The IMS E-Book

Miikka Poikselkä

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 827

Veröffentlichungsjahr: 2013

Beschreibung

The 3rd edition of this highly successful text builds on the achievement of the first two editions to provide comprehensive coverage of IMS. It continues to explore the concepts, architecture, protocols and functionalities of IMS while providing a wealth of new and updated information. It is written in a manner that allows readers to choose the level of knowledge and understanding they need to gain about the IMS.

With 35% new material, The IMS,IP Multimedia Concepts and Services, 3rd Edition has been completely revised to include updated chapters as well as totally new chapters on IMS multimedia telephony and IMS voice call continuity. Additional new material includes IMS transit, IMS local numbering, emergency sessions, identification of communication services in IMS, new authentication model for fixed access, NAT traversal and globally routable user agents URI. Detailed descriptions of protocol behaviour are provided on a level that can be used for implementation and testing.

Key features of the 3rd edition:

• Two new chapters on IMS multimedia telephony service and IMS Voice Call Continuity
• Updated information on Third Generation Partnership Project (3GPP) Release 7 level, including architecture, reference points and concepts
• Substantially extended coverage on IMS detailed procedures
• Completely rewritten and extended chapters on IMS services 

Leseprobe

Contents

Foreword

Preface

Acknowledgements

List of Figures

List of Tables

Part I IMS Architecture and Concepts

1 Introduction

1.1 What is the Internet Protocol Multimedia Subsystem (IMS)?

1.2 Fixed and Mobile Convergence

1.3 Example of IMS Services

1.4 Where did it come from?

1.5 Why a SIP Solution Based on 3GPP Standards?

2 IP Multimedia Subsystem Architecture

2.1 Architectural Requirements

2.2 Description of IMS-related Entities and Functionalities

2.3 IMS Reference Points

3 IMS Concepts

3.1 Overview

3.2 Registration

3.3 Mechanism to Register Multiple User Identities at a Go

3.4 Session Initiation

3.5 Identification

3.6 IP Multimedia Services Identity Module (ISIM)

3.7 Sharing a Single User Identity between Multiple Devices

3.8 Discovering the IMS Entry Point

3.9 S-CSCF Assignment

3.10 Mechanism for Controlling Bearer Traffic

3.11 Charging

3.12 User Profile

3.13 Service Provision

3.14 Connectivity between Traditional CS Users and IMS Users

3.15 IMS Transit

3.16 Support for Local Dialling Plans

3.17 IMS Emergency Sessions

3.18 SIP Compression

3.19 Combination of CS and IMS Services – Combinational Services

3.20 Voice Call Continuity

3.21 Security Services in the IMS

3.22 Interworking between IPv4 and IPv6 in the IMS

Part II IMS Services

4 Presence

4.1 Who will use the Presence Service?

4.2 Presence-Enhanced Services

4.3 Presence Contributing to Business

4.4 What is Presence?

4.5 Presence Service in IMS

4.6 Publishing Presence

4.7 Subscribing Presence

4.8 Watcher Information

4.9 Setting Presence Authorization

5 Group Management

5.1 Group Management’s Contribution to Business

5.2 What is Group Management?

5.3 What is XML Configuration Access Protocol?

5.4 What is Common Policy?

5.5 Resource List

5.6 XCAP Usage for Resource Lists

5.7 Open Mobile Alliance Solution for Group Management

5.8 Multimedia Telephony and Service Management

6 Push to Talk Over Cellular

6.1 PoC Architecture

6.2 PoC Features

6.3 User Plane

6.4 PoC Service Settings

7 Messaging

7.1 Overview of IMS Messaging

7.2 Immediate Messaging

7.3 Session-Based Messaging

7.4 Messaging Interworking

7.5 Instant Messaging by Open Mobile Alliance

8 Conferencing

8.1 IMS Conferencing Architecture and Principles

8.2 IMS Conferencing Procedures

9 Multimedia Telephony

9.1 Introduction

9.2 Multimedia Telephony Communication

9.3 Supplementary Services

Part III Detailed Procedures

10 Introduction to Detailed Procedures

10.1 The Example Scenario

10.2 Base Standards

11 An Example of IMS Registration

11.1 Overview

11.2 Initial Parameters and IMS Management Object

11.3 Signalling PDP Context Establishment

11.4 P-CSCF Discovery

11.5 SIP Registration and Registration Routing Aspects

11.6 Authentication

11.7 Access Security – IPsec SAs

11.8 SIP Security Mechanism Agreement

11.9 IMS Communication Service Identification and other Callee Capabilities

