The 3G IP Multimedia Subsystem (IMS)

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3GPP, or the Third Generation Partnership Project, was formed in late 1998 to specify the evolution of GSM into a third generation cellular system. Although much focus was placed on new higher bandwidth radio access methods, it was realized that the network infrastructure must also evolve in order to provide the rich services capable of taking advantage of higher bandwidths. The original GSM network infrastructure was very much circuit- and voicecentric. Although data capabilities were added over time the system retained much of its circuit-switched heritage and its inherent limitations. A new approach was needed....

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The 3G IP Multimedia Subsystem (IMS) The 3G IP Multimedia Subsystem (IMS): Merging the Internet and the Cellular Worlds Third Edition Gonzalo Camarillo and Miguel A . Garc ıa-Mart´n ´ ı © 2008 John Wiley & Sons, Ltd. ISBN: 978-0-470-51662-1
The 3G IP Multimedia Subsystem (IMS) Merging the Internet and the Cellular Worlds Third Edition Gonzalo Camarillo Ericsson, Finland Miguel A. Garc´a-Mart´n ı ı Ericsson, Spain A John Wiley and Sons, Ltd, Publication
This edition ﬁrst published 2008 c 2008 John Wiley & Sons Ltd First edition ﬁrst published 2004 c 2004 John Wiley & Sons Ltd Second edition ﬁrst published 2005 c 2005 John Wiley & Sons Ltd Registered ofﬁce John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom For details of our global editorial ofﬁces, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com. The right of the author to be identiﬁed as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988. 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 or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. 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. 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´a-Mart´n. – 3rd ed. ı ı p. cm. Includes bibliographical reference and index. ISBN 978-0-470-51662-1 (cloth) 1. Wireless communication systems. 2. Mobile communication systems. 3. Multimedia communications. 4. Internet Protocol multimedia subsystem. I. Garc´a-Mart´n, Miguel A. II. Title. ı ı TK5103.2.C35 2008 621.384–dc22 2008022139 A catalogue record for this book is available from the British Library. ISBN 978-0-470-51662-1 (HB) Set in 10/12pt Times by Sunrise Setting Ltd, Torquay, UK. Printed in Great Britain by Antony Rowe Ltd, Chippenham, England.
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´ and Mari-Luz, my aunt Feli, my brother Javier Jos´ who, through e e the distance, encouraged and supported me during this project. Miguel Angel
Contents Foreword by Stephen Hayes xxi Foreword by Allison Mankin and Jon Peterson xxiii About the Authors xxv Preface to the Third Edition xxvii Preface to the Second Edition xxix Preface to the First Edition xxxi Acknowledgements xxxiii Part I Introduction to the IMS 1 1 IMS Vision: Where Do We Want to Go? 5 1.1 The Internet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2 The Cellular World . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.3 Why do we need the IMS? . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.4 Relation between IMS and non-IMS Services . . . . . . . . . . . . . . . . . 8 2 The History of the IMS Standardization 9 2.1 Relations between IMS-related Standardization Bodies . . . . . . . . . . . . 9 2.2 Internet Engineering Task Force . . . . . . . . . . . . . . . . . . . . . . . . 10 2.2.1 Structure of the IETF . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.2.2 Working Group Operations . . . . . . . . . . . . . . . . . . . . . . 12 2.2.3 Types of RFCs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.3 Third Generation Partnership Project . . . . . . . . . . . . . . . . . . . . . 14 2.3.1 3GPP Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.3.2 3GPP Deliverables . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.4 Third Generation Partnership Project 2 . . . . . . . . . . . . . . . . . . . . 15 2.4.1 3GPP2 Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.4.2 3GPP2 Deliverables . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.5 IETF-3GPP/3GPP2 Collaboration . . . . . . . . . . . . . . . . . . . . . . . 18 2.5.1 Internet Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
CONTENTS viii 2.5.2 Operations and Management Area . . . . . . . . . . . . . . . . . . 19 2.5.3 Transport Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.6 Open Mobile Alliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.6.1 OMA Releases and Speciﬁcations . . . . . . . . . . . . . . . . . . 20 2.6.2 Relationship between OMA and 3GPP/3GPP2 . . . . . . . . . . . 22 2.6.3 Relationship between OMA and the IETF . . . . . . . . . . . . . . 22 3 General Principles of the IMS Architecture 25 3.1 From Circuit-switched to Packet-switched . . . . . . . . ....... ... . 25 3.1.1 GSM Circuit-switched . . . . . . . . . . . . . ....... ... . 25 3.1.2 GSM Packet-switched . . . . . . . . . . . . . ....... ... . 26 3.2 IMS Requirements . . . . . . . . . . . . . . . . . . . . ....... ... . 26 3.2.1 IP Multimedia Sessions . . . . . . . . . . . . . ....... ... . 27 3.2.2 QoS . . . . . . . . . . . . . . . . . . . . . . . ....... ... . 27 3.2.3 Interworking . . . . . . . . . . . . . . . . . . ....... ... . 28 3.2.4 Roaming . . . . . . . . . . . . . . . . . . . . ....... ... . 28 3.2.5 Service Control . . . . . . . . . . . . . . . . . ....... ... . 28 3.2.6 Rapid Service Creation . . . . . . . . . . . . . ....... ... . 29 3.2.7 Multiple Access . . . . . . . . . . . . . . . . . ....... ... . 29 3.3 Overview of Protocols used in the IMS . . . . . . . . . ....... ... . 29 3.3.1 Session Control Protocol . . . . . . . . . . . . ....... ... . 29 3.3.2 The AAA Protocol . . . . . . . . . . . . . . . ....... ... . 30 3.3.3 Other Protocols . . . . . . . . . . . . . . . . . ....... ... . 