Patent ID: 9584404
Date: 2017-02-28
CPC Classifications: H04L

Claim:
1. A method for forwarding an Internet Protocol (IP) unicast data packet, the method comprising, at a network node: using, by the network node, destination based shortest path routing algorithms for the network node to determine and pre-store a link to a primary neighbor in a primary path to a border node and a link to an alternate neighbor in an alternate path to the border node, wherein the border node offers the shortest path to an inter-region destination node, wherein the alternate path to the border node is longer than or equal to the primary path to the border node, wherein the alternate neighbor is a loop-free neighbor other than the primary neighbor and whose shortest path to the border node does not go through the network node that determined the alternate path, and wherein the shortest path between the alternate neighbor and the border node satisfies: where Distanceopt(N, ABR) is the shortest path between the alternate neighbor and the border node, Distanceopt(N, S) is the shortest path between the alternate neighbor and the network node, and Distanceopt(S,ABR) is the shortest path between the network node and the border node; forwarding, by the network node, the IP unicast data packet to the primary path through the primary neighbor, wherein the primary neighbor is one or more primary next-hops directly from the network node to the border node; switching over from the primary path to the alternate path upon failure of the primary path; and forwarding the IP unicast data packet to the alternate neighbor whose shortest path to the border node does not go through the network node that determined the alternate path.