11.10 Compression Negotiation

11.11 Access and Location Information

11.12 Charging-Related Information During Registration

11.13 User Identities

11.14 Re-Registration and Re-Authentication

11.15 De-Registration

11.16 GPRS-IMS-Bundled Authentication (GIBA)

12 An Example IMS Multimedia Telephony Session

12.1 Overview

12.2 Caller and Callee Identities

12.3 Routing

12.4 Compression Negotiation

12.5 Media Negotiation

12.6 Resource Reservation

12.7 Charging-Related Procedures During Session Establishment for Sessions

12.8 Release of a Session

12.9 Alternative IMS Session Establishment Procedures

12.10 Routing of GRUUs

12.11 Routing of PSIs

12.12 A Short Introduction to GPRS

13 An example IMS Voice Call Continuity Procedures

13.1 Overview

13.2 Configuring the Clients with Communication Continuity Configuration Parameters

13.3 Setting up the Initial Call and Call Anchoring

13.4 Domain Transfer: CS to IMS

13.5 Theresa adds Video to the Call

13.6 Domain Transfer: IMS to CS

13.7 Related Standards

References

List of Abbreviations

Index

This edition first published 2009

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Library of Congress Cataloging-in-Publication Data

Poikselka, Miikka.

The IMS : IP multimedia concepts and services / Miikka Poikselka, Georg Mayer. – 3rd ed.

p. cm.

Rev. ed. of: IMS / Miikka Poikselka … [et al.]. 2006

Includes bibliographical references and index.

ISBN 978-0-470-72196-4 (cloth)

1. Multimedia communications. 2. Wireless communication systems. 3. Mobile communication systems. I. Mayer, Georg, 1970- II. IMS. III. Title.

TK5105.15.P65 2008

621.382′ 12 – dc22

2008032207

British Library Cataloguing in Publication Data

A catalogue record for this book is available from the British Library

ISBN 978-0-470-72196-4

Foreword

The telecommunications industry is undergoing a fundamental change and the catalyst for this change is the business models and technologies of the Internet. The ubiquitous use of the Internet Protocol suite (IP) for voice, data, media and entertainment purposes, is driving the convergence of industries, services, networks and business models.

Network convergence is the route through which operators facilitate better access to end-user services and applications. IP provides a common foundation offering end-users seamless access to any service, any time, anywhere, and with any device. Full convergence is driven by enabling technologies such as HTTP/SIP, IPv6, VoIP, and the deployment of wireless broadband technologies such as WLAN, CDMA2000, and UMTS/HSPA.

The 3rd Generation Partnership Projects (3GPP and 3GPP2) have taken these developments into account whilst designing the IP-based Multimedia System (IMS). IMS is an overlay service provisioning platform through which telecommunications operators can utilise Internet technologies to their greatest advantage. It operates across fixed and mobile access technologies including WLAN, UMTS/HSPA, and DSL, along with many others.

The telecommunications industry has high expectations for IMS. This technology offers the prospect of new value chains and business models for operators on the one side, and the increase of the end-user experience through converged and blended services on the other.

This book provides a comprehensive overview of the IMS architecture, its concepts and interfaces, and is an excellent quick reference for IMS practitioners. It tackles questions such as: How can services be implemented with IMS? What are the procedures involved? What do typical call-flows look like?.

The authors are recognized contributors to the development and standardization of IMS and, with the first commercial deployments of IMS occurring in various countries, their effort and commitment is starting to pay off.

Mika Vehviläinen

Chief Operating Officer

Nokia Siemens Networks

Preface

Internet Protocol (IP) Multimedia Subsystem, better known as “IMS”, is based on the specification of Session Initiation Protocol (SIP) as standardized by Internet Engineering Task Force (IETF). But SIP as a protocol is only one part of it. IMS is more than just a protocol; it is an architecture for the convergence of data, speech, fixed and mobile networks and is based on a wide range of protocols, most of which have been developed by IETF. IMS combines and enhances them to allow real-time services on top of various kind of packet-switched technologies (GPRS, ADSL, WLAN, Cable, WiMAX, EPS).

