RFC 3522 (rfc3522) - Page 1 of 14
The Eifel Detection Algorithm for TCP
Alternative Format: Original Text Document
Network Working Group R. Ludwig
Request for Comments: 3522 M. Meyer
Category: Experimental Ericsson Research
April 2003
The Eifel Detection Algorithm for TCP
Status of this Memo
This memo defines an Experimental Protocol for the Internet
community. It does not specify an Internet standard of any kind.
Discussion and suggestions for improvement are requested.
Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
The Eifel detection algorithm allows a TCP sender to detect a
posteriori whether it has entered loss recovery unnecessarily. It
requires that the TCP Timestamps option defined in RFC 1323 be
enabled for a connection. The Eifel detection algorithm makes use of
the fact that the TCP Timestamps option eliminates the retransmission
ambiguity in TCP. Based on the timestamp of the first acceptable ACK
that arrives during loss recovery, it decides whether loss recovery
was entered unnecessarily. The Eifel detection algorithm provides a
basis for future TCP enhancements. This includes response algorithms
to back out of loss recovery by restoring a TCP sender's congestion
control state.
Terminology
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in [RFC 2119].
We refer to the first-time transmission of an octet as the 'original
transmit'. A subsequent transmission of the same octet is referred
to as a 'retransmit'. In most cases, this terminology can likewise
be applied to data segments as opposed to octets. However, with
repacketization, a segment can contain both first-time transmissions
and retransmissions of octets. In that case, this terminology is
only consistent when applied to octets. For the Eifel detection
algorithm, this makes no difference as it also operates correctly
when repacketization occurs.
Ludwig & Meyer Experimental