Circuit switching is used in public telephone networks and is the basis for private networks built on leased lines and using on-site circuit switches. Circuit switching was developed to handle voice traffic but can also handle digital data, although this latter use is often inefficient.
With circuit switching, a dedicated path is established between two stations for communication. Switching and transmission resources within the network are reserved for the exclusive use of the circuit for the duration of the connection.
The connection is transparent. Once it is established, it appears to attached devices as if there were a direct connection.
Packet switching was designed to provide a more efficient facility than circuit switching for bursty data traffic. With packet switching, a station transmits data in small blocks, called packets.
Each packet contains some portion of the user data plus control information needed for proper functioning of the network.
A key distinguishing element of packet-switching networks is whether the internal operation is datagram or virtual circuit. With internal virtual circuits, a route is defined between two endpoints and all packets for that virtual circuit follow the same route.
With internal datagrams, each packet is treated independently, and packets intended for the same destination may follow different routes.