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<pre>Network Working Group D. Meyer
Request for Comments: 3180 P. Lothberg
Obsoletes: <a href="./rfc2770">2770</a> Sprint
BCP: 53 September 2001
Category: Best Current Practice
<span class="h1">GLOP Addressing in 233/8</span>
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.
<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>. Introduction</span>
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 [<a href="#ref-IANA">IANA</a>] (e.g., [<a href="./rfc2365" title=""Administratively Scoped IP Multicast"">RFC2365</a>]). The IANA has allocated 223/8 as per <a href="./rfc2770">RFC</a>
<a href="./rfc2770">2770</a> [<a href="./rfc2770" title=""GLOP Addressing in 233/8"">RFC2770</a>]. This document obsoletes <a href="./rfc2770">RFC 2770</a>.
<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>. Problem Statement</span>
Multicast addresses have traditionally been allocated by a dynamic
mechanism such as SDR [<a href="./rfc2974" title=""Session Announcement Protocol"">RFC2974</a>]. 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 [<a href="./rfc2974" title=""Session Announcement Protocol"">RFC2974</a>]. 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.
<span class="grey">Meyer & Lothberg Best Current Practice [Page 1]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-2" ></span>
<span class="grey"><a href="./rfc3180">RFC 3180</a> GLOP Addressing in 233/8 September 2001</span>
The MALLOC working group has created a specific strategy for global
multicast address allocation [RFC2730, <a href="./rfc2909">RFC2909</a>]. 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.
<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>. Address Space</span>
The IANA has allocated 223/8 as per <a href="./rfc2770">RFC 2770</a> [<a href="./rfc2770" title=""GLOP Addressing in 233/8"">RFC2770</a>]. <a href="./rfc2770">RFC 2770</a>
describes the administration of the middle two octets of 233/8 in a
manner similar to that described in <a href="./rfc1797">RFC 1797</a>:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
<span class="h3"><a class="selflink" id="section-3.1" href="#section-3.1">3.1</a>. Example</span>
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.
<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>. Allocation</span>
As mentioned above, the allocation proposed here follows the <a href="./rfc1797">RFC 1797</a>
(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 <a href="./rfc1797">RFC 1797</a>, 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.
<span class="h3"><a class="selflink" id="section-4.1" href="#section-4.1">4.1</a>. Private AS Space</span>
The part of 233/8 that is mapped to the private AS space [<a href="./rfc1930" title=""Guidelines for creation, selection, and registration of an Autonomous System (AS)"">RFC1930</a>] is
assigned to the IRRs [<a href="./rfc3138" title=""Extended Assignments in 233/8"">RFC3138</a>].
<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>. Large AS Numbers</span>
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.
<span class="grey">Meyer & Lothberg Best Current Practice [Page 2]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-3" ></span>
<span class="grey"><a href="./rfc3180">RFC 3180</a> GLOP Addressing in 233/8 September 2001</span>
<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>. Security Considerations</span>
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.
<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>. IANA Considerations</span>
The IANA has assigned 233/8 for this purpose.
<span class="h2"><a class="selflink" id="section-8" href="#section-8">8</a>. Acknowledgments</span>
This proposal originated with Peter Lothberg's idea that we use the
same allocation (AS based) as described in <a href="./rfc1797">RFC 1797</a>. Randy Bush and
Mark Handley contributed many insightful comments, and Pete and
Natalie Whiting contributed greatly to the readability of this
document.
<span class="h2"><a class="selflink" id="section-9" href="#section-9">9</a>. References</span>
[<a id="ref-IANA">IANA</a>] <a href="http://www.iana.org/numbers.html">http://www.iana.org/numbers.html</a>
[<a id="ref-RFC1797">RFC1797</a>] IANA, "Class A Subnet Experiment", <a href="./rfc1797">RFC 1797</a>, April 1995.
[<a id="ref-RFC1930">RFC1930</a>] Hawkinson, J. and T. Bates, "Guidelines for creation,
selection, and registration of an Autonomous System (AS)",
<a href="./rfc1930">RFC 1930</a>, March 1996.
[<a id="ref-RFC2365">RFC2365</a>] Meyer, D., "Administratively Scoped IP Multicast", <a href="./rfc2365">RFC</a>
<a href="./rfc2365">2365</a>, July 1998.
[<a id="ref-RFC2374">RFC2374</a>] Hinden, R., O'Dell, M. and S. Deering, "An IPv6
Aggregatable Global Unicast Address Format", <a href="./rfc2374">RFC 2374</a>, July
1998.
[<a id="ref-RFC2730">RFC2730</a>] Hanna, S., Patel, B. and M. Shah, "Multicast Address
Dynamic Client Allocation Protocol (MADCAP)", <a href="./rfc2730">RFC 2730</a>,
December 1999.
[<a id="ref-RFC2770">RFC2770</a>] Meyer, D. and P. Lothberg, "GLOP Addressing in 233/8", <a href="./rfc2770">RFC</a>
<a href="./rfc2770">2770</a>, February 2000.
[<a id="ref-RFC2909">RFC2909</a>] Radoslavov, P., Estrin, D., Govindan, R., Handley, M.,
Kumar, S. and D. Thaler, "The Multicast Address-Set Claim
(MASC) Protocol", <a href="./rfc2909">RFC 2909</a>, September 2000.
<span class="grey">Meyer & Lothberg Best Current Practice [Page 3]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-4" ></span>
<span class="grey"><a href="./rfc3180">RFC 3180</a> GLOP Addressing in 233/8 September 2001</span>
[<a id="ref-RFC2974">RFC2974</a>] Handley, M., Perkins, C. and E. Whelan, "Session
Announcement Protocol", <a href="./rfc2974">RFC 2974</a>, October 2000.
[<a id="ref-RFC3138">RFC3138</a>] Meyer, D., "Extended Assignments in 233/8", <a href="./rfc3138">RFC 3138</a>, June
2001.
<span class="h2"><a class="selflink" id="section-10" href="#section-10">10</a>. Authors' Addresses</span>
David Meyer
Sprint
VARESA0104
12502 Sunrise Valley Drive
Reston VA, 20196
EMail: dmm@sprint.net
Peter Lothberg
Sprint
VARESA0104
12502 Sunrise Valley Drive
Reston VA, 20196
EMail: roll@sprint.net
<span class="grey">Meyer & Lothberg Best Current Practice [Page 4]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-5" ></span>
<span class="grey"><a href="./rfc3180">RFC 3180</a> GLOP Addressing in 233/8 September 2001</span>
<span class="h2"><a class="selflink" id="section-11" href="#section-11">11</a>. Full Copyright Statement</span>
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.
Meyer & Lothberg Best Current Practice [Page 5]
</pre>
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