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Computers: Wide area network (WAN)
Local area network connects a limited number of computers, which are located in a restricted location. When organizations, companies and home computers need to build a link with those computers located in distant areas they connect to Wide Area Network.
What is WAN?
WAN or Wide Area Network is a large network, which connects two or more local area networks (LANs) and personal computer users. By means of WAN you can collect and pass on information from your computer to any computer (if it has an Internet connection) around the globe.
LAN network components such as (Hub, Router, Switches NIC) and secondary network components such as (Multiplexer, access server, channel service unit, ISDN terminal) work together to create Wide Area Network. It is represented graphically as a cloud.
The best example of WAN is the Internet (so many LANs and WANs are combined to form the Internet) and video conferencing.
To make the point clear we will take the example:
There is a Central Bank in Pakistan, which has three branches 1) Bank A in Dubai, 2) Bank B in Jeddah and 3) Bank C in Bahrain. All three banks have LANs (Local Area Networks) in their office buildings. This means that branch manager and staff of Bank A can send and receive information and data from each other’s computers. But they cannot send and receive data outside the building or to bank A and Bank C.
Now the Central Bank in Pakistan connects its computer system with LANs of three banks from its central office. By means of WAN the Central Bank now communicates with the staff of each branch and get information about the employees, account holders and latest foreign currency rates. WAN interconnects computers of all the three branches so that they can have correspondence with each other.
How data travels in WAN
To print a document, to scan a picture and to listen to music a PC has to be connected to a printer, a scanner and speakers by means of different types of cables and wires.
In the similar fashion to send and receive data from its branches, the Central Bank also needs data highway. In the above example, cables can interconnect computers in a LAN but it is impractical to connect computers of Central Bank with computers of its branches in other countries via cables.
To overcome this difficulty Central Bank utilizes the service of “data transmission channels”. These channels include copper wires, fibre optic cables, microwave signals, radio signals and satellite based wireless networking. Besides connecting different network components in a computer network, they also ensure fast and easy transmission of files, documents and messages in Wide Area Network.
Data travels along the transmission channels in the form of Packets (frame Relay, X-25) or broken cells at irregular intervals (ATM).
In the figure below, the host computer with access server (A) at central office controls the overall computer network and sends commands and messages to LANs of its branches.
The front-end processor transmits data to multiplexer (B) via data transmission channels in the form of packets.
The multiplexer transmit data to router (C) which connect the LANs. It transmits data to the hub, which connects several computers in LANs.
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