Browse Prior Art Database

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.

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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...