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NE5000E Interfaces Kept Going Down

Publication Date:  2012-07-27 Views:  99 Downloads:  0
Issue Description
The traffic on a certain IP bearer network switched from the SDH system to the WDM system. In normal circumstances, it can be switched within 50 ms. Because the delay of 100 ms was configured on the datacom device connected with the transmission devices, the datacom devices should have not sensed the switchover. However, the interfaces on some datacom devices went Down. 

 
Alarm Information
The log showed that the interface kept going Up and then Down frequently. 

 
Handling Process
Finally, the engineer believed that the fault was caused by the inconsistency of the switching conditions. The lower-layer chip of the datacom device is sensitive. The chip can quickly identify LOS, LOF, and all kinds of error codes based on information about the interface. However, optical power differences on the master and slave links must reach 5 DB to ensure the switchover of the transmission device. Therefore, the lower-layer chip needs to obtain information about the optical powers on the master and slave links and compare the powers. This process involves power amplification and comparison, which takes some time. In the switchover, error codes must occur first. There is a delay before the interface perceives the reduction of the optical power by 5 DB. In this case, the transmission device is switched later than the datacom devices. Suppose the switchover of the transmission device is t1 later than that of the datacom device, the switchover takes t2, and the delay set in the datacom device is t3. If t1 plus t2 is larger than t3, the datacom device senses the switchover and the interface goes Down. 

 
Root Cause
1. Can the traffic be switched in 50 ms each time?
2. Did the datacom devices begin the switchover 100 ms later than the switchover of the transmission devices?
3. Did the switchover start at the same time on the two types of devices?
4. Were the conditions consistent for the switchover on the two types of devices? 

 
Suggestions
If any failure occurs when multiple devices are connected, find out the implementation mechanisms of different products. 

 

END