[ns] Received Packets Trace

[Hadar Burstin <HadarB@bandwiz.com>]

Hi,
In a certain topology, I'm trying to find out how many packets were received
at node n1.
I tried:
set tf [open recv.tr w]
$ns create-trace Recv $tf $n0 $n1
...simulation details ...

close $tf
exit 0

But the file recv.tr was empty. In the same simulation with
set tf [open queue.tr w]
$ns trace-queue $n0 $n1 $tf
...simulation details ...

close $tf
exit 0

The queue.tr file had many logs of received packets (event "r"). Does
someone know how come there was nothing written in the file when I used
"create-trace"?
(I'm working with ns-allinone-2.1b7a.) 

Thanks.