Lab 5 – Zero-Segment FRR

TI-LFA FRR protection operates on the principle of creating backup paths or local repair paths on each router, for every route in the routing table. As demonstrated in the previous lab, the Equal Cost Multi-Path (ECMP) backup and non-ECMP backup paths did not have any additional labels. TI-LFA can provide 100% backup path coverage by using adjacency-SIDs. However, a backup path using an explicit list of adjacency SIDs may encounter hardware limitations, due to the maximum number of labels in the label stack. Therefore, TI-LFA backup path calculation aims to find a backup path with the fewest additional labels on top of the destination label for efficient traffic routing.

In segment routing networks, the TI-LFA mechanism aims to enforce the post-convergence backup path, with as few segments encoded as labels as possible in the label stack. This is done to reduce overhead, accelerate lookup and forwarding, and simplify operations in the hardware. Using...