Path Protection Switching via Drop Side TCM Monitoring
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional path protection switching in Optical Transport Networks (OTN) experiences undesirably long protection switch times due to sympathetic switches triggered by client-side protection switching, which can exceed 100 ms, contrary to the goal of sub-50 ms protection switch times.
Innovation Solution
Implementing a method that monitors both drop side and line side Tandem Connection Monitoring (TCM) entities to differentiate between switching events, delaying path protection switching until defects persist only in the drop side TCM, indicating a switch fabric fault, and provisioning a new drop side TCM to prevent unnecessary path protection switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If path protection switching is implemented to protect against failures in the OTN network, then network reliability is improved, but protection switch times exceed 100 ms due to sympathetic switches triggered by client-side protection switching
Solution Approach 1:
The patent segments the monitoring function into separate drop side TCM entities and line side TCM entities. The drop side TCM monitors client-side protection switching events, while the line side TCM monitors OTN network failures. This segmentation allows the system to distinguish between client-side switching (which should not trigger path protection) and actual network failures (which should trigger path protection), thereby reducing unnecessary sympathetic switches and achieving sub-50 ms protection switch times while maintaining network reliability.
Solution Approach 2:
The patent introduces an intermediary mechanism that uses the line side TCM entity as a mediator between the drop side TCM entity and the path protection switching decision. The line side TCM acts as a filter that validates whether a defect detected by the drop side TCM is actually caused by a network failure or is merely a side effect of client-side protection switching. This intermediary approach prevents unnecessary path protection switching while ensuring real path failures are properly detected, resolving the contradiction between reliability and switch time.
2Reliability
If hold-off time is implemented on the OTN side during client-side switching, then sympathetic switches are reduced, but protection switch times exceed 100 ms
Solution Approach 1:
The patent applies preliminary action by having the line side TCM entity continuously monitor the OTN network state in advance, separate from the drop side TCM's client-side monitoring. When a defect is detected by the drop side TCM, the line side TCM has already been preparing to validate whether it's a genuine network failure. This preliminary monitoring setup allows the system to make faster switching decisions without needing hold-off time, achieving both sympathetic switch avoidance and sub-50 ms switch times.
Solution Approach 2:
The patent implements feedback through the interaction between drop side TCM and line side TCM entities. The line side TCM provides feedback information about the actual OTN network state to the control logic, which then determines whether to trigger path protection switching. This feedback mechanism eliminates the need for hold-off time by providing real-time validation of failure conditions, allowing immediate appropriate response while preventing unnecessary switches caused by client-side protection operations.
Data Source
AI summary
A method to avoid sympathetic switches in path switching protection due to client protection switching includes monitoring a drop side Tandem Connection Monitoring (TCM) entity and a line side TCM entity for a connection, wherein the drop side TCM is provisioned between a drop port of the node and a second drop port of a corresponding node, and wherein the line side TCM entity is provisioned between a plurality of line ports of the node and a second plurality of line ports of the corresponding node; responsive to detecting defects in both the drop side TCM entity and the line side TCM entity on a working line, implementing path protection switching of the working line; and, responsive to detecting defects only in the drop side TCM entity, implementing path protection switching of the working line responsive to persistence of the defects.