[Bloat] buffer sizing meeting notes

[Luca Muscariello]

On Sat, Aug 24, 2019 at 9:59 AM Sebastian Moeller <moeller0 at gmx.de> wrote:

> Another nugget from the notes (
> http://yuba.stanford.edu/~bspang/buffer-sizing-meeting/notes/):
>
> This looks like an argument for fq_codel/cake's use of time instead of
> queue length, OR an argument for fq, because in a non-overwhelmed fq_system
> the local bucket's queue length should be somewhat stronger correlated with
> the sojurn times, than the sojurn time of a packet though a shared queue,
> no?
>

I believe that using fq there are good implications in terms of buffer
sizing rules.
The focus is only on backlogged flows. The sparse flow queue can be sized
purely based on queue load.
Which is trivial queuing theory formulas with non-TCP traffic.

For backlogged flows, sizing is just like sizing a buffer for a single TCP
flow. So the computation
can be done based on estimations of the number of backlogged flows and by
setting the cut-off BDP based on the
largest (maximum) min RTT one want to serve optimally.  So AQM is really
needed to get optimality.
The number of backlogged flows could be estimated as a max value or an avg
value, and this of course
changes depending on the network segment (DC, residential, campus, access,
backhaul etc.).

Nick McKeown has done quite a lot of research on the topic (reported in the
slide deck), so I find hilarious the following in his slide deck
"Personal confession: I have no idea what the general answer is" about
sizing buffers!
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