31 3.4 Overview of IMS Architecture . . . . . . . . . . . . . . ....... ... . 31 3.4.1 The Databases: the HSS and the SLF . . . . . ....... ... . 32 3.4.2 The CSCF . . . . . . . . . . . . . . . . . . . . ....... ... . 33 3.4.2.1 The P-CSCF . . . . . . . . . . . . ....... ... . 33 3.4.2.2 P-CSCF Location . . . . . . . . . . ....... ... . 34 3.4.2.3 The I-CSCF . . . . . . . . . . . . . ....... ... . 34 3.4.2.4 I-CSCF Location . . . . . . . . . . ....... ... . 35 3.4.2.5 The S-CSCF . . . . . . . . . . . . ....... ... . 35 3.4.2.6 S-CSCF Location . . . . . . . . . . ....... ... . 35 3.4.3 The Application Server . . . . . . . . . . . . . ....... ... . 35 3.4.3.1 AS Location . . . . . . . . . . . . ....... ... . 37 3.4.4 The MRF . . . . . . . . . . . . . . . . . . . . ....... ... . 37 3.4.4.1 MRF Location . . . . . . . . . . . ....... ... . 37 3.4.5 The BGCF . . . . . . . . . . . . . . . . . . . ....... ... . 37 3.4.6 The IMS-ALG and the TrGW . . . . . . . . . ....... ... . 37 3.4.7 The PSTN/CS Gateway . . . . . . . . . . . . . ....... ... . 39 3.4.8 Home and Visited Networks . . . . . . . . . . ....... ... . 40 3.5 Identiﬁcation in the IMS . . . . . . . . . . . . . . . . . ....... ... . 42 3.5.1 Public User Identities . . . . . . . . . . . . . . ....... ... . 42 3.5.2 Private User Identities . . . . . . . . . . . . . ....... ... . 43 3.5.3 The Relation between Public User Identities and Private User Identities . . . . . . . . . . . . . . . . . . . . ....... ... . 43 3.5.4 Public Service Identities . . . . . . . . . . . . ....... ... . 43
CONTENTS ix 3.6 SIM, USIM, and ISIM in 3GPP . . . . . . . . . . . . . . . . . . . . . . . . 45 3.6.1 SIM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 3.6.2 USIM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 3.6.3 ISIM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.7 Next Generation Networks (NGN) . . . . . . . . . . . . . . . . . . . . . . . 49 3.7.1 NGN Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 3.7.2 The Core IMS in NGN . . . . . . . . . . . . . . . . . . . . . . . . 51 Part II The Signaling Plane in the IMS 55 4 Session Control on the Internet 59 4.1 SIP Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4.1.1 Session Descriptions and SDP . . . . . . . . . . . . . . . . . . . . 59 4.1.2 The Offer/Answer Model . . . . . . . . . . . . . . . . . . . . . . . 60 4.1.3 SIP and SIPS URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 61 4.1.4 User Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 4.2 SIP Entities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 4.2.1 Forking Proxies . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 4.2.2 Redirect Servers . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 4.3 Message Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 4.4 The Start Line in SIP Responses: the Status Line . . . . . . . . . . . . . . . 67 4.5 The Start Line in SIP Requests: the Request Line . . . . . . . . . . . . . . . 68 4.6 Header Fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 4.7 Message Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 4.8 SIP Transactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 4.9 Message Flow for Session Establishment . . . . . . . . . . . . . . . . . . . 72 4.10 SIP Dialogs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 4.10.1 Record-Route, Route, and Contact Header Fields . . . . . . . . 78 4.11 Extending SIP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 4.11.1 New Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 4.12 Caller Preferences and User Agent Capabilities . . . . . . . . . . . . . . . . 80 4.13 Reliability of Provisional Responses . . . . . . . . . . . . . . . . . . . . . . 81 4.14 Preconditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 4.15 Event Notiﬁcation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 4.15.1 High Notiﬁcation Rates . . . . . . . . . . . . . . . . . . . . . . . . 87 4.15.1.1 Event Throttling . . . . . . . . . . . . . . . . . . . . . 88 4.15.1.2 Conditional Event Notiﬁcation . . . . . . . . . . . . . . 88 4.16 Signaling Compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 4.16.1 SigComp Extended Operations . . . . . . . . . . . . . . . . . . . . 90 4.16.2 Static SIP/SDP Dictionary . . . . . . . . . . . . . . . . . . . . . . 91 4.17 Content Indirection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 4.18 The REFER Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 4.19 Globally Routable User Agent URIs (GRUU) . . . . . . . . . . . . . . . . . 96 4.20 NAT Traversal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 4.20.1 Types of NAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 4.20.2 STUN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 4.20.3 TURN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 4.20.4 ICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
CONTENTS x 5 Session Control in the IMS 111 5.1 Prerequisites for Operation in the IMS . . . . . . . . . . . . . . . . . . . . . 112 5.2 IPv4 and IPv6 in the IMS . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 5.3 IP Connectivity Access Network . . . . . . . . . . . . . . . . . . . . . . . . 114 5.4 P-CSCF Discovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 5.5 IMS-level Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 5.5.1 IMS Registration with an ISIM . . . . . . . . . . . . . . . . . . . . 117 5.5.2 IMS Registration with a USIM . . . . . . . . . . . . . . . . . . . . 125 5.5.2.1 Temporary Private User Identity . . . . . . . . . . . . . 126 5.5.2.2 Temporary Public User Identity . . . . . . . . . . . . . 127 5.5.2.3 Home Network Domain URI . . . . . . . . . . . . . . . 127 5.5.2.4 Registration Flow . . . . . . . . . . . . . . . . . . . . . 127 5.6 Subscription to the reg Event State . . . . . . . . . . . . . . . . . . . . . . 