Alternative Strategies for Managing Virtual Circuit Failure and Recovery in Local Area Computer Networks

A virtual circuit (or path) is a full-duplex logical connection between two processes. Two varieties of idealized virtual circuits that differ in their reliability characteristics can be distinguished: simple virtual circuits and reliable virtual circuits. Simple virtual circuits have the basic characteristic that data are transmitted across the circuit with no errors as long as the circuit is operational; however, the circuit may fail at any time. Reliable virtual circuits transmit data reliably at all times, in spite of link or processor failures: any recovery and/or reconfiguration that takes place to reconstruct a failed circuit is totally invisible to the two endpoints; any recovery and/or reconfiguration of a failed endpoint (process or processor) is invisible to the nonfailed end. A simple uniform mechanism for managing simple and reliable virtual circuits and for coping with failures of virtual circuits in a local area computer network is described. The mechanism supports the movement of Virtual circuit endpoints to different machines (as part of reconfiguration following failure, for example), and is robust with respect to the failure of any of the software components involved in the establishment and management of simple virtual circuits.