Assume that link state pass through (LPT) is enabled. When one end of a link fails and reports the ETH_LOS alarm, the LPT works to shut down the other end of the link. As a result, the other end also reports the ETH_LOS alarm. How can the engineers tell which ETH_LOS alarm results from the failure and which ETH_LOS alarm results from the LPT?
On OptiX OSN 3500 V100R006 or earlier, the ETH_LOS alarm due to a fiber cut cannot be told from the ETH_LOS alarm due to LPT. On OptiX OSN 3500 V100R007 or later, the LPT_RFI alarm is introduced to replace the ETH_LOS alarm due to LPT. In this way, the alarms can be told from each other.
The engineers cannot tell the failure point by alarm time. The LPT works shortly. In addition, the NEs may differ in time. Therefore, the alarm time is not the basis of determining the failure point.
Be familiar with this feature of the equipment.