Virtual Circuits

In Frame Relay, a Virtual Circuit (VC) is a logical connection between two endpoints. It is created by the Frame Relay network to establish a communication path between two DTE (Data Terminal Equipment) devices. A VC is identified by a Data Link Connection Identifier (DLCI) that is used to differentiate between multiple virtual circuits on the same physical link.

There are two types of virtual circuits in Frame Relay:

Permanent Virtual Circuits (PVC): As the name suggests, a PVC is a fixed virtual circuit between two Frame Relay devices that is permanently established and remains active until it is explicitly removed. It is a preconfigured connection that is established by the service provider. It is identified by a unique DLCI and is typically used for applications that require a permanent connection, such as a leased line.

Switched Virtual Circuits (SVC): An SVC is a temporary virtual circuit that is dynamically established on an as-needed basis. It is initiated by the sending device and is terminated when the communication is complete. SVCs are identified by a temporary DLCI assigned by the network during the setup process.

Virtual circuits provide a flexible way to manage bandwidth by allowing multiple connections to share a single physical link. By using DLCIs, Frame Relay devices can differentiate between different virtual circuits and route traffic to the correct destination.