Wide Area Network, or WAN, is a geographically distributed network composed of local area networks (LANs) joined into a single large network using services provided by common carriers. Wide area networks (WANS) are commonly implemented in enterprise networking environments in which company offices are in different cities, states, or countries or on different continents.
WAN technologies were previously limited to expensive leased lines such as T1 lines, slow packet-switching services such as X.25, cheap but low-bandwidth solutions such as modems, and dial-up Integrated Services Digital Network (ISDN) connections, but this has changed considerably in recent years. Frame relay services provide high-speed packet-switching services that offer more bandwidth than X.25, and virtual private networks (VPNs) created using Internet Protocol (IP) tunneling technologies enable companies to securely connect branch offices by using the Internet as a backbone service. Intranets and extranets provide remote and mobile users with access to company resources and applications and provide connectivity with business partners and resellers. Wireless networking technologies allow roaming users to access network resources by using cell-based technologies. Digital Subscriber Line (DSL) services provide T1 speeds at much lower costs than dedicated T1 circuits. These and other new technologies continue to evolve and proliferate, allowing enterprise network administrators to implement and administer a highly diverse range of WAN solutions.