Fast Reroute Methodologies

B.

Fast reroute (FRR) is a mechanism that allows for quick recovery of network traffic in the event of a link or node failure. When a failure occurs, the network reroutes traffic through an alternate path, without waiting for the control plane to recalculate a new path.

In the context of MPLS, there are two main FRR mechanisms: MPLS TE Fast Reroute (FRR) and IP Fast Reroute (IP FRR). Both mechanisms use backup paths to protect against link or node failures.

MPLS TE FRR requires the use of RSVP (Resource Reservation Protocol) to set up the backup paths. RSVP is a signaling protocol that allows for the reservation of network resources, such as bandwidth, along a path. The use of RSVP can add complexity to the network, as it requires the configuration of RSVP on all devices that participate in the MPLS TE FRR network.

On the other hand, IP FRR is a simpler mechanism that does not require the use of RSVP. IP FRR uses precomputed backup paths, called backup tunnels, to reroute traffic in the event of a failure. These backup tunnels are preconfigured on the routers in the network, using a variety of methods.

One of these methods is the auto tunnel backup feature, which is an implementation of IP FRR in Cisco IOS. With auto tunnel backup, routers automatically create backup tunnels for each destination, based on the shortest path to that destination. These backup tunnels are precomputed, so they do not require any signaling protocol like RSVP to set up.

Therefore, the answer to the question is E. Enabling the auto tunnel backup feature eliminates the need for RSVP configuration in the network. However, it should be noted that MPLS TE FRR can offer greater flexibility in terms of traffic engineering, but at the cost of added complexity. IP FRR, on the other hand, offers simplicity and fast convergence times, but with less control over traffic engineering.