The size of a network is limited due to size and distance constraints. However networks may be connected over a high speed communications link (called a WAN link) to link them together and thus become a WAN.

Most business organizations use WAN links to interconnect local area networks (LANs) at geographically dispersed sites. Over the years, as business organizations continue to grow both nationally and globally, the demand for WAN links has steadily increased. Call centers, for example, have moved off-shore; distributed computing has replaced large regional data centers; sales offices have expanded to new locations. As WAN links become integral to the day-to-day operations of the business organizations, the availability and reliability of WAN links has a direct, highly visible impact on business operations, employee productivity, and customer satisfaction.