Wide Area Network (WAN)

Wide Area Network (WAN)

A WAN is a data communications network that covers a relatively broad geographic area (i.e. one city to another and one country to another country) and that often uses transmission facilities provided by common carriers, such as telephone companies.

We will follow traditional usage and call these machines hosts.The hosts are connected by a communication subnet, or just subnet for short .the hosts are owned by the customers whereas the communication subnet is typically owned and operated by a telephone company or Internet service provider. The job of the subnet is to carry messages from host to host, just as telephone system which carries words from speaker to listener.

in most WAN's , the subnet consists of 2 distinct components:

-transmission lines :moves bits between machines.

-Switching elements : are specialized computers that connect three or more transmission lines.

the switching computers are commonly known as routers.

the figure shows how a WAN is useful for companies.