The Some Congestion Experienced ECN Codepoint
draft-morton-tsvwg-sce-00

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Transport Working Group                                        J. Morton
Internet-Draft                                          R.W. Grimes, Ed.
Updates3168, 8311 (if approved)                              3 July 2019
Intended status: Standards Track                                        
Expires: 4 January 2020

             The Some Congestion Experienced ECN Codepoint
                       draft-morton-tsvwg-sce-00

Abstract

   This memo reclassifies ECT(1) to be an early notification of
   congestion on ECT(0) marked packets, which can be used by AQM
   algorithms and transports as an earlier signal of congestion than CE.
   It is a simple, transparent, and backward compatible upgrade to
   existing IETF-approved AQMs, RFC3168, and nearly all congestion
   control algorithms.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 4 January 2020.

Copyright Notice

   Copyright (c) 2019 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
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   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

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   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.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   2
   4.  Some Congestion Experienced . . . . . . . . . . . . . . . . .   3
   5.  Examples of use . . . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  Codel-type AQMs . . . . . . . . . . . . . . . . . . . . .   5
     5.2.  RED-type AQMs (including PIE) . . . . . . . . . . . . . .   6
     5.3.  TCP . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     5.4.  Other . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  Related Work  . . . . . . . . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   10. Normative References  . . . . . . . . . . . . . . . . . . . .   8
   11. Informative References  . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119] and [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Introduction

   This memo reclassifies ECT(1) to be an early notification of
   congestion on ECT(0) marked packets, which can be used by AQM
   algorithms and transports as an earlier signal of congestion than CE
   ("Congestion Experienced").

   This memo limits its scope to the redefinition of the ECT(1)
   codepoint as SCE, "Some Congestion Experienced", with a few brief
   illustrations of how it may be used.

3.  Background

   [RFC3168] defines the lower two bits of the (former) TOS byte in the
   IPv4/6 header as the ECN field.  This may take four values: Not-ECT,
   ECT(0), ECT(1) or CE.

   Binary Keyword References

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   ------------------------------------------------------------

    00     Not-ECT (Not ECN-Capable Transport)     [RFC3168]
    01     ECT(1) (ECN-Capable Transport(1))       [RFC3168]
    10     ECT(0) (ECN-Capable Transport(0))       [RFC3168]
    11     CE (Congestion Experienced)             [RFC3168]

   Research has shown that the ECT(1) codepoint goes essentially unused,