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RFC 6660
Title: Encoding Three Pre-Congestion Notification (PCN)
States in the IP Header Using
a Single Diffserv Codepoint (DSCP)
Author: B. Briscoe, T. Moncaster,
M. Menth
Status: Standards Track
Stream: IETF
Date: July 2012
Mailbox: bob.briscoe@bt.com,
toby.moncaster@cl.cam.ac.uk,
menth@uni-tuebingen.de
Pages: 24
Characters: 52230
Obsoletes: RFC5696
I-D Tag: draft-ietf-pcn-3-in-1-encoding-11.txt
URL: http://www.rfc-editor.org/rfc/rfc6660.txt
The objective of Pre-Congestion Notification (PCN) is to protect the
quality of service (QoS) of inelastic flows within a Diffserv domain.
The overall rate of PCN-traffic is metered on every link in the PCN-
domain, and PCN-packets are appropriately marked when certain
configured rates are exceeded. Egress nodes pass information about
these PCN-marks to Decision Points that then decide whether to admit
or block new flow requests or to terminate some already admitted
flows during serious pre-congestion.
This document specifies how PCN-marks are to be encoded into the IP
header by reusing the Explicit Congestion Notification (ECN)
codepoints within a PCN-domain. The PCN wire protocol for non-IP
protocol headers will need to be defined elsewhere. Nonetheless,
this document clarifies the PCN encoding for MPLS in an informational
appendix. The encoding for IP provides for up to three different PCN
marking states using a single Diffserv codepoint (DSCP): not-marked
(NM), threshold-marked (ThM), and excess-traffic-marked (ETM).
Hence, it is called the 3-in-1 PCN encoding. This document obsoletes
RFC 5696. [STANDARDS-TRACK]
This document is a product of the Congestion and Pre-Congestion Notification Working Group of the IETF.
This is now a Proposed Standard Protocol.
STANDARDS TRACK: This document specifies an Internet standards track
protocol for the Internet community,and requests discussion and suggestions
for improvements. Please refer to the current edition of the Internet
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