Packet Drop with Qos setting

[Herman2018]

Hi, we have one lease line with bandwidth 500Mbps, the current max transmit is 70Mbps. we have configured traffic shaping on the outgoing interface, and set CIR to 500Mbps. After applied QoS, still see the packet drop. The router interface is 1Gbps.Can anyone please advise, thanks in advance! 

Below is the output of the command "show policy-map interface"

Class-map: class-default (match-any)
116687041259 packets, 71927177160795 bytes
5 minute offered rate 57946000 bps, drop rate 665000 bps
Match: any
Queueing
queue limit 346 packets
(queue depth/total drops/no-buffer drops) 0/619014583/0
(pkts output/bytes output) 115984267607/71009955393276
shape (average) cir 500000000, bc 2000000, be 2000000
target shape rate 500000000

[M02@rt37]

Hello @Herman2018 

From the output of the show policy-map interface command, it seems that your router is shaping the traffic to meet the desired average rate (CIR) of 500 Mbps. However, the traffic actually transmitted is significantly lower than the shaped rate (70 Mbps), which indicates that the shaping is not being applied correctly.

Burst size (BC) and excess burst size (BE) parameters may not be appropriately sized for your traffic patterns. Ensure that the burst sizes are adequate to accommodate short bursts of traffic without causing drops.

Also, check if there are any other factors causing congestion on the outbound interface, such as other QoS policies, high CPU utilization, or physical issues like duplex mismatches or interface errors.

(If you could) Experiment with adjusting the shaping parameters (CIR, BC, BE) to find a configuration that effectively controls the outbound traffic rate without causing drops. Start with conservative values and gradually increase them as needed.

Last, engage with Cisco TAC for further live assistance and troubleshooting.

[Herman2018]

Thanks M02@rt37 for your advice. will do further investigation. 

[M02@rt37]

You're so welcome @Herman2018 

[Joseph W. Doherty]

"After applied QoS, still see the packet drop."

So you saw packet drops before you applied QoS too?

Good chance the shaper is working correctly.

Although M02@rt37 is correct adjusting shaper values can impact throughput, that's both expert level knowledge and should consider how your WAN provider is controlling their CIR.

Could you expand upon ". . . the current max transmit is 70Mbps."?   I.e. exactly what that means.

BTW, possibly a clue to less than expected throughput is your drop rate average.

[Herman2018]

hi @Joseph W. Doherty , sorry for late reply because busy with daily works. What I meant about " the current max transmit is 70Mbps" is the value captured on Solarwinds. I think there is micro burst, which total amount of the traffics is more than 500mbps so that some traffics are dropped.