Topology independent fast reroute for node and SRLG local protection

1. A method, comprising:

identifying, by a device in a network, a shortest path tree for a point of local repair in the network that excludes at least one link between the point of local repair and a neighbor of the point of local repair in the network;

sequentially evaluating, by the device, member nodes of a branch of the shortest path tree from the point of local repair to a destination node in the shortest path tree by:

making, by the device, a determination as to whether a member node currently under evaluation is in a P-space of a reference member node in the branch between the member node currently under evaluation and the point of local repair, wherein the P-space for the reference node comprises a set of nodes that are reachable by the reference node without traversing the at least one link excluded from the shortest path tree;

adding, by the device, a repair segment associated with a member node that is in the P-space of the reference node to a repair segment list, when the determination indicates that the member node currently under evaluation is not in the P-space of the reference member node; and

setting, by the device, the member node currently under evaluation as the reference node, when the determination indicates that the member node currently under evaluation is not in the P-space of the reference member node; and

causing, by the device, one or more segment routing labels to be added to a header of a packet based on the repair segment list and in response to a failure in the network associated with the at least one link excluded from the shortest path tree.

2. The method as in claim 1 , wherein the shortest path tree excludes a shared risk link group (SRLG) associated with the at least one link excluded from the shortest path tree.

3. The method as in claim 1 , wherein the shortest path tree excludes the neighbor of the point of local repair.

4. The method as in claim 1 , further comprising:

applying, by the device, a tie-breaking strategy to select a repair segment to add to the repair segment list, when multiple repair segments are identified for an evaluated member node of the branch.

5. The method as in claim 4 , wherein applying the tie-breaking strategy comprises:

determining, by the device, whether any of the identified repair segments are outside of a budget associated with the repair segment list.

6. The method as in claim 1 , wherein the one or more segment routing labels comprises an adjacency segment label associated with the destination node.

7. The method as in claim 1 , further comprising:

detecting, by the device, the failure in the network associated with the at least one link excluded from the shortest path tree.

8. An apparatus, comprising:

one or more network interfaces to communicate with a network;

a processor coupled to the one or more network interfaces and configured to execute a process; and

a memory configured to store the process executable by the processor, the process when executed operable to:

identify a shortest path tree for a point of local repair in the network that excludes at least one link between the point of local repair and a neighbor of the point of local repair in the network;

sequentially evaluate member nodes of a branch of the shortest path tree from the point of local repair to a destination node in the shortest path tree by:

making a determination as to whether a member node currently under evaluation is in a P-space of a reference member node in the branch between the member node currently under evaluation and the point of local repair, wherein the P-space for the reference node comprises a set of nodes that are reachable by the reference node without traversing the at least one link excluded from the shortest path tree;

adding a repair segment associated with a member node that is in the P-space of the reference node to a repair segment list, when the determination indicates that the member node currently under evaluation is not in the P-space of the reference member node; and

setting the member node currently under evaluation as the reference node, when the determination indicates that the member node currently under evaluation is not in the P-space of the reference member node; and

cause one or more segment routing labels to be added to a header of a packet based on the repair segment list and in response to a failure in the network associated with the at least one link excluded from the shortest path tree.

9. The apparatus as in claim 8 , wherein the shortest path tree excludes a shared risk link group (SRLG) associated with the at least one link excluded from the shortest path tree.

10. The apparatus as in claim 8 , wherein the shortest path tree excludes the neighbor of the point of local repair.

11. The apparatus as in claim 8 , wherein the process when executed is further operable to:

apply a tie-breaking strategy to select a repair segment to add to the repair segment list, when multiple repair segments are identified for an evaluated member node of the branch.

12. The apparatus as in claim 11 , wherein the apparatus applies the tie-breaking strategy by:

determining whether any of the identified repair segments are outside of a budget associated with the repair segment list.

13. The apparatus as in claim 8 , wherein the one or more segment routing labels comprises an adjacency segment label associated with the destination node.

14. The apparatus as in claim 8 , wherein the process when executed is further operable to:

detect the failure in the network associated with the at least one link excluded from the shortest path tree.

15. A tangible, non-transitory, computer-readable medium storing program instructions that, when executed by a device in a network, cause the device to perform a process comprising:

identifying, by the device, a shortest path tree for a point of local repair in the network that excludes at least one link between the point of local repair and a neighbor of the point of local repair in the network;

sequentially evaluating, by the device, member nodes of a branch of the shortest path tree from the point of local repair to a destination node in the shortest path tree by:

making, by the device, a determination as to whether a member node currently under evaluation is in a P-space of a reference member node in the branch between the member node currently under evaluation and the point of local repair, wherein the P-space for the reference node comprises a set of nodes that are reachable by the reference node without traversing the at least one link excluded from the shortest path tree;

adding, by the device, a repair segment associated with a member node that is in the P-space of the reference node to a repair segment list, when the determination indicates that the member node currently under evaluation is not in the P-space of the reference member node; and

setting, by the device, the member node currently under evaluation as the reference node, when the determination indicates that the member node currently under evaluation is not in the P-space of the reference member node; and

causing, by the device, one or more segment routing labels to be added to a header of a packet based on the repair segment list and in response to a failure in the network associated with the at least one link excluded from the shortest path tree.

16. The computer-readable media as in claim 15 , wherein the shortest path tree excludes a shared risk link group (SRLG) associated with the at least one link excluded from the shortest path tree.

17. The computer-readable media as in claim 15 , wherein the shortest path tree excludes the neighbor of the point of local repair.

18. The computer-readable media as in claim 15 , wherein the process further comprises:

applying, by the device, a tie-breaking strategy to select a repair segment to add to the repair segment list, when multiple repair segments are identified for an evaluated member node of the branch.

19. The computer-readable media as in claim 18 , wherein applying the tie-breaking strategy comprises:

determining, by the device, whether any of the identified repair segments are outside of a budget associated with the repair segment list.

20. The computer-readable media as in claim 15 , wherein the one or more segment routing labels comprises an adjacency segment label associated with the destination node.