RFC 3708 (rfc3708) - Page 1 of 9

Using TCP Duplicate Selective Acknowledgement (DSACKs) and Stream Control Transmission Protocol (SCTP) Duplicate Transmission Sequence Numbers (TSNs) to Detect Spurious Retransmissions

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Network Working Group                                         E. Blanton
Request for Comments: 3708                             Purdue University
Category: Experimental                                         M. Allman
                                                                    ICIR
                                                           February 2004


      Using TCP Duplicate Selective Acknowledgement (DSACKs) and
         Stream Control Transmission Protocol (SCTP) Duplicate
        Transmission Sequence Numbers (TSNs) to Detect Spurious
                            Retransmissions

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 (2004).  All Rights Reserved.

Abstract

   TCP and Stream Control Transmission Protocol (SCTP) provide
   notification of duplicate segment receipt through Duplicate Selective
   Acknowledgement (DSACKs) and Duplicate Transmission Sequence Number
   (TSN) notification, respectively.  This document presents
   conservative methods of using this information to identify
   unnecessary retransmissions for various applications.

1.  Introduction

   TCP [RFC 793] and SCTP [RFC 2960] provide notification of duplicate
   segment receipt through duplicate selective acknowledgment (DSACK)
   [RFC 2883] and Duplicate TSN notifications, respectively.  Using this
   information, a TCP or SCTP sender can generally determine when a
   retransmission was sent in error.  This document presents two methods
   for using duplicate notifications.  The first method is simple and
   can be used for accounting applications.  The second method is a
   conservative algorithm to disambiguate unnecessary retransmissions
   from loss events for the purpose of undoing unnecessary congestion
   control changes.







Blanton & Allman              Experimental

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