SVC routing in network with static routing tables

A method of controlling a network node for use in establishing a call in a virtual circuit based communications network comprising a plurality of network nodes and employing hop-by-hop routing, the network node having a routing table which contains next hop information to adjacent nodes for routes leading to endpoints of the network, comprising the steps of:

• predefining a primary route and an alternate route for respective network endpoints as the next hop information in said routing table;
• receiving a setup message including a destination endpoint;
• searching the routing table based on the destination endpoint for corresponding next hop information;
• and
• attempting to forward the setup message on the primary route defined in the corresponding next hop information for the primary route;
• and
• if the primary route is not usable, then attempting to forward the setup message on the alternate route defined in the corresponding next hop information for the alternate route or cranking the call back to a preceding node in the communications network.

An apparatus used in a network node for establishing a call in a virtual circuit based communications network employing hop-by-hop routing, comprising:

• a routing table which contains next hop information to adjacent nodes corresponding to endpoints of the network, the routing table predefining for respective endpoints a primary route and an alternate route to the next hop;
• means for receiving a setup message having a destination endpoint;
• means for searching the routing table based on the destination endpoint for corresponding next hop routing information for the primary route;
• means for attempting to forward the setup message on the primary route defined in the corresponding next hop information for the primary route;
• and
• means, if the primary route is not usable, for attempting to forward the setup message on the alternate route defined in the corresponding next hop information for the alternate route or for cranking the call back to a preceding node in the communications network.

A method for establishing of a call in a virtual circuit based communications network having a plurality of network nodes and employing hop-by-hop routing, comprising the steps of:

• sending a setup message for said call through said network on a hop by hop basis, said setup message including an indication of hop count;
• adjusting the indication of hop count at each network node receiving said setup message, whereby that node effectively is counted as a hop traversed by the message;
• and
• clearing the call back through the network when the indication of hop count has reached a predetermined count.

A method of establishing a call in a virtual circuit based communications network comprising a plurality of network nodes and employing hop by hop routing, each network node having a routing table which contains next hop information to adjacent nodes corresponding to endpoints of the network, comprising the steps of:

• sending a setup message having a destination endpoint for said call through said network, said setup message including an indication of hop count;
• receiving said setup message at a network node;
• adjusting the indication of hop count, whereby the network node effectively is counted as a hop traversed by the message;
• clearing the call back through the network when the indication of hope count reaches a predetermined count;
• and
• otherwise forwarding the setup message another hop to an adjacent node in accordance with the next hop information for the destination endpoint contained in its routing table.