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Versions: (RFC 3171) 00 01 02 03 04 05 06 07 08 RFC 5771

INTERNET-DRAFT                                    Z. Albanna
draft-ietf-mboned-rfc3171bis-02.txt              K. Almeroth
                                                   M. Cotton
                                                    D. Meyer
Category                               Best Current Practice
Expires: September 2004                           March 2004

         IANA Guidelines for IPv4 Multicast Address Assignments
                 <draft-ietf-mboned-rfc3171bis-02.txt>



Status of this Document

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
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   This document is a product of the ABC working group.  Comments should
   be addressed to the authors, or the mailing list at

Copyright Notice

   Copyright (C) The Internet Society (2004). All Rights Reserved.








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                                Abstract


   The Internet Assigned Numbers Authority is charged with allocating
   parameter values for fields in protocols which have been designed,
   created or are maintained by the Internet Engineering Task Force.
   This document provides guidelines for the assignment of the IPv4 IP
   multicast address space.











































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                           Table of Contents


   1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . .   4
   2. Definition of Current Assignment Practice. . . . . . . . . . .   4
   3. Local Network Control Block (224.0.0/24) . . . . . . . . . . .   5
    3.1. Assignment Guidelines . . . . . . . . . . . . . . . . . . .   5
   4. Internetwork Control Block (224.0.1/24). . . . . . . . . . . .   5
    4.1. Assignment Guidelines . . . . . . . . . . . . . . . . . . .   5
   5. AD-HOC Block (224.0.2/24 - 224.0.255/24) . . . . . . . . . . .   5
    5.1. Assignment Guidelines . . . . . . . . . . . . . . . . . . .   6
   6. SDP/SAP Block (224.2/16) . . . . . . . . . . . . . . . . . . .   6
    6.1. Assignment Guidelines . . . . . . . . . . . . . . . . . . .   6
   7. Source Specific Multicast Block (232/8). . . . . . . . . . . .   6
    7.1. Assignment Guidelines . . . . . . . . . . . . . . . . . . .   6
   8. GLOP Block (233/8) . . . . . . . . . . . . . . . . . . . . . .   7
    8.1. Assignment Guidelines . . . . . . . . . . . . . . . . . . .   7
   9. Administratively Scoped Address Block (239/8). . . . . . . . .   7
    9.1. Assignment Guidelines . . . . . . . . . . . . . . . . . . .   7
     9.1.1. Relative Offsets . . . . . . . . . . . . . . . . . . . .   8
   10. Annual Review . . . . . . . . . . . . . . . . . . . . . . . .   8
    10.1. Address Reclamation. . . . . . . . . . . . . . . . . . . .   8
   11. Usable IPv4 Multicast Addresses . . . . . . . . . . . . . . .   8
    11.1. IGMP-snooping switches . . . . . . . . . . . . . . . . . .   9
    11.2. Unusable Inter-domain Groups . . . . . . . . . . . . . . .   9
     11.2.1. Administratively Scoped Addresses . . . . . . . . . . .   9
     11.2.2. Special Use IPv4 Source Addresses . . . . . . . . . . .  10
   12. Use of IANA Reserved Addresses. . . . . . . . . . . . . . . .  10
   13. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  10
   15. Security Considerations . . . . . . . . . . . . . . . . . . .  11
   16. Normative References. . . . . . . . . . . . . . . . . . . . .  12
   17. Informative References. . . . . . . . . . . . . . . . . . . .  12
   18. Author's Addresses. . . . . . . . . . . . . . . . . . . . . .  13
   19. Full Copyright Statement. . . . . . . . . . . . . . . . . . .  13
   20. Intellectual Property . . . . . . . . . . . . . . . . . . . .  14
   21. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .  14














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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 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 RFC 2119 [RFC 2119].



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)    RESERVED
   224.2.0.0   - 224.2.255.255   (224.2/16)    SDP/SAP Block
   224.3.0.0   - 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.









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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.



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 (224.0.2/24 - 224.0.255/24)


   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).





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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.



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



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   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
   infrastructure, 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 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.  Usable IPv4 Multicast Addresses


   Multicast datagrams that match the criteria in this section SHOULD
   NOT be used, even on local, unrouted subnetworks.