This book was written to provide a detailed insight into what IMS is – i.e., its concepts, architecture, service and protocols. Its intended audience ranges from marketing managers, research engineers, development and test engineers to university students. The book is written in a manner that allows readers to choose the level of knowledge they need and the depth of understanding of IMS they desire to achieve. The book is also very well suited as a reference.

The first few chapters in Part I provide a detailed overview of the system architecture and the entities that, when combined, are necessary to provide IMS. These chapters also present the reference points (interfaces) between these entities and introduces the protocols assigned to these interfaces. This part ends with extensive description of essential IMS concepts such as registration, session establishment, policy and charging control, service provisioning, security, IP version interworking.

In IMS, services are not limited to audio, but also include presence, group management, Push to talk over Cellular, messaging, conferencing and IMS Multimedia Telephony. In Part II of this book, we introduce these advanced services in IMS, including call flows. This part proves that the convergence of services and networks is not a myth, but will have real added value for the user.

SIP and SDP are two of the main building blocks within IMS and their usage gets complemented by a large number of important extensions. Part III goes step by step through an example IMS registration and IMS Multimedia Telephony and Voice Call Continuity at the protocol level, detailing the procedures taken at every entity.

Third Generation Partnership Project (3GPP) and IETF have worked together during recent years in an amazing way to bring about IMS and the protocols used by it. We, the authors, have had the chance to participate in many technical discussions regarding the architecture and protocols and are still very active in further discussions on the ever-improving protocols and communication systems. Some of these discussions, which often can be described as debates or negotiations, frequently take a long time to conclude and even more frequently do not result in an agreement or consensus on the technical solutions. We want to thank all the people in these standardization bodies as well as those in our own companies who have come up with ideas, have shown great patience and have worked hard to standardize this communication system of the future called IMS.

Acknowledgements

The authors of this book would like to extend their thanks to colleagues working in 3GPP and IETF for their great efforts in creating the IMS specifications and related protocols. The authors would also like to give special thanks to the following who helped in the writing of this book providing excellent review comments and suggestions:

Erkki Koivusalo, Hannu Hietalahti, Peter Leis, Tao Haukka, Markku Tuohino, Juha Räsänen, Peter Vestergaard, Tapio Paavonen, Kalle Luukkainen, Pavel Dostal, Jozsef Varga, Martin Öttl, Thomas Belling, Ulrich Wiehe, Krisztian Kiss, Hans Rohnert, Antti Laurila and Adamu Haruna.

The authors want to especially give thanks to Hisham Khartabil and Aki Niemi for the very good team work and their excellent and major contributions during the first two editions, without which this book would not have been possible.

The authors welcome any comments and suggestions for improvements or changes that could be used to improve future editions of this book. Our e-mail addresses are:

[email protected]

[email protected]

