RED early drop statistics

["Jeremy Ethridge" <jethridg@nortelnetworks.com>]

Hi,

I am attempting to collect statistics on a simulation with a bottleneck link
that uses the RED queue scheme.  I have attached a flow monitor to the
appropriate link.  I am able to collect aggregate statistics, such as
pdrops_ and parrivals_, as well as per-flow statistics; however, the value
for epdrops_ is always 0.

When I change only the RED parameter for linterm_, I see different results
in the total number of drops and the average queue size; but I still detect
no early drops.

Here is the code that I use to attach the flow monitor:

    set fm [$ns makeflowmon Fid]
    $fm attach [open flowfile.out w]
    set pktsInt_ [new Integrator]
    $fm set-pkts-integrator $pktsInt_
    $ns attach-fmon [$ns link $r0 $c0] $fm

I try to check the early drops (and total drops) with the following line:

    puts "[$fm set pdrops_] [$fm set epdrops_]"

If anyone has an idea what might be wrong or can provide an example of a
script that correctly detects early drops on a RED queue, I would greatly
appreciate the help.

Thanks in advance,
Jeremy.