130 5.7 Basic Session Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135 5.7.1 The IMS Terminal Sends an INVITE Request . . . . . . . . . . . . 138 5.7.2 The Originating P-CSCF Processes the INVITE Request . . . . . . 145 5.7.3 The Originating S-CSCF Processes the INVITE Request . . . . . . 146 5.7.4 The Terminating I-CSCF Processes the INVITE Request . . . . . . 150 5.7.5 The Terminating S-CSCF Processes the INVITE Request . . . . . . 151 5.7.6 The Terminating P-CSCF Processes the INVITE Request . . . . . . 154 5.7.7 The Callee’s Terminal Processes the INVITE Request . . . . . . . . 154 5.7.8 Processing the 183 Response . . . . . . . . . . . . . . . . . . . . . 158 5.7.9 The Caller’s IMS Terminal Processes the 183 Response . . . . . . . 159 5.7.10 The Callee’s IMS Terminal Processes the PRACK request . . . . . 159 5.7.11 Alerting the Callee . . . . . . . . . . . . . . . . . . . . . . . . . . 161 5.8 Application Servers: Providing Services to Users . . . . . . . . . . . . . . . 166 5.8.1 Generalities about Application Servers . . . . . . . . . . . . . . . . 167 5.8.2 Types of Application Servers . . . . . . . . . . . . . . . . . . . . . 169 5.8.2.1 The SIP Application Server . . . . . . . . . . . . . . . 169 5.8.2.2 The OSA-SCS . . . . . . . . . . . . . . . . . . . . . . 170 5.8.2.3 The IM-SSF Application Server . . . . . . . . . . . . . 170 5.8.3 The Session Setup Model through Application Servers . . . . . . . 171 5.8.3.1 Application Server Acting as a SIP User Agent . . . . . 172 5.8.3.2 Application Server Acting as a SIP Proxy Server . . . . 174 5.8.3.3 Application Server Acting as a SIP Redirect Server . . . 177 5.8.3.4 Application Server Acting as a SIP B2BUA . . . . . . . 178 5.8.4 Filter Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 5.8.5 An Example of Service Execution . . . . . . . . . . . . . . . . . . 184 5.9 Changes due to Next Generation Networks (NGN) . . . . . . . . . . . . . . 188 5.9.1 New SIP Functionality in NGN . . . . . . . . . . . . . . . . . . . 188 5.9.2 Unneeded IMS Functionality in NGN . . . . . . . . . . . . . . . . 189 5.10 Interworking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 5.10.1 SIP–PSTN Interworking . . . . . . . . . . . . . . . . . . . . . . . 189 5.10.1.1 Gateway Architecture in the IMS . . . . . . . . . . . . . 191 5.10.1.2 The BGCF . . . . . . . . . . . . . . . . . . . . . . . . 192 5.10.2 Interworking with Non-IMS SIP-based Networks . . . . . . . . . . 192 5.10.2.1 IPv4/IPv6 Interworking . . . . . . . . . . . . . . . . . . 192
CONTENTS xi 5.11 Combinational Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 5.12 Basic Sessions Not Requiring Resource Reservation . . . . . . . . . . . . . 197 5.12.1 The Callee Does Not Require Resource Reservation . . . . . . . . 198 5.12.2 The Caller Does Not Require Resource Reservation . . . . . . . . . 204 5.12.3 Neither the Caller Nor the Callee Require Resource Reservation . . 206 5.13 Globally Routable User Agent URIs (GRUU) in IMS . . . . . . . . . . . . . 206 5.14 IMS Communication Service Identiﬁer (ICSI) . . . . . . . . . . . . . . . . 209 5.15 IMS Application Reference Identiﬁer (IARI) . . . . . . . . . . . . . . . . . 212 5.16 NAT Traversal in the IMS . . . . . . . . . . . . . . . . . . . . . . . . . . . 213 6 AAA on the Internet 215 6.1 Authentication, Authorization, and Accounting . . . . . . . . . . . . . . . . 215 6.2 AAA Framework on the Internet . . . . . . . . . . . . . . . . . . . . . . . . 215 6.3 The Diameter Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217 6.3.1 Diameter Sessions . . . . . . . . . . . . . . . . . . . . . . . . . . 218 6.3.2 The Format of a Diameter Message . . . . . . . . . . . . . . . . . 219 6.3.3 Attribute-Value Pairs . . . . . . . . . . . . . . . . . . . . . . . . . 220 6.3.4 The AAA and AAAS URIs . . . . . . . . . . . . . . . . . . . . . . 221 6.3.5 Diameter Base Protocol Commands . . . . . . . . . . . . . . . . . 222 6.3.5.1 Abort Session Request and Answer (ASR, ASA) . . . . 223 6.3.5.2 Accounting Request and Answer (ACR, ACA) . . . . . 223 6.3.5.3 Capabilities Exchange Request and Answer (CER, CEA) 223 6.3.5.4 Device Watchdog Request and Answer (DWR, DWA) . 223 6.3.5.5 Disconnect Peer Request and Answer (DPR, DPA) . . . 223 6.3.5.6 Re-Authentication Request and Answer (RAR, RAA) . . 224 6.3.5.7 Session Termination Request and Answer (STR, STA) . 224 6.3.6 Diameter Base Protocol AVPs . . . . . . . . . . . . . . . . . . . . 224 7 AAA in the IMS 227 7.1 Authentication and Authorization in the IMS . . . . . . . . . . . . . . . . . 227 7.2 The Cx and Dx Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 7.2.1 Command Codes Deﬁned in the Diameter Application for the Cx Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 7.2.1.1 User Authorization Request and Answer (UAR, UAA) . 229 7.2.1.2 Multimedia Auth Request and Answer (MAR, MAA) . . 230 7.2.1.3 Server Assignment Request and Answer (SAR, SAA) . . 230 7.2.1.4 Location Information Request and Answer (LIR, LIA) . 231 7.2.1.5 Registration Termination Request and Answer (RTR, RTA) . . . . . . . . . . . . . . . . . . . . . . . . 232 7.2.1.6 Push Proﬁle Request and Answer (PPR, PPA) . . . . . . 232 7.2.2 AVPs Deﬁned in the Diameter Application for the Cx Interface . . . 232 7.2.2.1 Usage of Existing AVPs . . . . . . . . . . . . . . . . . 236 7.2.3 The User Proﬁle . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 7.3 The Sh Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238 7.3.1 Command Codes Deﬁned in the Diameter Application for the Sh Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 7.3.1.1 User Data Request and Answer (UDR, UDA) . . . . . . 239 7.3.1.2 Proﬁle Update Request and Answer (PUR, PUA) . . . . 240
