The Benefits of using Explicit Congestion Notification (ECN)
draft-ietf-aqm-ecn-benefits-05
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
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This Internet-Draft will expire on December 25, 2015.
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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
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