In fact we have OSN3500 network connected with NSN BSC's by optical fiber , so the optical boards between OSN and BSC's was be protected , suddenly the optical fibers of the main boards in OSN and BSC was be damage , so the switching to protection happened . and the traffic protected , but after the main fibers repairs the switching in OSN3500 return to the main board , but in BSC the active board still working as standby so after the switching happened in OSN3500 the traffic was be down
T_ALOS in OSN3500
E1_Fault in NSN BSC
1. check the history and current alarms in OSN3500 .
2. lets NSN engineer check history and current alarms .
3.check the optical powers in both sides OSN and BSC .
4.after i found all the E1's report T_ALOS alarm I check the time of first switch alarm from main to standby ,
5.I check when this alarm disappear and i compare it with the time of the T_ALOS and also with the alarms that appeared on NSN BSC ,
6. so i understand the problem have a relation with switching setting , so i make force switch for the main OSN board and the problem solved ,
7.after that I check with NSN engineer about the setting of the switching in NSN BSC and i found it was be non-revertive mode while in OSN it was be Revertive mode as we agree with customer .
8.finally I found in NSN BSC there is only one option for the switching mode its only non-revertive mode as NSN engineer confirmed , so I change the switching mode configuration in OSN to be Non-revertive mode .
then the problem solved also if the fiber damage .
before you configure with any other vendors or your equipments you must be sure about the switching mode configuration in the both sides