Difference between Switched Virtual Circuit (SVC) vs Permanent Virtual Circuit (PVC)

Refer Following links to subtopics on ATM tutorial:
ATM Network Architecture & Interfaces   ATM Protocol Stack  ATM services 

This page compares SVC (Switched Virtual Circuit) vs PVC (Permanent Virtual Circuit) and mentions difference between SVC (Switched Virtual Circuit) and PVC (Permanent Virtual Circuit). We will understand the concepts of SVC and PVC with respect to ATM/Frame Relay based networks.

Virtual Circuit: The circuit made between two stations at the start of communication using packet switching service is referred as Virtual Circuit. Virtual circuit can have bi-directional communication path between two DTEs or between DTE and DCE. Each of the paths in virtual circuits are identified by unique DLCI field. DLCI is the short form of Data Link Connection Identifier.

More than one virtual circuits are multiplexed on single physical circuit connection for transmission over network. This reduces network complexity and cost of network equipments. Refer difference between circuit switching and packet switching. circuit switching vs packet switching➤.

SVC-Switched Virtual Circuit


• Switched Virtual Circuits (SVCs) are temporary connections created for the purpose of information transfer. There are four steps to establish SVC connection viz. call setup, data transfer, Idle and call termination.

• Once the virtual circuit is cleared, it has to be re-establish in order to transmit any further data.

• As the circuit is not fixed (i.e. not open) all the time, the cost to use the SVC service is less. It is established on need basis in order to transmit data as required.

PVC-Permanent Virtual Circuit

• Permanent Virtual Circuits (PVCs) are permanent connections established for the sole purpose of frequent as well as consistent data transfer.

• As it is like leased line, PVC connection do not require to be be established using call setup or termination states. PVC will be either in data transfer mode or in IDle mode.

• In data transfer mode, data is transmitted between two DTE devices over virtual circuit path.

• In Idle mode, connection between DTEs is available but data transfer is not progressing.

• Unlike Switched Virtual Circuit, PVCs are not terminated during idle state.

• As this type of virtual circuit connection is permanent, data transfer can take place as soon as it is ready to transmit.

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