Browse Prior Art Database

TCP Performance Implications of Network Path Asymmetry (RFC3449)

IP.com Disclosure Number: IPCOM000010583D
Original Publication Date: 2002-Dec-01
Included in the Prior Art Database: 2002-Dec-19

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

H. Balakrishnan: AUTHOR [+4]

Abstract

This document describes TCP performance problems that arise because of asymmetric effects. These problems arise in several access networks, including bandwidth-asymmetric networks and packet radio subnetworks, for different underlying reasons. However, the end result on TCP performance is the same in both cases: performance often degrades significantly because of imperfection and variability in the ACK feedback from the receiver to the sender.

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Network Working Group                                    H. Balakrishnan

Request for Comments: 3449                                       MIT LCS

BCP: 69                                                V. N. Padmanabhan

Category: Best Current Practice                       Microsoft Research

                                                            G. Fairhurst

                                                       M. Sooriyabandara

                                            University of Aberdeen, U.K.

                                                           December 2002

                     TCP Performance Implications

                       of Network Path Asymmetry

Status of this Memo

   This document specifies an Internet Best Current Practices for the

   Internet Community, and requests discussion and suggestions for

   improvements.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   This document describes TCP performance problems that arise because

   of asymmetric effects.  These problems arise in several access

   networks, including bandwidth-asymmetric networks and packet radio

   subnetworks, for different underlying reasons.  However, the end

   result on TCP performance is the same in both cases: performance

   often degrades significantly because of imperfection and variability

   in the ACK feedback from the receiver to the sender.

   The document details several mitigations to these effects, which have

   either been proposed or evaluated in the literature, or are currently

   deployed in networks.  These solutions use a combination of local

   link-layer techniques, subnetwork, and end-to-end mechanisms,

   consisting of: (i) techniques to manage the channel used for the

   upstream bottleneck link carrying the ACKs, typically using header

   compression or reducing the frequency of TCP ACKs, (ii) techniques to

   handle this reduced ACK frequency to retain the TCP sender's

   acknowledgment-triggered self-clocking and (iii) techniques to

   schedule the data and ACK packets in the reverse direction to improve

   performance in the presence of two-way traffic.  Each technique is

   described, together with known issues, and recommendations for use.

   A summary of the recommendations is provided at the end of the

   document.

Balakrishnan et. al.     Best Current Practice                  [Page 1]

RFC 3449                PILC - Asymmetric Links            December 2002

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