Re: questions about errormodel

[Kevin Fall <kfall@ee.lbl.gov>]

> I don't understand all the parameters :
> 
>     set lossylink_ [$ns link $node_(r1) $node_(k1)]
>     set em [new ErrorModule Fid]
>     set errmodel [new ErrorModel/Periodic]
>     $errmodel unit pkt
>     $errmodel set offset_ 1.0
>     $errmodel set period_ 25.0
>     $lossylink_ errormodule $em
>     $em insert $errmodel
>     $em bind $errmodel 0
> 
> thanks for any help
> 
> Arnaud. 

The Periodic error model is parameterized like a periodic
function.  So, the offset is sort of like the phase offset,
indicating the first item to drop.   It will then drop every
period_ items.  I say "item" because what is dropped is
sensitive to the "unit" parameter.  The (current) choices
are "time", "byte", or "pkt".  If you choose time, the period
and offset are in units of seconds [new: not yet tested for Periodic],
if you choose "byte", the packet containing the specified bytes
are dropped, and if you choose "pkt", its in packet units.

Another item that may interest you.  There is a new error model
called "List".. For this one, you say:

	$errmodel droplist "1 3 2 15 89"

which will arrange to drop the specified [pkt containing byte #s
or pkts, time is not implemented].

- K