Description of the problem

Customer feedback, three points of 10G rate two-fiber bi-directional multiplexing segment ring, one of which is 9500 equipment (A8), two 3500 equipment (A6, A7). Configured a 155M service between the two 3500 devices, the route is a long path (through the 9500 device) to take the time slot is the second VC4.

Since the 155M optical port does not have access to the service has R-LOS, the line takes the second time slot, so the second VC4 of the line reports an AU-AIS alarm. the fiber-optic cable between A6 and A8 is interrupted, and this 155M service is inverted to the standby time slot. the 34th VC4 of the standby time slot of A8 (9500) reports an AU-AIS alarm, but the 34th VC4 of the network element in the A7 (3500) pass-through state There are no alarms.

Alarm messages

AU-AIS, R-LOS

Processing

1. Check the alarm blocking and find that the AU-AIS alarm of the 34th VC4 of A7 is not blocked.

2. Hanging meter test in the state of inversion, the service is normal.

3, consult the R&D, the R&D feedback in the pass-through state of the NG-SD equipment, do not detect the alarm of the standby time slot, but in the inverted state of the equipment will detect the alarm of the standby time slot. 9500 and 10G equipment in the pass-through state also detect the alarm of the standby time slot.

Root Cause

1. The alarm is blocked;

2. The processing mechanism of the backup time slot is different, and the host does not report;

Recommendations and Summary

1, for NG-SDH equipment, the alarm of the standby time slot is not detected in the wear-through state, which is inconvenient for fault localization, and it is necessary to loop back to locate the faulty site if service interruption occurs after the inversion.

2, in the normal state, if you need to detect whether the standby time slot is normal, you can configure the service that passes through and hang up the table to test, for the standby time slot configured with the service, NG-SDH detects the alarm.

3, although under normal circumstances METRO5000, OCS and NG-SDH equipment group multiplexing section of the ring network is not a problem, but the special circumstances of the subtle differences as maintenance engineers should also know.

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