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Virtual Circuit Packet Switching
Virtual circuits operate by establishing a formal connection between two devices in communication. When devices begin a session, they negotiate communication parameters, such as maximum message size, communication windows, and network paths. This negotiation establishes a virtual circuit, which is a well-defined path through the internetwork by which the devices communicate. This virtual circuit generally remains in effect until the devices stop communicating.

Virtual circuits are distinguished by the establishment of a logical connection. Virtual means that the network behaves as though a dedicated physical circuit has been established between the communicating devices. Even though no such physical circuit actually exists, the network presents the appearance of a physical connection to the devices at the ends of the circuit.

Virtual circuits frequently are employed in conjunction with connection-oriented services, which are discussed later in this chapter.