Requirements for Signaling of Pre-Congestion Information in a Diffserv Domain
RFC 6663

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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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   document authors.  All rights reserved.

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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