Burst size, drops before CIR

Hi everybody

We all know improper burst size could result in drops even CIR is not reached. The question is how can we find that optimum burst size which will not cause any drop as CIR approaches on Extreme switch


Traffic Generator------>p3--Extreme_switch--p2 --Accedian_NID ( LOOPBACK)

We are generating 47 MIG stream from the traffic generator.

Extreme switch has following configs:

Create meter METER_CIR

config meter METER_CIR 50000kbs max-burst size 8000kbs

Then we apply the meter on ingress on port 3 using ACL.

Even though the traffic stream is within CIR, we see drops because of improper burst size.

Do we have any formula on Extreme switch that help us find that optimum burst size ?

Much appreciated!!

2 replies

Userlevel 4
Hello Zeeshan,

I do not know of any way to find the optimum max-burst-size as traffic burst occur at different rates and sizes.
Userlevel 6
Hello, normally the CIR is done good. It depends on what kind of traffic generator you are using. If you use an application on windows the application tries to send a constant stream but still windows determines the rate it really egresses out of the NIC and it can be bursty and exceed the CIR. If you use a dedicated device like IXIA or Spirent the stream is really shaped to the value you configure on the IXIA/Spirent.
Could this explain the behavior ?