[Tmrg] Now, where were we...?

[michawe at ifi.uio.no (Michael Welzl)]

Hi,

This prompts me to ask a question that I've been pondering
ever since a hallway conversation that I had with Stanislav
Shalunov at the Stockholm IETF:


> 2. How reliable are implicit congestion indicators?  The prevailing
> wisdom in the IETF seems to be that "ECN=loss = congestion, delay =
> noise, nothing else is useful for congestion control".  What criteria
> would "delay" have to satisfy in order to be a useful indicator of
> congestion?  Should we listen to the average delay, the frequency with
> which delay exceeds a threshold, or the jitter?

Can delay ever be worse as a congestion indicator than
loss is? What kinds of misinterpretations can we have,
if we carefully interpret it?   (by which I mean, for instance,
updating "baseRTT" samples every once in a while
in order to account for path changes)

To be a bit more precise with my question, I pick the
"frequency with which delay exceeds a threshold" metric
from above.

Cheers,
Michael