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Congestion Exposure (ConEx) Concepts and Use Cases
RFC 6789

Internet Engineering Task Force (IETF)                   B. Briscoe, Ed.
Request for Comments: 6789                                            BT
Category: Informational                                   R. Woundy, Ed.
ISSN: 2070-1721                                                  Comcast
                                                          A. Cooper, Ed.
                                                                     CDT
                                                           December 2012

           Congestion Exposure (ConEx) Concepts and Use Cases

Abstract

   This document provides the entry point to the set of documentation
   about the Congestion Exposure (ConEx) protocol.  It explains the
   motivation for including a ConEx marking at the IP layer: to expose
   information about congestion to network nodes.  Although such
   information may have a number of uses, this document focuses on how
   the information communicated by the ConEx marking can serve as the
   basis for significantly more efficient and effective traffic
   management than what exists on the Internet today.

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/rfc6789.

Briscoe, et al.               Informational                     [Page 1]
RFC 6789              ConEx Concepts and Use Cases         December 2012

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.1.  Congestion . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.2.  Congestion-Volume  . . . . . . . . . . . . . . . . . . . .  5
     2.3.  Rest-of-Path Congestion  . . . . . . . . . . . . . . . . .  6
     2.4.  Definitions  . . . . . . . . . . . . . . . . . . . . . . .  6
   3.  Core Use Case: Informing Traffic Management  . . . . . . . . .  7
     3.1.  Use Case Description . . . . . . . . . . . . . . . . . . .  7
     3.2.  Additional Benefits  . . . . . . . . . . . . . . . . . . .  9
     3.3.  Comparison with Existing Approaches  . . . . . . . . . . .  9
   4.  Other Use Cases  . . . . . . . . . . . . . . . . . . . . . . . 11
   5.  Deployment Arrangements  . . . . . . . . . . . . . . . . . . . 12
   6.  Experimental Considerations  . . . . . . . . . . . . . . . . . 13
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 14
   9.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 15
   10. Informative References . . . . . . . . . . . . . . . . . . . . 15

1.  Introduction

   The power of Internet technology comes from multiplexing shared
   capacity with packets rather than circuits.  Network operators aim to
   provide sufficient shared capacity, but when too much packet load
   meets too little shared capacity, congestion results.  Congestion
   appears as either increased delay, dropped packets, or packets
   explicitly marked with Explicit Congestion Notification (ECN)
   markings [RFC3168].  As described in Figure 1, congestion control
   currently relies on the transport receiver detecting these
   'Congestion Signals' and informing the transport sender in
   'Congestion Feedback Signals'.  The sender is then expected to reduce
   its rate in response.

Briscoe, et al.               Informational                     [Page 2]
RFC 6789              ConEx Concepts and Use Cases         December 2012

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