Forward RTO-Recovery (F-RTO): An Algorithm for Detecting Spurious Retransmission Timeouts with TCP (RFC5682) (01-Sep-2009)

Network Working Group                                       P. Sarolahti Request for Comments: 5682                         Nokia Research Center Updates: 4138                                                    M. Kojo Category: Standards Track                         University of Helsinki                                                              K. Yamamoto                                                                  M. Hata                                                               NTT Docomo                                                           September 2009

         Forward RTO-Recovery (F-RTO): An Algorithm for Detecting                Spurious Retransmission Timeouts with TCP

Abstract

   The purpose of this document is to move the F-RTO (Forward    RTO-Recovery) functionality for TCP in RFC 4138 from    Experimental to Standards Track status.  The F-RTO support for Stream    Control Transmission Protocol (SCTP) in RFC 4138 remains with    Experimental status.  See Appendix B for the differences between this    document and RFC 4138.

   Spurious retransmission timeouts cause suboptimal TCP performance    because they often result in unnecessary retransmission of the last    window of data.  This document describes the F-RTO detection    algorithm for detecting spurious TCP retransmission timeouts.  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 a timeout, the F-RTO algorithm of the TCP sender    monitors the incoming acknowledgments to determine whether the    timeout was spurious.  It then decides whether to send new segments    or retransmit unacknowledged segments.  The algorithm effectively    helps to avoid additional unnecessary retransmissions and thereby    improves TCP performance in the case of a spurious timeout.

Status of This Memo

   This document specifies an Internet standards track protocol for the    Internet community, and requests discussion and suggestions for    improvements.  Please refer to the current edition of the "Internet    Official Protocol Standards" (STD 1) for the standardization state    and status of this protocol.  Distribution of this memo is unlimited.

Sarolahti, et al.           Standards Track                     [Page 1]
 RFC 5682                         F-RTO                 ...