Usually, the term Wide Area Network (WAN) refers to a network that covers a large geographical area, and employs communications subnets (circuits) to link the intermediate nodes. A major factor impacting WAN design & performance is a need which they lease communication subsets from telephone companies or other communications carriers. Typically transmission rates are 2 Mbps, 34 Mbps, 155 Mbps, 625 Mbps (or sometimes significantly more). The basic reason of the subnet is to transmit message from one end to another end by intermediate nodes.
In most WAN a subnet contains two types of elements: (i) Transmission lines (ii) Switching element.
Transmission lines also called as channels move about from one machine to another machine. The fundamental purpose of the switching element is to choose the outgoing path for forwarding the message.
Many WANs have been constructed, by including public switched networks, large corporate networks, banking networks, military networks, stock brokerage networks, & airline reservation networks. A WAN is completely owned and used by a single company is frequently referred to as an enterprises network.