Circuit switching reserves physical resources but is inefficient. Packet switching is efficient but packets may take different paths. Some services need the benefits of both: a logical “dedicated path” without reserving physical resources.
A logical connection where packets follow the same path through the network using pre-established routing state, without dedicating physical transmission resources.
- Connection establishment sets up routing state at each intermediate switch/router
- All packets in the flow follow the same path using the virtual circuit identifier
- No need for full destination address in each packet — just the VC ID
- Resources are allocated logically, not physically
- Connection teardown releases the VC state
- Logical path maintained for connection duration
- Packets share same route without per-packet routing decisions
- VC identifiers are local to each link (swapped at each hop)
- Contrasts with datagram: no per-packet routing vs per-packet routing
- Built from: Connection-Oriented Service — uses virtual circuits
- Built from: Circuit Switching — inspiration for VC concept
- Contrasts with: Datagram — independent per-packet routing
- Related: Three-Way Handshake — establishes VC state
- VC state at routers means router failures break all active VCs
- VC ID spaces are link-local, requiring translation at each hop
- Not used in modern IP networks (uses datagram approach instead)