Hi all,
I read the latest version of the draft, and I found it useful. The draft
addresses a comprehensive range of topics for AQM characterization. What I
am not so happy with, is the description of the corresponding experiments.
Some critical points of my first review
Hi,
while looking at the PIE presentation
http://www.ietf.org/proceedings/86/slides/slides-86-iccrg-5.pdf,
slide 6 shows that RED is far away from the PIE
queuing delay. However, I'm not sure that this comparison is
really fair if looking at the choice of the parameters.
The buffer limit is set
In the real world, the hardware buffer size is rarely matched to the real
BDP. There are several reasons for this, but a couple of fundamental ones
are:
- BDP varies with RTT, which is in general different for flows
simultaneously using the same link/queue to reach different remote hosts,
and
Delayed-based RED still would associate latency with drop probability:
drop probability will only go up when queueing latency goes up. A higher
drop probability can only be achieved via higher queueing latency. As we
proved in PIE, the two can be made independent. We can maintain low
latency
Hi Jonathan,
Am 13.08.2015 um 19:35 schrieb Jonathan Morton:
In the real world, the hardware buffer size is rarely matched to the
real BDP. There are several reasons for this, but a couple of
fundamental ones are:
- BDP varies with RTT, which is in general different for flows
To second Roland's point, the advantage of PIE over RED should not be entirely
in the use of delay-based thresholds instead of queue-length ones, otherwise it
could be argued that a version of RED with delay-based thresholds is not too
hard to design (Wolfram easily did it for his GSP scheme).
If you are interested, here's our 2001 paper showing all the limitations of RED
and explaining the rationale behind the PI controller. It explained how delay
and drop/ECN-mark can be decoupled for AQMs.
http://dna-pubs.cs.columbia.edu/citation/paperfile/23/MisraInfocom01-AQM-Controller.pdf
