CBWFQ scheduling

[kent.plummer]

Does anyone know how CBWFQ scheduling really works - Cisco doesn't seem to share the low level details on this.

I have a situation where the class class-default is being starved by other queues.

I'm flooding a link with simulated UDP traffic that I have defined separate queues for (i.e. not in the class-default queue) and have reserved 25% of the link bandwidth for. This non class-default traffic is consuming almost 100% of the link. The traffic in the class-default queue is effectively being starved.

I have Flow based WFQ and WRED enabled on the class-default queue. But have tried all combinations of this without success.

According to Cisco docs the max-reserved-bandwidth 75, should ensure that 25% of the bandwidth is reserved for the class-default queue. This doesn't appear to work from my testing.

It is possible to disable WFQ in the class-default queue and define "bandwidth [kbps]" for the queue. However WFQ is a far better choice for the default queue as it will still consider DSCP.

Has anyone experienced this? I'm testing on 12.2(29).

[rdamaso]

Can you show the config to me?

If I understood, if you change "bandwidth" per "priority" you can resolve this.

Or configure a policy into class that you have a "bandwidth" command to limit this traffic.

With "bandwidth" command, if the traffic exceeds the Kbps defined, it can fills your class-default generating starvation of this class.

Thanks.