OPTIMIZATION TO EXPAND IS-IS LEAF NODES DURING LFA COMPUTATION

摘要

A method and system implemented by a network device, where the network device is in a network having a plurality of nodes. The method computes a loop free alternative (LFA) next hop as a backup for a primary path next hop for intermediate system-intermediate system (IS-IS). The method improves LFA computation efficiency by minimizing expansion of prefixes. The method includes expanding all prefixes of the next LFA shortest path first (SPF) destination node and inheriting a next candidate next hop as a current LFA next hop where the next candidate next hop provides link or node protection and better protection than the current LFA next hop.

主权项

1. A method implemented by a network device in a network having a plurality of nodes, the method to compute a loop free alternative (LFA) next hop as a backup for a primary path next hop for intermediate system-intermediate system (IS-IS), where the method improves LFA computation efficiency by minimizing expansion of prefixes, the method comprising the steps of:
selecting a next candidate next hop from a set of neighbor next hops in the network to perform an LFA shortest path first (SPF) computation with the a neighbor node represented by the next candidate next hop as a root; selecting a next LFA SPF destination node in the network; computing LFA for the next LFA SPF destination node; checking whether the next candidate next hop provides link or node protection for the next LFA SPF destination node or the next LFA SPF destination node has a multi-homed prefix; checking whether the next candidate next hop provides better protection than a current LFA next hop for the next LFA SPF destination node or the next LFA SPF destination node has a multi-homed prefix; and expanding all prefixes of the next LFA SPF destination node and inherit the next candidate next hop as the current LFA next hop where the next candidate next hop provides link or node protection and better protection than the current LFA next hop.