- Email: [email protected]
Well organized introduction
books This book, part of the Essex Series in Telecommunication and Information Systems, is based on a series of courses for graduate students and professionals in related fields. The book gives an introductory presentation of computer networks. There are nine contributors, including the editor, each chapter being written by one or two of the contributors. The overall subject coverage is reasonably thorough. Nearly all the main parts of communication networks one would expect in such a book are included. Data communications (physical and data link layers; network layer, internetworking; endto-end or transport protocols; application layer protocols; integrated networks; LANs) are subjects of at least one section, and in several cases a chapter or two. There are also chapters on network management, distributed networks, and security issues. The main shortcoming in this coverage is the lack of discussion on the public telephone networks, and their relationship with computer networks. The editor clearly chose to make this book focus on computer networks, which is acceptable; but the relationship between these and the telecommunication networks is too close to ignore. There is a chapter on voice/data integration, but this is written from the viewpoint of the LAN rather than the broader relationship between telephone networks and computer networks. The introductory chapter provides an overview of the subject, a review of historical development of networks, and preview of the book. I commend the editor for including a section on the history of networks; this helps put things in perspec-
204
Well organized introduction tive. However, this section was disappointing, covering only the last 30 years or so, limited in scope to computers, and not including several major milestones, especially in the communications area. Chapter 2 discusses the lower layers of networking, or data communications. The physical and data link layers are well developed, and there is a great deal of complexity involved. The chapter is rather short, however: I expected a more thorough treatment of these layers, which are critical to all communications. Chapter 3 discusses WANs. The major issues in WANs such as addressing, routing, flow and congestion control are discussed. This is a readable introduction to the subject. The well-known protocols for flow control are discussed; and references to more in depth readings are provided. Chapters 4 and 5 discuss the OSI model. The first of these discusses the lower four layers, while Chapter 5 covers the application layers. All of the layers are covered, and there is a section on the need for standards. The two chapters are a thorough coverage of this critical network model. Chapter 6 covers selected proprietary networks. DECNet (Digital Equipment) and SNA (IBM) are covered, and compared with the OSI model. The X.25 protocol is also discussed. Chapters 7 and 8 are devoted to LANs. The first introduces the subject, discusses the media access control methods, and the physical layer, briefly. The three IEEE LAN standards are
each given about 3-4 pages each. The Cambridge ring FDDI, and PC nets are also briefly discussed. The chapter is quite thorough in its breadth of coverage, but the reader will need to go to other references for a thorough coverage. The next chapter presents performance results for LANs, and discusses reliability issues. It supplements the previous chapter by providing some additional depth on LANs. Interconnection of networks, or internetworks, are the subject of Chapter 9. Key topics of this important subject are mentioned and briefly introduced. Chapters 10 and 11 are on the subject of security. The first of these covers coding and the data encryption standard. Chapter 11 is a survey of security and access control. The topics covered include security analysis of a system or network, types of threats, methods of attack, and security measures to be taken. These chapters are thorough in covering key issues, and readable. They don't go into a great deal of depth, but they do provide a good introduction to security, with good reference lists at the end of the chapters. Distributed computing systems are the subject of Chapter 12. These may be seen as a special type of LAN. I was pleased to see the editor include this chapter; many networking books overlook such networks. Network management is covered in the next chapter, another important topic to which little attention has been given in the past. Chapter 14 is on integrated voice and data net-
Computer Communication Networks edited by Gill Waters McGraw-Hill, UK (199 I), £35.00, 370pp
computer communications
books works. I found the title of this chapter misleading; the discussion was primarily concerned with integrated LANs. The viewpoint was thus rather narrow. B-ISDN was mentioned only briefly. It was in this chapter that the relationship between the public telecoms networks
could have been brought out. As part of this, more attention should be given to ISDN and B-ISDN. Chapter 15 covers recent advances: topics discussed include VSAT networks (based on satellite communications); MANs; formal protocol modelling; and
:i:i:i: i: i:i:i:!$ i:i:!:i:i: i: i:i:i:i :i :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
i:!:!: i: !:!:i:£:Z: :~:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Valuable basic grounding The SAA Handbook by Dennis Linnel. Addison-Wesley, UK (1990), :[22.45, 386pp
vol 15 no 3 april 1992
