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 onrefer to as network elements or transmitting elements without loss of generality, cancommunicate 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.