RFC 2963 (rfc2963) - Page 1 of 19

A Rate Adaptive Shaper for Differentiated Services

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Network Working Group                                      O. Bonaventure
Request for Comments: 2963                                          FUNDP
Category: Informational                                     S. De Cnodder
                                                                  Alcatel
                                                             October 2000


           A Rate Adaptive Shaper for Differentiated Services

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

   This memo describes several Rate Adaptive Shapers (RAS) that can be
   used in combination with the single rate Three Color Markers (srTCM)
   and the two rate Three Color Marker (trTCM) described in RFC 2697 and
   RFC 2698, respectively.  These RAS improve the performance of TCP when
   a TCM is used at the ingress of a diffserv network by reducing the
   burstiness of the traffic.  With TCP traffic, this reduction of the
   burstiness is accompanied by a reduction of the number of marked
   packets and by an improved TCP goodput.  The proposed RAS can be used
   at the ingress of Diffserv networks providing the Assured Forwarding
   Per Hop Behavior (AF PHB).  They are especially useful when a TCM is
   used to mark traffic composed of a small number of TCP connections.

1. Introduction

   In DiffServ networks [RFC 2475], the incoming data traffic, with the
   AF PHB in particular, could be subject to marking where the purpose
   of this marking is to provide a low drop probability to a minimum
   part of the traffic whereas the excess will have a larger drop
   probability.  Such markers are mainly token bucket based such as the
   single rate Three Color Marker (srTCM) and two rate Three Color
   Marker (trTCM) described in [RFC 2697] and [RFC 2698], respectively.

   Similar markers were proposed for ATM networks and simulations have
   shown that their performance with TCP traffic was not always
   satisfactory and several researchers have shown that these
   performance problems could be solved in two ways:




Bonaventure & De Cnodder     Informational
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