CONTENTS xii 7.3.1.3 Subscribe Notiﬁcations Request and Answer (SNR, SNA) . . . . . . . . . . . . . . . . . . . . . . . 240 7.3.1.4 Push Notiﬁcation Request and Answer (PNR, PNA) . . 241 7.3.2 AVPs Deﬁned in the Diameter Application for the Sh Interface . . . 241 7.4 Accounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 8 Policy and Charging Control in the IMS 243 8.1 PCC Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 8.1.1 Session Establishment and Policy Control . . . . . . . . . . . . . . 244 8.1.2 SIP Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246 8.1.3 Proxy Access to SDP Bodies . . . . . . . . . . . . . . . . . . . . . 247 8.1.4 Status of the Signaling Bearer . . . . . . . . . . . . . . . . . . . . 248 8.1.5 The Rx Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 8.1.6 The Gx Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 8.2 Charging Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 8.3 Ofﬂine Charging Architecture . . . . . . . . . . . . . . . . . . . . . . . . . 251 8.3.1 Charging-related SIP Header Fields . . . . . . . . . . . . . . . . . 253 8.3.2 IMS Terminal in a Visited Network . . . . . . . . . . . . . . . . . 253 8.3.3 IMS Terminal in its Home Network . . . . . . . . . . . . . . . . . 255 8.3.4 The Rf Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . 258 8.3.5 The Ga Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . 258 8.4 Online Charging Architecture . . . . . . . . . . . . . . . . . . . . . . . . . 260 8.4.1 S-CSCF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260 8.4.2 Application Servers and the MRFC . . . . . . . . . . . . . . . . . 260 8.4.3 Types of Online Charging . . . . . . . . . . . . . . . . . . . . . . 261 8.4.3.1 Unit Determination . . . . . . . . . . . . . . . . . . . . 262 8.4.3.2 Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . 264 8.4.3.3 Tariff Changes . . . . . . . . . . . . . . . . . . . . . . 264 8.4.4 The Ro Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 8.4.5 The Re Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . 265 9 Quality of Service on the Internet 267 9.1 Integrated Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 9.1.1 RSVP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 9.1.2 State in the Network . . . . . . . . . . . . . . . . . . . . . . . . . 269 9.2 Differentiated Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 10 Quality of Service in the IMS 271 10.1 Policy Control and QoS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271 10.2 Instructions to Perform Resource Reservations . . . . . . . . . . . . . . . . 271 10.2.1 Proxy Modifying Bodies . . . . . . . . . . . . . . . . . . . . . . . 272 10.3 Reservations by the Terminals . . . . . . . . . . . . . . . . . . . . . . . . . 274 10.4 QoS in the Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275
CONTENTS xiii 11 Security on the Internet 277 11.1 HTTP Digest Access Authentication . . . . . . . . . . . . . . . . . . . . . . 277 11.1.1 Security Properties of Digest . . . . . . . . . . . . . . . . . . . . . 279 11.2 Certiﬁcates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 11.3 TLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280 11.3.1 SIP Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281 11.3.1.1 Client Authentication . . . . . . . . . . . . . . . . . . . 282 11.4 S/MIME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282 11.4.1 Self-signed Certiﬁcates . . . . . . . . . . . . . . . . . . . . . . . . 284 11.5 Authenticated Identity Body . . . . . . . . . . . . . . . . . . . . . . . . . . 285 11.6 IPsec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 11.6.1 ESP and AH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 11.6.2 Tunnel and Transport Modes . . . . . . . . . . . . . . . . . . . . . 287 11.6.3 Internet Key Exchange . . . . . . . . . . . . . . . . . . . . . . . . 291 11.6.3.1 IKE Security Association Establishment . . . . . . . . . 291 11.6.3.2 IPsec Security Association Establishment . . . . . . . . 291 11.7 Privacy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 11.8 Encrypting Media Streams . . . . . . . . . . . . . . . . . . . . . . . . . . . 292 11.8.1 MIKEY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292 12 Security in the IMS 293 12.1 Access Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293 12.1.1 Authentication and Authorization . . . . . . . . . . . . . . . . . . 294 12.1.1.1 HTTP Digest Access Authentication . . . . . . . . . . . 294 12.1.1.2 HTTP Digest Access Authentication using AKA . . . . 297 12.1.1.2.1 HTTP Digest Access Authentication with AKA: UICC Contains an ISIM . . . . . . . . . . . . . 297 12.1.1.2.2 HTTP Digest Access Authentication with AKA: UICC Contains a USIM . . . . . . . . . . . . . . 300 12.1.2 IPsec Security Association Establishment . . . . . . . . . . . . . . 300 12.1.3 TLS Connection Establishment . . . . . . . . . . . . . . . . . . . 302 12.1.4 IP-CAN Linked Authentication . . . . . . . . . . . . . . . . . . . 303 12.1.4.1 Early IMS Security Solution . . . . . . . . . . . . . . . 303 12.1.4.2 NASS-IMS Bundled Authentication . . . . . . . . . . . 306 12.2 Network Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308 12.2.1 TLS Usage for Network Security . . . . . . . . . . . . . . . . . . . 309 13 Emergency Calls on the Internet 311 13.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 13.2 Location Acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312 13.2.1 Manual Conﬁguration . . . . . . . . . . . . . . . . . . . . . . . . 313 13.2.2 Location Acquired from DHCP . . . . . . . . . . . . . . . . . . . 313 13.2.3 Location Acquired from Layer 2 Protocols . . . . . . . . . . . . . 314 13.2.4 Location Acquired from Application Layer Protocols . . . . . . . . 315 13.2.5 Location Acquired from a GPS . . . . . . . . . . . . . . . . . . . . 316 13.2.6 Wireless Triangulation . . . . . . . . . . . . . . . . . . . . . . . . 316 13.3 Identifying Emergency Calls . . . . . . . . . . . . . . . . . . . . . . . . . . 318 13.4 Locating the Closest PSAP . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
