Which option is a critical mechanism to optimize convergence speed when using MPLS FRR?

Question

Options

• AIGP timers
• BBandwidth reservation
• CShared risk link groups
• DDown detection

• A
  3% (1)
• B
  9% (3)
• C
  6% (2)
• D
  81% (26)

Explanation

Down Detection is the critical mechanism because MPLS FRR works by pre-computing backup paths before any failure occurs - meaning the only variable that determines how fast traffic switches over is how quickly the router detects the failure. Without rapid down detection (e.g., via BFD or link-layer signals), the pre-computed backup path sits idle even as traffic drops, negating FRR's sub-50ms convergence goal.

Why the distractors are wrong:

• A. IGP timers - FRR is specifically designed to reroute traffic before IGP reconvergence completes; relying on IGP timers for switchover speed defeats the entire purpose of FRR.
• B. Bandwidth reservation - Relevant to ensuring the backup path has capacity (a TE concern), but has no bearing on how fast the switchover is triggered.
• C. Shared Risk Link Groups (SRLGs) - SRLGs improve backup path diversity by avoiding co-routed links, but they influence path selection during planning, not convergence speed during a failure event.

Memory tip: Think of MPLS FRR as a loaded spare tire - the backup is ready to go, but you still need to notice the flat. Down Detection is what tells the router to make the switch; everything else is just preparation.

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