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Permanent WAN connections connect geographically separated LANs. The WAN connection typically uses leased lines for the physical connection between the separated LANs, and typically uses a router to establish and maintain the connection across the line, as long as the router is operational. There is no cost savings for disconnecting the link because the service provider of a leased line charges a fixed cost.
Network protocols use a permanent WAN connection in a manner similar to the way they use a LAN connection. The protocols exchange both user data and maintenance data, including dynamic route and service updates, across the connection. The bandwidth of a leased line usually ranges from about 56 Kbps to 2.048 Mbps, which is much less than that of a LAN. However, this bandwidth is usually sufficient because not all the traffic that occurs on a LAN needs to be routed across a WAN.
For example, when a user at a branch office needs to access a file on the local branch office server, the data traffic generated by the user accessing the file is not routed across the WAN. Data is routed across the WAN only when requests are made for services accessible through the WAN connection.
Dedicated network connections have the following disadvantages:
Cost ---Permanent WAN connectivity is expensive because of the monthly service charge required by the service provider for the permanent circuits. Charges for permanent services are based on the bandwidth provided, not on how much of the bandwidth is actually used.
Setup time ---Permanent network connections are set up by the service provider between fixed points. There is a time factor involved in setting up a permanent circuit and, once the circuit is established, a similar time factor is required to change the end points of the circuit.
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