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

[Pete Heist]

> On Jan 3, 2019, at 11:06 PM, Pete Heist <pete at heistp.net> wrote:
> 
> I’m almost sure I tested this exact scenario, and would not have put 8 up / 8 down on one IP and 1 up / 1 down on the other, which works with fairness for some reason.

I’m going to dial this statement back. I went back through my old tests and in my main series of a thousand tests or so, I was splitting the two uploads and downloads across four IPs, so that’s different. Then when we were testing fairness in combination with rtt keywords, I was in fact testing 2 up / 2 down on one IP and 8 up / 8 down on the other, which is a scenario that produces the expected results.

So unless I can find some other past tests, or build an old enough version to show that the behavior was different, I can’t be sure I ever tested it this way, and don’t know if it’s a regression or it just works as designed and I never realized it.

On the one hand the IP1=1/8, IP2=8/1 results are “fair” in the sense that one client gets his wish for 8 uploads and the other gets his wish for 8 downloads, like “hey, I’ll let you drown out my 1 download if you let me drown out your 1 upload” :) but on the other hand, when Jon says there should be a difference between the triple-isolate and dual modes, that’s not what we’re seeing here.