Computer communication networks: A case history: One computer network connects seven separate computers and allows users to access and share each other's resources

Computer networks consist of an interconnected collection of processors (hosts), network nodes (switches, communications switching computers) that connect the processors, and the communication links (transmission lines) [see Fig. 1]. They are used in electronic mail; inventory control; reservation systems; military command, control, and communication (C
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); office automation; and teleconferencing, among other applications. The goals of computer networks are to make it possible to share resources such as data bases, programs, and processors regardless of the physical location of the user and the resources; to provide the network user with the capability to communicate with other users; to provide reliable and alternative resources; to allow more than one processor to work on a particular problem (distribution); and to provide compatibility of dissimilar equipment and software.