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Versions: (draft-savola-mboned-addrarch) 00 01 02 03 04 05 06 07 RFC 6308

Internet Engineering Task Force                                P. Savola
Internet-Draft                                                 CSC/FUNET
Obsoletes: 2776,2908,2909 (if                              March 3, 2006
approved)
Intended status: Best Current
Practice
Expires: September 4, 2006


       Overview of the Internet Multicast Addressing Architecture
                   draft-ietf-mboned-addrarch-04.txt

Status of this Memo

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   This Internet-Draft will expire on September 4, 2006.

Copyright Notice

   Copyright (C) The Internet Society (2006).

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.



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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Terminology: Allocation or Assignment  . . . . . . . . . .  3
   2.  Multicast Address Allocation . . . . . . . . . . . . . . . . .  4
     2.1.  Derived Allocation . . . . . . . . . . . . . . . . . . . .  4
       2.1.1.  GLOP Allocation  . . . . . . . . . . . . . . . . . . .  4
       2.1.2.  Unicast-prefix -based Allocation . . . . . . . . . . .  4
     2.2.  Administratively Scoped Allocation . . . . . . . . . . . .  5
     2.3.  Static IANA Allocation . . . . . . . . . . . . . . . . . .  6
     2.4.  Dynamic Allocation . . . . . . . . . . . . . . . . . . . .  6
   3.  Multicast Address Assignment . . . . . . . . . . . . . . . . .  6
     3.1.  Derived Assignment . . . . . . . . . . . . . . . . . . . .  7
     3.2.  SSM Assignment inside the Node . . . . . . . . . . . . . .  7
     3.3.  Manually Configured Assignment . . . . . . . . . . . . . .  7
     3.4.  Static IANA Assignment . . . . . . . . . . . . . . . . . .  7
       3.4.1.  Global IANA Assignment . . . . . . . . . . . . . . . .  8
       3.4.2.  Scope-relative IANA Assignment . . . . . . . . . . . .  8
     3.5.  Dynamic Assignments  . . . . . . . . . . . . . . . . . . .  8
   4.  Summary and Future Directions  . . . . . . . . . . . . . . . .  9
     4.1.  Prefix Allocation  . . . . . . . . . . . . . . . . . . . . 10
     4.2.  Address Assignment . . . . . . . . . . . . . . . . . . . . 11
     4.3.  Future Actions . . . . . . . . . . . . . . . . . . . . . . 11
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 13
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 13
   Appendix A.  Changes . . . . . . . . . . . . . . . . . . . . . . . 15
     A.1.  Changes since -01  . . . . . . . . . . . . . . . . . . . . 15
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 16
   Intellectual Property and Copyright Statements . . . . . . . . . . 17


















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1.  Introduction

   Good, up-to-date documentation of IP multicast is close to 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 the Any Source Multicast (ASM) model.

   This memo obsoletes RFCs 2776, 2908, and 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) 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 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.







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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 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 when the AS number is greater than 255, 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], 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



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   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.  Administratively Scoped 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 administratively scoped allocations can be handled with
   unicast-prefix-based multicast addressing as described in
   Section 2.1.2, we'll just discuss IPv4 in this section.

   The IPv4 administratively scoped 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 the 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, and 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 or have hijacked a static IANA address assignment;
   this makes it challenging to implement proper propagation limiting --



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   which could be easier if such applications could have been assigned
   specific administratively scoped addresses instead.  This is an area
   of further future work.

   There has also been work on a protocol to automatically discover
   multicast scope zones [RFC2776], but it has never been widely
   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 3.4.1.  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-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].





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3.1.  Derived Assignment

   There are significantly fewer options for derived address assignment
   compared to derived allocation.  Derived multicast assignment has
   only been specified for IPv6 link-scoped multicast
   [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 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 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 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 an assignment for the



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   particular application directly from IANA.  There are two main forms
   of IANA assignment: global and scope-relative.  Guidelines for IANA
   are described in [RFC3171][I-D.ietf-mboned-rfc3171bis].

