Tanembaum-ComputerNetworks - 1 INTRODUCTION Each of the...

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1 INTRODUCTION Each of the past three centuries has been dominated by a single technology. The 18th century was the era of the great mechanical systems accompanying the Industrial Revolution. The 19th century was the age of the steam engine. During the 20th century, the key technology was information gathering, processing, and distribution. Among other developments, we saw the installation of worldwide telephone networks, the invention of radio and television, the birth and unprece- dented growth of the computer industry, and the launching of communication satellites. As a result of rapid technological progress, these areas are rapidly converging and the differences between collecting, transporting, storing, and processing infor- mation are quickly disappearing. Organizations with hundreds of offices spread over a wide geographical area routinely expect to be able to examine the current status of even their most remote outpost at the push of a button. As our ability to gather, process, and distribute information grows, the demand for ever more sophisticated information processing grows even faster. Although the computer industry is still young compared to other industries (e.g., automobiles and air transportation), computers have made spectacular pro- gress in a short time. During the first two decades of their existence, computer systems were highly centralized, usually within a single large room. Not infre- quently, this room had glass walls, through which visitors could gawk at the great electronic wonder inside. A medium-sized company or university might have had one or two computers, while large institutions had at most a few dozen. The idea 1
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2 INTRODUCTION CHAP. 1 that within twenty years equally powerful computers smaller than postage stamps would be mass produced by the millions was pure science fiction. The merging of computers and communications has had a profound influence on the way computer systems are organized. The concept of the ‘‘computer center’’ as a room with a large computer to which users bring their work for proc- essing is now totally obsolete. The old model of a single computer serving all of the organization’s computational needs has been replaced by one in which a large number of separate but interconnected computers do the job. These systems are called computer networks . The design and organization of these networks are the subjects of this book. Throughout the book we will use the term ‘‘computer network’’ to mean a col- lection of autonomous computers interconnected by a single technology. Two computers are said to be interconnected if they are able to exchange information. The connection need not be via a copper wire; fiber optics, microwaves, infrared, and communication satellites can also be used. Networks come in many sizes, shapes and forms, as we will see later. Although it may sound strange to some people, neither the Internet nor the World Wide Web is a computer network. By the end of this book, it should be clear why. The quick answer is: the Internet is
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This note was uploaded on 08/08/2011 for the course CS 310 taught by Professor Aartisingh during the Spring '11 term at National Institute of Technology, Calicut.

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Tanembaum-ComputerNetworks - 1 INTRODUCTION Each of the...

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