The topology is a ring and all the equipments are OSN 1500 with ECXL and Q1SL1 boards.
the relevant part of clock tracing flow is as follows. The standard SSM protocol is started.
West --->NE1-->NE2-->NE3-->NE4 <--- East
One day, the fiber between NE1 and NE2 broke, and NE2 reported CLK_NO_TRACE_MODE, LTI and S1_CHANGE alarms.
CLK_NO_TRACE_MODE, LTI and S1_CHANGE alarms.
Check the "Configuration quality" of NE4. It was found that all sources were set as "G.811". It's not right and result in this problem. All the sources should be "automatic extraction". Just modify it, then the abnormal alarms disppeared.
After the fiber between NE1 and NE2 broke, the normal process of clock tracing protection is as follows:
When the connection between NE1 and NE2 broke, at that moment, the clock tracing of NE2 will switch to internal source, then the quality of internal source will be sent to NE4 via NE3, NE4 found that it was lower than the source from east, so NE4 will switch, then NE3 will switch, then NE2 will switch to the east direction.
But now, because the The "Configuration quality" of NE4, all sources are set as "G.811", it will not switch. So NE2 will keep in tracing the internal source.