Circuit switching

Circuit switching is a communication method that reserves a dedicated path between endpoints for the duration of a connection. The reserved path provides a fixed sequence of resources rather than sharing transmission capacity packet by packet.

Call setup: The signaling process that establishes a communication connection before information transfer begins. Circuit switching first selects and reserves a path during this phase.
Packet switching: A communication method that divides data into packets and forwards them through shared network links. It shares link capacity dynamically instead of reserving an end-to-end circuit.
Public switched telephone network: The worldwide telephone system that connects subscribers through interconnected switching networks. Traditional telephone calls commonly used circuit-switched paths through this network.
Blocking probability: The probability that a request for service cannot be admitted because required resources are unavailable. A circuit call can be blocked when every suitable path is occupied.
Time-division multiplexing: A technique that assigns separate time slots to multiple signals sharing a transmission link. Reserved circuits can occupy recurring time slots on shared physical links.
Datagram: A self-contained packet sent without establishing a connection or guaranteeing delivery. Datagrams may take different routes, unlike signals on a fixed circuit.
Telephone exchange: A switching system that connects telephone lines and routes calls within a geographic area. Exchanges establish and release the local segments of telephone circuits.
Grade of service: A measure of the likelihood that a telecommunications service request is blocked or delayed. Telephone networks size circuit capacity around an acceptable call-blocking rate.
Frequency-division multiplexing: A technique that carries multiple signals on distinct frequency bands over the same medium. A circuit may reserve a frequency band rather than a time slot.
Virtual circuit: A packet-switched connection that follows a logically established route through a network. It resembles a reserved path but does not dedicate link capacity to the connection.

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