[ns] Expo Error model always gives the same transfer time

[gmc50 <gmc50@student.canterbury.ac.nz>]

Hi,

I try to use the ErrorMode/Expo to generate random errors in a
duplex-link but, monitoring the throughput and time it takes to send,
say, 4MBytes, I always get the same results for all my runs (e.g. 6
runs). Does anybody know why this happens and how I can get different
values for each run?

The code I use to generate the errors is:

set rate [list 20 2]
set unit pkt
set rate2 [list 50 3]
set ExpoLossModule1 [new ErrorMode/Expo $rate $unit]
$ns link-lossmodel $ExpoLossModule1 $n0 $n1
set ExpoLossModule2 [new ErrorMode/Expo $rate $unit]
$ns link-lossmodel2 $ExpoLossModule1 $n1 $n0

Any ideas would be very appreciated. Thank you very much,

Gustavo.