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Chapter 3 General Principles of the IMS Architecture The 3G IP Multimedia Subsystem (IMS) The 3G IP Multimedia Subsystem (IMS): Merging the Internet and the Cellular Worlds, Second Edition Gonzalo Camarillo and M iguel A . G ar cıa-´ M ar tın´ © 2006 John Wiley & Sons Ltd. ISBN: 0-470-01818-6 The 3G IP Multimedia Subsystem (IMS) Merging the Internet and the Cellular Worlds Second Edition Gonzalo Camarillo Ericsson, Finland Miguel A. Garc´ıa-Mart´ın Nokia Research Center, Finland John Wiley & Sons, Ltd Copyright c 2006 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): [email protected] 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. Requests to the Publisher should be addressed to the Permissions Department, John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex PO19 8SQ, England, or emailed to [email protected], or faxed to (+44) 1243 770620. Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The Publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the Publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought. 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 Camarillo, Gonzalo. The 3G IP multimedia subsystem (IMS) : merging the Internet and the cellular worlds / Gonzalo Camarillo, Miguel A. Garc´ıa-Mart´ın.–2nd ed. p. cm. Includes bibliographical references and index. ISBN-13: 978-0-470-01818-7 (cloth : alk. paper) ISBN-10: 0-470-01818-6 (cloth : alk. paper) 1. Wireless communication systems. 2. Mobile communication systems. 3. Multimedia communications. I. Garc´ıa-Mart´ın, Miguel A. II. Title. TK5103.2.C35 2006 621.384–dc22 2005026863 British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN-13 978-0-470-01818-7 (HB) ISBN-10 0-470-01818-6 (HB) Typeset by Sunrise Setting Ltd, Torquay, Devon, UK. Printed and bound in Great Britain by Antony Rowe Ltd, Chipenham, 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. To my parents, Anselmo and Isabel; my brothers, Alvaro, Daniel, and Ignacio; and Viviana. They all are a source of energy and motivation in everything I do. Gonzalo To my daughter Maria Elizabeth, who was born at the time I started writing this book, she is the sunshine of my life; my wife Jelena, who provided me with all the support and love I needed; my parents, Jos´e and Mari-Luz, my aunt Feli, my brother Javier Jos´e who, through the distance, encouraged and supported me during this project. Miguel Angel Contents Foreword by Stephen Hayes xvii Foreword by Allison Mankin and Jon Peterson xix About the Authors xxi Preface to the Second Edition xxiii Preface to the First Edition xxv Acknowledgements xxvii Part I Introduction to the IMS 1 1 IMS Vision: Where Do We Want to Go? 5 1.1 TheInternet.................................. 5 1.2 TheCellularWorld............................... 6 1.3 WhydoweneedtheIMS?........................... 6 1.4 RelationbetweenIMSandnon-IMSServices................. 8 2 The History of the IMS Standardization 9 2.1 RelationsbetweenIMS-relatedStandardizationBodies............ 9 2.2 InternetEngineeringTaskForce........................ 10 2.2.1 StructureoftheIETF......................... 10 2.2.2 WorkingGroupOperations...................... 11 2.2.3 TypesofRFCs............................ 12 2.3 ThirdGenerationPartnershipProject..................... 13 2.3.1 3GPPStructure............................ 14 2.3.2 3GPPDeliverables.......................... 15 2.4 ThirdGenerationPartnershipProject2 .................... 16 2.4.1 3GPP2Structure........................... 16 2.4.2 3GPP2Deliverables......................... 16 2.5 IETF-3GPP/3GPP2Collaboration....................... 17 2.5.1 InternetArea............................. 18 2.5.2 OperationsandManagementArea.................. 18 2.5.3 TransportArea............................ 19 viii CONTENTS 2.6 Open Mobile Alliance . .......................... 19 2.6.1 OMAReleasesandSpecifications.................. 20 2.6.2 RelationshipbetweenOMAand3GPP/3GPP2........... 21 2.6.3 RelationshipbetweenOMAandtheIETF.............. 22 3 General Principles of the IMS Architecture 23 3.1 FromCircuit-switchedtoPacket-switched................... 23 3.1.1 GSMCircuit-switched........................ 23 3.1.2 GSMPacket-switched........................ 24 3.2 IMSRequirements............................... 24 3.2.1 IP Multimedia Sessions . ...................... 25 3.2.2 QoS.................................. 25 3.2.3 Interworking............................. 26 3.2.4 Roaming............................... 26 3.2.5 ServiceControl............................ 26 3.2.6 RapidServiceCreation........................ 27 3.2.7 Multiple Access . .......................... 27 3.3 OverviewofProtocolsusedintheIMS.................... 27 3.3.1 SessionControlProtocol....................... 27 3.3.2 TheAAAProtocol.......................... 28 3.3.3 OtherProtocols............................ 29 3.4 OverviewofIMSArchitecture......................... 29 3.4.1 TheDatabases:theHSSandtheSLF................ 30 3.4.2 TheCSCF............................... 31 3.4.3 TheAS................................ 33 3.4.4 TheMRF............................... 35 3.4.5 TheBGCF.............................. 35 3.4.6 TheIMS-ALGandtheTrGW.................... 35 3.4.7 ThePSTN/CSGateway........................ 36 3.4.8 HomeandVisitedNetworks..................... 38 3.5 IdentificationintheIMS............................ 39 3.5.1 Public User Identities . ...................... 40 3.5.2 Private User Identities . ...................... 40 3.5.3 The Relation between Public and Private User Identities . 41 3.5.4 Public Service Identities . ...................... 42 3.6 SIM,USIM,andISIMin3GPP........................ 42 3.6.1 SIM.................................. 43 3.6.2 USIM................................. 43 3.6.3 ISIM................................. 45 Part II The Signaling Plane in the IMS 47 4 Session Control on the Internet 51 4.1 SIP Functionality . .......................... 51 4.1.1 SessionDescriptionsandSDP.................... 51 4.1.2 TheOffer/AnswerModel....................... 52 4.1.3 SIPandSIPSURIs.......................... 53 4.1.4 UserLocation............................. 54 CONTENTS ix 4.2 SIP Entities . .................................. 55 4.2.1 ForkingProxies............................ 57 4.2.2 RedirectServers........................... 58 4.3 MessageFormat................................ 59 4.4 The Start Line in SIP Responses: the Status Line ............... 59 4.5 TheStartLineinSIPRequests:theRequestLine............... 60 4.6 HeaderFields.................................. 60 4.7 MessageBody................................. 62 4.8 SIPTransactions................................ 63 4.9 MessageFlowforSessionEstablishment................... 64 4.10SIPDialogs................................... 67 4.10.1 Record-Route, Route,andContact HeaderFields........ 70 4.11ExtendingSIP................................. 70 4.11.1 New Methods . ........................... 72 4.12 Caller Preferences and User Agent Capabilities . ............... 72 4.13 Reliability of Provisional Responses . ................... 73 4.14Preconditions.................................. 76 4.15EventNotification............................... 77 4.15.1HighNotificationRates........................ 79 4.16SignalingCompression............................. 80 4.16.1SigCompExtendedOperations.................... 81 4.16.2StaticSIP/SDPDictionary...................... 82 4.17ContentIndirection............................... 82 4.18TheREFERMethod.............................. 85 5 Session Control in the IMS 87 5.1 PrerequisitesforOperationintheIMS..................... 88 5.2 IPv4andIPv6intheIMS........................... 89 5.3 IP Connectivity Access Network . ....................... 90 5.4 P-CSCFDiscovery..............................
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