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Modify the QoS Settings to Solve the Problem of Packet Loss in Services Attached to the NE40

Publication Date:  2012-07-27 Views:  50 Downloads:  2
Issue Description
Networking:
Services----5200G-------GE 7/0/1 NE40
At night, when the traffic is heavy, packets are found lost in the ping test conducted for the interface directly connected to the NE40.
In the ping test, a few small packets containing 56 bytes are lost at a ratio of 1/200.
In contrast, large packets containing 1500 bytes are lost at a much greater ratio. 
 
Alarm Information
Null
Handling Process
Check the router. The information displayed shows that the average traffic in five minutes is not heavy, but the count of packets discarded due to the limited interface capacity is found in the queues.
<NE40-1>dis qos queu sta g7/0/1 be
GigabitEthernet7/0/1 statistics:

forwarded : 53663237140/36450339747629 packets/bytes
discarded : 2731529/2142053544 packets/bytes

<NE40-1>dis qos queu sta g7/0/1 be
GigabitEthernet7/0/1 statistics:

forwarded : 53664169047/36450951048601 packets/bytes
discarded : 2731579/2142087412 packets/bytes
The preceding commands are executed to view the packet loss statistics in BE queues. When QoS is not configured on the GE interface, all packets, by default, are placed in the BE queue, for which the length of the corresponding cached queue cannot be configured on the equipment.
According to the current networking, it is unrealistic to adjust the network attached to the BAS. Therefore, the engineer has to modify the QoS settings on the NE40 to ensure that packet loss is avoided in the case of heavy traffic.
For details, see the appendix. 
 
Root Cause
1. The attached network is infected with virus, causing too many small packets.
If there are too many small packets involved in the attached services, the LPU will be congested with the queues. Then packets are probably discarded.
2. The link fails to carry the traffic as expected.
3. There are traffic bursts.
In the case of heavy traffic, packets may be lost. Therefore, the packet loss may be caused by traffic bursts, which often occur side by side with the first cause. 
 
Suggestions
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END