Problem Description

The OSN3500 SSN1EMS4 single board LPT function is triggered but there is no related alarm ( ETH_LOS ) in the front segment. a short-time service interruption occurs in the front-end router, the LPT function is enabled, and the service is interrupted. The SSN1EMS4 single board in the front end does not report the related alarm ( ETH_LOS ) because the EMS4 in the front end turns on the alarm dithering function.

Alarm information

One end reports the alarm LPT_RFI, the other end does not report ETH_LOS.

Processing

Disable the alarm dithering function of the relevant network element.

Root cause

LPT_RFI and ETH_LOS are implemented as follows:

LPT_RFI: 250ms, 100 priority task polling.

ETH_LOS: 1000ms, 140 priority task polling.

Alarm jitter: LPT_RFI alarms are reported to the host after 2 seconds of jitter, ETH_LOS alarms rely on the host's 2 seconds of jitter.

Host anti-shake: 2 times

Anti-shake process: LPT_RFI detects port link_down for 2 seconds and then reports to the host continuously, with an interval of 250ms. the host receives this alarm and decides whether to report to the network management immediately according to whether anti-shake is required (default is required). Since there are 2 times of anti-dithering, note that here it is two times not two seconds. Therefore, the host reports to the network management 500ms after receiving this alarm. As for the ETH_LOS task, the host reports to the network management only after 2 seconds after it receives the ETH_LOS alarm if it has to be anti-jittered 2 times and the single board reports once in 1 second.

So if the alarm time is very short, then only LPT_RFI will be shown on the network management, but no ETH_LOS alarm.

But according to the above analysis, if you use the :alm-set-condetect:disable command to remove the host's dithering function, then there is no problem as above.

Recommendations and Summary

If it happens that the LPT function is enabled but the opposite end single board does not report the related alarm, it is recommended to disable the alarm dithering function of the network element.