Wiley - NETWORKING IP for 3G.pdf - Wiley - andri98z

IP for 3G—Networking Technologies for

Mobile Communications

Dave Wisely,

Philip Eardley and

Louise Burness

BTexact Technologies

JOHN WILEY & SONS, LTD

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Wisley, Dave.

IP for 3G : networking technologies for mobile communications/Dave

Wisely, Philip

Eardley & Louise Burness.

p. cm.

Includes bibliographical references and index.

ISBN 0-471-48697-3

1. Wireless Internet. 2. Global system for mobile communications. 3. TCP/IP (Computer

network protocol) I. Eardley, Philip. II. Burness, Louise. III. Title.

TK5103.4885 .W573 2002

621.382'12—dc21

2002071377

British Library Cataloguing in Publication Data

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

ISBN 0-471-48697-3

Typeset in 10.5 pt Optima by Deerpark Publishing Services Ltd, Shannon, Ireland.

Printed and bound in Great Britain by Biddies Limited, Guildford and King's Lynn.

This book is printed on acid-free paper responsibly manufactured from sustainable forestry, in

which at least two trees are planted for each one used for paper production.

Acknowledgements

Our ideas about IP for 3G have evolved over several years, helped by stimulating discussions

with many colleagues and friends, including Fiona Mackenzie, Guilhem Ensuque, George

Tsirtsis and Alan O'Neill.

We'd like to thank those who've helped review various sections of the book, suggesting many

useful improvements, and those who educated us about various topics: Fernando Jover

Aparicio, Steve Buttery, Rahul Chaudhuri, Jeff Farr, David Higgins, Nigel Lobley, Rob

Mitchell, Peter Thorpe, the publishers and their anonymous reviewers. Particular thanks go to

Mel Bale.

We have also been active within the EU IST BRAIN project ( http://www.ist-brain.org ) and

our ideas about mobility management and QoS have been particularly influenced by our

BRAIN colleagues. We would like to acknowledge the contributions of the project partners in

these areas:

Siemens AG, British Telecommunications PLC, Agora Systems S.A., Ericsson Radio

Systems AB, France Tlcom - CNET, INRIA, King's College London, Nokia Corporation,

NTT DoCoMo, Sony International (Europe) GmbH, and T-Nova Deutsche Telekom

Innovationsgesellschaft mbH.

We also thank our family and friends for their forbearance during times of stress and

computer crashes.

Finally, many thanks to our employers, BTexact Technologies http://www.btexact.com , for

allowing us to publish and for all the support that they've given to us during the project.

Chapter 1: Introduction

1.1 Scope of the Book

For some years, commentators have been predicting the 'convergence' of the Internet and

mobile industries. But what does convergence mean? Is it just about mobile phones providing

Internet access? Will the coming together of two huge industries actually be much more about

collision than convergence? In truth, there are lots of possibilities about what convergence

might mean, such as:

• Internet providers also supply mobile phones - or vice versa, of course.

• The user's mobile phone is replaced with a palmtop computer.

• The mobile Internet leads to a whole range of new applications.

• The Internet and mobile systems run over the same network.

This book is about the convergence of the Internet - the 'IP' of our title - with mobile - the

'3G', as in 'third generation mobile phones'. The book largely focuses on technology - rather

than commercial or user-oriented considerations, for example - and in particular on the

network aspects. In other words, in terms of the list above, the book is about the final bullet:

about bringing the networking protocols and principles of IP into 3G networks. To achieve

this, we need to explain what 'IP' and '3G' are separately - in fact, this forms the bulk of the

book - before examining their 'convergence'.

The first chapter provides some initial 'high level' motivation for why 'IP for 3G' is considered

a good thing. The reasons fall into two main areas - engineering and economic.

The final chapter covers the technical detail about how IP could play a role in (evolving) 3G

networks. Where is it likely to appear first? In what ways can IP technologies contribute

further? What developments are needed for this to happen? What might the final 'converged'

network look like?

In between the two outer chapters come five inner chapters. These provide a comprehensive

introduction to the technical aspects of IP and 3G. IP and 3G are treated separately; this will

make them useful as stand-alone reference material. The aims of these inner chapters are:

• To explain what 3G is - Particularly to explore its architecture and the critical

networking aspects (such as security, quality of service and mobility management)

that characterise it ( Chapter 2 ).

• To introduce 'all about IP' - Particularly the Internet protocol stack, IP routing and

addressing, and security in IP networks ( Chapter 3 ).

• To survey critically, and give some personal perspectives about, on-going

developments in IP networks in areas that are likely to be most important:

• Call/session control - Examining what a session is and why session management

matters, and focusing on the SIP protocol (Session Initiation Protocol) ( Chapter 4 ).

• Mobility Management - Discussing what 'IP mobility' is, and summarising, analysing

and comparing some of the (many) protocols to solve it ( Chapter 5 ).

• QoS (Quality of Service) - Examining what QoS is, its key elements, the problems

posed by mobility and wireless networks; analysing some of the current and proposed

protocols for QoS; and proposing a solution for 'IP for 3G' ( Chapter 6 ).

