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The cross-connect board reports BUS_ERR alarms because the frame header (FH) jitter tolerance register of the N2EGS2 is not enabled.

Publication Date:  2012-07-24 Views:  115 Downloads:  0

Issue Description

The cross-connect board on the OptiX OSN 3500 have reported BUS_ERR alarms at irregular intervals for a long time. An alarm lasts for dozens of seconds to dozens of minutes. Reset the N2EGS2 in slot 12 and the cross-connect board. The fault remains. The NE software version is The cross-connect board is a UXCSA.

10    BUS_ERR   MJ   end   2007-5-15 8:20:43    2007-5-15 8:55:47    0x0c   0x04   0x04   0x01   0xff   

9       BUS_ERR   MJ   end   2007-5-15 8:55:54    2007-5-15 8:56:0     0x0c   0x04   0x06   0x01   0xff         

Alarm Information


Handling Process

1.Run the following OPTP commands to enable the FH jitter tolerance register. Observe the equipment for over 20 days. No BUS_ERR alarm is reported.
2.The FH jitter tolerance register is enabled for the NGSDH V1R2C02B025SP01 ( and later versions. The fault is removed after the version on site is upgraded to      

Root Cause

The parameters of the BUS_ERR alarms show that the fourth bus of the N2EGS2 in slot 12 experiences B1 bit errors and BUS_OFF. Because the cross-connect board is a UXCSA, it is impossible that the B1 bit errors or BUS_OFF alarms are caused by the connection to an extended subrack. We suspect that the quality of the signals sent by the bus conversion chip of the N2EGS2 are poor or the phase of the frame alignment bytes of the signals does not meet the requirement of the cross-connect board. The further analysis shows that the FH jitter tolerance register of the bus conversion chip of the N2EGS2 software ( is not enabled. In addition, sometimes the time sequence of the FHs does not meet the requirement of the cross-connect board. For these reasons, sometimes the BUS_ERR alarms occur on some boards and the services are affected.