A LAN is a network that connects computers and other devices in a relatively small area, typically a single building or a group of adjacent buildings.
Many WANs are built for one particular organization and are private. They are commonly implemented in enterprise networking environments to link offices in different cities, states, countries and even continents. WANs are also built by Internet service providers (ISPs) to provide connections from the LANs of their customers to the Internet. The Internet, which is a world-wide network of interconnected computer networks, is a WAN, and thus it is the largest WAN in existence.
WANs are commonly constructed using leased lines (i.e., dedicated telephone connections between two points that are set up for a company or other organization by a telecommunications common carrier), but they can also use conventional telephone lines and satellite links. At each end of the leased line a router connects to the LAN on one side and to a hub within the WAN on the other. A router is an electronic device and/or software that connects at least two networks and forwards packets (i.e., the fundamental unit of information transport in all modern computer networks) among them based on their IP addresses, network conditions, etc. A hub is a common connection point for multiple twisted pair copper wire cables or optical fiber cables in a LAN.
Created September 17, 2005. Updated August 9, 2006.