Baseline Encoding and Transport of Pre-Congestion Information
RFC 5696

Document Type RFC - Proposed Standard (November 2009; Errata)
Obsoleted by RFC 6660
Last updated 2013-03-02
Replaces draft-moncaster-pcn-baseline-encoding
Stream IETF
Formats plain text pdf html
Stream WG state (None)
Consensus Unknown
Document shepherd No shepherd assigned
IESG IESG state RFC 5696 (Proposed Standard)
Telechat date
Responsible AD Lars Eggert
Send notices to pcn-chairs@ietf.org, draft-ietf-pcn-baseline-encoding@ietf.org
Network Working Group                                       T. Moncaster
Request for Comments: 5696                                    B. Briscoe
Category: Standards Track                                             BT
                                                                M. Menth
                                                 University of Wuerzburg
                                                           November 2009

     Baseline Encoding and Transport of Pre-Congestion Information

Abstract

   The objective of the Pre-Congestion Notification (PCN) architecture
   is to protect the quality of service (QoS) of inelastic flows within
   a Diffserv domain.  It achieves this by marking packets belonging to
   PCN-flows when the rate of traffic exceeds certain configured
   thresholds on links in the domain.  These marks can then be evaluated
   to determine how close the domain is to being congested.  This
   document specifies how such marks are encoded into the IP header by
   redefining the Explicit Congestion Notification (ECN) codepoints
   within such domains.  The baseline encoding described here provides
   only two PCN encoding states: Not-marked and PCN-marked.  Future
   extensions to this encoding may be needed in order to provide more
   than one level of marking severity.

Status of This Memo

   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
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (c) 2009 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 BSD License.

Moncaster, et al.           Standards Track                     [Page 1]
RFC 5696                 Baseline PCN Encoding             November 2009

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Requirements Notation  . . . . . . . . . . . . . . . . . . . .  3
   3.  Terminology and Abbreviations  . . . . . . . . . . . . . . . .  3
     3.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
     3.2.  List of Abbreviations  . . . . . . . . . . . . . . . . . .  4
   4.  Encoding Two PCN States in IP  . . . . . . . . . . . . . . . .  4
     4.1.  Marking Packets  . . . . . . . . . . . . . . . . . . . . .  5
     4.2.  Valid and Invalid Codepoint Transitions  . . . . . . . . .  6
     4.3.  Rationale for Encoding . . . . . . . . . . . . . . . . . .  7
     4.4.  PCN-Compatible Diffserv Codepoints . . . . . . . . . . . .  7
       4.4.1.  Co-Existence of PCN and Not-PCN Traffic  . . . . . . .  8
   5.  Rules for Experimental Encoding Schemes  . . . . . . . . . . .  8
   6.  Backward Compatibility . . . . . . . . . . . . . . . . . . . .  9
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   8.  Conclusions  . . . . . . . . . . . . . . . . . . . . . . . . . 10
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 10
     10.2. Informative References . . . . . . . . . . . . . . . . . . 10
   Appendix A.  PCN Deployment Considerations (Informative) . . . . . 11
     A.1.  Choice of Suitable DSCPs . . . . . . . . . . . . . . . . . 11
     A.2.  Rationale for Using ECT(0) for Not-Marked  . . . . . . . . 12
Show full document text