   Multicast Address Allocation Servers (MAAS) to applications and
   nodes, with Multicast Address Dynamic Client Allocation Protocol
   (MADCAP) [RFC2730] as examples. an example.  Since then, there has been a
   proposal for DHCPv6 assignment
   [I-D.jdurand-assign-addr-ipv6-multicast-dhcpv6].

   Based on a multicast prefix, it [I-D.jdurand-assign-addr-ipv6-
   multicast-dhcpv6].

   It would be rather straightforward to deploy a dynamic assignment
   protocol which would lease group addresses based on a multicast
   prefix to the applications wishing to use multicast.  For example,
   only few have implemented MADCAP, and it's not significantly
   deployed.  Moreover, it is not clear how widely for example the APIs
   for communication between the multicast application and the MADCAP
   client operating at the host have been implemented [RFC2771].

   An entirely different approach is Session Announcement Protocol (SAP)
   [RFC2974].  In addition to advertising global multicast sessions, the
   protocol also has associated ranges of addresses for both IPv4 and
   IPv6 which can be used by SAP-aware applications to create new groups
   and new group addresses.  It is a rather tedious process to create  Creating a session (and obtain obtaining an
   address) this way is a rather tedious process which is why it isn't done all
   that often.  (Note that the IPv6 SAP address is unroutable in the
   inter-domain multicast.)

   A conclusion about dynamic assignment protocols is that:

   1.  multicast is not significantly attractive in the first place,

   2.  very many applications have a static IANA assignment and thus
       require no dynamic or manual assignment,

   3.  those that cannot be easily satisfied with IANA or manual
       assignment (i.e., where dynamic assignment would be desirable)
       are rather marginal, or

   4.  that there are other gaps why dynamic assignments are not seen as
       a useful approach (for example, issues related to service
       discovery/rendezvous).

   In consequence, more work on rendezvous/service discovery will would be
   needed to make dynamic assignment assignments more useful.

4.  Summary and Future Directions

   This section summarizes the mechanisms and analysis discussed in this
   memo, and presents some potential future directions.

4.1  Prefix Allocation

   Summary of prefix allocation methods for ASM is in Figure 1.

      +-------+--------------------------------+--------+--------+
      | Sect. | Prefix allocation method       | IPv4   | IPv6   |
      +-------+--------------------------------+--------+--------+
      | 2.1.1 | Derived: GLOP                  |  Yes   | NoNeed*|
      | 2.1.2 | Derived: Unicast-prefix -based |No -yet |  Yes   |
      |  2.2  | Separate Scope-relative        |  Yes   | NoNeed*|
      |  2.3  | Static IANA allocation         |   No   |   No   |
      |  2.4  | Dynamic allocation protocols   |   No   |   No   |
      +-------+--------------------------------+--------+--------+
      * = the need satisfied by IPv6 unicast-prefix -based allocation.

                                 Figure 1

   o  Only ASM is affected by the assignment/allocation issues (however,
      both ASM and SSM have roughly the same address discovery issues).

   o  GLOP allocations seem to provide a sufficient IPv4 multicast
      allocation mechanism for now, but could be extended in future.
      Scope-relative allocations provide the opportunity for internal
      IPv4 allocations.

   o  Unicast-prefix -based addresses and the derivatives provide good
      allocation strategy with IPv6, also for scoped multicast
      addresses.

   o  Dynamic allocations are a too complex and unnecessary mechanism.

   o  Static IANA allocations are an architecturally unacceptable
      approach.

4.2  Address Assignment

   Summary of address assignment methods is in Figure 2.

