F-RTO: An Algorithm for Detecting Spurious Retransmission Timeouts with TCP and SCTP

Document Type Replaced Internet-Draft (tsvwg WG)
Author Pasi Sarolahti 
Last updated 2005-05-26 (latest revision 2004-02-16)
Replaced by RFC 4138
Stream Internet Engineering Task Force (IETF)
Intended RFC status Experimental
Expired & archived
plain text pdf htmlized bibtex
Stream WG state WG Document
Document shepherd No shepherd assigned
IESG IESG state Replaced by draft-ietf-tcpm-frto
Action Holders
Consensus Boilerplate Unknown
Telechat date
Responsible AD Jon Peterson
IESG note Really in TCPM WG
Send notices to faber@isi.edu, mallman@icir.org

This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


Spurious retransmission timeouts (RTOs) cause suboptimal TCP performance, because they often result in unnecessary retransmission of the last window of data. This document describes the 'Forward RTO Recovery' (F-RTO) algorithm for detecting spurious TCP RTOs. F-RTO is a TCP sender only algorithm that does not require any TCP options to operate. After retransmitting the first unacknowledged segment triggered by an RTO, the F-RTO algorithm at a TCP sender monitors the incoming acknowledgements to determine whether the timeout was spurious and to decide whether to send new segments or retransmit unacknowledged segments. The algorithm effectively helps to avoid additional unnecessary retransmissions and thereby improves TCP performance in case of a spurious timeout. The F-RTO algorithm can also be applied with the SCTP protocol.


Pasi Sarolahti (pasi.sarolahti@nokia.com)

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)