• To provide a build-up to Chapter 7 , which aims to bring many of the issues together

and provide our perspective on how 'IP for 3G' could (or should) develop.

The topics covered by this book are wide-ranging and are under active development by the

world-wide research community - many details are changing rapidly - it is a very exciting area

in which to work. Parts of the book give our perspective on areas of active debate and

research.

1.2 IP for 3G

This section concerns 'IP for 3G' and explains what is meant by the terms 'IP' and '3G'. It also

hopefully positions it with regard to things that readers may already know about IP or 3G, i.e.

previous knowledge is helpful but not a prerequisite.

1.2.1 IP

What is meant by 'IP' in the context of this book?

IP stands for the 'Internet Protocol', which specifies how to segment data into packets, with a

header that (amongst other things) specifies the two end points between which the packet is to

be transferred. 'IP' in the context of this book should not be interpreted in such a narrow sense,

but rather more generally as a synonym for the 'Internet'. Indeed, perhaps 'Internet for 3G'

would be a more accurate title.

The word 'Internet' has several connotations. First, and most obviously, 'Internet' refers to

'surfing' - the user's activity of looking at web pages, ordering goods on-line, doing e-mail and

so on, which can involve accessing public sites or private (internal company) sites. This

whole field of applications and the user experience are not the focus of this book. Instead,

attention is focused on the underlying network and protocols that enable this user experience

and such a range of applications. Next, 'Internet' refers to the network, i.e. the routers and

links over which the IP packets generated by the application (the 'surfing') are transferred

from the source to the destination.

Then, there are the 'Internet' protocols - the family of protocols that the Internet network and

terminal run; things like TCP (Transmission Control Protocol, which regulates the source's

transmissions) and DHCP (Dynamic Host Configuration Protocol, which enables terminals to

obtain an IP address dynamically).

The term 'Internet' can also be used more loosely to refer to the IETF - the Internet

Engineering Task Force - which is the body that standardises Internet protocols. It is

noteworthy for its standardisation process being: (1) open - anyone can contribute (for free)

and attend meetings; (2) pragmatic - decisions are based on rough consensus and running

code.

The Internet standardisation process appears to be faster and more dynamic than that of

traditional mobile standardisation organisations - such as ETSI, for example. However, in

reality, they are trying to do rather different jobs. In the IETF, the emphasis is on protocols -

one protocol per function (thus, TCP for transport, HTTP for hypertext transport and so forth).

The IETF has only a very loose architecture and general architectural principles. Many details

of building IP systems are left to integrators and manufacturers. In contrast, the standards for

GSM, for example, are based around a fixed architecture and tightly defined interfaces (which

include protocols). The advantage of defining interfaces, as opposed to just protocols, is that

that much more of the design work has been done and equipment from different manufactures

will always inter-operate. As will be seen later, there is a large amount of work to be done to

turn the IETF protocols into something that resembles a mobile architecture, and Chapter 7

introduces some fixed elements and interfaces to accomplish this.

Finally, 'Internet' can also imply the 'design principles' that are inherent in the Internet

protocols.

Chapters 3–6 cover various Internet protocols. Later in this chapter, the reasons for why IP's

design principles are a good thing and therefore should be worked into 3G are discussed.

1.2.2 3G

What is meant by '3G' in the context of this book?

'3G' is short for 'third generation mobile systems'. 3G is the successor of 2G - the existing

digital mobile systems: GSM in most of the world, D-AMPS in the US, and PHS and PDC in

Japan. 2G in turn was the successor of 1G -the original analogue mobile systems. Just as for

'IP', the term '3G' also has several connotations.

First, '3G' as in its spectrum: the particular radio frequencies in which a 3G system can be

operated. 3G has entered the consciousness of the general public because of the recent selling

off of 3G spectrum in many countries and, in particular, the breathtaking prices reached in the

UK and Germany. From a user's perspective, '3G' is about the particular services it promises

to deliver. 1G and 2G were primarily designed to carry voice calls; although 2G's design also

includes 'short message services', the success of text messaging has been quite unexpected.

3G should deliver higher data rates (up to 2 Mbit/s is often claimed, though it is likely to be

much lower for many years and in many environments), with particular emphasis on

multimedia (like video calls) and data delivery.

The term '3G' also covers two technical aspects. First is the air interface, i.e. the particular

way in which the radio transmission is modulated in order to transfer information 'over the air'

to the receiver. For most of the 3G systems being launched over the next few years, the air

interface is a variant of W-CDMA (Wideband Code Division Multiple Access). The second

technical aspect of '3G' is its network. The network includes all the base stations, switches,

gateways, databases and the (wired) links between them, as well as the definition of the

interfaces between these various components (i.e. the architecture). Included here is how the

network performs functions such as security (e.g. authenticating the user), quality of service

(e.g. prioritising a video call over a data transfer) and mobility management (e.g. delivering

service when moving to the coverage of an adjacent base station). Several specific 3G systems

have been developed, including UMTS in Europe and cdma2000 in the US. A reasonable

summary is that the 3G network is based on an evolved 2G network.

All these topics, especially the networking aspects, are covered in more detail in Chapter 2 .

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