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].
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 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. Albanna, et al. Best Current Practice [Page 2]
RFC 3171 IANA IPv4 Multicast Guidelines August 2001 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. Albanna, et al. Best Current Practice [Page 3]
RFC 3171 IANA IPv4 Multicast Guidelines August 2001 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. Albanna, et al. Best Current Practice [Page 4]
RFC 3171 IANA IPv4 Multicast Guidelines August 2001 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. Albanna, et al. Best Current Practice [Page 5]
RFC 3171 IANA IPv4 Multicast Guidelines August 2001 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. 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", 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/ Albanna, et al. Best Current Practice [Page 7]
RFC 3171 IANA IPv4 Multicast Guidelines August 2001 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. Albanna, et al. Best Current Practice [Page 8]
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