Extended and updated 2nd edition

Extended and updated 2nd edition

Books Excellent undergraduate text Data Communications Networking Devices (3rd edn) by Gilbert Held, John Wiley& Sons, UK, 1992, £34.95, 653 pp Data C...

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Books Excellent undergraduate text Data Communications Networking Devices (3rd edn) by Gilbert Held, John Wiley& Sons, UK, 1992, £34.95, 653 pp Data Communications Networking Devices is the fourth of Mr Held's books that I have had the opportunity to review, and continues to expand the reputation Mr Held is acquiring as an authority in the area of computer communications. This is a very comprehensive book covering a wide range of topics, from fundamental concepts in communication theory fight through to intelligent modems and specialized communications equipments. As such, the book fulfils the twin functions of providing a very readable text that students will find accessible and useful, and also that of a comprehensive reference for the communications engineer who needs information on everything from the physical pin assignments for 25-way RS232 connections through to voice digitization and communications security. An additional bonus for the student is the inclusion of review questions at the end of each chapter to test understanding of the material presented. The problem in a work of this scope is not what to include, but what to leave out. It would have been relatively easy to add yet another volume to the already copious literature on packet switching, data modems and so forth, but Mr Held has resisted this temptation, having covered these topics comprehensively in his other, more specialized books. Instead, he has taken the opportunity to concentrate on some of the more unusual and exotic aspects of the technology, and has brought together in one volume several subject areas on which the literature is sparse. The broad areas

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covered include fundamental concepts, networks and internetworking, data transmission equipment, data concentration equipment, redundancy and reliability aids, automatic assistance devices, specialized devices and integrating networking devices. Several appendices include programs for Erlang traffic analysis and computing Poisson distribution. One topic which receives no mention, however, and one that is very difficult to obtain comprehensive information about is that of fax modems. These are becoming increasingly common, and will overtake conventional fax machines in the future due to their vastly superior flexibility. The protocols used with fax modems are quite different from the conventional data modem protocols, and there is

a clear need for information in this area. Perhaps Mr Held is saving this for a specialist text! As a lecturer in digital networks and teletraffic engineering, I have found the book useful both as a source text for material and as a reader to recommend to students who wish to become familiar with the up-to-date range of data communications devices aimed primarily towards the ISDN, both narrow- and broad-band. The book is aimed squarely at the undergraduate academic level, and this is reflected in the comprehensive and elementary treatment of each subject as it is introduced. The book is amply and well illustrated and offers good value for money. In summary, it is a pleasure to add this book to my library of Mr Held's works.

Dr S J Shepherd University of Bradford, UK

Extended and updated 2nd edition Optical Fiber Communications: Principles and Practice (2nd edition) by J M Senior, Prentice-Hall, UK, 1992, £24.95, 907 pp This is an extended and updated edition of an extremely successful publication devoted to an important area of communications technology: optical fibre communication technology. From the contents point of view, the book is expected to arouse interest among a wide readership. It is useful not only for students of electrical engineering majoring in communication technology and computer sciences, but also for practising engineers in need of gaining a background in this rapidly developing area. The book will also provide valuable information to those engaged in applied research and development. It is clear that the author not only has a vast theoretical and practical

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knowledge in this area, but also t h a t he is an outstanding teacher, able to interpret the most difficult issues precisely and comprehensively. Five fundamental problem areas of optical communications (optical fibres and optical cables, light sources and detectors, optical amplifiers and integrated optics, optical communication systems, and optical fibre measurements) are dealt with. Chapter 1 gives an introduction to the history of optical fibre communications systems, and discusses the advantages of this technology. The next four chapters discuss, on the one hand, theoretical fundamentals and physical principles of optical fibre transmission and basic types of optical fibres and their transmission characteristics, and, on the other hand, basic information on the technology of optical fibre manufacture, construction and

Books connection through splicing or fibre connectors. A particular focus concerns the property analysis of single-mode fibres. Chapters 6-9 discuss the fundamental physical principles of light sources and detectors, as well as the physical principles of optical detectors. The principles of the optical fibre direct detection receiver are described in detail, with particular emphasis on their properties. Chapter 10 deals with the principles and theory of amplifying optical signals, both by means of semiconductor laser amplifiers and of fibre amplifiers. This is followed by a discussion on integrated optics elements, such as optical beam splitters, switches, modulators, filters, sources and detectors, as well as optoelectronic integrated elements. Chapters 11 and 12 are devoted to optical communication systems. Detailed consideration is given to the principles of optical fibre communication systems using intensity modulation and the direct detection process, followed by an analysis of system requirements for both analogue and digital fibre systems. It is apparent from the attention devoted recently to coherent optical fibre communications that this is a future area of major exploitation. Hence, rightly,

coherent optical fibre systems are dealt with in some detail in Chapter 12, which covers all major aspects of this developing communications strategy. The final chapters give a general treatment of the main measurements which may be undertaken on optical fibres in both the laboratory and in the field, and describe the current and predicted applications of lightwave transmission via optical fibres in various technical areas. Every chapter is accompanied by practical worked examples which enable readers to obtain a more complete understanding of the issues explained in the book. Last but not least, extensive references provided at the end of every chapter provide a guide for further reading. The book is vast and comprehensive, both as to its extent of 900+ pages and the depth of issues discussed. Therefore, a complete glossary of symbols and abbreviations employed in the text together with a detailed index assist the reader in easy orientation within the book.

Miroslav Petrdsek Miroslav ~kop Czech Technical University of Prague Czech Republic

Comprehensive and very readable TCP/IP Network Administration by Craig Hunt, O'Reilly & Associates, Inc, USA, 1992, $29.95, 471 pp The TCP/IP protocols form the fundamental structure that connects most UNIX-based networks together. In particular, the international Internet network relies on TCP/IP for its communications. While the literature on UNIX is vast, one of the problems that always confronts systems adminis-

trators and managers sooner or later is that of connectivity, and specific guidance in this area in sparse. This book is designed to fill this gap in the literature, and does so very well indeed. Instead of merely giving a list of UNIX commands and functions to perform various tasks (which can be found in any UNIX systems reference), the book gives a comprehensive background of the technology and principles underlying TCP/IP before intro-

ducing the various UNIX utilities based on the system. This is of particular value to technicallyoriented staff who would like to know a little more about what is actually going on, and places the numerous options and switches available on most of the communications functions into context. In particular, the uses of the User Datagram Protocol - a much underestimated and useful service -are discussed, together with advice on access to the service from high level. After a comprehensive and readable discussion of the basic technology, the book covers introductory topics such as 'Getting started' and 'Basic configuraton', which are invaluable for the absolute novice to TCP/IP. Configuration of the interface is then covered together with a discussion on routing configuration. The routing information protocol (RIP) is discussed before introducing specific applications such as sendmail, which is covered in detail. Communication networks are notorious for obscure problems, and the chapter on troubleshooting will be very useful to anyone involved in the maintenance of the network. Use of the ping command is covered, as well as the ifconfig and arp commands. Possibly of greatest importance in the modern world is the chapter on network security. With many large organizations including the academic, financial, commercial and military communities, relying more and more heavily on networked communications, security must be one of the paramount concerns in network design and administration. Too often, a brief dismissal of security is added as an afterthought. Mr Hunt, however, offers a very useful and comprehensive guide to security, starting from the planning stages of threat assessment and writing a

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