20250 Loss of Tributary Frames (LOF)

Description

The Loss of Tributary Frames (LOF)) alarm is generated when the tributary of the optical port of BSC interface board fails to detect the information about the frame head over a period of time.

Attribute

Alarm ID	Alarm Severity	Alarm Type
20250	Major	Fault

Parameters

ID	Name	Meaning
1	Subrack No.	Subrack No.
2	Slot No.	Slot No.
3	Cpu No.	CPU No.
4	Tributary Unit No.	0 - 62(for E1 mode), 0 - 83(for T1 mode).
5	Site No.	The IDs of all sites whose OMLs are on the faulty E1/T1. If BTS are cascade connected,a maximum of 4 sites are shown.Only Abis E1/T1 alarm has this parameter.
6	Site Name	The Names of all sites whose OMLs are on the faulty E1/T1. If BTS are cascade connected,a maximum of 4 sites are shown.Only Abis E1/T1 alarm has this parameter.
7	Alarm Attribute	0=Normal, Alarms period are longer than the Transient Threshold. 1=Transient Count, The times and the period of the alarms whose periods are shorter than the Transient Threshold are summed up. If the sum result is longer than the Alarm Occurrence Period Threshold or Alarm Occurrence Times Threshold, an alarm so called Transient Count Alarm is triggered. Because Transient Count Alarm is based on accumulative result, the recovery of the alarm may occur at least one Summing Cycle later. The Summing Cycle can be query by MML "LST STATSLDWIN".

Impact on the System

The services carried on the tributary of the optical port are disrupted.

System Actions

If the APS function is enabled on the interface board, no handling is performed.

If the APS function is disabled on the interface board, the handling varies with the operation modes of the board.

When the active interface board is faulty, an active/standby switchover is performed if the standby board allows a switchover. Otherwise, no handling is performed.
When the standby interface board is faulty, no handling is performed.
When the faulty interface board works in independent mode, no handling is performed.

Possible Causes

The transmission equipment is faulty.
The peer NE is faulty.
The BSC interface board is faulty.

Procedure

Check the BSC interface board.
1. Perform a loopback on the optical ports of the BSC interface board. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. The BSC interface board is normal. Reconnect the optical port, and Go to 2.
  N => The alarm is not cleared. The BSC interface board is faulty. Go to b.
2. Reset the BSC interface board. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. The alarm handling is complete.
  N => The alarm is not cleared. Go to c.
3. Remove and then reinstall the BSC interface board. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. The alarm handling is complete.
  N => The alarm is not cleared. Go to d.
4. Replace the BSC interface board. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. The alarm handling is complete.
  N => The alarm is not cleared. Go to 2.
Check the interface board of the peer NE.
1. Check the type of the peer NE.
  Y => If the peer NE is the GMPS/GEPS/GTCS, Go to b. If the peer NE is the BTS, Go to f.
  N => The peer NE is not the GMPS/GEPS/GTCS or the BTS. Go to i.
2. Check whether the GOIUT in the peer GMPS/GEPS/GTCS is normal.
  Y => The GOIUT is normal. Contact the transmission engineers. The alarm handling is complete.
  N => The GOIUT is abnormal. Go to c.
3. Reset the board. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. The alarm handling is complete.
  N => The alarm is not cleared. Go to d.
4. Reinsert the GOIUT, and then check whether the alarm is cleared.
  Y => The alarm is cleared. The alarm handling is complete.
  N => The alarm is not cleared. Go to e.
5. Replace the GOIUT. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. The alarm handling is complete.
  N => The alarm is not cleared. The transmission between the GMPS/GEPS and the GTCS is faulty. Contact the transmission engineers. The alarm handling is complete.
6. On the BTS side, perform a loopback on the peer NE port towards the BSC. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. The E1 lightning protection board in the BTS is faulty. Go to g.
  N => The alarm is not cleared. The transmission equipment or transmission link between the BSC and the BTS is faulty. Contact the transmission engineers. The alarm handling is complete.
7. Reinsert the E1 lightning protection board, and then check whether the alarm is cleared.
  Y => The alarm is cleared. The alarm handling is complete.
  N => The alarm is not cleared. Go to h.
8. Replace the E1 lightning protection board in the BTS, and then check whether the alarm is cleared.
  Y => The alarm is cleared. The alarm handling is complete.
  N => The alarm is not cleared. Contact Huawei Customer Service Center.
9. Contact the maintenance engineers of the peer NE. On the peer NE side, perform a loopback on the port towards the BSC. Then, check whether the alarm is cleared.
  Y => The alarm is cleared. The peer NE is faulty. Contact the maintenance engineers of the peer NE. The alarm handling is complete.
  N => The alarm is not cleared. The transmission equipment or transmission link between the BSC and the peer NE is faulty. Contact the transmission engineers. The alarm handling is complete.