PCN 3-State Encoding Extension in a single DSCP

Document Type Replaced Internet-Draft (individual)
Last updated 2009-12-14 (latest revision 2008-10-27)
Replaced by RFC 6660
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


Pre-congestion notification (PCN) is a mechanism designed to protect the quality of service of inelastic flows. It does this by marking packets when traffic load on a link is approaching or has exceeded a threshold below the physical link rate. This document specifies an extension to the two-state PCN baseline encoding that enables three encoding states to be carried in the IP header without using more than one Diffserv codepoint. It presupposes a standards action has removed the limit of two encoding states in current tunnelling mechanisms.


Bob Briscoe (bob.briscoe@bt.com)

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)