Network Working Group                                          M. Cotton
Internet-Draft                                                     ICANN
Intended status: Best Current                                   D. Meyer
Practice                                                February 5, 2008
Expires: August 8, 2008
         IANA Guidelines for IPv4 Multicast Address Assignments
                   draft-cotton-v4mcast-guidelines-00
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Copyright Notice
   Copyright (C) The IETF Trust (2008).
Abstract
   This memo provides guidance for the Internet Assigned Numbers
   Authority (IANA) in assigning IPv4 multicast addresses.


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Table of Contents
   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Definition of Current Assignment Practice  . . . . . . . . . .  3
   4.  Local Network Control Block (224.0.0/24) . . . . . . . . . . .  4
     4.1.  Assignment Guidelines  . . . . . . . . . . . . . . . . . .  4
   5.  Internetwork Control Block (224.0.1/24)  . . . . . . . . . . .  4
     5.1.  Assignment Guidelines  . . . . . . . . . . . . . . . . . .  5
   6.  AD-HOC Blocks (including 224.0.2.0/24 - 224.0.255.0/24)  . . .  5
     6.1.  Assignment Guidelines  . . . . . . . . . . . . . . . . . .  5
   7.  SDP/SAP Block (224.2/16) . . . . . . . . . . . . . . . . . . .  5
     7.1.  Assignment Guidelines  . . . . . . . . . . . . . . . . . .  5
   8.  Source Specific Multicast Block (232/8)  . . . . . . . . . . .  5
     8.1.  Assignment Guidelines  . . . . . . . . . . . . . . . . . .  6
   9.  GLOP Block (233/8) . . . . . . . . . . . . . . . . . . . . . .  6
     9.1.  Assignment Guidelines  . . . . . . . . . . . . . . . . . .  6
     9.2.  Extended AD-HOC  . . . . . . . . . . . . . . . . . . . . .  6
   10. Administratively Scoped Address Block (239/8)  . . . . . . . .  6
     10.1. Assignment Guidelines  . . . . . . . . . . . . . . . . . .  7
   11. Application Form . . . . . . . . . . . . . . . . . . . . . . .  7
     11.1. Size of assignments of IPv4 Multicast Addresses  . . . . .  7
   12. Annual Review  . . . . . . . . . . . . . . . . . . . . . . . .  7
     12.1. Address Reclamation  . . . . . . . . . . . . . . . . . . .  8
     12.2. Positive renewal . . . . . . . . . . . . . . . . . . . . .  8
   13. Use of IANA Reserved Addresses . . . . . . . . . . . . . . . .  8
   14. IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   15. Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   16. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . .  8
   17. References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     17.1. Normative References . . . . . . . . . . . . . . . . . . .  9
     17.2. Informative References . . . . . . . . . . . . . . . . . .  9
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
   Intellectual Property and Copyright Statements . . . . . . . . . . 11





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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 [RFC2119].
   In general, due to the relatively small size of the IPv4 multicast
   address 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.  Terminology
   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in BCP 14, RFC 2119
   [RFC2119].
3.  Definition of Current Assignment Practice
   Unlike IPv4 unicast address assignment, where blocks of addresses are
   delegated to Regional Internet Registries (RIRs), IPv4 multicast
   addresses are assigned directly by the IANA.  Current registration
   groups appear as follows [IANA]:



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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      64769      AD-HOC Block
224.1.0.0   - 224.1.255.255    224.1/16   RESERVED
224.2.0.0   - 224.2.255.255    224.2/16   SDP/SAP Block
224.252.0.0 - 224.255.255.255  224.252/14 RESERVED
225.0.0.0   - 231.255.255.255  7 /8s      RESERVED
232.0.0.0   - 232.255.255.255  232/8     Source Specific Multicast Block
233.0.0.0   - 233.255.255.255  16515072   GLOP Block
233.252.0.0 - 233.255.255.255  233.252/14 AD-HOC Block
234.0.0.0   - 238.255.255.255  5 /8s      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.
4.  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].
4.1.  Assignment Guidelines
   Pursuant to section 4.4.2 of [RFC2780], assignments from the Local
   Network Control block follow an Expert Review, IESG Approval or
   Standards Action process.  See IANA [IANA] for the current set of
   assignments.
5.  Internetwork Control Block (224.0.1/24)
   Addresses in the Internetwork Control block are used for protocol