The Systems Application Architecture (SAA) represents an attempt by IBM to provide a common interface to three of its major computing systems (System 370, AS/400, PS/2). SAA aims to allow portability of not only application programs, but also programmer/user skills, by providing a common platform for developing and running applications, plus as a common user interface to the applications. Though launched in 1987, comparatively little has been written about the SAA other than IBM's own manuals. This book aims to provide an overview of SAA to applications developers, programmers, system administrators and other 'sophisticated' users. Different IBM systems supporting SAA are described in some detail. Different components making up the architecture are then explained. The depth to which the architecture is described is sufficient to provide a good introduction to its capabilities and objectives. It does'nt attempt to explain low level technical details. The four major components of the architecture (programming interface, communications support, user access, applications) are dealt with separately. The philosophy behind each is described, together with a detailed
description of the functions, and there are notes on how they are implemented. Any limitations imposed by the underlying computing systems are also discussed. Understandably concentrating on the IBM world, a discussion of related products (eg. AT&T's Application Operating Environment; ESPRIT's Advanced Network Systems Architecture) would have been valuable. It is only in the last chapter that the lack of existing SAA products is mentioned. However, in the final chapter the author states that "other than (for) demonstration purposes, the architecture is not usable", and proceeds to point out a number of deficiencies. The short term expectations are considered, and the potential benefits to IBM, its customers and to third party application developers are outlined. IBM's motives are questioned, with the suggestion that SAA may represent another lock-in strategy. The book provides a good overview of the architecture, to a satisfying level of detail, without becoming lost in technical intricacies. It should prove valuable for those needing to get a basic grounding in the concepts behind SAA.
Michael Warner University of Cambridge, UK
integrated services. The section on integrated services does provide additional information on these, but not enough to obviate my criticism above. Some subjects were emphasized more heavily than others. Two chapters were devoted to security, while only one short chapter was devoted to point-topoint communications. Two chapters were devoted to LANs, and only one to WANs. Two chapters were devoted to the OSI model; only one, totalling 14 pages, was devoted to internetworking, a critical topic. These represent choices made by the editor. If l wanted a book with a balanced overall coverage of computer communication networks, I would expect to see more on data communications and WANs, perhaps at the expense of security; yet some people might be interested in security, and for these the book makes the preferred choice. The chapters on distributed systems and NM are an asset; most books on computer networks don't cover these areas. In sum, this is a well organized introduction to computer networks. It is also well written. In its breadth of coverage it is quite thorough. The exception to this, and the most significant weakness, is the failure to explain or discuss the public telephone networks and their relationship to computer networks. Another weakness, for the instructor, is that there are no problems or exercises included in the book. These would be helpful to an instructor wishing to use it as a textbook for a course on networks.
G M Lundy Naval PostgraduateSchool, Monterey, CA, USA
205
204
Well organized introduction tive. However, this section was disappointing, covering only the last 30 years or so, limited in scope to computers, and not including several major milestones, especially in the communications area. Chapter 2 discusses the lower layers of networking, or data communications. The physical and data link layers are well developed, and there is a great deal of complexity involved. The chapter is rather short, however: I expected a more thorough treatment of these layers, which are critical to all communications. Chapter 3 discusses WANs. The major issues in WANs such as addressing, routing, flow and congestion control are discussed. This is a readable introduction to the subject. The well-known protocols for flow control are discussed; and references to more in depth readings are provided. Chapters 4 and 5 discuss the OSI model. The first of these discusses the lower four layers, while Chapter 5 covers the application layers. All of the layers are covered, and there is a section on the need for standards. The two chapters are a thorough coverage of this critical network model. Chapter 6 covers selected proprietary networks. DECNet (Digital Equipment) and SNA (IBM) are covered, and compared with the OSI model. The X.25 protocol is also discussed. Chapters 7 and 8 are devoted to LANs. The first introduces the subject, discusses the media access control methods, and the physical layer, briefly. The three IEEE LAN standards are
