Patent ID: 9438472
Filing Date: 2016-09-06
CPC Classification: H04L

Claim Text:
1. A method implemented by a network element functioning as a point of local repair (PLR), the method for determining a backup path for a fast reroute (FRR) process to be utilized in response to a network event invalidating a primary path to a destination node, where the method identifies at least one intermediate node as an extended remote loop free alternative that has a backup loop free alternative (LFA) path to a destination node in a network where no path meeting LFA conditions can be found for the PLR, the method comprising the steps of: calculating shortest paths from the PLR to each destination node in the network using a normal topology; calculating shortest paths from the PLR to each destination node in the network using a unit cost topology; selecting a next destination node D in the network without a calculated backup path from the PLR; determining a primary path next hop node F for the destination node D; determining whether an LFA path or remote LFA (RLFA) path exists from the PLR to the destination node D where the backup LFA path or RLFA path does not traverse the primary path next hop node F in the calculated shortest paths using the normal topology; determining whether a remote RLFA path exists from the PLR to the destination node D where the backup LFA path or RLFA path does not traverse the primary path next hop node F in the calculated shortest paths using the unit cost topology; determining an intermediate node on a shortest path from the PLR to the destination node D using topology that excludes the primary next hop node F and that meets LFA conditions, in response to determining that no LFA path or RLFA path exists from the PLR to the destination node D that does not traverse the primary next hop node F in the calculated shortest paths using the normal topology and the unit cost topology; and selecting the intermediate node on the shortest path as an intermediate destination for data traffic for destination node D to be utilized as the backup path to the destination node D during the FRR process.