Network Congestion Control Managing Internet Traffic
Network Congestion Control Managing Internet Traffic Michael Welzl Leopold Franzens University of Innsbruck Network Congestion Control Network Congestion Control Managing Internet Traffic Michael Welzl Leopold Franzens University of Innsbruck Copyright 2005 John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex PO19 8SQ, England Telephone (+44) 1243 779777 Email (for orders and customer service enquiries): cs-books@wiley.co.uk Visit our Home Page on www.wiley.com All Rights Reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except under the terms of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London W1T 4LP, UK, without the permission in writing of the Publisher. 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Other Wiley Editorial Offices John Wiley & Sons Inc., 111 River Street, Hoboken, NJ 07030, USA Jossey-Bass, 989 Market Street, San Francisco, CA 94103-1741, USA Wiley-VCH Verlag GmbH, Boschstr. 12, D-69469 Weinheim, Germany John Wiley & Sons Australia Ltd, 42 McDougall Street, Milton, Queensland 4064, Australia John Wiley & Sons (Asia) Pte Ltd, 2 Clementi Loop #02-01, Jin Xing Distripark, Singapore 129809 John Wiley & Sons Canada Ltd, 22 Worcester Road, Etobicoke, Ontario, Canada M9W 1L1 Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. Library of Congress Cataloging-in-Publication Data Welzl, Michael, 1973– Network congestion control : managing Internet traffic / Michael Welzl. p. cm. Includes bibliographical references and index. ISBN-13: 978-0-470-02528-4 (cloth : alk. paper) ISBN-10: 0-470-02528-X (cloth : alk. paper) 1. Internet. 2. Telecommunication–Traffic–Management. I. Title. TK5105.875.I57W454 2005 004.67 8–dc22 2005015429 British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN-13 978-0-470-02528-4 ISBN-10 0-470-02528-X Typeset in 10/12pt Times by Laserwords Private Limited, Chennai, India Printed and bound in Great Britain by Antony Rowe Ltd, Chippenham, Wiltshire This book is printed on acid-free paper responsibly manufactured from sustainable forestry in which at least two trees are planted for each one used for paper production. All my life, I enjoyed (and am still enjoying) a lot of support from many people – family, friends and colleagues alike, ranging from my grandmother and my girlfriend to my Ph.D. thesis supervisors. I sincerely thank them all for helping me along the way and dedicate this book to every one of them. This is not balderdash, I really mean it! Contents Foreword xi Preface xiii List of Tables xv List of Figures xvii 1 Introduction 1 1.1 Who should read this book? . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Contents . 2 1.3 Structure . 4 1.3.1 Reader’sguide . 5 2 Congestion control principles 7 2.1 What is congestion? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.1.1 Overprovisioningorcontrol? . 8 2.2 Congestion collapse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.3 Controlling congestion: design considerations . . . . . . . . . . . . . . . . . 13 2.3.1 Closed-loop versus open-loop control . . . . . . . . . . . . . . . . . 13 2.3.2 Congestion control and flow control . . . . . . . . . . . . . . . . . 14 2.4 Implicitfeedback 14 2.5 Source behaviour with binary feedback . . . . . . . . . . . . . . . . . . . . 16 2.5.1 MIMD,AIAD,AIMDandMIAD . 16 2.6 Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.6.1 Control theoretic modelling . . . . . . . . . . . . . . . . . . . . . . 19 2.6.2 HeterogeneousRTTs 20 2.6.3 Theconservationofpacketsprinciple . 21 2.7 Rate-based versus window-based control . . . . . . . . . . . . . . . . . . . 21 2.8 RTTestimation . 23 2.9 Trafficphaseeffects 24 2.9.1 Phaseeffectsindailylife . 26 2.10Queuemanagement . 26 2.10.1 Choosing the right queue length . . . . . . . . . . . . . . . . . . . . 27 2.10.2 Activequeuemanagement . 27 2.11 Scalability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 2.11.1 Theend-to-endargument . 28 [...]... Concluding remarks about AQM 4.5 Congestion control for multimedia applications 4.5.1 TCP-friendly congestion control mechanisms 4.5.2 The Datagram Congestion Control Protocol (DCCP) 4.5.3 Multicast congestion control 4.6 Better-than-TCP congestion control 4.6.1 Changing the response function 4.6.2 Delay as a congestion measure 4.6.3... future of Internet congestion control 6.1 Small deltas or big ideas? 6.1.1 TCP-friendliness considerations 6.1.2 A more aggressive framework 6.2 Incentive issues 6.2.1 The congestion response of UDP-based 6.2.2 Will VoIP cause congestion collapse? 6.2.3 DCCP deployment considerations 6.2.4 Congestion control and QoS 6.3 Tailor-made congestion control ... practical considerations of congestion, and gives an in-depth treatment of the subject Network Congestion Control: Managing Internet Traffic’ is a welcome addition to the Wiley Series in Communications Networking & Distributed Systems David Hutchison Lancaster University April 2005 Preface Some people raised their eyebrows when I told them that I was writing a book on congestion control, and said, ‘Is this... link, there are only two things that this device can do: buffer the packets or drop them Since such traffic spikes are typically Network Congestion Control: Managing Internet Traffic 2005 John Wiley & Sons, Ltd Michael Welzl 8 CONGESTION CONTROL PRINCIPLES limited in time, standard Internet routers usually place excess packets in a buffer, which roughly works like a basic FIFO (‘First In, First Out’) queue... control is all about In (Jain and Ramakrishnan 1988), the term congestion control is distinguished from the term congestion avoidance’ via its operational range (as seen in Figure 2.2 (b)): schemes that allow the network to operate at the knee are called congestion avoidance schemes, whereas congestion control just tries to keep the network to the left of the cliff In practice, it is hard to differentiate... for the admission control entity to measure the actual bandwidth usage, thereby adding feedback to the control and deviating from its strictly open character Open-loop control was called proactive (as opposed to reactive control) in (Keshav 1991a) Keshav also pointed out what we have just seen: that these two control modes are not mutually exclusive 2.3.2 Congestion control and flow control Since intermediate... This may be a little too much for someone who would just like to become acquainted with the field Network Congestion Control: Managing Internet Traffic 2005 John Wiley & Sons, Ltd Michael Welzl 2 INTRODUCTION (e.g a network administrator who is merely interested in some specifics about the dynamic behaviour of network traffic) In my opinion, starting with these research papers is also inefficient It is a... difficult to control a network that has just enough bandwidth than an overprovisioned one Network administrators will require more time to do their task 2.1 WHAT IS CONGESTION? 9 and perhaps need special training, which means that these networks cost more money Moreover, there is an increased risk of network failures, which once again leads to customer complaints • With an overprovisioned network, an... replace congestion control with terms such as ‘high performance networking’, ‘high speed communication’ and so on over the last couple of years Do not let this confuse you – it is the same goal with slightly different environment conditions This is a very important point, as it explains why we need congestion control at all nowadays Here it is again: Congestion control is about using the network as efficiently... research efforts Chapter 3 presents technology that you can expect to encounter in the Internet of today It consists of two parts: first, congestion control in end systems is explained In the present Internet, this is synonymous with the word ‘TCP’ The second part focuses on congestion control – related mechanisms within the network Currently, there is not much going on here, and therefore, this part is short: . Network Congestion Control Managing Internet Traffic Michael Welzl Leopold Franzens University of Innsbruck Network Congestion Control. practical considerations of congestion, and gives an in-depth treatment of the subject. Network Congestion Control: Managing Internet Traffic’ is a welcome