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The LTP function of EMS4 board is triggered, but the downstream device does not reports related alarm.

Publication Date:  2012-07-25 Views:  42 Downloads:  0
Issue Description
The LPT function of the EMS4 board of the OSN 3500 is triggered, but the front end reports no related alarm (ETH_LOS). When something is wrong with a signal of the front-end router, the LTP function is enabled, the back-end laser is shut down, and the services on the entire link are switched to another link. The function of protection against alarm jitter is enabled on the front-end EMS4 board, so the front-end EMS4 board does not report related alarms such as ETH_LOS. 
Alarm Information
LPT_RFI alarm reported at one end. No ETH_LOS alarm is reported at the other end. 
Handling Process
Disable the function of alarm jitter protection of the relevant NE.  
Root Cause
LPT_RFI and ETH_LOS are implemented as follows:
LPT_RFI: detected at intervals of 250 ms. A task of detecting LPT_RFI alarms has a priority of 100.
ETH_LOS: detected at intervals of 1,000 ms. A task of detecting LPT_RFI alarms has a priority of 140.
Alarm jitter protection: An LPT_RFI alarm is reported to the NE after the alarm lasts for 2s. An ETH_LOS alarm depends on the 2s-period of alarm jitter protection of an NE.
Alarm jitter protection of the NE: An NE reports an alarm after the NE receives the alarm report twice.
Jitter protection process: For a task of detecting LPT_RFI alarms, after the link of a port keeps down for 2s, an LPT-RFI alarm is reported to the NE continuously at intervals of 250 ms. After receiving the alarm, the NE reports or does not report it to the network management system immediately, depending on whether alarm jitter protection is required (By default, alarm jitter protection is required). The NE reports the alarm to the network management system 500 ms (not 2s) later, that is, after the NE receives the alarm report twice for protection against alarm jitter. For a task of detecting ETH_LOS alarms, the NE reports an ETH_LOS alarm to the network management system 2s later if the NE receives the alarm report twice for protection against alarm jitter before the NE reports the alarm to the network management system and if the board reports the alarm every second.
Hence, if an alarm lasts for a short period, only an LPT_RFI alarm instead of an ETH_LOS alarm is displayed on the network management system.
According to the preceding analysis, the problem does not occur when the function of alarm jitter protection of the NE is disabled by using the :alm-set-condetect:disable command. 
 
Suggestions
If the LPT function is enabled but the peer board does not report a related alarm, disable the function of alarm jitter protection of the NE. 

END