set ns [new Simulator]
set f [open out.tr w]
$ns trace-all $f
set nf [open out.nam w]
$ns namtrace-all $nf
set n(0) [$ns node]
set n(1) [$ns node]
set n(2) [$ns node]
$ns duplex-link $n(0) $n(1) 1Mb 1ms DropTail
set tcp [new Agent/TCP]
$ns attach-agent $n(1) $tcp
set ftp [new Application/FTP]
$ftp attach-agent $tcp
$ns duplex-link $n(1) $n(2) 1Mb 1ms DropTail
$ns duplex-link $n(2) $n(0) 1Mb 1ms DropTail
set tcpsink [new Agent/TCPSink]
$ns attach-agent $n(0) $tcpsink
$ns connect $tcp $tcpsink
proc finish {} {
global ns nf
$ns flush-trace
close $nf
puts "running nam......"
exec nam out.nam &
exit 0
}
$ns at 2.5 "finish"
$ns run