A shared path established between two hosts through a packet network on command, i.e., via signaling as the call is placed. Once the path is selected, all packets in a given session travel the same path, which is selected in consideration of both the condition of the network and the load on it at the instant the connection is required. Thereby, an SVC bypasses failed and congested switches and circuits and improves overall performance through automatic load balancing.Although SVCs are defined in frame relay specifications, they are unusual in public networks due to the carrier's fear that frame relay SVCs would cannibalize more expensive services like ISDN and long distance voice. Rather, frame relay networks employ permanent virtual circuits (PVC), which are predetermined, preprogrammed paths. Globally, X.25 networks largely are based on SVCs. See also channel, circuit, frame, frame relay, load balancing, packet, path, PVC, virtual circuit, and X.25.