3.4.1.  Global IANA Assignment

   Globally unique address assignment is seen as lucrative because it's
   the simplest approach for application developers since they can then
   hard-code the multicast 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, there is an architectural scaling
   problem with this approach, as it encourages a "land-grab" of the
   limited multicast address space.

   [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 global
   static IANA assignment and while some of which are really needed,
   some of which probably should not have been granted.  Conversely,
   there are some applications that have not obtained a static IANA
   assignment, yet should have requested an assignment and been granted
   one.

3.4.2.  Scope-relative IANA Assignment

   IANA also assigns numbers as an integer offset from the highest
   address in each IPv4 administrative scope as described in [RFC2365].
   For example, the SLPv2 discovery scope-relative offset is "2", so
   SLPv2 discovery address within IPv4 Local-Scope (239.255.0.0/16) is
   "239.255.255.253", within the IPv4 Organization Local-Scope
   (239.192.0.0/14) it is "239.195.255.253", and so on.

   Similar scope-relative assignments also exist with IPv6 [RFC2375].
   As IPv6 multicast addresses have much more flexible scoping, scope-
   relative assignments are also applicable to global scopes.  The
   assignment policies are described in [RFC3307].

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



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   (MADCAP) [RFC2730] as an example.  Since then, there has been a
   proposal for DHCPv6 assignment
   [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.  Creating a session (and obtaining an
   address) 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 would be
   needed to make dynamic 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.







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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  | Administratively scoped        |  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.
      Administratively scoped 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 generally an architecturally
      unacceptable approach.


















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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    |
      |  3.4.1 | Global IANA/RIR assignment     |LastResort|LastResort|
      |  3.4.2 | Scope-relative IANA assignment |  Yes     |   Yes    |
      |  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  Global IANA assignment has been done extensively in the past, but
      it needs to be tightened down to prevent problems caused by "land-
      grabbing".  Scope-relative IANA assignment is acceptable but the
      size of the pool is not very high.  Inter-domain routing of IPv6
      IANA-assigned prefixes is likely going to be challenging.

   o  Dynamic assignment, e.g., MADCAP has been implemented, but there
      is no wide deployment, so a solution is there.  However, either
      there are other gaps in the multicast architecture or there is no
      sufficient demand for it in the first place when manual and static
      IANA assignments are 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 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.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.




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   o  The IETF should consider whether to specify more ranges of the
      IPv4 administratively scoped 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,
   Jerome Durand, John Kristoff, and Dave Price 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 3.4.1.

   (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.



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   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., "A Method for Generating Link Scoped IPv6
              Multicast Addresses", 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", draft-ietf-ssm-arch-07 (work in progress),
              October 2005.

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




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   [I-D.ietf-mboned-addrdisc-problems]
              Savola, P., "Lightweight Multicast Address Discovery
              Problem Space", draft-ietf-mboned-addrdisc-problems-01
              (work in progress), November 2005.

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

   [I-D.ietf-mboned-rfc3171bis]
              Albanna, Z., Almeroth, K., Cotton, M., and D. Meyer, "IANA
              Guidelines for IPv4 Multicast 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",
              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",
              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.

   [RFC2375]  Hinden, R. and S. Deering, "IPv6 Multicast Address
              Assignments", RFC 2375, July 1998.

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

   [RFC2730]  Hanna, S., Patel, 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.



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

   [RFC2908]  Thaler, D., Handley, 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., and D. Thaler, "The Multicast Address-Set Claim
              (MASC) Protocol", RFC 2909, September 2000.

   [RFC2974]  Handley, M., Perkins, 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.,
              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/>.


Appendix A.  Changes

   (To be removed prior to publication as an RFC.)

A.1.  Changes since -01

   o  Mention the mechanisms which haven't been so succesful: eGLOP and
      MZAP.

   o  Remove the appendices on multicast address discovery (a separate
      draft now) and IPv4 unicast-prefix-based multicast addressing.

   o  Add a note on administraively scoped address space and the
      expansion ambiguity.

   o  Remove the references to draft-ietf-mboned-ipv6-issues-xx.txt

   o  Minor editorial cleanups.





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Author's Address

   Pekka Savola
   CSC - Scientific Computing Ltd.
   Espoo
   Finland

   Email: psavola@funet.fi











































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