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

[Toke Høiland-Jørgensen]

Sebastian Moeller <moeller0 at gmx.de> writes:

> Hi Toke,
>
>> On Jan 18, 2019, at 14:33, Toke Høiland-Jørgensen <toke at redhat.com> wrote:
>> 
>> Georgios Amanakis <gamanakis at gmail.com> writes:
>> 
>>> Yes, exactly. Would be interesting to hear what Jonathan, Toke and
>>> others think. I want to see if fairness is preserved in this case with
>>> sparse flows only. Could flent do this?
>> 
>> Well, sparse flows are (by definition) not building a queue, so it
>> doesn't really make sense to talk about fairness for them. How would you
>> measure that?
>> 
>> This is also the reason I agree that they shouldn't be counted for host
>> fairness calculation purposes, BTW...
>
> That leads to a question (revealing my lack of detailed knowledge) if
> there is a sufficient number of new flows (that should qualify as
> new/sparse) that servicing all of them takes longer than each queue
> accumulating new packets, at what point in time are these flows
> considered "unworthy" of sparse flow boosting? Or differetly how i
> cake going to deal with a UDP flood where the 5 tuple hash is
> different for all packets (say by spoofing ports or randomly picking
> dst addresses)?

Well, what is considered a sparse flow is a function of both the flow
rate itself, *as well as* the link rate, number of competing flows, etc.
So a flow can be sparse on one link, but turn into a bulk flow on
another because that link has less capacity.

I explore this in some detail here:
https://doi.org/10.1109/LCOMM.2018.2871457

-Toke