[Cake] triple flow isolation

[Jonathan Morton]

> On 14 Jan, 2016, at 20:53, moeller0 <moeller0 at gmx.de> wrote:
> 
> So I have not grokked the triple algorithm fully (aka not at all), but I already know that what user’s are looking for is fairness by internal host IPs. Now, since as I explained before ingress and egress really are too flexible to use as direction pointers, I assume we are looking for some configuration parameter that contains a direction; so as long as “triple” allows to request fairness by source IP or by destination IP (since these might change depending on the interface cake is running on) all will be fine. I just do not see how a simple unidirectional parameter like “triple-iso” will allow to take the fact into account that ingress and egress are only relative to the sqm interface and do not necessarily align with the internal/WAN ingress and egress… But as I said before I do not claim I understand what triple-iso intends to accomplish in detail.

The short version is that, in theory at least, I’ve found a way to ensure fairness without needing to know which side of the interface is which.  By accounting for *both* source and destination host fairness at the same time, and not placing one above the other in importance, it should all work out in the end.  The method by which I do so is probably interesting enough to write a paper about, once I’ve got it working in practice.

At this point, I strongly suspect I’ve made an implementation blunder, since even single-stepping through the theoretical algorithm’s behaviour, packet by packet, produces approximately the desired results - which are however not reproduced in actual measurements on my LAN.  Time to add more stats to the multitude already present!

If you want to be explicit about directionality, that’s what the two new “dual” modes are for.  The “triple isolation” algorithm is still used, but the undesired attribute is ignored.  The “triple” mode combines their effects.

 - Jonathan Morton