Addressing Failures in Ring Topologies

E.

Remote IP Fast Reroute (FRR) is a mechanism used to address failures in ring topologies. It is a feature that is commonly used in MPLS-based networks. In the event of a failure in a ring topology, Remote IP Fast Reroute provides a mechanism to quickly redirect traffic to a backup path.

Out of the given options, B is the correct answer. Routers in the ring topology establish an MPLS TE tunnel with both edge ring routers. This MPLS TE tunnel is used as a backup path in the event of a failure in the ring.

When the ring topology is operational, traffic flows around the ring in a clockwise or anti-clockwise direction. When a failure occurs, the MPLS TE tunnel is used as a backup path. This backup path bypasses the failed link or node and restores the connectivity.

Option A is incorrect because targeted LDP session is used for label distribution and not for providing backup path in case of failures. Option C is incorrect because GRE tunnels are not used in MPLS-based networks. Option D is incorrect because establishing a GRE tunnel with the closest PQ node in the ring does not provide a backup path for the entire ring topology. Option E is incorrect because establishing a targeted LDP session with the closest router that is in a PQ space does not provide a backup path for the entire ring topology. Option F is incorrect because establishing an MPLS TE tunnel with all PQ nodes in the ring is not necessary and may result in inefficient use of network resources.