[ovs-discuss] Maximum bandwidth not being reached

[Sofia Marques]

Hi there.

I have a scenario where I'm using opendaylight and ovs switch where I have
installed qos according to the following:

- Qos max rate of 100 Mbps;
- Queue 1 with max rate of 100 Mbps, min rate of 30 Mbps, priority 1;
- Queue 2 with max rate of 50 Mbps, min rate of 20 Mbps, priority 2;
- Queue 3 with max rate of 30 Mbps, min rate of 10 Mbps, priority 3;
- Queue 4 with max rate of 10 Mbps, min rate of 1 Mbps, priority 4;

I have assigned 5 flows to each queue and I'm running iperf UDP tests for
each of them with the following bandwidth specifications:

- Flows for queue 1 with 6 Mbps;
- Flows for queue 2 with 4 Mbps;
- Flows for queue 3 with 2 Mbps;
- Flows for queue 4 with 1 Mbps;

Everything works perfectly, with every flow reaching the specified
bandwidth.

But when I increase the number of flows for each queue to 10, they do not
reach the speficied bandwidth. If I'm not mistaken, every queue min rate is
guaranteed, which means that 30+20+10+1 = 61 Mbps are used. Which leaves
100-61=39 Mbps to be used. I believe that 30 Mbps would be assigned to
queue 1 to reach its desired bandwidth since it is the queue with higher
priority and the 9 Mbps left would go to queue 2. But this is not
happening, and neither queue 1 and queue 2 are assigned with this left
bandwidth. I can see that each flow on queue 1 only reaches about 5 Mbps
and in queue 2 around 3 Mbps. Am I getting this wrong or this problem has
some other explanation?

I would appreciate any help to understand what is happening.
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