CONTENTS xiv 13.5 Issuing the Emergency Call . . . . . . . . . . . . . . . . . . . . . . . . . . 321 13.5.1 The Terminal Acquires its Location . . . . . . . . . . . . . . . . . 322 13.5.2 The Terminal Does Not Have its Own Location . . . . . . . . . . . 325 14 Emergency Calls in the IMS 329 14.1 Architecture for Supporting Emergency Calls in IMS . . . . . . . . . . . . . 329 14.2 Establishing an Emergency Call in IMS . . . . . . . . . . . . . . . . . . . . 332 14.3 IMS Registration for Emergency Calls . . . . . . . . . . . . . . . . . . . . . 333 14.4 Call Back from the PSAP to a User . . . . . . . . . . . . . . . . . . . . . . 334 14.5 Anonymous Calls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335 14.6 Emergency Calls in Fixed Broadband Accesses . . . . . . . . . . . . . . . . 336 Part III The Media Plane in the IMS 337 15 Media Encoding 341 15.1 Speech Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 15.1.1 Pulse Code Modulation . . . . . . . . . . . . . . . . . . . . . . . . 342 15.1.2 Linear Prediction . . . . . . . . . . . . . . . . . . . . . . . . . . . 343 15.1.3 GSM-FR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344 15.1.4 AMR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345 15.1.4.1 AMR Modes . . . . . . . . . . . . . . . . . . . . . . . 345 15.1.4.2 LPC Coefﬁcients Calculation . . . . . . . . . . . . . . . 347 15.1.4.3 Codebooks . . . . . . . . . . . . . . . . . . . . . . . . 347 15.1.4.4 Adaptive Codebook . . . . . . . . . . . . . . . . . . . . 347 15.1.4.5 Fixed Codebook . . . . . . . . . . . . . . . . . . . . . 348 15.1.4.6 Gains . . . . . . . . . . . . . . . . . . . . . . . . . . . 348 15.1.5 AMR-WB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348 15.1.6 SMV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348 15.2 Video Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353 15.2.1 Common Video Codecs . . . . . . . . . . . . . . . . . . . . . . . 354 15.2.2 H.263 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355 15.2.3 Image Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . 355 15.2.4 Temporal Correlation . . . . . . . . . . . . . . . . . . . . . . . . . 355 15.2.5 Spatial Correlation . . . . . . . . . . . . . . . . . . . . . . . . . . 356 15.3 Text Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356 15.4 Mandatory Codecs in the IMS . . . . . . . . . . . . . . . . . . . . . . . . . 356 16 Media Transport 359 16.1 Reliable Media Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . 359 16.2 Unreliable Media Transport . . . . . . . . . . . . . . . . . . . . . . . . . . 360 16.2.1 DCCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360 16.2.2 RTP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361 16.2.3 RTCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363 16.2.4 SRTP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364 16.3 Media Transport in the IMS . . . . . . . . . . . . . . . . . . . . . . . . . . 364
CONTENTS xv Part IV Building Services with the IMS 367 17 Service Conﬁguration on the Internet 371 17.1 The XML Conﬁguration Access Protocol (XCAP) . . . . . . . . . . . . . . 371 17.1.1 XCAP Application Usage . . . . . . . . . . . . . . . . . . . . . . 373 17.2 An Overview of XML . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374 17.2.1 XML Namespaces . . . . . . . . . . . . . . . . . . . . . . . . . . 376 17.3 HTTP URIs that Identify XCAP Resources . . . . . . . . . . . . . . . . . . 376 17.4 XCAP Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 17.4.1 Create or Replace Operations . . . . . . . . . . . . . . . . . . . . 378 17.4.2 Delete Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 17.4.3 Fetching Operations . . . . . . . . . . . . . . . . . . . . . . . . . 380 17.5 Entity Tags and Conditional Operations . . . . . . . . . . . . . . . . . . . . 380 17.6 Subscriptions to Changes in XML Documents . . . . . . . . . . . . . . . . 383 17.7 XML Patch Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386 18 Service Conﬁguration in the IMS 389 18.1 XDM architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389 18.2 Downloading an XML Document, Attribute, or Element . . . . . . . . . . . 391 18.3 Directory Retrieval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393 18.4 Data Search with XDM . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397 18.5 Subscribing to Changes in XML Documents . . . . . . . . . . . . . . . . . 403 19 The Presence Service on the Internet 405 19.1 Overview of the Presence Service . . . . . . . . . . . . . . . . . . . . . . . 405 19.1.1 The pres URI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407 19.2 The Presence Life Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407 19.3 Presence Subscriptions and Notiﬁcations . . . . . . . . . . . . . . . . . . . 409 19.4 Presence Publication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 19.5 Presence Information Data Format (PIDF) . . . . . . . . . . . . . . . . . . 412 19.5.1 Contents of the PIDF . . . . . . . . . . . . . . . . . . . . . . . . . 413 19.6 The Presence Data Model for SIP . . . . . . . . . . . . . . . . . . . . . . . 414 19.7 Mapping the SIP Presence Data Model to the PIDF . . . . . . . . . . . . . . 416 19.8 Rich PIDF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416 19.8.1 Contents of the RPID . . . . . . . . . . . . . . . . . . . . . . . . . 417 19.9 CIPID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419 19.10 Timed Presence Extension to the PIDF . . . . . . . . . . . . . . . . . . . . 419 19.11 Presence Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421 19.11.1 Service Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . 423 19.11.2 Device Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . 424 19.11.3 An Example of the Presence Capabilities Document . . . . . . . . 424 19.12 Geographical Location in Presence . . . . . . . . . . . . . . . . . . . . . . 424 19.13 Watcher Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427 19.14 Watcher Authorization: Presence Authorization Rules . . . . . . . . . . . . 430 19.14.1 Common Policy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 430 19.14.2 Presence Authorization Policy Documents . . . . . . . . . . . . . . 431