      +-------+--------------------------------+----------+----------+
      | Sect. | Address assignment method      | IPv4     | IPv6     |
      +-------+--------------------------------+----------+----------+
      |  3.1  | Derived: link-scope addresses  |  No      |   Yes    |
      |  3.2  | SSM (inside the node)          |  Yes     |   Yes    |
      |  3.3  | Manual assignment              |  Yes     |   Yes    |
      |  3.4  | Static IANA IANA/RIR assignment     |LastResort|LastResort|
      |  3.5  | Dynamic assignment protocols   |  Yes     |   Yes    |
      +-------+--------------------------------+----------+----------+

                                 Figure 2

   o  Manually configured assignment is what's typically done today, and
      works to a sufficient degree in smaller scale.

   o  Static IANA assignment has been done extensively in the past, but
      it needs to be tightened down to prevent problems caused by
      "land-grabbing". "land-
      grabbing".

   o  Dynamic assignment, e.g., using MADCAP have been implemented, but
      there is no wide deployment, so a solution is there -- but there.  However,
      either there are other gaps in the multicast architecture or there
      is no
      need sufficient demand for it in the first place, place when manual configuration is
      possible, and
      static IANA assignments are still there. available.  Assignments using SAP also
      exist but are not common; global SAP assignment is unfeasible with
      IPv6.

   o  Derived assignments are only applicable in a fringe case of
      link-scoped link-
      scoped multicast.

4.3  Future Actions

   o  Multicast address discovery/"rendezvous" needs to be analyzed at
      more length, and an adequate solution provided; the result also
      needs to be written down to be shown to the IANA static assignment
      requestors.  See [I-D.savola-mboned-address-discovery-problems]
      and Appendix B [I-D.ietf-mboned-addrdisc-problems] for more.

   o  IPv6 multicast DAD and/or multicast prefix communication
      mechanisms should be analyzed (e.g.,
      [I-D.jdurand-ipv6-multicast-ra]): whether there is demand or not,
      and specify if yes.

   o  The IETF should consider whether to specify more ranges of the
      IPv4 scope-relative address space for static allocation for
      applications which should not be routed over the Internet (such as
      backup software, etc. -- so that these wouldn't need to use global
      addresses which should never leak in any case).

   o  The IETF should seriously consider its static IANA allocations
      policy, e.g., "locking it down" to a stricter policy (like "IETF
      Consensus") and looking at developing the discovery/rendezvous
      functions, if necessary.

5.  Acknowledgements

   Tutoring a couple multicast-related papers, the latest by Kaarle
   Ritvanen [RITVANEN] convinced the author that the up-to-date
   multicast address assignment/allocation documentation is necessary.

   Multicast address allocations/assignments were discussed at the
   MBONED WG session at IETF59 [MBONED-IETF59].

   Dave Thaler, James Lingard, and Beau Williamson provided useful
   feedback for the preliminary version of this memo.  Myung-Ki Shin and
   Jerome Durand also suggested improvements.

6.  IANA Considerations

   This memo includes no request to IANA, but as the allocation and
   assignment of multicast addresses are related to IANA functions, it
   wouldn't hurt if the IANA reviewed this entire memo.

   IANA considerations in sections 4.1.1 and 4.1.2 of [RFC2908] still
   apply to the administratively scoped prefixes.

   IANA may be interested in reviewing the accuracy of the statement on
   eGLOP address assignments in Section 3.4.

   (RFC-editor: please remove this section at publication.)

7.  Security Considerations

   This memo only describes different approaches to allocating and
   assigning multicast addresses, and this has no security
   considerations; the security analysis of the mentioned protocols is
   out of scope of this memo.

   Obviously, especially the dynamic assignment protocols are inherently
   vulnerable to resource exhaustion attacks, as discussed e.g., in
   [RFC2730].

8.  References

8.1  Normative References

   [I-D.ietf-ipv6-link-scoped-mcast]
              Park, J., "Link "A Method for Generating Link Scoped IPv6
              Multicast Addresses",
              Internet-Draft draft-ietf-ipv6-link-scoped-mcast-08,
              December 2004.

   [I-D.ietf-mboned-rfc3171bis]
              Albanna, Z., Almeroth, K., Cotton, M. and D. Meyer, "IANA
              Guidelines for IPv4 Multicast Address Assignments",
              Internet-Draft draft-ietf-mboned-rfc3171bis-02, March
              2004.

   [I-D.ietf-ssm-arch]
              Holbrook, H. draft-ietf-ipv6-link-scoped-mcast-09
              (work in progress), July 2005.

