DIGITAL DATA MESSAGE TRANSMISSION NETWORKS AND THE ESTABLISHING OF COMMUNICATION PATHS THEREIN

A digital data message transmission network of interconnected network elements (12,14,16,18,20; 32,34,36,40,44), maintains topology data bases (112) recording the potentially available communication routes through the network and the status of the network elements thereof, each node originating a message interrogating base to ascertain a suitable route; when connected into a route, whether completed or not, recording the adjacent elements; when detecting the failure of any next adjacent link or node sending a ROUTE FAILURE MESSAGE to the route end(s) available to it to update the topology data base(s) for such route(s), whereby the route maintenance message traffic within the network is limited while ensuring that the topology data base associated with the origin of a route that does not establish and the topology data base or bases associated with both ends of all failed established route incorporating that failed element are correspondingly updated.