Capacity Requirements for the One-to-One Backup Option in MPLS Fast Reroute

MPLS fast reroute (MPLS-FRR) mechanisms deviate the traffic in case of network failures at the router closest to the outage location to achieve an extremely fast reaction time. We review the one-to-one backup and the facility backup that are options for MPLS-FRR to deviate the traffic via a detour or a bypass around the failed elements, respectively. Basically, the backup paths can take the shortest path that avoids the outage location from the point of local repair to the tail-end router or to the merge point with the primary path. We suggest two simple modifications that lead to a new path layout which can be implemented by one-to-one and by facility backup. We evaluate the backup capacity requirements, the length of the backup paths, and the number of backup paths per primary path in a parametric study regarding the network characteristics. Our proposals save a considerable amount of backup capacity compared to the standard mechanisms. They are suitable for application in practice since they are simple and conform to the standards.