1.2 Circuit Switching
Circuit switching is based upon the sender and receiver utilising the full communication channel for the duration of the communication. This type of switching can be found in the Public Switched Telephone Network (PSTN) where telephone calls were initiated by the person dialling and the channel being set up when the person receiving the call answers. This is a connection oriented channel that exists as long as the telephone call lasts.
The main advantages of circuit switching is that it is highly reliable for its purpose, i.e. voice communication, and also that once the circuit is set up, the communication is fast and generally error free.
The drawbacks include the overhead of initial channel set up and the time it takes for the channel to be set up. There is also the issue of the single point of failure causing a disruption in communications.
To address the shortcomings of circuit switching, packet switching was introduced, which rather than using dedicated channels for communication, divided messages into smaller packets which could then be delivered using different routes if required.
Have a look at this wikipedia resource on circuit switching.
Next: Packet Switching