Node-protection and path attribute collection with remote loop free alternates

A network device comprising:

• a memory;
• and
• processing circuitry coupled to the memory, wherein the processing circuitry is configured to execute a link-state routing protocol for exchanging link-state routing information to maintain network topology for a network;
• and
• a physical network interface configured to send and receive link-state routing updates in accordance with the link-state routing protocol,
• wherein the processing circuitry is configured to execute a route selection module configured to, for each of a plurality of candidate remote loop-free alternate (LFA) next hops identified based on the network topology, perform a respective forward shortest path first (SPF) computation having the respective candidate remote LFA next hop as a root to compute a respective path segment between the respective candidate remote LFA next hop and a destination network device in the network, wherein each of the candidate remote LFA next hops comprises the tail-end node of a respective potential repair tunnel between the network device and the candidate remote LFA next hop for forwarding network traffic from the network device to the destination network device, and store, for each of the SPF computations, path attributes of respective path segments between each of the plurality of candidate remote LFA next hops and the destination network device,
• wherein the route selection module is configured to select, based at least in part on the stored path attributes of the path segments and whether the computed path segments include a primary next hop node, a remote LFA next hop from the plurality of candidate remote LFA next hops to be stored as an alternate next hop for forwarding network traffic from the network device to the destination network device, such that the selected remote LFA next hop provides node protection to the primary next hop node on a shortest path from the network device to the destination device, and
• wherein the route selection module is configured to update forwarding information stored by the network device to install the selected remote LFA next hop as the alternate next hop for forwarding network traffic from the network device to the destination network device.

A non-transitory computer-readable storage medium comprising instructions for causing a programmable processor of a network device to:

• for each of a plurality of candidate remote loop-free alternate (LFA) next hops, perform a respective forward shortest path first (SPF) computation having the respective candidate remote LFA next hop as a root to compute a respective path segment between the respective candidate remote LFA next hop and a destination network device in a network, wherein each of the candidate remote LFA next hops comprises the tail-end node of a respective potential repair tunnel between the network device and the candidate remote LFA next hop for forwarding network traffic from the network device to the destination network device;
• store, for each of the SPF computations, path attributes of respective path segments between each of the plurality of candidate remote LFA next hops and the destination network device;
• select, based at least in part on the stored path attributes of the path segments and whether the computed path segments include a primary next hop node, a remote LFA next hop from the plurality of candidate remote LFA next hops to be stored as an alternate next hop for forwarding network traffic from the network device to the destination network device, such that the selected remote LFA next hop provides node protection to the primary next hop node on a shortest path from the network device to the destination device;
• and
• update forwarding information stored by the network device to install the selected remote LFA next hop as the alternate next hop for forwarding network traffic from the network device to the destination network device.