Network Working Group D. Meyer
Request for Comments: 2770 Cisco Systems
Category: EXPerimental P. Lothberg
Sprint
February 2000
GLOP Addressing in 233/8
Status of this Memo
This memo defines an Experimental Protocol for the Internet
community. It does not specify an Internet standard of any kind.
Discussion and suggestions for improvement are requested.
Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2000). All Rights Reserved.
Abstract
This describes an experimental policy for use of the class D address
space using 233/8 as the experimental statically assigned subset of
the class D address space. This new experimental allocation is in
addition to those described on [IANA] (e.g. [RFC2365]).
This memo is a prodUCt of the Multicast Deployment Working Group
(MBONED) in the Operations and Management Area of the Internet
Engineering Task Force. Submit comments to <mboned@ns.uoregon.edu> or
the authors.
1. Problem Statement
Multicast addresses have traditionally been allocated by a dynamic
mechanism such as SDR [SAP]. However, many current multicast
deployment models are not amenable to dynamic allocation. For
example, many content aggregators require group addresses which are
fixed on a time scale which is not amenable to allocation by a
mechanism such as described in [SAP]. Perhaps more seriously, since
there isn"t 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 is looking at a specific strategy for global
multicast address allocation [MADCAP, MASC]. This experiment will
proceed in parallel. MADCAP may be employed within AS"s, if so
desired.
This document proposes an experimental method of statically
allocating multicast addresses with global scope. This experiment
will last for a period of one year, but may be extended as described
in section 6.
2. Address Space
For purposes of the experiment described here, the IANA has allocated
233/8. The remaining 24 bits will be administered in a manner similar
to that described in RFC1797:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2.1. 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.
3. Allocation
As mentioned above, the allocation proposed here follows the RFC1797
(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 RFC1797, using the AS number in this way allows
the experiment to get underway quickly in that it automatically
allocates some addresses to each service provider and does not
require a registration step.
3.1. Private AS Space
The address space mapped to the private AS space [RFC1930] is
reserved for future allocation.
4. Transition from GLOP to Other Address Allocation Schemes
It may not be necessary to transition from the address allocation
scheme described here to a more dynamic approach (see, e.g., [MASC]).
The reasoning here is that the statically assigned addresses taken
from 233/8 may be sufficient for those applications which must have
static addressing, and any other addressing can come from either a
dynamic mechanism such as [MASC], the administratively scoped address
space [RFC2365], or the Single-source address space [SS].
5. Security Considerations
The approach described here may have the effect of reduced exposure
to denial of space attacks based on dynamic allocation. Further,
since dynamic assignment does not cross domain boundaries, well known
intra-domain security techniques can be applied.
6. IANA Considerations
IANA has allocated 233/8 for experimental assignments. This
assignment should timeout one year after the assignment is made. The
assignment may be renewed at that time. It should be noted that the
experiment described here is in the same spirit the experiment
described in [RFC1797].
7. Acknowledgments
This idea originated with Peter Lothberg"s idea that we use the same
allocation (AS based) as described in RFC1797 in the class D address
space. Randy Bush and Mark Handley contributed many insightful
comments.
8. References
[RFC2730] Hanna, S., Patel, B. and M. Shah, "Multicast Address
Dynamic Client Allocation Protocol (MADCAP)", RFC2730,
December 1999.
[MASC] D. Estrin, et al., "The Multicast Address-Set Claim (MASC)
Protocol", Work in Progress.
[MSDP] D. Farinacci et al., "Multicast Source Discovery Protocol
(MSDP)", Work in Progress.
[IANA] www.isi.edu/in-notes/iana/assignments/multicast-addresses
[RFC1797] IANA, "Class A Subnet Experiment", RFC1797, April 1995.
[RFC1930] Hawkinson, J. and T. Bates, "Guidelines for creation,
selection, and registration of an Autonomous System (AS)",
RFC1930, 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", RFC2374, July
1998.
[SAP] Handley, M., "SAP: Session Announcement Protocol", Work in
Progress.
[SS] www.isi.edu/in-notes/iana/assignments/single-source-
multicast
9. Authors" Addresses
David Meyer
Cisco Systems, Inc.
170 W. Tasman Drive
San Jose, CA 95134-1706
United States
EMail: dmm@cisco.com
Peter Lothberg
Sprint
VARESA0104
12502 Sunrise Valley Drive
Reston VA, 20196
EMail: roll@sprint.net
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