peeN IAI 31 SAS

The Cambridge distributed computing system. (International computer science series) Bibliography: p. Includes index. 1. Electronic data processing—Distributed processing. Foreword The development during the last five years or so of wide band local communication systems is likely to have a large impact on our view of what a computer system should be. These communication systems have a bandwidth that is two or more orders of magnitude greater than that of an ordinary telephone line, while still being much less than that of an internal computer bus. The work described in this book is based on the Cambridge Digital Communication Ring, the design study for which was published in 1975. It is, however, only at the lowest levels of protocol that it matters greatly what the underlying transport system is and much of the system engineering described could equally well have been based, for example, on an Ethernet. The ring enables services of various kinds to be put at the disposal of users connected to the ring, the most obvious being a filing service and a service for producing hard copy. In much of the work that has been reported from elsewhere, users have been provided with their own personal computers. An alternative approach is to provide a bank of centrally located computers and to allow users to attach one or more of these to their terminals and retain them for their exclusive use until they have finished with them. Work along these latter lines would appear to have progressed further in the Computer Laboratory of the University of Cambridge than it has elsewhere. The problems raised, especially those of resource management, are of much interest from a systems point of view. The authors describe a model system that they have in operation and give their views as to how further development should proceed. It is, perhaps, worth observing that vi Cambridge distributed system the ring used to implement the system also supports other activities; for example, a user at a terminal is able to log in to one of several time-sharing systems. Similarly, a user with a personal computer could be connected to the ring and would enjoy the benefits of the services provided. The chapter that many readers will find particularly timely is one on protection and authentication. These topics have been the subject of much debate and they take on a new aspect when seen from the standpoint of …