512 parallel FTP sessions very slow?

[Maarten Litmaath <litmaath@fnal.gov>]

Dear NS experts,
we are in the process of evaluating NS for simulating a 512x512 switch
(we know that NS does not support switches yet, so that we would have to
write some code ourselves; will that change, by the way?).
To get an idea of the speed of NS we tried the following little script:
it runs 512 parallel FTP sessions.
We found that on a Sparc-20 it took 1.5 hours for 1 ms of simulation!!!
Are we doing something wrong?
Thanks,
	Maarten (Fermilab CD/CMS dept.)

#----------------------------------------------------------------------
set ns [new Simulator]

$ns set-address-format expanded

set maxnode 512

for {set i 0} {$i < $maxnode} {incr i} {
    set node($i) [$ns node]
    set k [expr $i + $maxnode]
    set node($k) [$ns node]
    $ns duplex-link $node($i) $node($k) 640Mb 0.1ms DropTail
    $ns queue-limit $node($i) $node($k) 10
    set tcp [$ns create-connection TCP $node($i) TCPSink $node($k) 0]
    set ftp [$tcp attach-source FTP]
    $ns at 0.000 "$ftp start"
    $ns at 0.001 "$ftp stop"
}

$ns at 0.002 "$ns halt"
$ns run
#----------------------------------------------------------------------