CONTENTS xvi 19.14.3 Uploading Presence Authorization Policy Documents to the Presence Agent . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433 19.14.4 Watcher Authorization: Complete Example . . . . . . . . . . . . . 433 19.15 URI-list Services and Resource Lists . . . . . . . . . . . . . . . . . . . . . 434 19.16 Presence Optimizations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437 19.16.1 Partial Notiﬁcation of Presence Information . . . . . . . . . . . . . 437 19.16.2 Partial Presence Publication . . . . . . . . . . . . . . . . . . . . . 438 19.16.3 Event Notiﬁcation Filtering . . . . . . . . . . . . . . . . . . . . . . 439 20 The Presence Service in the IMS 443 20.1 The Foundation of Services . . . . . . . . . . . . . . . . . . . . . . . . . . 443 20.2 Presence Architecture in the IMS . . . . . . . . . . . . . . . . . . . . . . . 443 20.3 Presence Publication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444 20.4 Watcher Subscription . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446 20.5 Watcher Information and Authorization of Watchers . . . . . . . . . . . . . 447 20.6 Presence Optimizations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 449 20.7 OMA Extensions to PIDF . . . . . . . . . . . . . . . . . . . . . . . . . . . 450 21 Instant Messaging on the Internet 453 21.1 The im URI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 453 21.2 Modes of Instant Messages . . . . . . . . . . . . . . . . . . . . . . . . . . 454 21.3 Pager-mode Instant Messaging . . . . . . . . . . . . . . . . . . . . . . . . . 454 21.3.1 Congestion Control with MESSAGE . . . . . . . . . . . . . . . . . 454 21.4 Session-based Instant Messaging . . . . . . . . . . . . . . . . . . . . . . . 455 21.4.1 The MSRP and MSRPS URLs . . . . . . . . . . . . . . . . . . . . 456 21.4.2 MSRP Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 456 21.4.3 Extensions to SDP due to MSRP . . . . . . . . . . . . . . . . . . . 459 21.4.4 MSRP Core Functionality . . . . . . . . . . . . . . . . . . . . . . 460 21.4.5 Status and Reports . . . . . . . . . . . . . . . . . . . . . . . . . . 461 21.4.6 MSRP Relays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464 21.5 The “isComposing” Indication . . . . . . . . . . . . . . . . . . . . . . . . . 468 21.6 Messaging Multiple Parties . . . . . . . . . . . . . . . . . . . . . . . . . . 470 21.6.1 MESSAGE URI-List Services . . . . . . . . . . . . . . . . . . . . 470 21.6.2 Chat Rooms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 472 21.7 File Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476 22 The Instant Messaging Service in the IMS 477 22.1 Pager-mode Instant Messaging in the IMS . . . . . . . . . . . . . . . . . . . 477 22.2 Pager-mode Instant Messaging to Multiple Recipients . . . . . . . . . . . . 478 22.3 Session-based Instant Messaging in the IMS . . . . . . . . . . . . . . . . . 478 22.4 File Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482 23 Conferencing on the Internet 483 23.1 Conferencing Standardization at the IETF . . . . . . . . . . . . . . . . . . . 483 23.2 The SIPPING Conferencing Framework . . . . . . . . . . . . . . . . . . . . 484 23.2.1 Signaling Architecture . . . . . . . . . . . . . . . . . . . . . . . . 485 23.2.2 Media Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . 488
CONTENTS xvii 23.3 The XCON Conferencing Framework . . . . . . . . . . . . . . . . . . . . . 489 23.3.1 Conference Objects . . . . . . . . . . . . . . . . . . . . . . . . . . 490 23.3.2 Conference Control Server . . . . . . . . . . . . . . . . . . . . . . 491 23.3.3 Foci and Notiﬁcation Service . . . . . . . . . . . . . . . . . . . . . 492 23.3.4 Floor Control Server . . . . . . . . . . . . . . . . . . . . . . . . . 492 23.4 The Binary Floor Control Protocol (BFCP) . . . . . . . . . . . . . . . . . . 493 23.4.1 Contacting the Floor Control Server . . . . . . . . . . . . . . . . . 494 23.4.1.1 Inside an Offer/Answer Exchange . . . . . . . . . . . . 494 23.4.1.2 Outside an Offer/Answer Exchange . . . . . . . . . . . 495 23.4.2 BFCP Message Flow . . . . . . . . . . . . . . . . . . . . . . . . . 495 23.4.3 BFCP Primitives . . . . . . . . . . . . . . . . . . . . . . . . . . . 497 23.4.4 BFCP Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . 497 24 Conferencing in the IMS 499 24.1 The IMS Conferencing Service . . . . . . . . . . . . . . . . . . . . . . . . 499 24.1.1 Creating and Joining a Conference . . . . . . . . . . . . . . . . . . 499 24.1.2 Other Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 502 24.2 Relation with the Work in TISPAN and OMA . . . . . . . . . . . . . . . . . 502 25 Push-to-talk over Cellular 503 25.1 PoC Standardization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 503 25.2 IETF Work Relevant to PoC . . . . . . . . . . . . . . . . . . . . . . . . . . 504 25.2.1 URI-list Services . . . . . . . . . . . . . . . . . . . . . . . . . . . 504 25.2.1.1 Multiple REFER . . . . . . . . . . . . . . . . . . . . . 505 25.2.1.2 URI-list Format . . . . . . . . . . . . . . . . . . . . . . 506 25.2.1.3 Consent-based Communications . . . . . . . . . . . . . 506 25.2.2 Event Package for PoC Settings . . . . . . . . . . . . . . . . . . . 508 25.2.3 SIP Header Fields . . . . . . . . . . . . . . . . . . . . . . . . . . . 508 25.3 Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508 25.4 Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510 25.5 PoC Server Roles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511 25.6 PoC Session Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512 25.6.1 One-to-one PoC Sessions . . . . . . . . . . . . . . . . . . . . . . . 