Hub-embedded system for automated network fault detection and isolation

Abstract

An automatic loop-elimination system embodied in a network hub minimizes the impact of port deactivation by deactivating only one port at a time. To reduce the likelihood of concurrent examination of ports (of different hubs) coupled to other hubs, the port at which examination begins is randomized at network startup. To reduce the likelihood of concurrently examined ports (of different hubs) being deactivated at the same time, a brief re-poll of port utilization is run just before deactivation; if the first deactivation eliminates the loop, the second port is not deactivated. For each hub, the method cycles through the ports three times, progressively including more heavily cascaded ports. This progressive relaxation of a cascade constraint preferentially deactivates ports coupled to end-node devices before ports coupled to other hubs. Thus, the invention provides for fast and convenient automatic loop elimination without requiring external hardware or software. The network management system applies to network problems other than loops and to automatic corrective actions that merely filter, rather than disable, a port.