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

[Pete Heist]

> On Jan 4, 2019, at 3:08 AM, Georgios Amanakis <gamanakis at gmail.com> wrote:
> 
> On Thu, 2019-01-03 at 23:06 +0100, Pete Heist wrote:
>> Both have cake at 100mbit only on egress, with dual-srchost on client
>> and dual-dsthost on server. With this setup (and probably previous
>> ones, I just didn’t test it this way), bi-directional fairness with
>> these flow counts works:
>> 
>> 	IP1 8-flow TCP up: 46.4
>> 	IP2 1-flow TCP up: 47.3
>> 	IP1 8-flow TCP down: 46.8
>> 	IP2 1-flow TCP down: 46.7
>> 
>> but with the original flow counts reported it’s still similarly
>> imbalanced as before:
>> 
>> 	IP1 8-flow TCP up: 82.9
>> 	IP2 1-flow TCP up: 10.9
>> 	IP1 1-flow TCP down: 10.8
>> 	IP2 8-flow TCP down: 83.3
> 
> I just tested on archlinux, latest 4.20 on the router, iproute2 4.19.0,
> using flent 1.2.2/netserver in a setup similar to Pete's:
> 
> client 1,2 <----> router <----> server
> 
> The results are the same with Pete's.

One more scenario to add, IP1: 1 up / 1 down, IP2: 1 up / 8 down. In the graph, IP1 = host1, IP2 = host2, sorry for the longer labels, and watch out that the position of the hosts changes.

dual keywords: https://www.heistp.net/downloads/fairness_1_1_1_8/bar_combine_fairness_1_1_1_8.svg <https://www.heistp.net/downloads/fairness_1_1_1_8/bar_combine_fairness_1_1_1_8.svg>

host keywords: https://www.heistp.net/downloads/fairness_1_1_1_8_host/bar_combine_fairness_1_1_1_8_host.svg <https://www.heistp.net/downloads/fairness_1_1_1_8_host/bar_combine_fairness_1_1_1_8_host.svg>

Also not what I’d expect, but host 2’s upload does get slowed down, even disproportionately, in response to the extra aggregate download he gets. Up and down are more balanced with the “host” keywords, but without flow fairness there’s higher inter-flow latency.
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