Wide Area Networks
Wide Area Networks covers a large geographical area. It consist a number of interconnected of switching nodes. The transmission of data from one device to another takes place through these switching nodes. Usually two LANs combine to form WAN.
WANs are implemented using different technologies some of which are explained below.
Circuit switching is a dedicated communication path between two stations through the nodes of the network. It consists of a physical link between the nodes. Data generated by the stations are transmitted by through these physical dedicated paths. The incoming data is routed to specific outgoing channel by each node without delay. The example of circuit switching is the telephone network.
In packet switching the data is transmitted in a sequence of small chunks called packets. At each node, the entire packet is received, stored and then transmitted to the next node. These packets are transmitted on the network along some path between stations. Packet switching does not consist of dedicated path for communication between stations. Packet switching networks are generally used for terminal-to-terminal computer and computer-to-computer communication.
Frame relay is based on modern high-speed telecommunication systems. It removed all overheads in the early communication technologies. These overheads were used to detect and remove errors by adding additional bits to produce redundancy, and extra processing at the end stations. In packet-switching, networks were designed with data rate of about 64 kbps to the end user. Whereas frame relay by removing most of the overheads in packet-switching provided a high data rate up to 2 Mbps.
Asynchronous Transfer Mode (ATM), also called cell relay is peak development in circuit switching and packet switching. ATM uses fixed length packets called cells rather than variable length packets used in frame relay. It provides a...