    Network Working Group                                         Z. Albanna
    Request for Comments: 3171                              Juniper Networks
    BCP: 51                                                      K. Almeroth
    Category: Best Current Practice                                     UCSB
                                                                    D. Meyer
                                                                      Sprint
                                                                 M. Schipper
                                                                        IANA
                                                                 August 2001

             IANA Guidelines for IPv4 Multicast Address Assignments

    Status of this Memo

       This document specifies an Internet Best Current Practices for the
       Internet Community, and requests discussion and suggestions for
       improvements.  Distribution of this memo is unlimited.

    Copyright Notice

       Copyright (C) The Internet Society (2001).  All Rights Reserved.

    Abstract

       This memo provides guidance for the Internet Assigned Numbers
       Authority (IANA) in assigning IPv4 multicast addresses.

    1. Introduction

       The Internet Assigned Numbers Authority (IANA) (www.iana.org) is
       charged with allocating parameter values for fields in protocols
       which have been designed, created or are maintained by the Internet
       Engineering Task Force (IETF).  RFC 2780 [RFC2780] provides the IANA
       guidance in the assignment of parameters for fields in newly
       developed protocols.  This memo expands on section 4.4.2 of RFC 2780
       and attempts to codify existing IANA practice used in the assignment
       IPv4 multicast addresses.

       The terms "Specification Required", "Expert Review", "IESG Approval",
       "IETF Consensus", and "Standards Action", are used in this memo to
       refer to the processes described in [RFC2434].  The keywords MUST,
       MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED, SHALL, SHALL NOT,
       SHOULD, SHOULD NOT are to be interpreted as defined in RFC 2119
       [RFC2119].

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       In general, due to the relatively small size of the IPv4 multicast
       addresses space, further assignment of IPv4 multicast address space
       is recommended only in limited circumstances.  Specifically, the IANA
       should only assign addresses in those cases where the dynamic
       selection (SDP/SAP), GLOP, SSM or Administratively Scoped address
       spaces cannot be used.  The guidelines described below are reflected
       in http://www.iana.org/numbers.html.

    2. Definition of Current Assignment Practice

       Unlike IPv4 unicast address assignment, where blocks of addresses are
       delegated to regional registries, IPv4 multicast addresses are
       assigned directly by the IANA.  Current assignments appear as follows
       [IANA]:

       224.0.0.0   - 224.0.0.255     (224.0.0/24)  Local Network Control Block
       224.0.1.0   - 224.0.1.255     (224.0.1/24)  Internetwork Control Block
       224.0.2.0   - 224.0.255.0                   AD-HOC Block
       224.1.0.0   - 224.1.255.255   (224.1/16)    ST Multicast Groups
       224.2.0.0   - 224.2.255.255   (224.2/16)    SDP/SAP Block
       224.252.0.0 - 224.255.255.255               DIS Transient Block
       225.0.0.0   - 231.255.255.255               RESERVED
       232.0.0.0   - 232.255.255.255 (232/8)       Source Specific Multicast
                                                   Block
       233.0.0.0   - 233.255.255.255 (233/8)       GLOP Block
       234.0.0.0   - 238.255.255.255               RESERVED
       239.0.0.0   - 239.255.255.255 (239/8)       Administratively Scoped
                                                   Block

       The IANA generally assigns addresses from the Local Network Control,
       Internetwork Control, and AD-HOC blocks.  Assignment guidelines for
       each of these blocks, as well as for the Source Specific Multicast,
       GLOP and Administratively Scoped Blocks, are described below.

    3. Local Network Control Block (224.0.0/24)

       Addresses in the Local Network Control block are used for protocol
       control traffic that is not forwarded off link.  Examples of this
       type of use include OSPFIGP All Routers (224.0.0.5) [RFC2328].

    3.1. Assignment Guidelines

       Pursuant to section 4.4.2 of RFC 2780 [RFC2780], assignments from the
       Local Network Control block follow an Expert Review, IESG Approval or
       Standards Action process.  See [IANA] for the current set of
       assignments.

