Circuit switching

Circuit switching establishes a dedicated path between the two ends of a conversation before any data is sent, keeps that path and its capacity reserved for the whole session, and releases it at the end. The traditional public switched telephone network is the classic example. Because the path is fixed, delay is low and constant, which suits steady real-time traffic such as voice. The cost is efficiency: the reserved capacity sits idle whenever neither party is sending.

The contrast is packet switching, where data is split into packets that share links with other traffic and may take different routes, trading variable delay for far better use of capacity. Most modern networks, including Voice over IP, run on packet switching. One trap is the virtual circuit, used by older carrier services such as Frame Relay and ATM: it gives a packet-switched network a defined logical path, but it is still packet switching underneath. A dedicated circuit is also not a confidential one. A leased line or telephone circuit carries data unencrypted unless something else encrypts it.

Exam relevance: questions in this area tend to give a description (fixed path, constant latency, reserved bandwidth, or bursty traffic sharing links) and ask which switching method it describes. Candidates are expected to keep virtual circuits on the packet switching side.