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Pre-Congestion Notification (PCN) Architecture
RFC 5559

Network Working Group                                    P. Eardley, Ed.
Request for Comments: 5559                                            BT
Category: Informational                                        June 2009

             Pre-Congestion Notification (PCN) Architecture

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Abstract

   This document describes a general architecture for flow admission and
   termination based on pre-congestion information in order to protect
   the quality of service of established, inelastic flows within a
   single Diffserv domain.

Eardley                      Informational                      [Page 1]
RFC 5559                    PCN Architecture                   June 2009

Table of Contents

   1. Introduction ....................................................3
      1.1. Overview of PCN ............................................3
      1.2. Example Use Case for PCN ...................................4
      1.3. Applicability of PCN .......................................7
      1.4. Documents about PCN ........................................8
   2. Terminology .....................................................9
   3. High-Level Functional Architecture .............................11
      3.1. Flow Admission ............................................13
      3.2. Flow Termination ..........................................14
      3.3. Flow Admission and/or Flow Termination When There Are Only
           Two PCN Encoding States ...................................15
      3.4. Information Transport .....................................16
      3.5. PCN-Traffic ...............................................16
      3.6. Backwards Compatibility ...................................17
   4. Detailed Functional Architecture ...............................18
      4.1. PCN-Interior-Node Functions ...............................19
      4.2. PCN-Ingress-Node Functions ................................19
      4.3. PCN-Egress-Node Functions .................................20
      4.4. Admission Control Functions ...............................21
      4.5. Flow Termination Functions ................................22
      4.6. Addressing ................................................22
      4.7. Tunnelling ................................................23
      4.8. Fault Handling ............................................25
   5. Operations and Management ......................................25
      5.1. Fault Operations and Management ...........................25
      5.2. Configuration Operations and Management ...................26
           5.2.1. System Options .....................................27
           5.2.2. Parameters .........................................28
      5.3. Accounting Operations and Management ......................30
      5.4. Performance and Provisioning Operations and Management ....30
      5.5. Security Operations and Management ........................31
   6. Applicability of PCN ...........................................32
      6.1. Benefits ..................................................32
      6.2. Deployment Scenarios ......................................33
      6.3. Assumptions and Constraints on Scope ......................35
           6.3.1. Assumption 1: Trust and Support of PCN -
                  Controlled Environment .............................36
           6.3.2. Assumption 2: Real-Time Applications ...............36
           6.3.3. Assumption 3: Many Flows and Additional Load .......37

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