Introduction

In the beginning, there was a single computer. Soon it connected to other computers and became a local area network (LAN). LANs allowed files, printers, and applications to be shared freely and securely throughout an organization. For a short time, a LAN was sufficient in most organizations, but soon the need arose to interconnect LANs to provide enterprisewide data availability.

As you might imagine, connecting LANs together provided a challenge simply because of the distances separating them. Some were across town, and some were thousands of miles apart, which was a long way to run a segment of coaxial cable.

New technologies such as X.25 were introduced that could span these distances, and the wide area network (WAN) was born. Some technologies used by WANs are different from those used by LANs, and some WAN technologies are more complex than LAN technologies. Basically, though, a WAN does exactly what a LAN does: It provides connectivity between computers.