A computer communication network established in a large scale. Wide range means that geographically, it can surpass a city, a country or even the whole world. Therefore, the requirements for communication are high and the complexity is high. WAN is called WAN for short.

In practical application, WAN can be interconnected with LAN, that is, LAN can be the terminal system of WAN.

The organization of WAN must be carried out according to certain network architecture and corresponding protocols, so as to realize the interconnection and cooperation of different systems.