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   control that must be forwarded through the Internet.  Examples
   include 224.0.1.1 (NTP [RFC2030]) and 224.0.1.68 (mdhcpdiscover
   [RFC2730]).
5.1.  Assignment Guidelines
   Pursuant to section 4.4.2 of [RFC2780], assignments from the
   Internetwork Control block follow an Expert Review, IESG Approval or
   Standards Action process.  See IANA [IANA] for the current set of
   assignments.
6.  AD-HOC Blocks (including 224.0.2.0/24 - 224.0.255.0/24)
   Addresses in the AD-HOC blocks 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 ).
6.1.  Assignment Guidelines
   In general, the IANA SHOULD NOT assign addressing in the AD-HOC
   Block.  However, the IANA MAY under special circumstances, assign
   addresses from this block.  Pursuant to section 4.4.2 of [RFC2780],
   assignments from the AD-HOC block follow an Expert Review, IESG
   Approval or Standards Action process.  See IANA [IANA] for the
   current set of assignments.
7.  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]).
7.1.  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.
8.  Source Specific Multicast Block (232/8)
   The Source Specific Multicast (SSM) is an extension of IP Multicast

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   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 [IANA].
8.1.  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.
9.  GLOP Block (233/8)
   Addresses in the GLOP block are globally scoped statically assigned
   addresses.  The assignment is made, for a domain with 16 bit
   Autonomous System Number (ASN), by mapping a domain's autonomous the
   number, expressed in octets as X.Y, system number into the middle two
   octets of of the GLOP block, yielding an assignment of 233.X.Y.0/24.
   The mapping and assignment is defined in [RFC3180].  Domains with 32
   bit ASN should apply for space in the Extended AD-HOC block.
9.1.  Assignment Guidelines
   Because addresses in the GLOP block are algorithmically pre-assigned,
   no IANA assignment policy is required.
9.2.  Extended AD-HOC
   [RFC3138] delegated assignment of the GLOP sub-block mapped by the
   [RFC1930] private AS space (233.252.0.0 - 233.255.255.255) to the
   RIRs.  This space was known as eGLOP.  The RIRs did not develop
   policies or the mechanisms for the assignment of the eGLOP space and
   it is important to make this space available for use by network
   operators.  It is therefore appropriate to obsolete RFC 3138 and
   classify this address range as available for AD-HOC assignment as per
   the guidelines in section 5.
10.  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].

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10.1.  Assignment Guidelines
   Since addresses in this block are local to a domain, no IANA
   assignment policy is required.
10.1.1.  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
   [RFC3180] 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 [RFC2780], assignments of Relative Offsets follow an
   Expert Review, IESG Approval or Standards Action process.  See IANA
   [IANA] for the current set of assignments.
11.  Application Form
   Requests for multicast address assignments can be submitted through
   the application form on the IANA web site at:
   <http://www.iana.org/cgi-bin/multicast.pl>
   It is important to submit sufficient detail to allow the IESG
   designated expert to review the application.  If the details given in
   the request are not clear, or further information is needed, the IESG
   designated expert may request additional information before assigning
   an address.
11.1.  Size of assignments of IPv4 Multicast Addresses
   Occasionally, more than one multicast address is required.  In these
   cases multiple addresses are available.  Where are very large number
   of addresses is required, the assignment will be staged, with
   additional stages only being made after the complete use of the
   initial assignment(s).
12.  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.

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12.1.  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).
12.2.  Positive renewal
   It is occasionally appropriate to make temporary assignments that are
   can be renewed if appropriate.  In cases where this happens the
   registrant needs to positively request an extension to the temporary
   assignment or the addresses assigned.  When the IANA has not received
   a request to renew the registration of a temporary assignment within
   30 days of the expiry of the assignment it MUST be removed from the
   multicast registry.
   Addresses returned to the IANA when a temporary assignment ends MUST
   NOT be assigned for at least one calendar year.
13.  Use of IANA Reserved Addresses
   Applications MUST NOT use addressing in the IANA reserved blocks.
14.  IANA Considerations
   This document is all about IANA Considerations.
15.  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.
16.  Acknowledgments
   The authors would like to thank Joe St. Sauver, John Meylor, Randy
   Bush, Thomas Narten, Marshall Eubanks, Zaid Albanna (co-author of
   RFC3171), Kevin Almeroth (co-author of RFC3171) and Leo Vegoda for
   their constructive feedback and comments.

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17.  References
17.1.  Normative References
   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.
17.2.  Informative References
   [IANA]     IANA, "IANA Matrix for Protocol Parameter Assignment/
              Registration Procedures",
              <http://www.iana.org/numbers.html>.
   [RFC1190]  Casner, S., Lynn, C., Park, P., Schroder, K., and C.
              Topolcic, "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)",
              BCP 6, 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.
   [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

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              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.
   [RFC3180]  Meyer, D. and P. Lothberg, "GLOP Addressing in 233/8",
              BCP 53, RFC 3180, September 2001.
Authors' Addresses
   Michelle Cotton
   Internet Corporation for Assigned Names and Numbers
   4676 Admiralty Way, Suite 330
   Marina del Rey  90292
   United States
   Phone: +310-823-9358
   Email: michelle.cotton@icann.org
   URI:   http://www.iana.org/
   David Meyer
   Email: dmm@1-4-5.net






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Full Copyright Statement
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