Background of fast rerouting

Network incidents, such as link failures and node failures, can disrupt the seamless flow of data within a network. Network resiliency is the ability of a network to withstand and recover from such disruptions. When incidents occur, IGP convergence comes into play, recalculating the routing table to find alternative paths through resilient resources. However, during this convergence period, there’s a risk of traffic blackholes, where data may get lost or delayed. Hence, it’s crucial to have the ability to forward traffic even during convergence to ensure data continuity and a seamless user experience.

Traditional MPLS networks, using RSVP-TE, install a pre-established backup Label Switch Path (LSP) to quickly reroute traffic if there are network failures. However, this approach increases the load on routers, as the backup LSPs function as additional RSVP-TE sessions, requiring routers to manage more sessions. When a failure occurs, the...