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    4. Internetwork Control Block (224.0.1/24)

       Addresses in the Internetwork Control block are used for protocol
       control that must be forwarded through the Internet.  Examples
       include 224.0.1.1 (NTP [RFC2030]) and 224.0.1.68 (mdhcpdiscover
       [RFC2730]).

    4.1. Assignment Guidelines

       Pursuant to section 4.4.2 of RFC 2780 [RFC2780], assignments from the
       Internetwork Control block follow an Expert Review, IESG Approval or
       Standards Action process.  See [IANA] for the current set of
       assignments.

    5. AD-HOC Block (224.0.2.0/24 - 224.0.255.0/24)

       Addresses in the AD-HOC block have traditionally been assigned for
       those applications that don't fit in either the Local or Internetwork
       Control blocks.  These addresses are globally routed and are
       typically used by applications that require small blocks of
       addressing (e.g., less than a /24).

    5.1. Assignment Guidelines

       In general, the IANA SHOULD NOT assign addressing in the AD-HOC
       Block.  However, the IANA may under special special circumstances,
       assign addressing from this block.  Pursuant to section 4.4.2 of RFC
       2780 [RFC2780], assignments from the AD-HOC block follow an Expert
       Review, IESG Approval or Standards Action process.  See [IANA] for
       the current set of assignments.

    6. SDP/SAP Block (224.2/16)

       Addresses in the SDP/SAP block are used by applications that receive
       addresses through the Session Announcement Protocol [RFC2974] for use
       via applications like the session directory tool (such as SDR [SDR]).

    6.1. Assignment Guidelines

       Since addresses in the SDP/SAP block are chosen randomly from the
       range of addresses not already in use [RFC2974], no IANA assignment
       policy is required.  Note that while no additional IANA assignment is
       required, addresses in the SDP/SAP block are explicitly for use by
       SDP/SAP and MUST NOT be used for other purposes.

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    7. Source Specific Multicast Block (232/8)

       The Source Specific Multicast (SSM) is an extension of IP Multicast
       in which traffic is forwarded to receivers from only those multicast
       sources for which the receivers have explicitly expressed interest,
       and is primarily targeted at one-to-many (broadcast) applications.
       Note that this block as initially assigned to the VMTP transient
       groups [IANA].

    7.1. Assignment Guidelines

       Because the SSM model essentially makes the entire multicast address
       space local to the host, no IANA assignment policy is required.
       Note, however, that while no additional IANA assignment is required,
       addresses in the SSM block are explicitly for use by SSM and MUST NOT
       be used for other purposes.

    8. GLOP Block (233/8)

       Addresses in the GLOP block are globally scoped statically assigned
       addresses.  The assignment is made by mapping a domain's autonomous
       system number into the middle two octets of 233.X.Y.0/24.  The
       mapping and assignment is defined in [RFC2770].

    8.1. Assignment Guidelines

       Because addresses in the GLOP block are algorithmically pre-assigned,
       no IANA assignment policy is required.  In addition, RFC 3138
       [RFC3138] delegates assignment of the GLOP sub-block mapped by the
       RFC 1930 [RFC1930] private AS space (233.252.0.0 - 233.255.255.255)
       to the Internet Routing Registries.  Note that while no additional
       IANA assignment is required, addresses in the GLOP  block are
       assigned for use as defined in RFC 2770 and MUST NOT be used for
       other purposes.

    9. Administratively Scoped Address Block (239/8)

       Addresses in the Administratively Scoped Address block are for local
       use within a domain and are described in [RFC2365].

    9.1. Assignment Guidelines

       Since addresses in this block are local to a domain, no IANA
       assignment policy is required.

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    9.1.1. Relative Offsets

       The relative offsets [RFC2365] are used to ensure that a service can
       be located independent of the extent of the enclosing scope (see RFC
       2770 for details).  Since there are only 256 such offsets, the IANA
       should only assign a relative offset to a protocol that provides an
       infrastructure supporting service.  Examples of such services include
       the Session Announcement Protocol [RFC2974].  Pursuant to section
       4.4.2 of RFC 2780 [RFC2780], assignments of Relative Offsets follow
       an Expert Review, IESG Approval or Standards Action process.  See
       [IANA] for the current set of assignments.

