[ovs-discuss] QoS Egress Port Traffic Shaping (linux-hfsc ) not Working as Expected for UDP Traffic

[Ramzah Rehman]

Edit: I have 2 VMs not physical servers.

Best Regards,
Ramzah Rehman


On Fri, Dec 14, 2018 at 5:53 PM Ramzah Rehman <ramzahrehman at gmail.com>
wrote:

>  I have two servers connected via 1Gbps cable. I have installed OVS 2.8 on
> server one. I have a switch named OVS_BR_LEAF_1 on it. I experimented with
> QoS traffic shaping. I have connected eth3 of server one to ovs-switch on
> port 2. I want traffic going from server one to server two to observer QoS
> traffic rate that I specify.
>
> I added following configuration:
>
> #ovs-vsctl -- set port eth3 qos=@newqos -- --id=@newqos create qos
> type=linux-hfsc other-config:max-rate=1000000000 queues:1=@q1 -- --id=@q1
> create queue other-config:min-rate=x other-config:max-rate=x
>
> I have following flow entries in my switch:
> #vs-ofctl add-flow OVS_BR_LEAF_1
> priority=6000,in_port=LOCAL,actions=set_queue:1,normal
> #ovs-ofctl add-flow OVS_BR_LEAF_1 priority=6000,in_port=2,actions=normal
>
> Then I checked throughput for TCP traffic (from server one to two) via
> iperf and got following results:
>
> got 846 Mbps for x=900 Mbps
> got 757 Mbps for x=800 Mbps
> got 653 Mbps for x=700 Mbps
> got 428 Mbps for x=450 Mbps
> got 381 Mbps for x=400 Mbps
> got 287 Mbps for x=300 Mbps
> got 239 Mbps for x=250 Mbps
> got 192 Mbps for x=200 Mbps
>
> Seems like traffic shaping is working fine for TCP traffic. However, for
> UDP, I got these results:
>
> 148 Mbps for x=800 Mbps
> 185 Mbps for x=300 Mbps
> 131 Mbps for x=200 Mbps
> 93 Mbps for x=100 Mbps
> 77 Mbps for x=80 Mbps
> 28.9 Mbps for x=30 Mbps
> 19.3 Mbps for x=20 Mbps
>
> For UDP, traffic shaping works fine till x=100Mpbs, but for higher values
> is shows unexpected behavior. Is there an explanation?
>
> Please help.
>
> Best Regards,
> Ramzah Rehman
>
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