Emulator installation help needed

["Sunila R. Ainapure" <ainapure@aim.baylor.edu>]

I am having problems with running the ns emulator example script,
'pingdemo.tcl' and, of course, any other emulator script.

The steps I followed are as follows:

1. Installed FreeBSD 2.2.8. (The NS docs say that the emulator was tested
under 2.2.5.  2.2.8 was the closest version we could find.)  The machine has
1 ethernet card.
2. compiled ns and nse - ns works fine.
3. made the necessary changes to the script like changing $myname and
$myaddr to the IP address of the machine I am using and changed the
interface $ifname to the ethernet card on the machine (ep0).

I get the following errors when I try to execute the script
(command : nse pingdemo.tcl)

"pcap/live object (_o11) couldn't open packet source ep0: /dev/bf0:
Devicee not configured
(_o11 cmd line 1)
 invoked from within
"_o11 cmd open readonly ep0"
 invoked from within
"catch "$self cmd $args" ret"
 (procedure "_011" line 2)
  (SplitObject unknown line 2)
   invoked from within
"$bpf2 open readonly $ifname"
 (procedure "thisdemo"    line 21)
 (PingDemo emsetup line 21)
  invoked from within
"$self emsetup"
 (procedure "thisdemo" line 5)
 (PingDemo run line 5)
  invoked from within
"thisdemo run"
(file "pingdemo.tcl" line 198)
"
_____________

Anyone seen this problem before?

- One concern I have is that ns complains about an old version of Perl (v.
4.0) possibly causing problems.  I don't think this is the cause of this
particular problem, but what
version of Perl does it expect.
- Is there some additional configuration/installation required for using BPF
or does it work with the standard install?  Am I supposed to configure bpf0
or anything else to make the
script work?  If yes please let me know how to do it.
- What about pcap?  Do I need to find a newer version?

We are simply trying to set up the emulator so that we can experiment with
the effects of
delay and loss on socket programs written for a networking class.  Ideally,
we would like to
have the sender program be able to send to the receiver where the packets
traverse the
emulator network.  The sender and receiver programs can run on the same or
separate machines,
whatever works.  Any suggestions on how to make this work?  Do we need a
machine with 2 ethernet cards? - 1 for receiving packets from and another
for sending it to after passing it
through the emulator?

If anyone has successfully executed this or any other emulator script,
please let me know the details.

I'd appreciate any help with this.
Thank you.

-Sunila.