Pseudowire Failover via Pre-Updated Hardware Entries
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Solution Overview
Problem
Existing pseudowire (PW) redundancy protection methods face challenges in quickly switching from a primary PW to a backup PW, leading to potential packet loss due to the time required to update hardware protection switching and reception entries when a link failure is detected.
Innovation Solution
The method involves updating the hardware protection switching and reception entries in advance and using Bidirectional Forwarding Detection (BFD) sessions to facilitate a priority switch from the primary PW to the backup PW when a failure is detected, minimizing packet loss by enabling the backup PW to receive packets promptly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hardware protection switching and reception entries are updated in real-time when failure is detected, then switching accuracy is improved, but switching time increases causing packet loss
Solution Approach 1:
The patent pre-updates the hardware reception entry with the backup pseudowire information before failure occurs. When failure is detected, the hardware protection switching entry is updated to point to the pre-prepared backup entry, enabling immediate switching without real-time update delays. This preliminary preparation of backup routing information resolves the contradiction by eliminating the time-consuming real-time update process while maintaining accurate failure response.
2Speed
If BFD session detection interval is shortened to detect failure faster, then detection speed is improved, but false detection rate increases
Solution Approach 1:
The patent combines multiple BFD detection sessions from different pseudowires into a unified failure detection mechanism. By merging detection results from both primary and backup pseudowires, the system achieves faster detection through shorter intervals while maintaining reliability through cross-validation of multiple detection streams, reducing false positives that would occur with single-session rapid detection.
3Device complexity
If only one pseudowire is provided between two CEs, then device complexity is reduced, but communication reliability deteriorates when failure occurs
Solution Approach 1:
The patent implements automatic failure detection and switching between pseudowires without manual intervention. The system self-monitors pseudowire health through BFD sessions and automatically switches to backup pseudowires upon failure detection, maintaining communication reliability while keeping the configuration simple. This self-service mechanism eliminates the need for complex manual redundancy management while ensuring continuous communication.
Data Source
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AI summary
Provided is a method and device for switching a primary/backup PW. When a primary PW is detected having changed into a Down status by a BFD session corresponding to the primary PW, PE searches for a matching switching information entry. When bFS in the switching information entry indicates transmission switching is supported, and Failover value indicates that a packet is forwarded via a backup PW, the PE updates Failover value in a hardware protection switching entry to the Failover value in the switching information entry. When bRX in the switching information entry indicates reception switching is supported, the PE updates drop identifier in a hardware reception entry to a value indicating that a packet is received, and updates the bFS to a value indicating that transmission switching is not supported; and the PE reports a Down event of the primary PW.