Network Data gram Approach

In datagram approach to packet switching, each packet is transmitted independently from all other. This approach can cause the datagram’s of a transmission to arrive at their destination out of the order. The datagram networks are sometimes referred to as connectionless networks. A switch in a datagram network uses a routing table that is based on the destination address. Switching in the Internet is done by using the datagram approach to packet switching at the network layer.

Virtual circuit Approach

In the virtual circuit approach to packet switching, the relationship between all packets belonging to a message is preserved. A single route is selected between source and destination at the beginning of the session. When data are sent, all packets of the transmission travel one after another along the route. The packets may arrive at the destination with different delays if resource allocation is on demand. There exist two types of virtual circuit switching techniques switched virtual circuit (SVC) and Permanent Virtual Circuit (PVC).

Switched virtual circuit (SVC)

in this approach a virtual circuit is created and exists only for the duration of the current specific exchange.

Permanent Virtual Circuit (PVC)

In PVC the same virtual circuit is provided between two systems and because it is always in place, it can be used without connection establishment and connection termination.

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