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INTERNET-DRAFT J. Hawkinson
draft-ietf-mboned-pruning-02.txt BBN Planet
Category: Best Current Practice 30 July 1997
Multicast pruning a necessity
Status of this Memo
This document specifies a Best Current Practice for the Internet
Community, and requests discussion and suggestions for improvements.
Distribution of this memo is unlimited.
Internet Drafts
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
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ftp.isi.edu (US West Coast).
Abstract
This document calls for the MBone to be free of non-pruning multicast
as soon as possible, due to the high cost to the Internet of the
traffic resulting from them. Consensus is that [DATE 1 month from RFC
publication] is the goal date for elimating non-pruning multicast
routers.
It cites several ways to eliminate non-pruning multicast from a
network, allowing per-site flexibility.
This is a product of the Multicast Deployment Working Group in the
Operational Requirements area of the Internet Engineering Task Force.
Submit comments to <mboned@ns.uoregon.edu> or the author.
Discussion
The MBone (Multicast Backbone) of the Internet is composed of a DVMRP
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backbone connected to regions that may be running other multicast
routing protocols.
DVMRP versions prior to 3 do not support pruning. Every multicast
packet transmitted is delivered to every non-pruning router (subject
to scoping rules), regardless of the presence of members of that
group. Network paths between each source and each non-pruning router
are thus forced to carry all multicast traffic from those sources.
This behavior is fundamentally incompatible with a scalable multicast
backbone.
Effective [DATE], the MBone community will no longer accept such
non-pruning implementations as a part of the MBone. Such
implementations should be upgraded or disconnected from the MBone
prior to that date. Service providers should assist their customers
in these processes.
DVMRP implementations that do not support pruning include mrouted
versions prior to 3, and Cisco Systems IOS prior to version 11.0(3).
3Com's NETBuilder routers and LANplex switches have supported pruning
as long as DVMRP has been available for them (releases 8.3 and 7.0,
respectively). Bay Networks' implementation supports pruning in
version 9.00 and up.
In the case where the existing infrastructure cannot be upgraded to
support pruning, sites may wish to consider deploying lightweight
multicast routers instead. For instance, popular free unixes (e.g.
FreeBSD, NetBSD, and Linux) that run on cheap PC hardware all support
pruning multicast using mrouted.
Within non-DVMRP regions, software that does not support DVMRP
pruning but does support a similar mechanism of a different protocol
(such as CBT, MOSPF, or PIM) is acceptable, as long as the border
routers of such a region can translate that mechansism into DVMRP
pruning.
Security Considerations
Security considerations are not addressed in this memo.
References
[IPMULTI] S.E. Deering, "Host extensions for IP multicasting", RFC1112,
1 August 1989.
[MREQ] R. Braudes, S. Zabele, "Requirements for Multicast Protocols",
RFC1458, 26 May 1993.
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[DVMRP] T. Pusateri, "Distance Vector Multicast Routing Protocol",
Work in progress (internet-draft).
Author's Address
John Hawkinson
BBN Planet
150 CambridgePark Drive
Cambridge, MA 02140
phone: +1 617 873 3180
email: jhawk@bbnplanet.com
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