A Wide Area Network (WAN) is best described as a data network that covers a relatively broad geographic distance. Unlike a LAN, which is usually localized within a relatively small area such as a single office, building, or small campus, a WAN will typically span distances of anywhere from a few, to thousands of kilometers. Besides distance, LANs and WANs are generally differentiated by network ownership. With a LAN, companies typically own and operate all of the equipment that interconnects devices – switches, routers, wiring, and so forth. This is usually not the case with a WAN, where a service provider (such as a local telecommunications carrier) generally owns the network links and switching equipment.
In order to interconnect geographically dispersed locations, companies will usually provision services from a telecommunications carrier, generally renting or leasing links on a monthly basis. The speed and cost of these links can vary greatly, depending upon bandwidth requirements, distances to be spanned, and available technologies. As a general rule, WANs are implemented at speeds much slower than their LAN counterparts, with higher bandwidth requirements significantly increasing monthly costs. This is a function of simple economics – providers have made huge investments in building their networks and are doing their best to make money. For companies, choosing the most appropriate WAN technology involves finding a cost-effective solution that meets their performance, reliability, and scalability requirements.