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rfc:rfc3171

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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