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OSN 500 550 580 V100R008C50 Alarms and Performance Events Reference 02

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Performance Event Meaning

The MSBBE event indicates the background block error of the multiplex section (MS).

Performance Event Attributes

Performance Event ID Performance Event Type


SDH performance event

Impact on the System

If bit errors occur in the services, identify the causes and rectify the fault immediately. Otherwise, alarms will be generated and the signal transmission quality will be affected. If bit errors exceed the B2 bit error threshold-crossing threshold and degrade threshold, the B2_EXC and B2_SD alarms will be generated.

Possible Causes

The MSBBE event is an errored block not occurring as part of multiplex section unavailable time and multiplex section severely errored second.

External causes:

  • The fiber performance is degraded, and the fiber has high attenuation.

  • The fiber connector is dirty or incorrect.
  • The equipment is poorly grounded.
  • There is a severe interference source around the equipment.
  • The working temperature is high or low, and the opposite equipment cannot tolerate such temperature.

Equipment problems:

  • The signal attenuation on the receive side of the line board is excessive, the transmit circuit at the opposite end is faulty, or the receive circuit at the local end is faulty.

  • The synchronization performance of the clock is poor.
  • The cross-connect unit and the line board poorly match.
  • The board becomes faulty, or the performance of the board is degraded.

Relevant Alarms

Alarm Name Correlation


B2 bit errors crossing the threshold


Signals degraded (B2)


  1. Eliminate external causes, such as poor grounding, high operating temperature, low or high received optical power of the line board. Then, check whether bit errors occur on the line boards.
  2. If all the line boards of an NE have bit errors, the clock unit may be faulty. In this case, replace the CXL board.
  3. If only a line board reports that bit errors exist, the local line board may be faulty or that the opposite NE or fibers are faulty. Perform a loopback to locate the fault and replace the faulty board.



Updated: 2019-01-21

Document ID: EDOC1100020975

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