513 25.6.2 Ad-hoc PoC Group . . . . . . . . . . . . . . . . . . . . . . . . . . 514 25.6.3 Pre-arranged PoC Group . . . . . . . . . . . . . . . . . . . . . . . 514 25.6.4 Chat PoC Group . . . . . . . . . . . . . . . . . . . . . . . . . . . 515 25.7 Adding Users to a PoC Session . . . . . . . . . . . . . . . . . . . . . . . . 516 25.8 Group Advertisements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 517 25.9 Session Establishment Types . . . . . . . . . . . . . . . . . . . . . . . . . . 518 25.10 Answer Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 520 25.11 Right-to-send-media Indication Types . . . . . . . . . . . . . . . . . . . . . 521 25.12 Participant Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523 25.13 Barring and Instant Personal Alerts . . . . . . . . . . . . . . . . . . . . . . 523 25.14 Full Duplex Call Follow On . . . . . . . . . . . . . . . . . . . . . . . . . . 523 25.15 The User Plane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523 25.15.1 Media Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . 524 25.15.2 Media Burst Control Protocol . . . . . . . . . . . . . . . . . . . . 524 25.15.2.1 Message Encoding . . . . . . . . . . . . . . . . . . . . 524
CONTENTS xviii 25.15.2.2 Message Reliability . . . . . . . . . . . . . . . . . . . . 525 25.15.2.3 Message Types . . . . . . . . . . . . . . . . . . . . . . 525 25.15.2.4 Message Flow . . . . . . . . . . . . . . . . . . . . . . . 526 25.16 Simultaneous PoC Sessions . . . . . . . . . . . . . . . . . . . . . . . . . . 527 25.17 Charging in PoC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528 26 Multimedia Telephony Services: PSTN/ISDN Simulation Services 529 26.1 Providing Audible Announcements . . . . . . . . . . . . . . . . . . . . . . 530 26.1.1 Announcement at the Time a Session is Being Established . . . . . 530 26.1.2 Announcement During the Duration of the Session . . . . . . . . . 535 26.1.3 Announcement at the End of the Session . . . . . . . . . . . . . . . 535 26.1.4 Announcement When a Session is Rejected . . . . . . . . . . . . . 535 26.2 Communication Diversion (CDIV) and Communication Forwarding . . . . . 536 26.3 Communication Diversion Notiﬁcation (CDIVN) . . . . . . . . . . . . . . . 537 26.4 Conference (CONF) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539 26.5 Message Waiting Indication (MWI) . . . . . . . . . . . . . . . . . . . . . . 539 26.6 Originating Identiﬁcation Presentation/Restriction (OIP, OIR) . . . . . . . . 542 26.7 Terminating Identiﬁcation Presentation/Restriction (TIP, TIR) . . . . . . . . 543 26.8 Anonymous Communication Rejection (ACR) and Communication Barring (CB) . . . . . . . . . . . . . . . . . . . . . . . . . 543 26.9 Advice of Charge (AoC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 545 26.10 Completion of Communications to Busy Subscriber (CCBS) and Completion of Communications on No Reply (CCNR) . . . . . . . . . . . . 548 26.11 Malicious Communication Identiﬁcation (MCID) . . . . . . . . . . . . . . . 549 26.12 Communication Hold (HOLD) . . . . . . . . . . . . . . . . . . . . . . . . . 551 26.13 Explicit Communication Transfer (ECT) . . . . . . . . . . . . . . . . . . . 553 26.14 User Settings in PSTN/ISDN Simulation Services . . . . . . . . . . . . . . 557 27 Voice Call Continuity 559 27.1 Overview of Voice Call Continuity . . . . . . . . . . . . . . . . . . . . . . 559 27.2 VCC Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561 27.3 Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563 27.4 Call Origination and Anchoring . . . . . . . . . . . . . . . . . . . . . . . . 563 27.4.1 IMS Originated Call Leg . . . . . . . . . . . . . . . . . . . . . . . 563 27.4.2 CS Originated Call Leg using CAMEL Services . . . . . . . . . . . 564 27.4.3 CS Originated Call Leg using CAMEL and ISUP Call Diversion . . 566 27.5 Call Termination and Anchoring . . . . . . . . . . . . . . . . . . . . . . . . 567 27.5.1 IMS Terminated Call Leg . . . . . . . . . . . . . . . . . . . . . . . 568 27.5.2 CS Terminated Call Leg . . . . . . . . . . . . . . . . . . . . . . . 569 27.5.3 CS Originated Call is Terminated in the IMS using CAMEL . . . . 570 27.5.4 CS Originated Call is Terminated in the CS Domain . . . . . . . . 571 27.6 Domain Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 572 27.6.1 Transfer from the CS Domain to the IMS Domain . . . . . . . . . . 572 27.6.2 Transfer from the IMS Domain to the CS Domain . . . . . . . . . . 574
CONTENTS xix Appendix A List of IMS-related Speciﬁcations 577 A.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577 A.2 3GPP Speciﬁcations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577 A.3 ETSI NGN Speciﬁcations . . . . . . . . . . . . . . . . . . . . . . . . . . . 578 A.4 OMA Speciﬁcations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 578 References 589 Index 607
Foreword by Stephen Hayes 3GPP, or the Third Generation Partnership Project, was formed in late 1998 to specify the evolution of GSM into a third generation cellular system. Although much focus was placed on new higher bandwidth radio access methods, it was realized that the network infrastructure must also evolve in order to provide the rich services capable of taking advantage of higher bandwidths. The original GSM network infrastructure was very much circuit- and voice- centric. Although data capabilities were added over time the system retained much of its circuit-switched heritage and its inherent limitations. A new approach was needed. IMS, or the IP Multimedia Subsystem, represented that new approach. The development of IMS was very much a collaborative effort between the leading cellular standards organization (3GPP) and the leading Internet standards organization (IETF). IETF provided the base technology and protocol speciﬁcations, while 3GPP developed the architectural framework and protocol integration required to provide the capabilities expected