2.4 Packet Switching in a Virtual Circuit

In packet switching mode, the message which is to be transmitted from participant A to B is divided into packets. Each packet is provided with destination and control information and is seperately transmitted via the network.

Packet switching can be realized in two different operational modes: connectionless and connection-oriented.

Before starting data transmission in the connection-oriented transmission mode, the path from participant A to B across the network is determined. Thus a virtual circuit is set up. Similar to circuit switching we can distinguish three different phases of a virtual circuit: the set-up, the connection phase and the termination. Each transmitted packet takes the same path via the network. In this way, the packets arrive at their destination in correct order and no additional sequence number is required. Packets which belong to a virtual circuit only need a reduced address information to reach their destination. Consequently, the packet overhead is reduced. During the connection phase of the virtual circuit, the links contained in its transmission path are not exclusively available for it alone but may also be used by other virtual circuits in the network as well.