One way to handle heavy network traffic is to divide it between multiple internetworked LANs. Today the most commonly used internetworking devices are high-speed routers, especially in wide area internetworks linking geographically remote sites. But routers are also heavily used in building and campus internetworks. Bridges have also been popular, even though they offer less functionality than routers, because they are less expensive to purchase, implement, and maintain. LAN switches are a new class of internetworking device, and many people believe that switched internetworks will become the most common design for linking building and campus LANs in the future.
Many organizations have LANs located at sites that are geographically distant from each other.
Routers were originally designed to allow users to connect these remote LANs across a wide area network, but bridges can also be used for this purpose. By placing routers or bridges on LANs at two distant sites and connecting them with a telecommunications link, a user on one of the LANs can access resources on the other LAN as if those resources were local. Bridges and routers link adjacent LANs. Local bridges and routers were first used to extend the area a network could cover by allowing users to connect two adjacent LANs to maintain performance by reducing the number of users per segment. To provide network connectivity for more people, or extend it to cover a larger area, it is sometimes necessary to link two different LANs or LAN segments.