High speed protection switching in label switched networks through pre-computation of alternate routes

Abstract

Method of providing a recovery plan for a connection in a communications network when the connection is disrupted by a failure of a switch, switch or link in the network. In a provisioning phase, a primary plan and recovery plan for a connection to be protected in a communications network are developed. Forwarding information in the form of mapping or forwarding tables is derived from the plans and is distributed to each of the switches in the network. In the event of a failure each switch receives notice of the failure and switches to the recovery plan related to the failure. If and when the failure is repaired or cleared, each switch then switches back to its primary plan. Determining a recovery plan during the provisioning phase is based on the rule that a unit of failure is a switch or group of switches in the network rather than a link, regardless of the actual cause of the failure. This simplifies the mapping tables at each switch and reduces the time for each switch to switch to a recovery plan based on the failure as reported by the other switches in the network. Recovery plan routes are based on a quality of service metric such as the metric of not exceeding a predetermined fraction of the capacity of the links involved in the recovery plan routes.