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How to handle the problem of abnormal ECC communication caused by abnormal optical power of the OTU of WDM equipment

Publication Date:  2012-07-25 Views:  40 Downloads:  0
Issue Description
Obe Metro WDM project, the SC2 boards are configured and the OTU boards provide the electrical supervision channel (ESC) function. One day, the customer reports that NE A falls out of management. A Huawei engineer goes to the network management center. The engineer checks NE A through ECC link management of adjacent NEs on the T2000 and finds that NE A runs properly. The engineer logs in to NE A through the command line. NE A stops responding after two simple commands are run. The engineer suspects that the problem is caused by ECC bit errors. The customer adds OLP equipment of manufacturer Z to the WDM ring. As a result, the OTU boards of many NEs report alarms to indicate that the optical power is too low. 
Alarm Information
IN_PWR_LOW 
Handling Process
1. View the optical power of the SC2 board on the network management system. The optical power is normal.
2. Remotely guide the managed operation (MO) service provider to remove the SCC and SC2 boards of NE A and then insert them again. The fault persists.
3. Remotely guide the MO service provider to log in to NE A through the T2000 and command line on the site. The login is normal. NE A does not stop responding after commands are run. You can exclude the possibility of failure of the SCC or SC2 board.
4. View the ECC routing table carefully on the network management system. You can find that the ESC function works between certain NEs. Run the :cm-get-chanerror command and you can find that LG, NO, CR, and AB errors continuously increase. The corresponding OTU board reports an IN_PWR_LOW alarm, so you can determine that this is the cause of the failure.
5. Disable the ESC function of the OTU boards of all NEs. The fault is cleared. 
 
Root Cause
1. The optical power of the SC2 board at an office is abnormal.
2. The SCC board of NE A works improperly.
3. The SC2 board of NE A works improperly.
4. By default, ECC is enabled for the OTU board. Currently, ECC communication is implemented through the ESC function. Bit errors of ECC communication are caused by abnormal optical power of the OUT board. 
 
Suggestions
For WDM equipment configured with an SC2, SC1, TC2, or TC1 board, many OTU boards provide the ESC function and the function is enabled by default. To prevent abnormal optical power of the OTU boards on ECC communication, you should disable the ESC function of the OTU boards for all the NEs on a ring. 

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