List of Figures

Figure 1.1

IMS in converged networks

Figure 1.2

Convergence of networks

Figure 1.3

Multimedia messaging

Figure 1.4

The role of the IMS in the packet switched networks

Figure 1.5

Road to standardized common IMS standards

Figure 2.1

IMS connectivity options when a user is roaming

Figure 2.2

Overview of IMS security

Figure 2.3

IMS charging overview

Figure 2.4

IMS/CS roaming alternatives

Figure 2.5

IMS and layered architecture

Figure 2.6

Access independence

Figure 2.7

S-CSCF routing and basic IMS session setup

Figure 2.8

Structure of HSS

Figure 2.9

Relationship between different application server types

Figure 2.10

Signalling conversion in the SGW

Figure 2.11

Possible deployments for Interconnection Border Control Function

Figure 2.12

IMS architecture

Figure 2.13

HSS resolution using the SLF

Figure 3.1

High-level IMS registration flow

Figure 3.2

Example of implicit registration sets

Figure 3.3

High-level IMS session establishment flow

Figure 3.4

Relationship of user identities

Figure 3.5

Relationship between user identities including shared identity

Figure 3.6

Relationship between UE, GRUU and Public User Identities

Figure 3.7

Sharing a single user identity between multiple devices

Figure 3.8

A GPRS specific mechanism for discovering P-CSCF

Figure 3.9

A generic mechanism for discovering P-CSCF

Figure 3.10

Example of S-CSCF assignment

Figure 3.11

Policy control entities

Figure 3.12

Bearer authorization in UE initiated model

Figure 3.13

Example of IMS based gating in the Access Gateway

Figure 3.14

Subscription to IMS signaling bearer status

Figure 3.15

Bearer authorization in network initiated model

Figure 3.16

IMS charging architecture

Figure 3.17

Example of offline charging

Figure 3.18

Session- and event-based offline charging example

Figure 3.19

Session- and event-based online charging example

Figure 3.20

IMS charging correlation

Figure 3.21

Distribution of charging information

Figure 3.22

Structure of IMS user profile

Figure 3.23

Media authorization in S-CSCF

Figure 3.24

Shared initial filter criteria

Figure 3.25

Structure of initial filter criteria

Figure 3.26

Structure of service point trigger

Figure 3.27

IMS-CS interworking configuration when an IMS user calls a CS user

Figure 3.28

IMS-CS interworking configuration when a CS user calls an IMS user

Figure 3.29

IMS transit solution for PSTN/ISDN

Figure 3.30

IMS as a general transit network

Figure 3.31

Derivation rules for local dialing plans

Figure 3.32

IMS emergency session setup

Figure 3.33

Signalling compression architecture

Figure 3.34

Capability exchange during an ongoing CS call

Figure 3.35

Example for parallel connections when combining IMS and CS services

Figure 3.36

Voice call continuity and IMS originated call

Figure 3.37

Voice call continuity and CS originated call

Figure 3.38

Voice call continuity and terminated call

Figure 3.39

Domain transfer from CS to IMS

Figure 3.40

Domain transfer from IMS to CS

Figure 3.41

Security architecture of the IMS

Figure 3.42

NASS bundled authentication

Figure 3.43

Security domains in the IMS

Figure 3.44

NDS/IP and SEGs

Figure 3.45

Generic bootstrapping architecture

Figure 3.46

Application layer gateway in IMS

Figure 3.47

Routing based on SIP Outbound flows

Figure 3.48

UE discovers reflexive and relayed addresses via STUN/TURN

Figure 3.49

Simplified STUN/TURN/ICE flow

Figure 3.50

End-to-end and interconnection scenarios

Figure 3.51

IPv6 to IPv4 tunnelling mechanism

Figure 4.1

Dynamic presence

Figure 4.2

Examples of enhanced presence service

Figure 4.3

Overview of presence

Figure 4.4

Presence architecture

Figure 4.5

Presence publication

Figure 4.6

Subscription to presence information

Figure 4.7

Subscription to watcher information

Figure 5.1

XCAP operations

Figure 5.2

Common policy data model

Figure 5.3

Presence subscription example flow, no RLS

Figure 5.4

Presence subscription example flow, with RLS

Figure 5.5

Example resource list flow

Figure 5.6

OMA XDM architecture

Figure 5.7

Storing conversation history metadata and retrieving it

Figure 6.1

Push to talk over cellular

Figure 6.2

Voice call versus push to talk over cellular

Figure 6.3

Push to talk over cellular architecture

Figure 6.4

PoC server architecture

Figure 6.5

Different PoC communication models

Figure 6.6

Pre-established PoC session setup

Figure 6.7

On-demand PoC session setup using an unconfirmed mode in the terminating network

Figure 6.8

Incoming session treatment decision tree showing impact of access control list and user’s answer mode