   [I-D.ietf-ssm-arch]
              Holbrook, H. and B. Cain, "Source-Specific Multicast for
              IP", Internet-Draft draft-ietf-ssm-arch-06, draft-ietf-ssm-arch-06 (work in progress),
              September 2004.

   [RFC2365]  Meyer, D., "Administratively Scoped IP Multicast", BCP 23,
              RFC 2365, July 1998.

   [RFC3171]  Albanna, Z., Almeroth, K., Meyer, D., and M. Schipper,
              "IANA Guidelines for IPv4 Multicast Address Assignments",
              BCP 51, RFC 3171, August 2001.

   [RFC3180]  Meyer, D. and P. Lothberg, "GLOP Addressing in 233/8",
              BCP 53, RFC 3180, September 2001.

   [RFC3306]  Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6
              Multicast Addresses", RFC 3306, August 2002.

   [RFC3307]  Haberman, B., "Allocation Guidelines for IPv6 Multicast
              Addresses", RFC 3307, August 2002.

   [RFC3513]  Hinden, R. and S. Deering, "Internet Protocol Version 6
              (IPv6) Addressing Architecture", RFC 3513, April 2003.

   [RFC3956]  Savola, P. and B. Haberman, "Embedding the Rendezvous
              Point (RP) Address in an IPv6 Multicast Address",
              RFC 3956, November 2004.

8.2  Informative References

   [I-D.iab-dns-choices]
              Faltstrom, P. and R. Austein, "Design Choices When
              Expanding DNS", Internet-Draft draft-iab-dns-choices-00,
              October 2004.

   [I-D.ietf-malloc-aap]
              Handley, M. and S. Hanna, "Multicast Address Allocation
              Protocol (AAP)", June 2000.

   [I-D.ietf-mboned-addrdisc-problems]
              Savola, P., "Lightweight Multicast Address Discovery
              Problem Space", draft-ietf-mboned-addrdisc-problems-00
              (work in progress), March 2005.

   [I-D.ietf-mboned-ipv4-uni-based-mcast]
              Thaler, D., "Unicast-Prefix-based IPv4 Multicast
              Addresses",
              Internet-Draft draft-ietf-mboned-ipv4-uni-based-mcast-02, draft-ietf-mboned-ipv4-uni-based-mcast-02
              (work in progress), October 2004.

   [I-D.ietf-mboned-ipv6-multicast-issues]
              Savola, P., "IPv6

   [I-D.ietf-mboned-rfc3171bis]
              Albanna, Z., Almeroth, K., Cotton, M., and D. Meyer, "IANA
              Guidelines for IPv4 Multicast Deployment Issues",
              Internet-Draft draft-ietf-mboned-ipv6-multicast-issues-01,
              September Address Assignments",
              draft-ietf-mboned-rfc3171bis-02 (work in progress),
              March 2004.

   [I-D.jdurand-assign-addr-ipv6-multicast-dhcpv6]
              Durand, J., "IPv6 multicast address assignment with
              DHCPv6",
              , June 2004.
              draft-jdurand-assign-addr-ipv6-multicast-dhcpv6-01 (work
              in progress), February 2005.

   [I-D.jdurand-ipv6-multicast-ra]
              Durand, J. and P. Savola, "Route Advertisement Option for
              IPv6 Multicast Prefixes",
              Internet-Draft draft-jdurand-ipv6-multicast-ra-00,
              February 2005.

   [I-D.palet-v6ops-tun-auto-disc]
              Palet, J. and M. Diaz, "Analysis of IPv6 Tunnel End-point
              Discovery Mechanisms",
              Internet-Draft draft-palet-v6ops-tun-auto-disc-03, January
              2005.

   [I-D.savola-mboned-address-discovery-problems]
              Savola, P., "Lightweight Multicast Address Discovery
              Problem Space",
              ,
              draft-jdurand-ipv6-multicast-ra-00 (work in progress),
              February 2005.

   [MBONED-IETF59]
              "MBONED WG session at IETF59",
              <http://www.ietf.org/proceedings/04mar/172.htm>.

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, March 1997.

