[Ecn-sane] tsvwg preso for sce is up

[Dave Taht]

SCE: https://www.youtube.com/watch?v=FDK88vdE5r0&t=1h15m

A couple notes:

at 1:25:20 - mirja had asked what the sce marking threshold was, not
the codel parameters (I think). I think she wanted to know the
sce_threshold?

At 1:27, I'd really love the flent files to be able to zoom in on that
data, It's unclear how low the ping overhead is. A 100Mbit result
using native
ethernet and bql at the bottleneck instead of cake with a rate limit
might be interesting. Gbit also.... (have 10gbit in my lab)

1:27:49 Gorry said "This looks like FQ", and no, it's the real
convergence of two SCE AQMed flows at 50mbit, 80ms rtt as Jonathan
pointed out, which
takes 45 seconds. And that brought to mind, what is your intuition?
What would you expect for convergence using fq? And what is it?

1:31:18 One thing long since vanished from the l4s debate is that
codel achieves a ~5ms queue depth, where pie only gets 16ms. The need
for "ultra-low-latency" is less when you get that kind of result in
most cases from your aqm.

I've always felt that pie could be improved - the principal flaws
being the rate estimator - and the update interval. fq-pie on bsd
borrows
codel's rate estimator.

But I digress.

Flent has a default sample rate of 200ms, which means that it can miss
some details. You can sample instead at rates as low as 20ms, although
this is murder on your local cpu and can heisenbug the tests. It's
generally a good idea to be sampling at double the rate you care about
(nyquist
theorim), so a 40ms sample rate here would have shown more detail.

If you really, really want more detail than that, packet captures are
a way to go. Got any?


-- 

Dave Täht
CTO, TekLibre, LLC
http://www.teklibre.com
Tel: 1-831-205-9740