The basic ideas in all types of communication are that there must be three ingredients for the communication to be effective. First, there must be two entities, dubbed a sender and a receiver. These two must have something they need to share. Second, there must be a medium through which the sharable item is channeled. This is the transmission medium. Finally, there must be an agreed-on set of communication rules or protocols. These three apply to every category or structure of communication.
In this chapter, we will focus on these three components in a computer network. But what is a computer network? The reader should be aware that our use of the phrase computer network , from now on, will refer to the traditional computer network.
A computer network is a distributed system consisting of loosely coupled computers and other devices. Any two of these devices, which we will from now on refer to as network elements or transmitting elements without loss of generality, can communicate with each other through a communication medium. In order for these connected devices to be considered a communicating network, there must be a set of communicating rules or protocols each device in the network must follow to communicate with another device in the network. The resulting combination
consisting of hardware and software is a computer communication network or computer network in short. Figure 1.1 shows a computer network.
The hardware component is made of network elements consisting of a collection of nodes that include the end systems commonly called hosts and intermediate switching elements that include hubs, bridges, routers, and gateways that, without loss of generality, we will call network elements.
Network elements may own resources individually, that is, locally or globally. Network software consists of all application programs and network protocols that are used to synchronize, coordinate, and bring about the sharing and exchange of data among the network elements.
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