Network Working Group D. Meyer Request for Comments: 3180 P. Lothberg Obsoletes: 2770 Sprint BCP: 53 September 2001 Category: Best Current Practice GLOP Addressing in 233/8 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 document defines the policy for the use of 233/8 for statically assigned multicast addresses. 1. Introduction It is envisioned that the primary use of this space will be many-to- many applications. This allocation is in addition to those described on [IANA] (e.g., [RFC2365]). The IANA has allocated 223/8 as per RFC 2770 [RFC2770]. This document obsoletes RFC 2770. 2. Problem Statement Multicast addresses have traditionally been allocated by a dynamic mechanism such as SDR [RFC2974]. However, many current multicast deployment models are not amenable to dynamic allocation. For example, many content aggregators require group addresses that are fixed on a time scale that is not amenable to allocation by a mechanism such as described in [RFC2974]. Perhaps more seriously, since there is not general consensus by providers, content aggregators, or application writers as to the allocation mechanism, the Internet is left without a coherent multicast address allocation scheme.
The MALLOC working group has created a specific strategy for global multicast address allocation [RFC2730, RFC2909]. However, this approach has not been widely implemented or deployed. This document proposes a solution for a subset of the problem, namely, those cases not covered by Source Specific Multicast. 3. Address Space The IANA has allocated 223/8 as per RFC 2770 [RFC2770]. RFC 2770 describes the administration of the middle two octets of 233/8 in a manner similar to that described in RFC 1797: 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 233 | 16 bits AS | local bits | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3.1. Example Consider, for example, AS 5662. Written in binary, left padded with 0s, we get 0001011000011110. Mapping the high order octet to the second octet of the address, and the low order octet to the third octet, we get 233.22.30/24. 4. Allocation As mentioned above, the allocation proposed here follows the RFC 1797 (case 1) allocation scheme, modified as follows: the high-order octet has the value 233, and the next 16 bits are a previously assigned Autonomous System number (AS), as registered by a network registry and listed in the RWhois database system. This allows a single /24 per AS. As was the case with RFC 1797, using the AS number in this way allows automatic assignment of a single /24 to each service provider and does not require an additional registration step. 4.1. Private AS Space The part of 233/8 that is mapped to the private AS space [RFC1930] is assigned to the IRRs [RFC3138]. 5. Large AS Numbers It is important to note that this approach will work only for two octet AS numbers. In particular, it does not work for any AS number extension scheme.
6. Security Considerations The approach described here may have the effect of reduced exposure to denial-of-service attacks based on dynamic allocation. Further, since dynamic assignment does not cross domain boundaries, well-known intra-domain security techniques can be applied. 7. IANA Considerations The IANA has assigned 233/8 for this purpose. 8. Acknowledgments This proposal originated with Peter Lothberg's idea that we use the same allocation (AS based) as described in RFC 1797. Randy Bush and Mark Handley contributed many insightful comments, and Pete and Natalie Whiting contributed greatly to the readability of this document. 9. References [IANA] http://www.iana.org/numbers.html [RFC1797] IANA, "Class A Subnet Experiment", RFC 1797, April 1995. [RFC1930] Hawkinson, J. and T. Bates, "Guidelines for creation, selection, and registration of an Autonomous System (AS)", RFC 1930, March 1996. [RFC2365] Meyer, D., "Administratively Scoped IP Multicast", RFC 2365, July 1998. [RFC2374] Hinden, R., O'Dell, M. and S. Deering, "An IPv6 Aggregatable Global Unicast Address Format", RFC 2374, July 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. [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. 10. Authors' Addresses David Meyer Sprint VARESA0104 12502 Sunrise Valley Drive Reston VA, 20196 EMail: firstname.lastname@example.org Peter Lothberg Sprint VARESA0104 12502 Sunrise Valley Drive Reston VA, 20196 EMail: email@example.com
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