    10. Annual Review

       Given the dynamic nature of IPv4 multicast and its associated infra-
       structure, and the previously undocumented IPv4 multicast address
       assignment guidelines, the IANA should conduct an annual review of
       currently assigned addresses.

    10.1. Address Reclamation

       During the review described above, addresses that were mis-assigned
       should, where possible, be reclaimed or reassigned.

       The IANA should also review assignments in the AD-HOC, DIS Transient
       Groups, and ST Multicast Groups blocks and reclaim those addresses
       that are not in use on the global Internet (i.e, those applications
       which can use SSM, GLOP, or Administratively Scoped addressing, or
       are not globally routed).

    11. Use of IANA Reserved Addresses

       Applications MUST NOT use addressing in the IANA reserved blocks.

    12. Security Considerations

       The assignment guidelines described in this document do not alter the
       security properties of either the Any Source or Source Specific
       multicast service models.

    13. Acknowledgments

       The authors would like to thank Joe St. Sauver, John Meylor, Randy
       Bush, and Thomas Narten for their constructive feedback and comments.

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    14. Authors' Addresses

       Zaid Albanna
       1149 N. Mathilda Ave
       Sunnyvale, CA. 94089

       EMail: zaid@juniper.net

       Kevin Almeroth
       UC Santa Barbara
       Santa Barbara, CA.

       EMail: almeroth@cs.ucsb.edu

       David Meyer
       Sprint E|Solutions

       EMail: dmm@sprint.net

       Michelle Schipper
       IANA Administrator
       Internet Assigned Numbers Authority
       4676 Admiralty Way, Suite 330
       Marina del Rey, CA 90292

       EMail: iana@iana.org

    15. References

       [IANA]    http://www.iana.org/numbers.html

       [RFC1190] Topolcic, C., "Experimental Internet Stream Protocol,
                 Version 2 (ST-II)", RFC 1190, October 1990.

       [RFC1930] Hawkinson, J. and T. Bates, "Guidelines for creation,
                 selection, and registration of an Autonomous System (AS)",
                 RFC 1930, March 1996.

       [RFC2026] Bradner, S., "The Internet Standards Process -- Revision
                 3", BCP 9, RFC 2026, October 1996.

       [RFC2030] Mills, D., "Simple Network Time Protocol (SNTP) Version 4
                 for IPv4, IPv6 and OSI", RFC 2030, October 1996.

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    RFC 3171             IANA IPv4 Multicast Guidelines          August 2001

       [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
                 Requirement Levels", BCP 14, RFC 2119, March 1997.

       [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.

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

       [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
                 IANA Considerations Section in RFCs", BCP 26, RFC 2434,
                 October 1998.

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

       [RFC2770] Meyer, D. and P. Lothberg, "GLOP Addressing in 233/8", RFC
                 2770, February 2000.

       [RFC2780] Bradner, S. and V. Paxson, "IANA Allocation Guidelines For
                 Values In the Internet Protocol and Related Headers", BCP
                 37, RFC 2780, March 2000.

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

       [RFC2909] Thaler, D., Handley, M. and D. Estrin, "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.

       [SDR]     http://www-mice.cs.ucl.ac.uk/multimedia/software/

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    16. Full Copyright Statement

       Copyright (C) The Internet Society (2001).  All Rights Reserved.

       This document and translations of it may be copied and furnished to
       others, and derivative works that comment on or otherwise explain it
       or assist in its implementation may be prepared, copied, published
       and distributed, in whole or in part, without restriction of any
       kind, provided that the above copyright notice and this paragraph are
       included on all such copies and derivative works.  However, this
       document itself may not be modified in any way, such as by removing
       the copyright notice or references to the Internet Society or other
       Internet organizations, except as needed for the purpose of
       developing Internet standards in which case the procedures for
       copyrights defined in the Internet Standards process must be
       followed, or as required to translate it into languages other than
       English.

       The limited permissions granted above are perpetual and will not be
       revoked by the Internet Society or its successors or assigns.

       This document and the information contained herein is provided on an
       "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
       TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
       BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
       HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
       MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

    Acknowledgement

       Funding for the RFC Editor function is currently provided by the
       Internet Society.

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