The 3G IP Multimedia Subsystem (IMS) ´ıa- M ar t´ın The 3G IP Multimedia Subsystem (IMS): Merging the Internet and the Cellular Worlds Third Edition Gonzalo Camarillo and Miguel A. Garc © 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 ´ ıa-Mart ´ ın Ericsson, Spain A J ohn Wile y 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. 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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´ıa-Mart´ın. – 3rd ed. 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´ıa-Mart´ın, Miguel A. II. Title. 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´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 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 I MS 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 12 2.2.3 TypesofRFCs 12 2.3 ThirdGenerationPartnershipProject 14 2.3.1 3GPPStructure 15 2.3.2 3GPPDeliverables 15 2.4 ThirdGenerationPartnershipProject2 15 2.4.1 3GPP2Structure 16 2.4.2 3GPP2Deliverables 17 2.5 IETF-3GPP/3GPP2Collaboration 18 2.5.1 InternetArea 18 viii CONTENTS 2.5.2 OperationsandManagementArea 19 2.5.3 TransportArea 19 2.6 Open Mobile Alliance . . . 20 2.6.1 OMAReleasesandSpecifications 20 2.6.2 RelationshipbetweenOMAand3GPP/3GPP2 22 2.6.3 RelationshipbetweenOMAandtheIETF 22 3 General Principles of the IMS Architecture 25 3.1 FromCircuit-switchedtoPacket-switched 25 3.1.1 GSMCircuit-switched 25 3.1.2 GSMPacket-switched 26 3.2 IMSRequirements 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 ServiceControl 28 3.2.6 RapidServiceCreation 29 3.2.7 Multiple Access . . 29 3.3 OverviewofProtocolsusedintheIMS 29 3.3.1 SessionControlProtocol 29 3.3.2 TheAAAProtocol 30 3.3.3 OtherProtocols 31 3.4 OverviewofIMSArchitecture 31 3.4.1 TheDatabases:theHSSandtheSLF 32 3.4.2 TheCSCF 33 3.4.2.1 TheP-CSCF 33 3.4.2.2 P-CSCFLocation 34 3.4.2.3 TheI-CSCF 34 3.4.2.4 I-CSCFLocation 35 3.4.2.5 TheS-CSCF 35 3.4.2.6 S-CSCFLocation 35 3.4.3 TheApplicationServer 35 3.4.3.1 ASLocation 37 3.4.4 TheMRF 37 3.4.4.1 MRFLocation 37 3.4.5 TheBGCF 37 3.4.6 TheIMS-ALGandtheTrGW 37 3.4.7 ThePSTN/CSGateway 39 3.4.8 HomeandVisitedNetworks 40 3.5 IdentificationintheIMS 42 3.5.1 Public User Identities . . . 42 3.5.2 Private User Iden tities . . 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,andISIMin3GPP 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 NGNOverview 49 3.7.2 TheCoreIMSinNGN 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 SessionDescriptionsandSDP 59 4.1.2 TheOffer/AnswerModel 60 4.1.3 SIPandSIPSURIs 61 4.1.4 UserLocation 62 4.2 SIP Entities . 63 4.2.1 ForkingProxies 65 4.2.2 RedirectServers 66 4.3 MessageFormat 67 4.4 The Start Line in SIP Responses: the Status Line 67 4.5 TheStartLineinSIPRequests:theRequestLine 68 4.6 HeaderFields 68 4.7 MessageBody 70 4.8 SIPTransactions 71 4.9 MessageFlowforSessionEstablishment 72 4.10 SIPDialogs 75 4.10.1 Record-Route, Route,andContact HeaderFields 78 4.11 ExtendingSIP 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 EventNotification 85 4.15.1 HighNotificationRates 87 4.15.1.1 Event Thr ottling . . 88 4.15.1.2 ConditionalEventNotification 88 4.16 SignalingCompression 89 4.16.1 SigCompExtendedOperations 90 4.16.2 StaticSIP/SDPDictionary 91 4.17 ContentIndirection 91 4.18 TheREFERMethod 93 4.19 GloballyRoutableUserAgentURIs(GRUU) 96 4.20 NATTraversal 100 4.20.1 TypesofNAT 101 4.20.2 STUN 105 4.20.3 TURN 105 4.20.4 ICE 106 x CONTENTS 5 Session Control in the IMS 111 5.1 PrerequisitesforOperationintheIMS 112 5.2 IPv4andIPv6intheIMS 113 5.3 IP Connectivity Access Network . . 114 5.4 P-CSCFDiscovery 115 5.5 IMS-levelRegistration 117 5.5.1 IMSRegistrationwithanISIM 117 5.5.2 IMSRegistrationwithaUSIM 125 5.5.2.1 Temporary Private User Identity . . 126 5.5.2.2 Temporary Public User Identity . . 127 5.5.2.3 HomeNetworkDomainURI 127 5.5.2.4 RegistrationFlow 127 5.6 Subscription to the reg EventState 130 5.7 BasicSessionSetup 135 5.7.1 TheIMSTerminalSendsanINVITERequest 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 TheCallee’sTerminalProcessestheINVITERequest 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 AlertingtheCallee 161 5.8 ApplicationServers:ProvidingServicestoUsers 166 5.8.1 Generalities about Application Servers . . . . . 167 5.8.2 TypesofApplicationServers 169 5.8.2.1 TheSIPApplicationServer 169 5.8.2.2 TheOSA-SCS 170 5.8.2.3 TheIM-SSFApplicationServer 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 ApplicationServerActingasaSIPB2BUA 178 5.8.4 Filter Criteria . . . 180 5.8.5 AnExampleofServiceExecution 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–PSTNInterworking 189 5.10.1.1 GatewayArchitectureintheIMS 191 5.10.1.2 TheBGCF 192 5.10.2 InterworkingwithNon-IMSSIP-basedNetworks 192 5.10.2.1 IPv4/IPv6Interworking 192 CONTENTS xi 5.11 CombinationalServices 196 5.12 BasicSessionsNotRequiringResourceReservation 197 5.12.1 TheCalleeDoesNotRequireResourceReservation 198 5.12.2 TheCallerDoesNotRequireResourceReservation 204 5.12.3 Neither the Caller Nor the Callee Require Resource Reservation . . 