It is a telecommunication network which allow to transfer data or resources from one node to another node. Computer networks support so many application and services such as to the digital video, world wide web, digital audio, storages servers and shared use of the application. Computer network can be classified in the way of transmission medium to carry their signals, the network’s size, topology, communication protocol, organizational intent and traffic control mechanism. The internet is known as the best-known computer network. It also support the open system, closed system, network devices such as router, switch, hub, bridge , the layout pattern by which devices are connected to each other is called as network topology. Such as star, bus, mesh, ring. OSI model is also the important part of the computer network. The set of algorithm or rules which clarified the way of communication between the networks. Few of such as IP, TCP, FTP and so on.