Circuit switching is a WAN connectivity technique that allows circuits to be created across a network on demand, and then terminated once they are no longer required. The perfect example of circuit switching in action is a normal telephone call – after you pick up the phone and dial a number, a circuit is created between your phone and the phone of the person you are calling. The circuit is static, meaning that the path over which data (or voice) travels is the same for the duration of the call. Once you hang up, the circuit is terminated.
Circuit switching is commonly used to interconnect networks in cases where a permanent connection is not required. For example, a company might need to transfer data to a branch office just once or twice a day. In cases such as this, the cost of a permanent link wouldn’t be justified. While beneficial in cases where data traffic requirements are low, circuit switched connections generally provide slower throughput rates than other technologies. Examples of circuit switched WAN technologies include traditional analog dialup links using modems and ISDN connections.