Figure 6.9

User plane Protocol entities

Figure 6.10

RTP control Protocol APP packet format

Figure 7.1

Instant messaging types

Figure 7.2

Immediate messaging flow

Figure 7.3

Session-based messaging flow

Figure 7.4

Example of terminating SMS over IP

Figure 7.5

Example of originating SMS over IP

Figure 7.6

OMA IM architecture

Figure 7.7

OMA IM server architecture

Figure 7.8

Originating immediate message in OMA IM

Figure 7.9

Terminating immediate message in OMA IM

Figure 7.10

Large message mode in OMA IM

Figure 7.11

Different IM session types

Figure 7.12

OMA IM session initiation

Figure 7.13

OMA IM session termination

Figure 7.14

Conversation history function

Figure 7.15

Store and forward functionality for IM users

Figure 7.16

OMA IM user plane

Figure 7.17

OMA IM user plane for deferred messaging and conversation history

Figure 8.1

IMS conferencing architecture

Figure 8.2

Ad-hoc conference creation

Figure 8.3

User calling into a conference

Figure 8.4

Referring users into a conference via conference AS/MRFC

Figure 8.5

Floor control with BFCP

Figure 9.1

Example of incoming communication barring supplementary service

Figure 9.2

Example of outgoing communication barring supplementary service

Figure 9.3

Example of communication diversion supplementary service

Figure 9.4

Example of communication hold supplementary service

Figure 9.5

Example of conference supplementary service

Figure 9.6

Example of explicit call transfer

Figure 10.1

The example scenario

Figure 11.1

Initial registration flow

Figure 11.2

Discovering the P-CSCF via DHCP/DNS

Figure 11.3

Routing during registration

Figure 11.4

Third party register by S-CSCF

Figure 11.5

Authentication information flows during IMS registration

Figure 11.6

SA establishment during initial registration

Figure 11.7

Two sets of SAs during re-authentication

Figure 11.8

Taking a new set of SAs into use and dropping an old set of SAs

Figure 11.9

Request and response routing between UE and P-CSCF over UDP

Figure 11.10

Request and response routing between UE and P-CSCF over TCP

Figure 11.11

Sip-Sec-Agree during initial registration

Figure 11.12

Tobias’s subscription to his registration-state information

Figure 11.13

P-CSCF subscription to Tobias’s registration-state information

Figure 11.14

User-initiated re-registration (without re-authentication)

Figure 11.15

Network-initiated re-authentication

Figure 11.16

User-initiated de-registration

Figure 11.17

Network-initiated de-registration

Figure 11.18

Example early IMS security flow

Figure 12.1

IMS session establishment call flow

Figure 12.2

Routing an initial INVITE request and its responses

Figure 12.3

Routing of subsequent requests and their responses

Figure 12.4

Routing to an application server

Figure 12.5

Registration of feature tags

Figure 12.6

Routing based on caller preferences

Figure 12.7

Routing based on caller preferences: require

Figure 12.8

Routing based on caller preferences: explicit

Figure 12.9

Routing based on caller preferences: require; explicit

Figure 12.10

SDP offer/answer in IMS

Figure 12.11

SIP, SDP offer/answer and preconditions during session establishment

Figure 12.12

SIP session establishment without preconditions

Figure 12.13

Media streams and transport in the example scenario

Figure 12.14

Worst case scenario for media policing

Figure 12.15

Theresa releases the session

Figure 12.16

P-CSCF terminates a session

Figure 12.17

S-CSCF terminates a session

Figure 12.18

Session establishment – resources available at A side

Figure 12.19

Session establishment – uni-directional stream with resource reservation on both sides

Figure 12.20

Session establishment – resources available at B side

Figure 12.21

Session establishment – network initiated resources at B side

Figure 12.22

Session establishment – network initiated resources at A side

Figure 12.23

Session establishment – resources available on both sides

Figure 12.24

Session establishment – early media and ringback tones

Figure 12.25

Session establishment towards a non-IMS terminal

Figure 12.26

Session establishment from a non-IMS terminal

Figure 12.27

Routing of GRUU

Figure 12.28

Routing from a user to a PSI

Figure 12.29

Routing from a PSI to a user

Figure 12.30

Routing from an AS to a PSI

Figure 12.31

PDP context types

Figure 13.1

Basic interworking of CS and IMS calls at MGCF

Figure 13.2

Basic dialog mapping at Tobias’s VCC AS (DTF), acting as a SIP B2BUA

Figure 13.3

VCC Anchoring – simplified call flow

Figure 13.4

VCC – connections after anchoring

Figure 13.5

VCC – connections After CS to PS Domain Transfer (A-Side)

