21001 LAPD Link Congestion

Description

If the length of the LAPD send queue is greater than the upper limit of the set congestion threshold, this alarm is reported. After the LAPD link congestion alarm is reported, the LAPD link congestion recovery alarm is generated if the length of the LAPD send queue is smaller than the lower limit of the set congestion threshold.

Attribute

Alarm ID	Alarm Severity	Alarm Type
21001	Major	Fault

Parameters

ID	Name	Meaning
1	Link No.	Number of the congested link
2	Subrack No.	Number of the subrack where the board carrying the congested link is located
3	Slot No.	Number of the slot where the board carrying the congested link is located
4	Port No.	Number of the port corresponding to the congested link
5	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 improper threshold settings or the overgreat traffic volume will slow down the service processing speed.
The faulty E1 cable or the faulty peer end will disrupt the services.

System Actions

When the system reports the alarm, it also reports the LAPD link status to the MTLS (upper-layer module corresponding to LAPD). Then the MTLS automatically performs flow control according to the link status and sets the congestion attribute of the LAPD link to the congested state.
At the same time, the messages are sent to the peer end (BTS or PCU). If the length of the message queue is smaller than the lower congestion limit, a recovery alarm is automatically reported and the link status is reported to the MTLS. Set the congestion attribute of the LAPD link to the decongested state. The MTLS can delivers messages.

Possible Causes

The setting of the congestion threshold is unreasonable. The recommended values of the upper and lower limits are 80 and 60 separately.
The singling traffic is overgreat and temporary congestion is caused.
The E1 cable that connects the BSC and the BTS or the BSC and the PCU is faulty. (The cable is loose or damaged).
The BTS or the PCU at the peer end is faulty.

Procedure

After the congestion alarm is reported for one minute, Check whether the alarm can be cleared automatically.
Y => The alarm handling is complete.

N => Go to 2.
Check whether the threshold setting is reasonable. The recommended values of the upper and lower limits are 80 and 60 separately.
Y => Go to 3.

N => Change the threshold.
Check whether the connection of the E1 cable is loose or faulty.
Y => Go to 4.

N => Go to 5.
Tighten or change the E1 cable.
Y=>The alarm is cleared. The alarm handling is complete.

N=>The alarm persists. Go to 5.
Check whether the BTS or the PCU at the peer end is abnormal.
Y => Notify the maintenance personnel at the peer end to handle the alarm. The alarm handling is complete.

N => Please contact Huawei Customer Service Center.