Microloop Protection for MPLS Networks via Interface Exclusion
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Solution Overview
Problem
Computer networks using hop-by-hop routing techniques, such as MPLS and IGP, face issues with small transient loops due to link failures or topology changes, leading to potential congestion and network instability.
Innovation Solution
Implementing a method where label switching routers advertise labels via LDP and compute paths to suppress LDP label mapping messages from interfaces that would lead to microloops, using exclusion lists in the forwarding plane to discard packets received on specific interfaces, thereby preventing loop formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If label switching routers advertise labels via LDP out all network interfaces, then label distribution coverage is improved, but microloop formation risk increases
Solution Approach 1:
The patent applies local quality by making the label advertisement behavior interface-specific rather than uniform across all interfaces. Each router interface is evaluated individually to determine whether it should advertise labels based on its role in the computed path to the destination. This allows the system to maintain comprehensive label distribution where needed while preventing microloops at specific interfaces, thus resolving the contradiction between coverage and stability.
Solution Approach 2:
The patent implements preliminary action by computing the path to the destination and identifying interfaces that would cause microloops before labels are advertised. The router determines the set of interfaces to exclude from label advertisement in advance, based on path computation, and then applies this exclusion when distributing labels via LDP. This preventive approach ensures labels are not advertised on interfaces that would create loops, maintaining network stability while preserving necessary label distribution.
2Reliability
If LDP label mapping messages are suppressed from certain interfaces, then microloop formation is prevented, but label distribution completeness deteriorates
Solution Approach 1:
The patent suppresses label mapping messages only from specific interfaces that would create microloops, rather than suppressing them globally. The suppression is applied locally at the interface level based on path computation results. This ensures that label distribution remains complete for all necessary interfaces while preventing loops only where needed, thus resolving the contradiction between reliability and information completeness.
3Measurement precision
If exclusion lists are implemented in the forwarding plane, then packet forwarding accuracy is improved, but forwarding complexity increases
Solution Approach 1:
The patent implements preliminary action by pre-computing the set of interfaces to exclude from label advertisement and pre-populating the exclusion list in the forwarding plane before packets arrive. The forwarding plane simply checks whether the incoming interface is in the pre-computed exclusion set, rather than performing complex path analysis in real-time. This approach improves forwarding accuracy by ensuring consistent loop prevention while minimizing the complexity of the forwarding decision process.
Data Source
AI summary
Techniques of this disclosure enable loop protection for networks that utilize hop-by-hop routing, such as networks that utilize multi-protocol label switching (MPLS) label distribution and interior gateway protocol (IGP) routing. As described herein, the techniques provide protection from any small transient loops that may emerge due to link failure or other topology change events in networks that utilize hop-by-hop routing techniques.