#Create a simulator object
set ns [new Simulator]

#Define different colors for data flows (for NAM)

$ns color 1 Blue
$ns color 2 Red

#Open the NAM trace file
set nf [open out.nam w]
$ns namtrace-all $nf

#Define a 'finish' procedure
proc finish {} {
        global ns nf
        $ns flush-trace
        #Close the NAM trace file
        close $nf
        #Execute NAM on the trace file
        exec nam out.nam &
        exit 0
}

#create four nodes

set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]

#set labels of nodes
$n0 label TCP
$n1 label SINK

#create the links
$ns duplex-link $n0 $n1 2Mb 5ms DropTail
$ns duplex-link $n2 $n3 2Mb 5ms DropTail
$ns duplex-link $n0 $n3 1.5Mb 15ms RED
$ns duplex-link $n2 $n1 1.5Mb 15ms RED

#setting queue size of link (n0-n1) to 20
$ns queue-limit $n0 $n1 20

#adjust position of the nodes
$ns duplex-link-op $n0 $n1 orient right
$ns duplex-link-op $n0 $n3 orient right-down
$ns duplex-link-op $n2 $n3 orient right
$ns duplex-link-op $n2 $n1 orient right-up

#Monitor the queue for link (n0-n1)
$ns duplex-link-op $n0 $n1 queuePos 1


#setup TCP agents
set tcp0 [new Agent/TCP]
$ns attach-agent $n0 $tcp0

set tcp1 [new Agent/TCP]
$ns attach-agent $n2 $tcp1

set tcp2 [new Agent/TCP]
$ns attach-agent $n0 $tcp2

set tcp3 [new Agent/TCP]
$ns attach-agent $n2 $tcp3

#make connections
set sink0 [new Agent/TCPSink]
$ns attach-agent $n1 $sink0
$ns connect $tcp0 $sink0


set sink1 [new Agent/TCPSink]
$ns attach-agent $n1 $sink1
$ns connect $tcp1 $sink1

set sink2 [new Agent/TCPSink]
$ns attach-agent $n3 $sink2
$ns connect $tcp2 $sink2

set sink3 [new Agent/TCPSink]
$ns attach-agent $n3 $sink3
$ns connect $tcp3 $sink3

#Setup FTP over TCP connection

set ftp0 [new Application/FTP]
$ftp0 attach-agent $tcp0

set ftp1 [new Application/FTP]
$ftp1 attach-agent $tcp1

set ftp2 [new Application/FTP]
$ftp2 attach-agent $tcp2

set ftp3 [new Application/FTP]
$ftp3 attach-agent $tcp3

#Schedule events for FTP agents
$ns at 0.1 "$ftp0 start"
$ns at 5.0 "$ftp0 stop"

$ns at 0.1 "$ftp1 start"
$ns at 5.0 "$ftp1 stop"


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

#Run the simulation
$ns run