Switched virtual circuits (SVCs) are generally set up on a per-call basis and are disconnected when the call is terminated; however, a permanent virtual circuit (PVC) can be established as an option to provide a dedicated circuit link between two facilities. PVC configuration is usually preconfigured by the service provider. Unlike SVCs, PVC are usually very seldom broken/disconnected.
A switched virtual circuit (SVC) is a virtual circuit that is dynamically established on demand and is torn down when transmission is complete, for example after a phone call or a file download. SVCs are used in situations where data transmission is sporadic and/or not always between the same data terminal equipment (DTE) endpoints.
A permanent virtual circuit (PVC) is a virtual circuit established for repeated/continuous use between the same DTE. In a PVC, the long-term association is identical to the data transfer phase of a virtual call. Permanent virtual circuits eliminate the need for repeated call set-up and clearing.
- Frame relay is typically used to provide PVCs.
- ATM provides both switched virtual connections and permanent virtual connections, as they are called in ATM terminology.
- X.25 provides both virtual calls and PVCs, although not all X.25 service providers or DTE implementations support PVCs as their use was much less common than SVCs