Fast Reroute

Key Points

• Designed for rapid failure recovery
• Uses preplanned alternate paths or local repair mechanisms
• Common in carrier and IP backbones
• Reduces disruption during link or node failures
• Enables sub-second or near-instant protection against failures
• Relies on precomputed protection paths to keep traffic moving locally

Definition

Fast Reroute is a routing protection technique that switches traffic to a precomputed alternate path very quickly after a failure, designed to minimize disruption.

Concept

Fast Reroute is a networking term used for rapid traffic protection when a path or node fails. It exists to reduce service interruption before normal routing convergence completes. It is used in carrier networks, IP backbones, and other routed systems that need fast recovery. The technique relies on precomputed protection paths or local repair mechanisms to keep traffic moving without waiting for full routing convergence.

Explainer

Fast Reroute is a routing protection mechanism that rapidly moves traffic to a precomputed alternate path when a link or node fails. It works by preparing backup forwarding behavior in advance so traffic can be redirected locally and quickly without waiting for full routing convergence. It is used in service provider backbones, IP transport, and other routed networks that require fast recovery.

Constraints include accurate precomputation, backup path feasibility, topology changes, and resource reservation for protection paths. Failure modes include protection path failure, incomplete coverage of failure cases, suboptimal alternate routing, and traffic loss if local repair is not ready. Tradeoffs involve very fast restoration versus extra planning complexity, more protection state versus better resilience, and lower disruption versus potentially less efficient use of network resources.

Fast Reroute matters because many networks need sub-second or near-instant protection against failures. Cross-industry relevance is strong in telecom, carrier networks, and critical IP transport.