#Create a simulator object
set ns [new Simulator]

#Define a 'finish' procedure
proc finish {} {
    global ns tcp

    $ns flush-trace
    exit 0
}

#Create five nodes
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]

#Create links between the nodes
$ns duplex-link $n0 $n2 10Mb 5ms DropTail
$ns duplex-link $n1 $n2 10Mb 5ms DropTail
$ns duplex-link $n2 $n3 10Mb 20ms DropTail

#Set Queue Size of link (n2-n3) to 20
$ns queue-limit $n2 $n3 20

#Setup the first TCP connection
set tcp [new Agent/TCP]
$tcp set class_ 2
$ns attach-agent $n0 $tcp
set sink [new Agent/TCPSink]
$ns attach-agent $n3 $sink
$ns connect $tcp $sink
$tcp set fid_ 1

#Setup a FTP over TCP connection
set ftp [new Application/FTP]
$ftp attach-agent $tcp
$ftp set type_ FTP

#Setup the second TCP connection
set tcp [new Agent/TCP]
$tcp set class_ 2
$ns attach-agent $n0 $tcp
set sink [new Agent/TCPSink]
$ns attach-agent $n3 $sink
$ns connect $tcp $sink
$tcp set fid_ 1

#Setup a FTP over TCP connection
set ftp [new Application/FTP]
$ftp attach-agent $tcp
$ftp set type_ FTP

#Schedule events for the CBR and FTP agents
$ns at 1.0 "$ftp start"
$ns at 4.0 "$ftp stop"

#Call the finish procedure after 5 seconds of simulation time
$ns at 5.0 "finish"

#Run the simulation
$ns run