Requirements for Signaling of Pre-Congestion Information in a Diffserv Domain
RFC 6663
Internet Engineering Task Force (IETF) G. Karagiannis
Request for Comments: 6663 University of Twente
Category: Informational T. Taylor
ISSN: 2070-1721 Huawei
K. Chan
Consultant
M. Menth
University of Tuebingen
P. Eardley
BT
July 2012
Requirements for Signaling of Pre-Congestion Information
in a Diffserv Domain
Abstract
Pre-Congestion Notification (PCN) is a means for protecting quality
of service for inelastic traffic admitted to a Diffserv domain. The
overall PCN architecture is described in RFC 5559. This memo
describes the requirements for the signaling applied within the PCN-
domain: (1) PCN-feedback-information is carried from the PCN-egress-
node to the Decision Point; (2) the Decision Point may ask the PCN-
ingress-node to measure, and report back, the rate of sent PCN-
traffic between that PCN-ingress-node and PCN-egress-node. The
Decision Point may be either collocated with the PCN-ingress-node or
a centralized node (in the first case, (2) is not required). The
signaling requirements pertain in particular to two edge behaviors,
Controlled Load (CL) and Single Marking (SM).
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6663.
Karagiannis, et al. Informational [Page 1]
RFC 6663 PCN Signaling Requirements July 2012
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Table of Contents
1. Introduction ....................................................2
1.1. Requirements Language ......................................3
2. Signaling Requirements for Messages from the PCN-Egress-Nodes
to Decision Point(s) ............................................3
3. Signaling Requirements for Messages between Decision Point(s)
and PCN-Ingress-Nodes ...........................................5
4. Security Considerations .........................................5
5. Acknowledgments .................................................6
6. References ......................................................6
6.1. Normative References .......................................6
6.2. Informative References .....................................6
1. Introduction
The main objective of Pre-Congestion Notification (PCN) is to support
the quality of service (QoS) of inelastic flows within a Diffserv
domain in a simple, scalable, and robust fashion. Two mechanisms are
used: admission control and flow termination. Admission control is
used to decide whether to admit or block a new flow request, while
flow termination is used in abnormal circumstances to decide whether
to terminate some of the existing flows. To support these two
features, the overall rate of PCN-traffic is metered on every link in
the domain, and PCN-packets are appropriately marked when certain
configured rates are exceeded. These configured rates are below the
rate of the link, thus providing notification to boundary nodes about
overloads before any congestion occurs (hence "pre-congestion"
notification). The PCN-egress-nodes measure the rates of differently
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