of a world- class mobile system, such as inter-operator roaming, differentiated QoS, and robust charging. Since the initial speciﬁcation of IMS, IMS has been adopted by 3GPP2 (the other major cellular standards organization) and it is the leading contender as the base of the ITU work on Next Generation Networks. In the upcoming decades an understanding of IMS will be as important and fundamental for the well-rounded telecom engineer as ISUP knowledge was in previous decades. IMS is a system. It is designed to provide robust multimedia services across roaming boundaries and over diverse access technologies. To understand IMS, you must understand the underlying protocols and how IMS uses them within its architectural framework. This book facilitates that understanding by explaining ﬁrst the underlying protocols, such as SIP, and then explaining how IMS makes use of those protocols. This approach allows the user to easily grasp the complex relationship between the protocols and entities as developed in the IETF and their usage and extensions as deﬁned in IMS. The two authors are uniquely qualiﬁed to explain not just the inner workings of IMS but also the rationale and tradeoffs behind the various design choices. Miguel Angel Garc´a- ı Mart´n was and still is a key contributor within 3GPP. He was one of the principal designers ı of IMS and authored the initial protocol requirements draft as well as other 3GPP-speciﬁc SIP drafts and RFCs. Gonzalo Camarillo was similarly a key contributor within IETF, where he is currently a SIPPING WG co-chair. He has written many RFCs that are key components of IMS. Both authors have been involved with IMS since its inception and do a good job of explaining not only what IMS is but also how it came to be. Stephen Hayes Chair – 3GPP Core Network
Foreword by Allison Mankin and Jon Peterson The Session Initiation Protocol (SIP) is one of the most active initiatives underway in the Internet Engineering Task Force (IETF) today. While the IETF has standardized a number of Internet applications that have turned out to be quite successful (notably, email and the web), few efforts in the IETF have been as ambitious as SIP. Unlike previous attempts to bring telephony over the Internet, which relied extensively on the existing protocols and operational models of the Public Switched Telephone Network (PSTN), SIP elected to use the best parts of email and web technology as its building blocks, and to construct a framework for establishing real-time communication – be it voice, video, instant messaging, or what have you – that is truly native to the Internet. SIP is a rendezvous protocol – a protocol that allows endpoints on the Internet to discover one another and negotiate the characteristics of a session they would like to share. It converges on the best way for users to communicate, given their preferences, and the capabilities of devices they have at their disposal. Even though it establishes sessions over numerous communications media, it allows policies and services to be provided at the rendezvous level, which greatly simpliﬁes the way end-users and operators manage their needs. This approach has garnered the attention of almost all of the major vendors and service providers interested in telephony today. But the adoption of SIP by 3GPP has been a special, deﬁnitive success for SIP in the global marketplace. 3GPP promises to place SIP ﬁrmly in the hands of millions of consumers worldwide, ushering in a whole new paradigm of Internet- based mobile multimedia communications. The IP Multimedia Subsystem (IMS) of 3GPP is the core of this strategy, and it is a SIP-based core. The IETF has created and continues to develop SIP, and the other protocols for real- time communication and infrastructure: RTP, SDP, DNS, Diameter, . . . As 3GPP builds its successive IMS releases, towards a SIP-based multimedia Internet, IETF and 3GPP have grown into a close, working partnership, initiated by our liaison (RFC3113). Both committed to the Internet style afforded by SIP, two worlds with very different perspectives, the 3GPP world of mobile wireless telephony, and the IETF world of the packet Internet, have learned each other’s considerations. There remain some differences, in the security models, in some aspects of network control. It’s a tribute to the communications, the design work, and not least, to work by the authors of the present volume, that such differences have nonetheless resulted in interoperable SIP, SIP with a coherent character. Gonzalo Camarillo has been one of the protagonists in SIP’s development. In addition to his work editing the core SIP speciﬁcation (RFC3261) within the IETF, Gonzalo has
FOREWORD BY ALLISON MANKIN AND JON PETERSON xxiv chaired the SIPPING Working Group of the IETF (which studies new applications of SIP) and authored numerous documents related to interworking SIP with the traditional telephone network, ensuring that SIP is IPv6 compliant, and using SIP in a wireless context. Miguel A. Garc´a-Mart´n is one of the principal designers of the IMS, and has also ı ı somehow found the time to be one of the main voices for 3GPP within the IETF SIP community. The application of SIP to the mobile handset domain gave rise to numerous new requirements for SIP functionality, many of which would not be obvious to designers unfamiliar with the intricacies of wireless roaming, bandwidth constraints, and so on. As such, Miguel provided some very valuable guidance to the IETF which ensured that SIP is well-tooled to one of its most promising applications. This book is a milestone presenting the ﬁrst in-depth coverage of the 3GPP SIP architecture. It is difﬁcult to overestimate the importance of the 3GPP deployment, and this book will position readers to participate in the engineering of that network. Allison Mankin Jon Peterson Directors of the Transport Area of the IETF