Figure 13.6

VCC – connections After PS to CS Domain Transfer (B-Side)

List of Tables

Table 2.1

Cx commands

Table 2.2

Sh commands

Table 2.3

Summary of reference points

Table 3.1

Information in the PCRF#1

Table 3.2

IP QoS class mapping to UMTS QoS

Table 3.3

The maximum data rates and QoS class in the PCRF#1

Table 3.4

Requested QoS parameters

Table 3.5

The maximum authorized traffic class per media type in the UE

Table 3.6

The values of the maximum authorized UMTS QoS parameters as calculated by UE #1 (Tobias) from the example

Table 3.7

The values of the maximum authorized UMTS QoS parameters as calculated by UE #1 from the example

Table 3.8

Rx commands

Table 3.9

Summary of offline charging functions

Table 3.10

Examples of local dialling strings

Table 3.11

Authentication and key agreement parameters

Table 6.1

PoC server functional distribution

Table 6.2

Summary of different PoC session setup combinations

Table 6.3

Mapping of subtype bit patterns to TBCP Protocol messages

Table 7.1

OMA IM service settings and possible values

Table 10.1

Location of CSCFs and GPRS access for the example scenario

Table 11.1

Routing-related headers

Table 11.2

Filter criteria in Tobias’s S-CSCF

Table 11.3

Tobias’s public user identities

Table 11.4

GIBA registration scenarios

Table 12.1

Filter criteria in Tobias’s S-CSCF

Table 13.1

VCC Related Telephone Numbers and Addresses

Table 13.2

VCC Related Routing Numbers and SIP Addresses

Table 13.3

SIP dialogs at Tobias’s VCC AS (B2BUA)

Table 13.4

SIP dialogs at Theresa’s VCC AS (B2BUA)

Part I

IMS Architecture and Concepts

1

Introduction

1.1 What is the Internet Protocol Multimedia Subsystem (IMS)?

Fixed and mobile networks have gone through a major transition in the past 20 years. In the mobile world, first-generation (1G) systems were introduced in the mid-1980s. These networks offered basic services for users. The main emphasis was on speech and speech-related services. Second-generation (2G) systems in the 1990s brought some data services and more sophisticated supplementary services to the users. The third generation (3G and 3.5G) and its evolution (LTE) is now enabling faster data rates and various multimedia services. In the fixed side, traditional Public Switched Telephone Network (PSTN) and Integrated Services Digital Network (ISDN) networks have dominated traditional voice and video communication. In recent years the usage of the Internet has exploded and more and more users are taking advantage of faster and cheaper Internet connection such as Asymmetric Digital Subscriber Line (ADSL). These types of Internet connections enable always-on connectivity, which is a necessity for people to start using real-time communication means – e.g., chatting applications, online gaming, Voice over IP (VoIP).

At the moment we are experiencing the fast convergence of fixed and mobile worlds as the penetration of mobile devices is increasing on a yearly basis. These mobile devices have large, high-precision displays, they have built-in cameras and a lot of resources for applications. They are always-on always-connected application devices. This redefines applications. Applications are no longer isolated entities exchanging information only with the user interface. The next generation of more exciting applications are peer-to-peer entities, which facilitate sharing: shared browsing, shared whiteboard, shared game experience, shared two-way radio session (i.e., Push to Talk Over Cellular). The concept of being connected will be redefined. Dialling a number and talking will soon be seen as a narrow subset of networking. The ability to establish a peer-to-peer connection between the new Internet Protocol (IP) enabled devices is the key required ingredient. This new paradigm of communications reaches far beyond the capabilities of the Plain Old Telephone Service (POTS).

In order to communicate, IP-based applications must have a mechanism to reach the correspondent. The telephone network currently provides this critical task of establishing a connection. By dialling the peer, the network can establish an ad hoc connection between any two terminals over the IP network. This critical IP connectivity capability is offered only in isolated and single-service provider environments in the Internet; closed systems compete on user base, where user lock-in is key and interworking between service providers is an unwelcome feature. Therefore, we need a global system – the IP Multimedia Subsystem (IMS). It allows applications in IP-enabled devices to establish peer-to-peer and peer-to-content connections easily and securely. Our definition for the IMS is: