Which two design solutions ensure sub-50 msec of the convergence time after a link failure...

To achieve sub-50 millisecond convergence after a link or node failure, the design must rely on precomputed protection paths and local repair mechanisms in the data plane. The following mechanisms meet this requirement:

B. Ti-LFA (Topology Independent Loop-Free Alternate): A next-generation fast reroute method used in Segment Routing. It offers local protection by computing loop-free backup paths that are independent of the specific failure type (node or link). It ' s capable of sub-50 ms convergence by rerouting traffic immediately on failure.

D. MPLS-FRR (Fast Reroute): A traditional mechanism in MPLS networks that provides pre-signaled backup Label Switched Paths (LSPs). It enables fast switchover upon failure detection—also under 50 ms.

Other options:

A. BFD: Provides fast failure detection, but does not provide the actual traffic reroute mechanism.

C. Minimal BGP scan time: Impacts control plane responsiveness but not sub-50 ms convergence.

E. IGP fast hello: Improves failure detection but alone doesn’t guarantee traffic reroute under 50 ms.

==========