Distributed protocol for improving the survivability of telecommunications trunk networks

A protocol carried out at each node in a network comprising a plurality of reconfigurable cross-connect nodes interconnected by links to reconfigure the network in the event of a failure event, said protocol comprising the steps of:

• at each node, maintaining an array indicating the status of all of the links in the network,
• at each node, storing a plurality of predetermined configuration tables corresponding to a plurality of possible patterns of non-working links,
• at each node, sequentially testing all of the links associated with the node which are indicated by the array to be working,
• if a specific link is determined as a result of the testing step to be non-working, updating the array, sending a message on all links associated with the node indicating that the specific link is non-working, and reconfiguring the node in accordance with the predetermined configuration table corresponding to the pattern of non-working links indicated by the updated array if the node is not already in this configuration,
• if a specific link is determined as a result of the testing step to be working, determining if a message has been received via the specific link indicating that another link in the network is non-working and,
• if a message has been received via the specific link indicating that another link in the network is non-working and the array does not already indicate that the other link is non-working, updating the array, sending a message on all links associated with the node indicating that the other link is non-working, and reconfiguring the node in accordance with the predetermined configuration table corresponding to the pattern of non-working links indicated by the updated array if the node is not already in this configuration.

A method for reconfiguring a telecommunications network comprising a plurality of reconfigurable cross-connect nodes interconnected by links when a failure event occurs, said method comprising the step of

• storing at each node a precomputed configuration table corresponding to each of a plurality of possible network topologies which result from a plurality of possible failure events,
• after a specific failure event occurs, detecting the specific failure event at a node,
• generating messages of the failure event from the node detecting the failure event over the links associated with said detecting node to other nodes connected to said detecting node by associated links,
• sending from node to node the messages generated in said generating step such that the network nodes converge to a consistent and correct picture of the existing network topology, and
• reconfiguring the nodes in accordance with the specific precomputed configuration tables which correspond to the specific existing network topology.