[ns] ErrorModel unit bit not working?

[Steve Chen]

All-

I have used the following code directly from ns manual, it works just fine.
But when I change the unit to bit there was no discarded packets. Anyone has
a fix?

set loss_module [new ErrorModel}
$loss_module set rate_ 0.01
$loss_module unit pkt
$loss_module ranvar [new RandomVariable/Uniform]
$loss_module drop-target [new Agent/Null]

Thanks in advance,
Steve