As shown in Figure 1, NE1 is the gateway NE and only convergence services are configured between NE1 and other NEs. The clock source of NE1 is the external clock source, and other NEs trace the west line clock source. When the services between NE1 and NE6 become abnormal, the PQ1 boards on NE1 and NE6 report the LPBBE and LPES performance events. Bit errors exist in the paths where the performance events are generated. At the same time, the history alarms show that NE6 reports the TEMP_OVER alarm within a period of time.
Figure 1 Topology of the transmission network
1.Perform inloop for the SL16 board in slot 5, and then the performance events on NE1 are cleared. After the inloop is released, the performance events are generated again. It indicates that the fault may exist on NE5 or NE6.
2.Perform outloop for the SL16 board in slot 6, and then the performance events on NE1 are cleared. After the outloop is released, the performance events are generated again. It indicates that the fault may exist on NE6.
3.Replace the original PQ1 and SL16 boards on NE6 with the corresponding standby boards, but the performance events persist.
4.It indicates that the cross-connect unit is fault. Hence, replace the EXCSA board. Then, the performance events are cleared. The air-conditioner on NE6 is faulty. Then, the ambient temperature becomes very high in the narrow equipment room, and as a result damages the cross-connect unit.
If NE1 and NE6 report performance events, the fault may exist on NE1, NE5, or NE6. In this case, you can locate the fault by performing loopback. If NE6 reports the temperature alarm, the ambient temperature may be very high, and thus the PQ1 or EXCSA board becomes faulty.