each given about 3-4 pages each. The Cambridge ring FDDI, and PC nets are also briefly discussed. The chapter is quite thorough in its breadth of coverage, but the reader will need to go to other references for a thorough coverage. The next chapter presents performance results for LANs, and discusses reliability issues. It supplements the previous chapter by providing some additional depth on LANs. Interconnection of networks, or internetworks, are the subject of Chapter 9. Key topics of this important subject are mentioned and briefly introduced. Chapters 10 and 11 are on the subject of security. The first of these covers coding and the data encryption standard. Chapter 11 is a survey of security and access control. The topics covered include security analysis of a system or network, types of threats, methods of attack, and security measures to be taken. These chapters are thorough in covering key issues, and readable. They don't go into a great deal of depth, but they do provide a good introduction to security, with good reference lists at the end of the chapters. Distributed computing systems are the subject of Chapter 12. These may be seen as a special type of LAN. I was pleased to see the editor include this chapter; many networking books overlook such networks. Network management is covered in the next chapter, another important topic to which little attention has been given in the past. Chapter 14 is on integrated voice and data net-
Computer Communication Networks edited by Gill Waters McGraw-Hill, UK (199 I), £35.00, 370pp
computer communications
books works. I found the title of this chapter misleading; the discussion was primarily concerned with integrated LANs. The viewpoint was thus rather narrow. B-ISDN was mentioned only briefly. It was in this chapter that the relationship between the public telecoms networks
could have been brought out. As part of this, more attention should be given to ISDN and B-ISDN. Chapter 15 covers recent advances: topics discussed include VSAT networks (based on satellite communications); MANs; formal protocol modelling; and
:i:i:i: i: i:i:i:!$ i:i:!:i:i: i: i:i:i:i :i :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
i:!:!: i: !:!:i:£:Z: :~:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Valuable basic grounding The SAA Handbook by Dennis Linnel. Addison-Wesley, UK (1990), :[22.45, 386pp
vol 15 no 3 april 1992
The Systems Application Architecture (SAA) represents an attempt by IBM to provide a common interface to three of its major computing systems (System 370, AS/400, PS/2). SAA aims to allow portability of not only application programs, but also programmer/user skills, by providing a common platform for developing and running applications, plus as a common user interface to the applications. Though launched in 1987, comparatively little has been written about the SAA other than IBM's own manuals. This book aims to provide an overview of SAA to applications developers, programmers, system administrators and other 'sophisticated' users. Different IBM systems supporting SAA are described in some detail. Different components making up the architecture are then explained. The depth to which the architecture is described is sufficient to provide a good introduction to its capabilities and objectives. It does'nt attempt to explain low level technical details. The four major components of the architecture (programming interface, communications support, user access, applications) are dealt with separately. The philosophy behind each is described, together with a detailed
description of the functions, and there are notes on how they are implemented. Any limitations imposed by the underlying computing systems are also discussed. Understandably concentrating on the IBM world, a discussion of related products (eg. AT&T's Application Operating Environment; ESPRIT's Advanced Network Systems Architecture) would have been valuable. It is only in the last chapter that the lack of existing SAA products is mentioned. However, in the final chapter the author states that "other than (for) demonstration purposes, the architecture is not usable", and proceeds to point out a number of deficiencies. The short term expectations are considered, and the potential benefits to IBM, its customers and to third party application developers are outlined. IBM's motives are questioned, with the suggestion that SAA may represent another lock-in strategy. The book provides a good overview of the architecture, to a satisfying level of detail, without becoming lost in technical intricacies. It should prove valuable for those needing to get a basic grounding in the concepts behind SAA.
Michael Warner University of Cambridge, UK
integrated services. The section on integrated services does provide additional information on these, but not enough to obviate my criticism above. Some subjects were emphasized more heavily than others. Two chapters were devoted to security, while only one short chapter was devoted to point-topoint communications. Two chapters were devoted to LANs, and only one to WANs. Two chapters were devoted to the OSI model; only one, totalling 14 pages, was devoted to internetworking, a critical topic. These represent choices made by the editor. If l wanted a book with a balanced overall coverage of computer communication networks, I would expect to see more on data communications and WANs, perhaps at the expense of security; yet some people might be interested in security, and for these the book makes the preferred choice. The chapters on distributed systems and NM are an asset; most books on computer networks don't cover these areas. In sum, this is a well organized introduction to computer networks. It is also well written. In its breadth of coverage it is quite thorough. The exception to this, and the most significant weakness, is the failure to explain or discuss the public telephone networks and their relationship to computer networks. Another weakness, for the instructor, is that there are no problems or exercises included in the book. These would be helpful to an instructor wishing to use it as a textbook for a course on networks.
G M Lundy Naval PostgraduateSchool, Monterey, CA, USA
205