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Computer Science
Computer Catlog
Comm Network - TOC

Introduction


    A computer network is the infrastructure that allows two or more computers (called hosts) to communicate with each other. The network achieves this by providing a set of rules for communication, called protocols, which should be observed by all participating hosts. The need for a protocol should be obvious: it allows different computers from different vendors and with different operating characteristics to 'speak the same language'.


    This chapter introduces the fundamental concepts of computer networks. We will first look at constituent network components and various network types, and then describe a reference model for network protocol architectures which we will expand upon throughout the rest of this book. We will also discuss the role of international standards and major standards organizations.

Network Components


     The network is made up of two types of components: nodes and communication lines. The nodes typically handle the network protocols and provide switching capabilities. A node is usually itself a computer (general or special) which runs specific network software. The communication lines may take many different shapes and forms, even in the same network. Examples include: copper wire cables, optical fiber, radio channels, and telephone lines.


    A host is connected to the network by a separate communication line which connects it to one of the nodes. In most cases, more than one host may be connected to the same node. From a host's point of view, the entire network may be viewed as a black box, to which many other hosts are connected. Each host has a unique address allocated to it by the network. For a host to communicate with another host, it needs to know the latter's address. All communication between hosts passes through the nodes, which in turn determine how to route messages across the network, from one point to another.
Abstract Network


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