206 5.13 GloballyRoutableUserAgentURIs(GRUU)inIMS 206 5.14 IMSCommunicationServiceIdentifier(ICSI) 209 5.15 IMSApplicationReferenceIdentifier(IARI) 212 5.16 NATTraversalintheIMS 213 6 AAA on the Internet 215 6.1 Authentication,Authorization,andAccounting 215 6.2 AAAFrameworkontheInternet 215 6.3 TheDiameterProtocol 217 6.3.1 DiameterSessions 218 6.3.2 TheFormatofaDiameterMessage 219 6.3.3 Attribute-ValuePairs 220 6.3.4 The AAA and AAAS URIs . . . 221 6.3.5 DiameterBaseProtocolCommands 222 6.3.5.1 AbortSessionRequestandAnswer(ASR,ASA) 223 6.3.5.2 AccountingRequestandAnswer(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 DiameterBaseProtocolAVPs 224 7 AAA in the IMS 227 7.1 AuthenticationandAuthorizationintheIMS 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 PushProfileRequestandAnswer(PPR,PPA) 232 7.2.2 AVPs Defined in the Diameter Application for the Cx Interface . . . 232 7.2.2.1 UsageofExistingAVPs 236 7.2.3 TheUserProfile 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 UserDataRequestandAnswer(UDR,UDA) 239 7.3.1.2 ProfileUpdateRequestandAnswer(PUR,PUA) 240 xii CONTENTS 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 PCCArchitecture 243 8.1.1 SessionEstablishmentandPolicyControl 244 8.1.2 SIPProcedures 246 8.1.3 Proxy Access to SDP Bodies . . . 247 8.1.4 StatusoftheSignalingBearer 248 8.1.5 The Rx Interface 249 8.1.6 The Gx Interface 249 8.2 ChargingArchitecture 251 8.3 OfflineChargingArchitecture 251 8.3.1 Charging-relatedSIPHeaderFields 253 8.3.2 IMSTerminalinaVisitedNetwork 253 8.3.3 IMSTerminalinitsHomeNetwork 255 8.3.4 The Rf Interface 258 8.3.5 The Ga Interface 258 8.4 OnlineChargingArchitecture 260 8.4.1 S-CSCF 260 8.4.2 ApplicationServersandtheMRFC 260 8.4.3 TypesofOnlineCharging 261 8.4.3.1 UnitDetermination 262 8.4.3.2 Rating 264 8.4.3.3 TariffChanges 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 IntegratedServices 267 9.1.1 RSVP 267 9.1.2 StateintheNetwork 269 9.2 DifferentiatedServices 269 10 Quality of Service in the IMS 271 10.1 PolicyControlandQoS 271 10.2 InstructionstoPerformResourceReservations 271 10.2.1 ProxyModifyingBodies 272 10.3 ReservationsbytheTerminals 274 10.4 QoSintheNetwork 275 [...]... Internetbased 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 realtime 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... 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... co-authored several specifications used in the IMS In particular, he is a co-author of the main SIP specification, RFC 3261 Gonzalo is a member of the IAB (Internet Architecture Board) and the IETF liaison manager to 3GPP In addition, he co-chairs the IETF SIPPING working group, which handles the requirements from 3GPP and 3GPP2 related to SIP, and the IETF HIP (Host Identity Protocol) working group,... 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 xxiv FOREWORD BY ALLISON MANKIN AND JON PETERSON chaired the SIPPING Working Group of the IETF... 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,... 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´aı Mart´n was and still is a key contributor within 3GPP He was one of the principal designers... 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 About the Authors Gonzalo Camarillo Gonzalo Camarillo leads the Multimedia Signaling Research Laboratory of Ericsson in Helsinki, Finland He is an active participant in the IETF, where he... 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. .. distributed the topics in this book into four parts: an introduction, the signaling plane in the IMS, the media plane in the IMS, and IMS service examples All four parts follow a similar structure; they provide both Internet and IMS perspectives on each topic First, we describe how each technology works on the Internet Then, we see how the same technology is adapted to work in the IMS Following these two... highlight the gains the operators obtain from the IMS Besides, we discuss what the user can expect from the IMS In addition, we describe how existing services, such as GPRS, WAP, SMS, MMS, and video-telephony over circuits relate to the IMS Part II deals with the signaling plane of the IMS, which includes protocols, such as SIP (Session Initiation Protocol), SDP (Session Description Protocol), Diameter, IPsec, . The 3G IP Multimedia Subsystem (IMS) ´ıa- M ar t´ın The 3G IP Multimedia Subsystem (IMS): Merging the Internet and the Cellular Worlds Third Edition Gonzalo. mobile multimedia communications. The IP Multim edia 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. ContentsofthePIDF 413 19.6 ThePresenceDataModelforSIP 414 19.7 MappingtheSIPPresenceDataModeltothePIDF 416 19.8 RichPIDF 416 19.8.1 ContentsoftheRPID 417 19.9 CIPID 419 19.10TimedPresenceExtensiontothePIDF