In circuit switching, the sender needs to reserve a physical pathway before transmitting a message. A typical example of circuit switching is analog telephony. A circuit switched connection allows for temporary exclusive use of a set of end-to-end physical resources.
In contrast to circuit switching, dedicated circuits provide constant, long-term access to an end-to-end physical pathway. Also in contrast to circuit switching, packet switching does not provision a physical circuit for a particular message at all. Rather, packet switching sends individually addressed protocol data units (packets) onto shared transport media, assuming that network systems will route each packet to the destination and that the destination will be able to reassemble the full message on that end.
Some common examples of circuit switched data technologies include ISDN and analog dial-up modems. With the growing use of broadband, always-on, Internet access, circuit switched data communications are becoming less common.