The Some Congestion Experienced ECN Codepoint
draft-morton-tsvwg-sce-01

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Transport Working Group                                        J. Morton
Internet-Draft                                          R.W. Grimes, Ed.
Updates3168, 8311 (if approved)                          4 November 2019
Intended status: Experimental                                           
Expires: 7 May 2020

             The Some Congestion Experienced ECN Codepoint
                       draft-morton-tsvwg-sce-01

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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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 7 May 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
   Provisions Relating to IETF Documents (https://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

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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  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Some Congestion Experienced . . . . . . . . . . . . . . . . .   4
   5.  Examples of use . . . . . . . . . . . . . . . . . . . . . . .   6
     5.1.  Codel-type AQMs . . . . . . . . . . . . . . . . . . . . .   6
     5.2.  RED-type AQMs (including PIE) . . . . . . . . . . . . . .   7
     5.3.  TCP . . . . . . . . . . . . . . . . . . . . . . . . . . .   8
     5.4.  Other . . . . . . . . . . . . . . . . . . . . . . . . . .   8
   6.  Compatibility . . . . . . . . . . . . . . . . . . . . . . . .   8
     6.1.  Existing ECN & AQM Deployments  . . . . . . . . . . . . .   8
     6.2.  L4S . . . . . . . . . . . . . . . . . . . . . . . . . . .   8
   7.  Related Work  . . . . . . . . . . . . . . . . . . . . . . . .   9
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   11. Normative References  . . . . . . . . . . . . . . . . . . . .  10
   12. Informative References  . . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

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

   Traditional TCP congestion control exhibits a "sawtooth" pattern
   which, in the most favourable cases, oscillates around the optimum
   operating point of maximum throughput and minimum delay, which exists
   at the point where the congestion window equals path BDP.  The term
   "sawtooth" brings to mind the straight-edged graphs of TCP Reno, but
   the equally common TCP CUBIC is essentially similar in character, as
   are other AIMD-derived algorithms.

   A number of proposals have sought to improve this, but introduce
   various other tradoffs in return.  TCP Vegas is consistently
   outcompeted by standard TCPs, DCTCP proved to be too aggressive for
   deployment in the public Internet, and while BBR appears to have
   avoided both of these problems, its complexity makes it difficult to

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