   [RFC2608]  Guttman, E., Perkins, C., Veizades, J. J., and M. Day,
              "Service Location Protocol, Version 2", RFC 2608,
              June 1999.

   [RFC2730]  Hanna, S., Patel, B. B., and M. Shah, "Multicast Address
              Dynamic Client Allocation Protocol (MADCAP)", RFC 2730,
              December 1999.

   [RFC2771]  Finlayson, R., "An Abstract API for Multicast Address
              Allocation", RFC 2771, February 2000.

   [RFC2776]  Handley, M., Thaler, D., and R. Kermode, "Multicast-Scope
              Zone Announcement Protocol (MZAP)", RFC 2776,
              February 2000.

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

   [RFC2909]  Radoslavov, P., Estrin, D., Govindan, R., Handley, M.,
              Kumar, S. S., and D. Thaler, "The Multicast Address-Set Claim
              (MASC) Protocol", RFC 2909, September 2000.

   [RFC2974]  Handley, M., Perkins, C. C., and E. Whelan, "Session
              Announcement Protocol", RFC 2974, October 2000.

   [RFC3138]  Meyer, D., "Extended Assignments in 233/8", RFC 3138,
              June 2001.

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RITVANEN]
              Ritvanen, K., "Multicast Routing and Addressing", HUT
              Report, Seminar on Internetworking, May 2004,
              <http://www.tml.hut.fi/Studies/T-110.551/2004/papers/>.

Author's Address

   Pekka Savola
   CSC - Scientific Computing Ltd.
   Espoo
   Finland

   Email: psavola@funet.fi

Appendix A.  Open Issues

   (This section will  Changes

   (To be removed or merged with the rest before
   publication..)

   o  Is the case for IPv4 Unicast-Prefix Base Multicast addressing
      sufficiently strong, or could those organizations just get an AS
      number themselves if they really wanted prior to do multicast?

Appendix B.  Multicast Address Discovery

   [[ NOTE IN DRAFT: publication as an RFC.)

A.1  Changes since -01

   o  Mention the intent of this section has mechanisms which haven't been mostly
   superceded by [I-D.savola-mboned-address-discovery-problems] so succesful: eGLOP and
   therefore it is put in the appendix, with pending removal in
      MZAP.

   o  Remove the
   future.

   As was noted in Section 3, appendices on multicast address discovery (i.e., service
   discovery or "rendezvous") is a problem with multicast address
   assignment.  In particular, an acceptable mechanism (mechanisms such
   as Service Location Protocol (SLP) [RFC2608] seem to have been
   considered too complex) seems to be missing which the hosts wishing
   to participate in a group could use to find the address of that group
   [MBONED-IETF59].

   It is worth noting that as long as not deploying an address
   assignment (a separate
      draft now) and service discovery protocols/mechanisms means that one
   can get IPv4 unicast-prefix based multicast addressing.

   o  Add a static note on scope-relative address assignment from IANA, there is little
   interest from the application developers to actually do anything
   except try to get the assignment from IANA.  Conclusion: if we want
   to use non-IANA processes, the assignments must be either forbidden
   completely, or made sufficiently difficult that it's easier for the
   application developers to take another route if a feasible mechanism
   is available.

   There are two issues in the service discovery:

   1.  The session initiator being able to publish the session somehow, space and

   2.  The session participants finding out about the session (rather
       than creating their own).

   When manually configured or static IANA assignments are used, 1)
   should be relatively straightforward (if something needs to be
   manually configured or statically assigned, putting it e.g., in DNS
   should not be a problem).  However, this is still more complex for
   dynamic or derived assignments because it implies that the host or
   the application has expansion
      ambiguity.

   o  Remove the right references to make that publication on its own,
   rather than through a manual process by an administrator.

   2) is always a challenge, but could leverage for example DNS (e.g.,
   by relying on using SRV records with the DNS search path, as
   described in [I-D.iab-dns-choices] and
   [I-D.palet-v6ops-tun-auto-disc]). draft-ietf-mboned-ipv6-issues-xx.txt

   o  Minor editorial cleanups.

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