Wide-Area Network (WAN), also called long haul network, is a network that covers a broad area using leased telecommunication lines. WAN includes any telecommunications network which links across metropolitan, regional, national or international boundaries. In general, a WAN connects different smaller networks, such as local area networks (LAN) and metropolitan area networks (MAN). This ensures that computers and users in one location can communicate with the other locations. WAN implementation can be done either with the help of the public transmission system or a private network. Compared to the small area network, like LAN or MAN, WAN is applied more in business and government. They use WANs to transmit data among their staffs, clients or even the suppliers from different geographical location. Actually, this type of telecommunication helps them solving the location limitation of communication.
In general, the data transfer rate of WAN is higher than LAN while the signal propagation delay of WAN is much larger than LAN. The typical rate of a WAN is usually from 56kbps to 155Mbps. And with the increasing development of technology, there are also 622Mbps, 2.4 Gbps and even higher-speed WANs. The signal propagation delay can be from a few milliseconds to hundreds of milliseconds (when using the satellite channel). Main features of WANs is as the following: