The basic concept of WAN: usually refers to a long-distance network with a wide coverage. The WAN is the core part of the Internet, and its task is to transport data sent by the host over a long distance. The links connecting the switch nodes of the wide area network are all high-speed links, and the distance can be an optical fiber line of thousands of kilometers or a point-to-point satellite link of tens of thousands of kilometers. Therefore, the first consideration for the WAN is that the communication capacity must be large enough to support the increasing communication volume.
The wide area network is composed of some nodal switches and links connected to these switches. The nodal switches perform the function of storing and forwarding packets. The nodes are all point-to-point connections, but in order to improve the reliability of the network, usually one node switch is often connected to multiple node switches.
From the perspective of hierarchy, the WAN and LAN are very different, because the protocols used by the LAN are mainly at the data link layer (and a small amount of physical layer), while the protocols used by the WAN are mainly at the network layer.
