When the OptiX OSN 1500 is connected to the 155 Mbit/s optical port of the router of
company C, the LP_RDI alarm is generated in the 2 Mbit/s service. The relevant analysis
shows that the higher order path overheads of the line board are in the pass-through state,
which results in the lower order service interruption. Hence, the overhead mode must be
correctly set before a higher order service is changed to a lower order service.
Fault Type
- Equipment Interconnection Failure
- Service interruption
- LP-RDI
Symptom
During network expansion, the SLQ1 board of the OptiX OSN 1500 is connected directly
to the optical card of the router of company C. The network is configured with 1+1 linear
multiplex section protection (MSP). One end of the MSP line is the 2 Mbit/s service and
the other end is the 155 Mbit/s optical service. The LP_RDI alarm is reported in the
2 Mbit/s service.
Cause Analysis
Check the optical transmission paths, timeslot interconnection, router hardware, and
overhead modes of the SDH boards.
Procedure
1. After you confirm that the physical connections are normal, the receive optical power
of both the SLQ1 board and the optical interface of company C is normal, no optical power
alarm is generated on the receive side, but the link status of the router of company C is down.
2. Query the alarm. It is found that no abnormal alarms are generated on the SLQ1 board,
but the LP_RDI alarm is reported in the 2 Mbit/s service on the other end.
Perform inloop at the optical port that is interconnected with the SLQ1 board. It is found that
the LP_RDI alarm in the 2 Mbit/s service is cleared. It indicates that the optical transmission
paths are normal.
3. Perform outloop at the optical port that is interconnected to the SLQ1 board. It is found that
the link status of the router of company C is up. In this case, it is suspected that the fault exists
in the timeslot interconnection.
4. Check the relevant information. It is found that the first VC-12s of the VC-4s on the SLQ1 board
carry the services and that the first VC-12s of the VC-4s on the router of company C carry the services.
Add a 2 Mbit/s service in the twenty-second VC-12 on the SLQ1 board that corresponds to the second
VC-12 on the router of company C. It is found that the LP_RDI persists in the 2 Mbit/s service at the
opposite end. In this case, it is suspected that the local end fails to receive the optical signals.
Reset the router and then restart the router. It is found that the fault persists.
5. Check the SDH service configuration. The original service of the optical port that is interconnected
to the SLQ1 board at the local end is a VC-4 service. Delete this VC-4 service and add a VC-12 service.
In this case, the overhead mode should be Termination. Query the overhead mode. It is found that
the actual overhead mode is Pass-Through. Then, change the overhead mode to Termination.
It is found that the LP_RDI alarm is cleared and that the services are normal.
Reference Information
When you configure a lower order service, the higher order path overheads must be set to the
Terminal mode. Otherwise, the services may be interrupted.
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