CertiGuide to A+ (A+ 4 Real)  9  Chapter 13: Basic Networking Terminology       9  Wide Area Networking (WAN)

ATM 1 Modem, IDSN, DSL and More

The most inexpensive way to create WAN connection is circuit switching. With the minimum of expenses on the equipment and means, the creation of a WAN is possible.

Circuit switching is a method in which a dedicated physical circuit is established, maintained, and terminated through a carrier network for each communication session. Circuit switching operates much like a normal telephone call. ISDN is an example of a circuit-switched WAN technology.

Circuit-switched connections from one site to another are brought up when needed and generally require low bandwidth. Telephone service connections are limited to 56.6 kbps, and ISDN BRI connections are limited to 128 kbps. Circuit-switched connections are used primarily to connect remote users and mobile users to corporate LANs. They are also used as backup lines for higher-speed circuits, such as Frame Relay and dedicated lines.

Two opportunities inherent with Circuit switching access:

• Dial on demand used with modem access, allows establishing a connection through regular intervals of time according to the prescribed timetable, or establish the connection when the user sends an inquiry to the remote resource, which allows to save money resources and to establish connection only as required.
  
  
• Bandwidth on demand, allows increasing bandwidth if necessary, for example for ISDN. Cheapest of a circuit switched method is dial-up, created by usual analog telephone networks through the modem.

ATM 1 Modem, IDSN, DSL and More