WANs
A WAN (Wide Area Network) spans an area with a scale of a country or a continent. Communication links or subnets which employ packet switched networks interconnect the servers on a WAN. In a packet switched network, the data being sent are chopped into number of packets that may or may not reach their common destination via the same route. A packet switched network has the advantages of being able to handle computer data traffic efficiently, although it has the disadvantages of having variable delays in delivering data packets to their destinations.

The well known Internet is the world’s largest computer network. It is a large collection of incompatible servers and computers, interconnected together via gateways, spanning over almost the whole globe. All the computers on the Internet communicate using a specific protocol known as the Internet Protocol (IP). Traditionally, the Internet was mainly to support four applications: Email, news, remote login and file transfer. However it has turned out to be much more. The new application, the World Wide Web (WWW) has put multimedia pages containing text, pictures, audio and video onto the Internet. Nevertheless, due to the limited bandwidth and the unpredictable delays caused by packet switched communication networks, the Internet cannot offer time critical or real time applications.