Circuit switching(CS) is a switching technique in which a physical line is switched between the sender and the receiver. The switching is done via the individual exchanges, which are interconnected in a switching hierarchy: Local Switching, Node Switching, Main Switching, Central Switching. Line switching can be time-division multiplex(TDM) or space-division multiplex( SDM).
Line switching consists of the switching phases: Connection setup, connection and disconnection. After connection setup, a connection established by circuit switching is available with its full transmission bandwidth until the connection is cleared. This means that during circuit switching, the bandwidth that is not needed remains unused.
A fixed line path is searched for to establish a connection. This is reserved for the entire duration of the connection and used exclusively for communication between the partners involved. The advantages of line switching over other switching methods are delay-free transmission and full transparency to all higher- layer protocols. Routing during the setup phase is relatively static and requires hardly any computing power.
Disadvantages of circuit switching are the relatively long times required to establish and terminate connections, the lack of alternate paths in the event of an error, and the relatively poor utilization of the available transmission bandwidth.
With Multirate Circuit Switching( MRCS), traditional circuit switching has a method that achieves higher data rates through channel bundling. Fast Circuit Switching( FCS) is also a further development of circuit switching with significantly shorter connection set-up and disconnection times.