NS 2 assignment (TCP traffic flow)

set ns [new Simulator]
set nf [open out.nam w]
$ns namtrace-all $nf
proc finish {} {
global ns nf
$ns flush-trace
close $nf
exec nam out.nam &
exit 0
}
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]
set n4 [$ns node]
set n5 [$ns node]

$ns duplex-link $n0 $n1 1Mb 20ms DropTail
$ns duplex-link $n0 $n2 1Mb 20ms DropTail
$ns duplex-link $n1 $n3 1Mb 20ms DropTail
$ns duplex-link $n2 $n4 1Mb 20ms DropTail
$ns duplex-link $n4 $n5 1Mb 20ms DropTail
$ns duplex-link $n3 $n5 1Mb 20ms DropTail


set u0 [new Agent/TCP]
set u1 [new Agent/TCPSink]
set u2 [new Agent/TCP]
set u3 [new Agent/TCPSink]



$ns attach-agent $n0 $u0
$ns attach-agent $n5 $u1
$ns attach-agent $n2 $u2
$ns attach-agent $n3 $u3


$ns connect $u0 $u1
$ns connect $u2 $u3

set c0 [new Application/Traffic/CBR]
$c0 set packetSize_ 500
$c0 set interval_ 0.005
$c0 attach-agent $u0
$ns at 0.5 "$c0 start"
$ns at 9.0 "$c0 stop"

set c1 [new Application/Traffic/CBR]
$c1 set packetSize_ 500
$c1 set interval_ 0.005
$c0 attach-agent $u2


$ns at 10.0 "finish"
$ns run



save it with a name simulation.tcl
At terminal type ns2 simulation.tcl