BFD Session Failure Detection Synchronization
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Solution Overview
Problem
In Bidirectional Forwarding Detection (BFD) systems, the existing method for failure detection can misinform about link failures due to differences in delays in delivering BFD session parameters from negotiation modules to detection modules, leading to incorrect failure reporting.
Innovation Solution
A method where one side of the BFD session starts failure detection only after receiving the first BFD packet from the opposite side, using a BFD packet sending timer and a detection timer to periodically check for packet receipt, and if not received within a predetermined time, reports a failure on the forwarding engine, avoiding misinformed link failure notifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If failure detection is started immediately after BFD session establishment, then detection speed is improved, but incorrect failure reporting occurs due to parameter delivery delay differences
Solution Approach 1:
The patent applies preliminary action by starting the detection timer only after the first BFD packet is successfully received, rather than immediately after session establishment. This ensures that parameter delivery is complete on both sides before detection begins, preventing false failures while maintaining rapid detection through the timer mechanism.
Solution Approach 2:
The patent uses feedback by monitoring the receipt of BFD packets and using this information to control the start of failure detection. The detection timer is triggered based on feedback from successful packet reception, ensuring that detection only begins when both endpoints are ready, thus eliminating false positives while preserving detection speed.
2Loss of time
If BFD session parameters are delivered quickly from negotiation module to detection module, then detection responsiveness is improved, but delay differences between two ends cause misinformed failure notifications
Solution Approach 1:
The patent achieves equipotentiality by ensuring both endpoints are at the same readiness state before detection begins. By waiting for the first BFD packet from the opposite end, both routers are guaranteed to have received and processed parameters, eliminating the delay difference problem that causes false failures.
Solution Approach 2:
The patent applies preliminary action by completing parameter delivery and verification on both ends before initiating failure detection. The first BFD packet serves as a preliminary confirmation that parameter delivery is complete, ensuring synchronized readiness without requiring complex delay coordination.
Data Source
AI summary
A method for failure detection on a bidirectional forwarding link mainly includes: sending, by one side of a BFD session, a BFD packet to the opposite side of the BFD session, and detecting a BFD packet sent by the opposite side, and starting, by the local side of the BFD session, BFD session detection when receiving a first BFD packet sent from the opposite side. By the method of the invention, it can be avoided that a router misinforms that failure occurs on a BFD session link due to difference of delays needed to deliver a BFD session parameter from a negotiation module of the router to a detection module.