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OSN 500 550 580 V100R008C50 Alarms and Performance Events Reference 02

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The ATMPW_UNKNOWNCELL_EXC alarm indicates that the number of unknown ATM cells exceeds the specified threshold within a certain period of time (2s by default). This alarm is cleared when the number of unknown ATM cells is lower than the specified threshold within another period of time (10s by default).


Alarm Severity Alarm Type


Communication alarm



Impact on the System

The NE discards the detected unknown ATM cells, the packet loss ratio increases, and the service performance is affected. If the packet loss ratio is high, the service may be interrupted.

Possible Causes

Possible causes of the ATMPW_UNKNOWNCELL_EXC alarm are as follows:

  • PW control words are inconsistent.
  • PW types are inconsistent.
  • Physical links are incorrectly connected.


  1. Check whether the ATM service configurations are the same at both ends of the PW, such as the control word and PW type.

    If... Then...

    PW types are inconsistent

    Change PW types to the same. Check whether the alarm is cleared. If the alarm persists, go to the next step.

    PW types are consistent

    Go to the next step.

  2. Check whether optical fibers or cables are correctly connected.

    If... Then...

    Physical links are incorrectly connected

    Rectify the cable or fiber connections. Check whether the alarm is cleared. If the alarm persists, go to the next step.

    Physical links are connected correctly

    Contact Huawei technical support engineers to handle the alarm.

Related Information


Updated: 2019-01-21

Document ID: EDOC1100020975

Views: 75706

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