OTN Transient Management for Clock Source Switching
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Solution Overview
Problem
Optical Transport Networks (OTNs) experience transient alignment errors and out-of-frame issues during clock adjustments, leading to spurious alarms and data path errors when switching between shelf and line timing sources, which can cause network-wide disruptions and restoration events.
Innovation Solution
Implementing a transient management system that includes a network element-based control algorithm to adjust transmission clocks and a network-based algorithm for managing ODUk connections, using a local clock and adjacency protocol to mitigate transients by slowly adapting timing changes and orderly creating cross-connections during mode changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If clock adjustments are made during mode changes on an OTN line, then the OTN connection can switch between different timing sources (shelf timing and line timing), but transient alignment errors and out-of-frame issues occur leading to spurious alarms
Solution Approach 1:
The system performs preliminary actions by detecting mode changes before they occur and proactively adjusting timing parameters. The transient management system monitors OTN line status and preemptively modifies clock switching behavior to prevent alignment errors before they propagate through the network
Solution Approach 2:
A transient management system acts as an intermediary between the clock switching mechanism and the OTN connection. This intermediary layer buffers and smooths the transition between timing sources, preventing direct propagation of transients to downstream nodes while still enabling timing source switching
2Adaptability or versatility
If mode changes occur when switching between 1:1 mapped ODUk containers and multiplexed ODUk containers, then the OTN connection can adapt to different container configurations, but clock adjustments cause transients to travel across the network end-to-end
Solution Approach 1:
The transient management system segments the network into individual hop sections, managing clock transitions locally at each node rather than allowing end-to-end propagation. Each node independently handles mode changes, containing transients to local segments and preventing network-wide impact
Solution Approach 2:
The system applies different timing management characteristics to different locations in the network. Nodes experiencing mode changes apply local transient suppression techniques, while intermediate nodes maintain stable timing without introducing additional adjustments, creating location-specific optimization
3Ease of operation
If nothing is done to manage transients during ODUk service addition, then the system maintains simple operation, but users experience spurious alarms and data path errors leading to link failures
Solution Approach 1:
The transient management system operates autonomously without requiring manual intervention. It automatically detects mode changes, identifies upcoming clock adjustments, and applies appropriate transient suppression techniques, making the system self-managing while maintaining operational simplicity for users
Data Source
AI summary
An Optical Transport Network (OTN) transient management method, OTN node, and OTN network includes operating an OTN connection in a first mode in a network, the OTN connection traverses at least two nodes in the network, requesting a change in the OTN connection to a second mode which will cause a network transient, the change includes a timing change on the OTN connection affecting the at least two nodes, and performing transient management at the at least two nodes to mitigate the network transient, the transient management prevents spurious alarms due to the change between the first mode and the second mode.