Wide Area Network (WAN)

Wide Area Networks, or WANs, connect a geographically diverse group of computers within a state, country, or even across several states or countries. WANs typically are connected by telephone lines, other types of communication lines, or radio waves. Quite often, smaller local area networks (LANs) are linked together to form a WAN. This is accomplished via dedicated private lines, leased from telecommunications firms like Sprint and AT&T, or by Switched Multi-Megabit Data Services (SMDS) technology, developed in 1995 to eliminate the need for a leased line.

WAN technology has been refined over a period of several decades. It first emerged in the mid-twentieth century with the advent of networks like ARPAnet. Developed in 1969 by the Department of Defense, ARPAnet and several other networks eventually evolved into the Internet, the largest WAN in the world. The packet switching technology most commonly used with WANs surfaced in the 1960s, and standard packet switching protocol, known as X.25, was developed in 1976. To increase network

speed, packet switching allows for the parceling of data into smaller chunks, known as packets, prior to transmission. These packets can travel independently via alternate routes, and they are reassembled once they reach their target. Although X.25 remained the most popular WAN packet switching protocol for years, other packet switching protocols used with increasing frequency by WAN developers and administrators include the Internet standard, Transmission Control Protocol/Internet Protocol (TCP/IP), and Frame Relay, used most often by WANs connected via high speed T-1 and T-3 lines.

WANs are used for a variety of purposes. A corporation with offices in several locations may use a WAN to form an intranet. Quite often, the individual offices will use their own LANs for things like internal messaging, data processing functions, and hardware and software sharing. When these LANs are joined together to form a WAN, similar data sharing and messaging capabilities become possible across a much broader geographic area. Businesses wanting to link up with their suppliers or distributors may create a WAN as a means of establishing an extranet. For example, an extranet could provide a sales representative with electronic access to information in about the time it might take to deliver a product, or the availability of a product. Some WANs bring together various types of communications, such as data, video, and voice. Some organizations, including companies, universities, research centers, hospitals, and libraries, use WANs to connect to the Internet.