Circuit Switching
Circuit switching is a process that establishes connections on demand and permits exclusive use of those connections until they are released. A circuit-switched network is a type of network in which a physical path is obtained for, and dedicated to, a single connection between two end-points in the network during the connection. The traditional voice phone service using PSTN (not the voice over IP) is circuit-switched. The telephone company reserves a specific physical path to the number you are calling during your call and the physical lines involved are used exclusively between the parties at the two end-points.
Circuit-switching is often compared with packet-switching. The main difference in Packet Switching from Circuit Switching is that the communication lines are not dedicated to passing messages from the source to the destination. Circuit Switching is ideal when data must be transmitted quickly, must arrive in sequencing order and at a constant arrival rate. Thus, when transmitting real time data, such as audio and video when quality of service (QOS) is highly desired, a Circuit Switched network is often used. Packet Switching is more efficient and robust for data that is bursty in its nature and can withstand delays and jitter in transmission, such as e-mail messages and Web pages.
Some packet-switched networks, such as the X.25 and ATM networks, are able to have virtual circuit-switching. A virtual circuit-switched connection is a dedicated logical connection that allows sharing of the physical path among multiple virtual circuit connections.