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Network Working Group                                         Z. AlbannaRequest for Comments: 3171                              Juniper NetworksBCP: 51                                                      K. AlmerothCategory: Best Current Practice                                     UCSB                                                                D. Meyer                                                                  Sprint                                                             M. Schipper                                                                    IANA                                                             August 2001IANA Guidelines for IPv4 Multicast Address AssignmentsStatus 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 onsection 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 inRFC 2119   [RFC2119].Albanna, et al.          Best Current Practice                  [Page 1]

RFC 3171             IANA IPv4 Multicast Guidelines          August 2001   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   inhttp://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 tosection 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.Albanna, et al.          Best Current Practice                  [Page 2]

RFC 3171             IANA IPv4 Multicast Guidelines          August 20014. 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 tosection 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 ofRFC2780 [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.Albanna, et al.          Best Current Practice                  [Page 3]

RFC 3171             IANA IPv4 Multicast Guidelines          August 20017. 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 theRFC 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 inRFC 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.Albanna, et al.          Best Current Practice                  [Page 4]

RFC 3171             IANA IPv4 Multicast Guidelines          August 20019.1.1. Relative Offsets   The relative offsets [RFC2365] are used to ensure that a service can   be located independent of the extent of the enclosing scope (seeRFC2770 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 tosection4.4.2 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.Albanna, et al.          Best Current Practice                  [Page 5]

RFC 3171             IANA IPv4 Multicast Guidelines          August 200114. 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.org15. 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.Albanna, et al.          Best Current Practice                  [Page 6]

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",RFC2770, February 2000.   [RFC2780] Bradner, S. and V. Paxson, "IANA Allocation Guidelines For             Values In the Internet Protocol and Related Headers",BCP37,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/Albanna, et al.          Best Current Practice                  [Page 7]

RFC 3171             IANA IPv4 Multicast Guidelines          August 200116. 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.Albanna, et al.          Best Current Practice                  [Page 8]