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Back Computer Computer Engineering Dictionary Computer Networks Virtual Circuits - Definition & Types of Virtual Circuits, Permanent, Switched Virtual Circuits

Virtual Circuits - Definition & Types of Virtual Circuits, Permanent, Switched Virtual Circuits

A Virtual Circuit is a connection oriented ,logical (not physical) communication link between two end systems on a packet switched network. By packet Switched, it means that a virtual circuit allows data and information to transfer in the form of packets.

The size of the packet may vary and this is the main distinguishing factor between circuit switched and virtual circuits. These packets are assigned numbers known as virtual circuit numbers which the router uses to send through the network.

Virtual Circuit chooses among multiple paths available to connect the two end systems. Although multiple paths are available but the point to note is that it connects only two end systems at a time.

Virtual circuits are used mostly in ATM (Asynchronous Transfer Mode), Frame relay, General Packet Radio Service (GPRS), IP or Internet. The figure shows a virtual circuit network. Virtual circuit

Types Of Virtual Circuits:

Virtual Circuits can be divided into two types:

  1. Permanent Virtual Circuits
  2. Switched Virtual Circuits

Permanent Virtual Circuits:

Permanent Virtual Circuits (PVC) are used for a permanent or dedicated provision of a path and stays connected all the time. As this circuit is Connected permanently, it eliminates the need for repeated connection setup and termination. PVC's are typically used on Frame Relay networks.

Switched Virtual Circuits:

Switched Virtual Circuit are used where a temporary connection is required between the two end systems i.e it disconnects when the data transfer is complete. ATM provides both switched virtual connection as well as permanent virtual connections.

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