Re: [ippm] draft-duffield-ippm-burst-loss-metrics-01

[Vinayak Hegde <vinayakh at gmail.com>]

On Sun, Nov 1, 2009 at 8:05 PM, Yaakov Stein <yaakov_s at rad.com> wrote:
> I read the aforementioned draft with interest, as I believe that it is
> important to have a way of quantifying the burstiness of packet loss.
[Snip]

I agree to what Yaakov has said with regards to time. When I think for
burstiness, I would like to have a metric which can be scaled to
multiple packets in succession, so while this draft might start with a
pair of packets, it might be inadequate. The reason being, I would
like to have a better sample with higher resolution of measurement.
Quantification of bursty loss will be more accurate in terms of
percentage when more packets are involved in succession. Also the
order of loss of individual packets in a stream (a bunch of packets
used for measurement) might not be important, what would matter is the
aggregate sample such as there was a loss of 1 packet on average when
10 bursts of 10 packets were used as compared to a loss of 1 loss-pair
per 10 loss-pair packets.

The only counterexample that I can think of is when some packets are
more important that others and there is a periodic 'SYNC' packet send
in a stream. The loss of the SYNC packet would be higher as compared
to other packets if it is a periodic loss every X interval.

Additional comments:

In section 4., a geometric distribution is mentioned. It is not clear
to me why a geometric distribution might be used between successive
time (exponential backoff/damping oscillations). any precedent for
this ?

In section 4.3 / 4.4 What are the use cases for m <= n Why would m be
<= n is not immediately clear.

In section 4.7 Should there be a reference to asymmetric losses ? For
example in a video conferencing app with two participant there is loss
in one direction but not the other leading to loss in video/audio
quality.

In section 5.1 Why is there a differentiation between (1,0) and (0,1)
packets. In burstiness, shouldn't the aggregate statistics matter  and
not the order of loss ?

Finally the selection function is mentioned in several places in the
draft. A couple of examples of each with real-life scenarios could be
useful.

-- Vinayak