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11.1.  IGMP-snooping switches


   RFC 1112 [RFC1112] describes the mapping of IPv4 Multicast Group
   addresses to Ethernet MAC addresses, as follows:

     An IP host group address is mapped to an Ethernet multicast
     address by placing the low-order 23-bits of the IP address into
     the low-order 23 bits of the Ethernet multicast address
     01-00-5E-00-00-00 (hex).   Because there are 28 significant bits
     in an IP host group address, more than one host group address
     may map to the same Ethernet multicast address.

   Now, note that multicast group addresses in the 224.0.0.0/24 range
   are used for local subnetwork control (see section 3 above). Under
   the RFC 1112 mapping, this maps to the Ethernet multicast address
   range 01-00-5E-00-00-XX, where XX is 00 through FF. Ethernet frames
   within this range are always processed in the control plane of many
   popular network devices, such as IGMP-snooping switches.

   Because of the many-to-one mapping of IPv4 Multicast Group Addresses
   to Ethernet MAC addresses, it is possible to overwhelm the control
   plane of network devices by sending to group addresses that map into
   the 01-00-5E-00-00-XX (hex) range.

   IGMP-snooping network devices must also flood these frames to all
   outgoing ports, so the damage may extend to end systems and routers.



11.2.  Unusable Inter-domain Groups


   Multicast datagrams that match the criteria in this section SHOULD
   NOT be routed between administrative domains.



11.2.1.  Administratively Scoped Addresses


   RFC 2365 [RFC2365] defines 239.0.0.0/8 for use within an
   administrative domain.  As such, datagrams with group addresses that
   match 239.0.0.0/8 SHOULD NOT be passed between administrative
   domains.






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11.2.2.  Special Use IPv4 Source Addresses



   RFC 1918 [RFC1918] defines certain ranges of IPv4 unicast addresses
   that can be used within an administrative domain.  Multicast
   datagrams are no exception to the rule that datagrams addressed
   within these ranges SHOULD NOT be passed between administrative
   domains. Examples include 127.0.0.0/8, which is widely used for
   internal host addressing, and is generally not valid on datagrams
   passed between hosts. 0.0.0.0/8 and 169.254.0.0/16 are also valid
   only in the context of local links.  Such source addresses are not
   valid for datagrams passed between networks[RFC330]. Finally
   192.0.2.0/24 is reserved for documentation and example code.
   [RFC3330].



12.  Use of IANA Reserved Addresses


   Applications MUST NOT use addressing in the IANA reserved blocks.



13.  IANA Considerations


   This document provides guidelines for the IANA to use in assigning
   IPv4 multicast addresses. It does not create any new namespaces for
   the IANA to manage [RFC2434].



14.  Acknowledgments


   The authors would like to thank Scott Bradner, Randy Bush, John
   Meylor, Thomas Narten, Joe St. Sauver, and Beau Williamson for their
   constructive feedback and comments. Bill Nickless contributed the
   text in section 11 describing IPv4 multicast unusable group and
   source addresses.









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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.













































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16.  Normative References


   [RFC1112]       Deering, S., "Host extensions for IP
                   multicasting", RFC 1112, August, 1989.

   [RFC1918]       Rekhter, Y. et. al., "Address Allocation for
                   Private Internets", RFC 1918, February, 1996.

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

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

   [RFC3330]       IANA, "Special-Use IPv4 Addresses", RFC 3330,
                   September, 2002.




17.  Informative References


   [IANA]          http://www.iana.org/assignments/multicast-addresses

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

   [RFC2028]       Hovey, R. and S. Bradner, "The Organizations
                   Involved in the IETF Standards Process", RFC
                   2028/BCP 11, October, 1996.

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














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18.  Author's Addresses



   Zaid Albanna
   Email: zaid@juniper.net

   Kevin Almeroth
   Email: almeroth@cs.ucsb.edu

   David Meyer
   Email: dmm@1-4-5.net

   Michelle S. Cotton
   Email: iana@iana.org



19.  Full Copyright Statement

   Copyright (C) The Internet Society (2004). This document is subject
   to the rights, licenses and restrictions contained in BCP 78 and
   except as set forth therein, the authors retain all their rights.


   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.



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20.  Intellectual Property


   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
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   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
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   this standard.  Please address the information to the IETF at ietf-
   ipr@ietf.org.


21.  Acknowledgement


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




















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