[Cake] dual-src/dsthost unfairness, only with bi-directional traffic

[Pete Heist]

I ran my original iperf3 test with and without the patch, through my one-armed router with hfsc+cake on egress each direction at 100Mbit:

Unpatched:

IP1 1-flow TCP up: 11.3
IP2 8-flow TCP up: 90.1
IP1 8-flow TCP down: 89.8
IP2 1-flow TCP down: 11.3
Jain’s fairness index, directional: 0.623 up, 0.631 down
Jain’s fairness index, aggregate: 0.997

Patched:

IP1 1-flow TCP up: 51.0
IP2 8-flow TCP up: 51.0
IP1 8-flow TCP down: 50.7
IP2 1-flow TCP down: 50.6
Jain’s fairness index, directional: 1.0 up, 0.999 down
Jain’s fairness index, aggregate: 0.999

So this confirms George’s result. :)

Obviously if we look at _aggregate_ fairness it’s essentially the same in both cases. I think directional fairness is what users would expect though.

Can anyone think of any potentially pathological cases from considering only bulk flows for fairness, that I can test? Otherwise, I’d like to see this idea taken in...

> On Jan 16, 2019, at 4:47 AM, gamanakis at gmail.com wrote:
> 
> Of course I pasted the results for IP1 and IP2 the wrong way. Sorry!
> These are the correct results, along with the *.flent.gz files.
> 
> IP1: 
> flent -H 192.168.1.2 tcp_8down &
> Data file written to ./tcp_8down-2019-01-15T223703.709305.flent.gz.
> Summary of tcp_8down test run at 2019-01-16 03:37:03.709305:
> 
>                             avg       median          # data pts
> Ping (ms) ICMP   :         0.78         0.72 ms              342
> TCP download avg :         6.03         5.83 Mbits/s         301
> TCP download sum :        48.24        46.65 Mbits/s         301
> TCP download::1  :         6.03         5.83 Mbits/s         298
> TCP download::2  :         6.03         5.83 Mbits/s         297
> TCP download::3  :         6.03         5.83 Mbits/s         297
> TCP download::4  :         6.03         5.83 Mbits/s         298
> TCP download::5  :         6.03         5.83 Mbits/s         298
> TCP download::6  :         6.03         5.83 Mbits/s         298
> TCP download::7  :         6.03         5.83 Mbits/s         297
> TCP download::8  :         6.03         5.83 Mbits/s         298
> 
> 
> flent -H 192.168.1.2 tcp_1up &
> Data file written to ./tcp_1up-2019-01-15T223704.711193.flent.gz.
> Summary of tcp_1up test run at 2019-01-16 03:37:04.711193:
> 
>                           avg       median          # data pts
> Ping (ms) ICMP :         0.79         0.73 ms              342
> TCP upload     :        48.12        46.69 Mbits/s         294
> 
> 
> 
> IP2:
> flent -H 192.168.1.2 tcp_1down &
> Data file written to ./tcp_1down-2019-01-15T223705.693550.flent.gz.
> Summary of tcp_1down test run at 2019-01-16 03:37:05.693550:
> 
>                           avg       median          # data pts
> Ping (ms) ICMP :         0.77         0.69 ms              341
> TCP download   :        48.10        46.65 Mbits/s         300
> 
> 
> flent -H 192.168.1.2 tcp_8up &
> Data file written to ./tcp_8up-2019-01-15T223706.706614.flent.gz.
> Summary of tcp_8up test run at 2019-01-16 03:37:06.706614:
> 
>                           avg       median          # data pts
> Ping (ms) ICMP :         0.74         0.70 ms              341
> TCP upload avg :         6.03         5.83 Mbits/s         301
> TCP upload sum :        48.25        46.63 Mbits/s         301
> TCP upload::1  :         6.04         5.86 Mbits/s         226
> TCP upload::2  :         6.03         5.86 Mbits/s         226
> TCP upload::3  :         6.03         5.86 Mbits/s         226
> TCP upload::4  :         6.03         5.86 Mbits/s         225
> TCP upload::5  :         6.03         5.86 Mbits/s         226
> TCP upload::6  :         6.03         5.86 Mbits/s         226
> TCP upload::7  :         6.03         5.78 Mbits/s         220
> TCP upload::8  :         6.03         5.88 Mbits/s         277
> 
> 
> <tcp_8up-2019-01-15T223706.706614.flent.gz><tcp_8down-2019-01-15T223703.709305.flent.gz><tcp_1up-2019-01-15T223704.711193.flent.gz><tcp_1down-2019-01-15T223705.693550.flent.gz>