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Ethernet Service Fails due to the Parameter Modification of the Ethernet Board FCS32

Publication Date:  2012-07-25 Views:  76 Downloads:  0
Issue Description
The OptiX OSN 3500 (EFS0) and 155/622H (EFT board) in a network provide the Ethernet EPL service. The port mac7 of the EFS0 board corresponds to the mac2 port of the EFT board and the vctrunk is bound with 10xVC-12s. The customer provides the feedback that the service is interrupted, but no alarm information is reported. 
Alarm Information
Lower-order error bits occur in the EFT board of the Metro 155/622H.
A large number of error bits exist in intermediate lines. 
Handling Process
1. The engineers check the configuration and port attributes. The configuration and port attributes are correct.
2. The engineers query the protocol configuration of the EFS0 board. The configuration is correct. The engineers then query the EFT board configuration of the Metro 155/622H. It is found that the check parameter FCS32 is canceled, but the FCS32 setting of the EFS0 board is normal. It is learnt from the user feedback that the check parameter FCS32 of the EFT board has been modified before.
3. The engineers change the check bit of the EFT board to FCS32. Then, the service is restored and the FCS_ERR alarm is reported normally.
4. After the error bits are cleared, the FCS_ERR alarm disappears and the service is restored.
5. Because the user modifies the FCS parameter in only one end, the unchecked data frames are directly discarded in the peer end. As a result, the service fails. Besides, because the FCS check is not carried out, the FCS_ERR alarm is not reported even when error bits are detected on the line. 
Root Cause
The faults in the Ethernet service are often caused by the following reasons:
1. The data configuration of the SDH and Ethernet is correct (basis).
2. The attributes of the interconnection port between the Ethernet board and datacom board are configured incorrectly, such as the duplex mode and port mode.
3. Error bits exist in the line. In this case, the Ethernet board reports the FCS_ERR alarm.
4. The parameter configuration of the Ethernet board is incorrect.
The customer doubts the following:
A large number of error bits are detected in the line, but why the FCS_ERR alarm is not reported? 
Huawei Ethernet boards often use the default protocols and parameter settings. The default settings of all the boards are the same and the Ethernet boards can work normally in the deployment. Engineers must check whether the protocol and parameter are changed in the routine maintenance.