Backup Path Validation to Prevent Micro-Loops During Re-Convergence
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Solution Overview
Problem
Micro-loops occur during network re-convergence due to uncorrelated events terminating local timers prematurely, increasing the likelihood of forwarding loops in large deployments.
Innovation Solution
Implement a timer mechanism that is not directly controlled by advertised events, allowing nodes to validate the backup path's validity before resuming normal forwarding, thereby preventing micro-loops during re-convergence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the local timer is immediately terminated in response to any uncorrelated event, then the node can quickly resume normal forwarding processing, but the backup path may be invalidated before convergence is complete, increasing micro-loop risk
Solution Approach 1:
The patent applies dynamics by making the timer termination condition adaptive rather than static. The timer continues running when uncorrelated events occur, but terminates only when correlated events indicate the backup path is no longer needed. This dynamic adjustment allows the system to resume normal forwarding quickly when safe while preventing premature termination that could cause micro-loops.
Solution Approach 2:
The patent implements feedback by continuously monitoring topology changes and using this information to control timer termination. When topology changes indicate the backup path becomes invalid, the timer is terminated. This feedback mechanism ensures the timer responds to actual network conditions rather than following a fixed termination schedule, balancing productivity and reliability.
2Reliability
If the local timer continues running during large deployments with many uncorrelated events, then micro-loop risk is reduced, but the node delays resuming normal forwarding processing
Solution Approach 1:
The patent uses feedback from topology change notifications to control timer termination. The timer responds to feedback about actual network conditions (correlated events) rather than continuing indefinitely or terminating on every event. This allows the timer to run long enough to prevent micro-loops in large deployments while terminating promptly when the backup path is no longer needed, minimizing forwarding delays.
Solution Approach 2:
The patent changes the timer's behavior parameter based on event correlation. Instead of a fixed termination policy, the timer dynamically adjusts its runtime based on whether events are correlated with the original failure. This parameter change allows the timer to extend during periods of uncertainty (reducing micro-loop risk) while shortening when conditions stabilize (reducing processing delay).
Data Source
AI summary
A node in a deployment uses a mechanism to avoid micro-loop losses during re-convergence after a failed resource, such as a link or a node, includes running a local timer for a period of time. The node uses a loop-free backup path to forward traffic while the timer is running instead of using its forwarding tables. Use of the backup path reduces the risk of a micro-loop while the deployment re-converges, In response to the node receiving an event message, the timer is allowed to continue running as the backup path is validated. Normal forwarding processing resumes when the timer expires or when the timer is aborted in response to determining that the backup path is invalid.