The 3GIP Multimedia Subsystem (IMS) Merging the Internet and the Cellular Worlds

Third Edition

Gonzalo Camarillo Ericsson, Finland

Miguel A. Garcia-Martin Ericsson, Spain

®WILEY A John Wiley and Sons, Ltd, Publication

Contents

Foreword by Stephen Hayes xxi

Foreword by AUison 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 StructureofthelETF 10 2.2.2 Working Group Operations 12 2.2.3 TypesofRFCs 12

2.3 Third Generation Partnership Project 14 2.3.1 3GPP Strucrure 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

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

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 TheCSCF 33

3.4.2.1 TheP-CSCF 33 3.4.2.2 P-CSCF Location 34 3.4.2.3 Thel-CSCF 34 3.4.2.4 I-CSCF Location 35 3.4.2.5 TheS-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 TheMRF 37 3.4.4.1 MRF Location 37

3.4.5 TheBGCF 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 NGNOverview 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 UserLocation 62

4.2 SIPEntities 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 ExtendingSIP 78

4.11.1 NewMethods 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 NATTraversal 100

4.20.1 TypesofNAT 101 4.20.2 STUN 105 4.20.3 TURN 105 4.20.4 ICE 106

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 TheOSA-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 TheBGCF 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, PRA) 232

7.2.2 AVPs Defined in the Diameter Application for the Cx Interface . . . 232 7.2.2.1 UsageofExistingAVPs 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

Xll

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 Typesof Online Charging 261

8.4.3.1 Unit Determination 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 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 xni

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 SIPUsage 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

XIV CONTENTS

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 AMRModes 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 AnOverviewofXML 374

17.2.1 XML Namespaces 376 17.3 HTTP UPJs 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 ThepresURl 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 Rieh 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

xvi CONTENTS

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 MSRPOverview 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 MSRPRelays 464

21.5 The "isComposing" Indication 468 21.6 Messaging Multiple Parties 470

21.6.1 MESSAGE URI-List Services 470 21.6.2 ChatRooms 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 xvn

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 BFCPEncoding 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 OtherActions 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 Füll Duplex Call FollowOn 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

XVU1

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.l Introduction 577 A.2 3GPP Specifications 577 A.3 ETSI NGN Specifications 578 A.4 OMA Specifications 578

References 589

Index 607