The Benefits of Using Explicit Congestion Notification (ECN)
RFC 8087
Internet Engineering Task Force (IETF) G. Fairhurst
Request for Comments: 8087 University of Aberdeen
Category: Informational M. Welzl
ISSN: 2070-1721 University of Oslo
March 2017
The Benefits of Using Explicit Congestion Notification (ECN)
Abstract
The goal of this document is to describe the potential benefits of
applications using 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
Congestion Experienced (CE) 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 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 7841.
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/rfc8087.
Fairhurst & Welzl Informational [Page 1]
RFC 8087 Benefits of ECN March 2017
Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Benefit of Using ECN to Avoid Congestion Loss . . . . . . . . 5
2.1. Improved Throughput . . . . . . . . . . . . . . . . . . . 5
2.2. Reduced Head-of-Line Blocking . . . . . . . . . . . . . . 6
2.3. Reduced Probability of RTO Expiry . . . . . . . . . . . . 6
2.4. Applications That Do Not Retransmit Lost Packets . . . . 7
2.5. Making Incipient Congestion Visible . . . . . . . . . . . 8
2.6. Opportunities for New Transport Mechanisms . . . . . . . 8
3. Network Support for ECN . . . . . . . . . . . . . . . . . . . 9
3.1. The ECN Field . . . . . . . . . . . . . . . . . . . . . . 10
3.2. Forwarding ECN-Capable IP Packets . . . . . . . . . . . . 10
3.3. Enabling ECN in Network Devices . . . . . . . . . . . . . 11
3.4. Coexistence of ECN and Non-ECN Flows . . . . . . . . . . 11
3.5. Bleaching and Middlebox Requirements to Deploy ECN . . . 11
3.6. Tunneling ECN and the Use of ECN by Lower-Layer Networks 12
4. Using ECN across the Internet . . . . . . . . . . . . . . . . 12
4.1. Partial Deployment . . . . . . . . . . . . . . . . . . . 13
4.2. Detecting Whether a Path Really Supports ECN . . . . . . 13
4.3. Detecting ECN-Receiver Feedback Cheating . . . . . . . . 14
5. Summary: Enabling ECN in Network Devices and Hosts . . . . . 14
6. Security Considerations . . . . . . . . . . . . . . . . . . . 15
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.1. Normative References . . . . . . . . . . . . . . . . . . 16
7.2. Informative References . . . . . . . . . . . . . . . . . 16
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
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RFC 8087 Benefits of ECN March 2017
1. Introduction
Internet transports (such as TCP and Stream Control Transmission
Protocol (SCTP)) are implemented in endpoints (Internet hosts) and
are designed to detect and react to network congestion. Congestion
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