[...]... SYSTEMS 17 1.3 TYPES OF DISTRIBUTED SYSTEMS Before starting to discuss the principles of distributed systems, let us first take a closer look at the various types of distributed systems In the following we make a distinction between distributed computing systems, distributed information systems, and distributed embedded systems 1.3.1 Distributed Computing Systems An important class of distributed systems. .. 626 14.1.6 Synchronization 627 14.1.7 Consistency and Replication 628 14.1.8 Fault Tolerance 629 14.1.9 Security 630 14.1.10 Distributed Object-Based Systems 631 14.1.11 Distributed File Systems 632 14.1.12 Distributed Web-Based Systems 632 14.1.13 Distributed Coordination-Based Systems 633 14,2 ALPHABETICAL BIBLIOGRAPHY 634 INDEX 669 PREFACE Distributed systems form a rapidly changing field of computer... DEFINITION OF A DISTRIBUTED SYSTEM 3 In order to support heterogeneous computers and networks while offering a single-system view, distributed systems are often organized by means of a layer of software-that is, logically placed between a higher-level layer consisting of users and applications, and a layer underneath consisting of operating systems and basic communication facilities, as shown in Fig 1-1 Accordingly,... 5] 6 ] 1.5.3 Sharing Files in Coda 518 ] 1.6 CONSISTENCY AND REPLICATION 5] 9 11.6.1 Client-Side Caching 520 11.6.2 Server-Side Replication 524 11.6.3 Replication in Peer-to-Peer File Systems 526 11.6.4 File Replication in Grid Systems 528 11.7 FAULT TOLERANCE 529 11.7.1 Handling Byzantine Failures 529 11.7.2 High Availability in Peer-to-Peer Systems 531 11.8 SECURITY 532 11.8.] Security in NFS 533... wide-area systems requires a great deal of care (and not a little patience) Another problem that hinders geographical scalability is that communication in wide-area networks is inherently unreliable, and virtually always point-to-point In contrast, local-area networks generally provide highly reliable communication facilities based on broadcasting, making it much easier to develop distributed systems. .. Availability in Peer-to-Peer Systems 531 11.8 SECURITY 532 11.8.] Security in NFS 533 11.8.2 Decentralized Authentication 536 1] 8.3 Secure Peer-to-Peer File-Sharing Systems 539 11.9 SUMMARY 541 12 DISTRIBUTED WEB-BASED SYSTEMS 12.1 ARCHITECTURE 546 12.1.1 Traditional Web-Based Systems 546 12.1.2 Web Services 551 12.2 PROCESSES 554 12.2.1 Clients 554 12.2.2 The Apache Web Server 556 12.2.3 Web Server Clusters... Accordingly, such a distributed system is sometimes called middleware Figure I-I A distributed system organized as middleware The middleware layer extends over multiple machines, and offers each application the same interface Fig 1-1 shows four networked computers and three applications, of which application B is distributed across computers 2 and 3 Each application is offered the same interface The distributed. .. in Chap 10 on object-based distributed systems This approach allowed us to condense the material, but also to make it more enjoyable to read and study Of course we continue to draw extensively from practice to explain what distributed systems are all about Various aspects of real-life systems such as WebSphere MQ, DNS, GPS, Apache, CORBA, Ice, NFS, Akamai, TIBlRendezvous Jini, and many more are discussed... thousands of dollars each As a result, most organizations had only a handful of computers, and for lack of a way to connect them, these operated independently from one another Starting around the the mid-1980s, however, two advances in technology began to change that situation The first was the development of powerful microprocessors Initially, these were 8-bit machines, but soon 1 6-, 3 2-, and 64-bit... of distributed systems One important characteristic is that differences between the various computers and the ways in which they communicate are mostly hidden from users The same holds for the internal organization of the distributed system Another important characteristic is that users and applications can interact with a distributed system in a consistent and uniform way, regardless of where and . principles and paradigms I Andrew S. Tanenbaum, Maarten Van Steen. p. em. Includes bibliographical references and index. ISBN 0-1 3-2 3922 7-5 1. Electronic data processing Distributed processing. 2. Distributed. Consistency and Replication 628 14.1.8 Fault Tolerance 629 14.1.9 Security 630 14.1.10 Distributed Object-Based Systems 631 14.1.11 Distributed File Systems 632 14.1.12 Distributed Web-Based Systems. 9 1.2.5 Pitfalls 16 1.3 TYPES OF DISTRIBUTED SYSTEMS 17 1.3.1 Distributed Computing Systems 17 1.3.2 Distributed Information Systems 20 1.3.3 Distributed Pervasive Systems 24 1.4 SUMMARY 30 2 ARCHITECTURES