ns: scheduler going backwards in time

["Claudio E. Casetti" <casetti@polito.it>]

Hello,
           I just stumbled upon a rather wierd behavior of NS. Here's what
happens: I'm trying to simulate a scenario featuring 20 FTP sources going
on and off; before starting the simulation, I use the tcl interface to
explicitly schedule "start" and "stop" times for each source, i.e.:

    $ns at $mytime "$on_off1 start"

where $on_off1 is an instance of one of the FTP sources and $mytime is a
generic time instant.

Apparently, everything runs smoothly until, midway through the simulation, I
start getting the "ns: scheduler going backwards in time" message (meaning ns
is trying to dispatch an event that was supposed to 'happen' before its
current, virtual clock).

I'm using ns "as is", I haven't changed a line of code (ns version 2.1b4), and
I'm only interacting with it through simple tcl commands.

Has anyone experienced similar problems?

Claudio Casetti

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   |                       Claudio Casetti                               |
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