The Benefits of using Explicit Congestion Notification (ECN)
draft-ietf-aqm-ecn-benefits-05

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Network Working Group                                       G. Fairhurst
Internet-Draft                                    University of Aberdeen
Intended status: Informational                                  M. Welzl
Expires: December 25, 2015                            University of Oslo
                                                           June 23, 2015

      The Benefits of using Explicit Congestion Notification (ECN)
                     draft-ietf-aqm-ecn-benefits-05

Abstract

   The goal of this document is to describe the potential benefits when
   applications use a transport that enables Explicit Congestion
   Notification (ECN).  The document outlines the principal gains in
   terms of increased throughput, reduced delay and other benefits when
   ECN is used over a network path that includes equipment that supports
   ECN-marking.  It also discusses challenges for successful deployment
   of ECN.  It does not propose new algorithms to use ECN, nor does it
   describe the details of implementation of ECN in endpoint devices
   (Internet hosts), routers or other network devices.

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
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   This Internet-Draft will expire on December 25, 2015.

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   Copyright (c) 2015 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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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents

Fairhurst & Welzl       Expires December 25, 2015               [Page 1]
Internet-Draft               Benefits of ECN                   June 2015

   carefully, as they describe your rights and restrictions with respect
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Benefit of using ECN to avoid Congestion Loss . . . . . . . .   4
     2.1.  Improved Throughput . . . . . . . . . . . . . . . . . . .   4
     2.2.  Reduced Head-of-Line Blocking . . . . . . . . . . . . . .   5
     2.3.  Reduced Probability of RTO Expiry . . . . . . . . . . . .   5
     2.4.  Applications that do not Retransmit Lost Packets  . . . .   6
     2.5.  Making Incipient Congestion Visible . . . . . . . . . . .   7
     2.6.  Opportunities for new Transport Mechanisms  . . . . . . .   7
   3.  Network Support for ECN . . . . . . . . . . . . . . . . . . .   8
     3.1.  The ECN Field . . . . . . . . . . . . . . . . . . . . . .   9
     3.2.  Forwarding ECN-Capable IP Packets . . . . . . . . . . . .   9
     3.3.  Enabling ECN in Network Devices . . . . . . . . . . . . .   9
     3.4.  Co-existance of ECN and non-ECN flows . . . . . . . . . .  10
     3.5.  Bleaching and Middlebox Requirements to deploy ECN  . . .  10
     3.6.  Tunneling ECN and the use of ECN by Lower Layer Networks   11
   4.  Using ECN across the Internet . . . . . . . . . . . . . . . .  11
     4.1.  Partial Deployment  . . . . . . . . . . . . . . . . . . .  11
     4.2.  Detecting whether a Path Really Supports ECN  . . . . . .  12
     4.3.  Detecting ECN Receiver Feedback Cheating  . . . . . . . .  12
   5.  Summary: Enabling ECN in Network Devices and Hosts  . . . . .  12
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   9.  Revision Information  . . . . . . . . . . . . . . . . . . . .  15
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  16
     10.2.  Informative References . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   Internet Transports (such as TCP and SCTP) are implemented in
   endpoints (Internet hosts) and are designed to detect and react to
   network congestion.  Congestion may be detected by loss of an IP