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The Eifel Detection Algorithm for TCP (RFC3522)

IP.com Disclosure Number: IPCOM000012307D
Original Publication Date: 2003-Apr-01
Included in the Prior Art Database: 2003-Apr-30
Document File: 15 page(s) / 34K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

R. Ludwig: AUTHOR [+2]

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.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 9% of the total text.

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 [RFC2119].

   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                      [Page 1]

RFC 3522         The Eifel Detection Algorithm for TCP        April 2003

   We use the term 'acceptable ACK' as defined in [RFC793].  That is an

   ACK that acknowledges previously unacknowledged data.  We use the

   term 'duplicate ACK', and the variable 'dupacks' as defined in

   [WS95].  The variable 'dupacks' is a counter of duplicate ACKs that

   have already been received by a TCP sender before the fast retransmit

   is se...