Chapter 2: ISDN Helps People Work Together

Linking LANs Together

One of the most basic connections between people who work together today is the high-speed local area network, or LAN. These small networks typically offer transmission speeds of 10 to 30Mbps (megabits per second) through dedicated fiber optic or coaxial cables.

Unfortunately, LANs also have some serious constraints:

The size of a LAN must be carefully monitored. Too many users, or too much traffic, can rapidly overload even the fastest network.

Physical distances are strictly limited. Most LANs must be geographically confined to a single floor, or at best to several floors in a single building.

The costs of extending LANs or linking them through traditional means can be prohibitive.

Which means that many LANs today function as islands. In a typical organization, in fact, there are often as many LANs as there are departments, with very few interconnected in practical, usable ways. The result: administrative messages and interdepartmental mail, as well as access to information stored on other systems - prices, specifications, customer data, orders, manufacturing and delivery schedules, inventory levels, engineering drawings and much, much more - are still relegated to mail carts, bulletin boards and a seemingly endless flow of paper.