RFC 2884 (rfc2884) - Page 1 of 18
Performance Evaluation of Explicit Congestion Notification (ECN) in IP Networks
Alternative Format: Original Text Document
Network Working Group J. Hadi Salim
Request for Comments: 2884 Nortel Networks
Category: Informational U. Ahmed
Carleton University
July 2000
Performance Evaluation of Explicit Congestion Notification (ECN)
in IP Networks
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2000). All Rights Reserved.
Abstract
This memo presents a performance study of the Explicit Congestion
Notification (ECN) mechanism in the TCP/IP protocol using our
implementation on the Linux Operating System. ECN is an end-to-end
congestion avoidance mechanism proposed by [6] and incorporated into
RFC 2481[7]. We study the behavior of ECN for both bulk and
transactional transfers. Our experiments show that there is
improvement in throughput over NON ECN (TCP employing any of Reno,
SACK/FACK or NewReno congestion control) in the case of bulk
transfers and substantial improvement for transactional transfers.
A more complete pdf version of this document is available at:
http://www7.nortel.com:8080/CTL/ecnperf.pdf
This memo in its current revision is missing a lot of the visual
representations and experimental results found in the pdf version.
1. Introduction
In current IP networks, congestion management is left to the
protocols running on top of IP. An IP router when congested simply
drops packets. TCP is the dominant transport protocol today [26].
TCP infers that there is congestion in the network by detecting
packet drops (RFC 2581). Congestion control algorithms [11] [15] [21]
are then invoked to alleviate congestion. TCP initially sends at a
higher rate (slow start) until it detects a packet loss. A packet
loss is inferred by the receipt of 3 duplicate ACKs or detected by a
Salim & Ahmed Informational
