Next we need to paste the below code to the Main.tcl file and save the file in the ns-2.35 folder.

Code:

set ns [new Simulator]

$ns color 0 blue

$ns color 1 red

$ns color 2 white

set n0 [$ns node]

set n1 [$ns node]

set n2 [$ns node]

set n3 [$ns node]

set f [open out.tr w]

$ns trace-all $f

set nf [open out.nam w]

$ns namtrace-all $nf

$ns duplex-link $n0 $n2 5Mb 2ms DropTail

$ns duplex-link $n1 $n2 5Mb 2ms DropTail

$ns duplex-link $n2 $n3 1.5Mb 10ms DropTail

$ns duplex-link-op $n0 $n2 orient right-up

$ns duplex-link-op $n1 $n2 orient right-down

$ns duplex-link-op $n2 $n3 orient right

$ns duplex-link-op $n2 $n3 queuePos 0.5

set udp0 [new Agent/UDP]

$ns attach-agent $n0 $udp0

set cbr0 [new Application/Traffic/CBR]

$cbr0 attach-agent $udp0

set udp1 [new Agent/UDP]

$ns attach-agent $n3 $udp1

$udp1 set class_ 1

set cbr1 [new Application/Traffic/CBR]

$cbr1 attach-agent $udp1

set null0 [new Agent/Null]

$ns attach-agent $n3 $null0

set null1 [new Agent/Null]

$ns attach-agent $n1 $null1

$ns connect $udp0 $null0

$ns connect $udp1 $null1

$ns at 1.0 “$cbr0 start”

$ns at 1.1 “$cbr1 start”

set tcp [new Agent/TCP]

$tcp set class_ 2

set sink [new Agent/TCPSink]

$ns attach-agent $n0 $tcp

$ns attach-agent $n3 $sink

$ns connect $tcp $sink

set ftp [new Application/FTP]

$ftp attach-agent $tcp

$ns at 1.2 “$ftp start”

$ns at 1.35 “$ns detach-agent $n0 $tcp ; $ns detach-agent $n3 $sink”

puts [$cbr0 set packetSize_]

puts [$cbr0 set interval_]

$ns at 3.0 “finish”

proc finish {} {

          global ns f nf

          $ns flush-trace

          close $f

          close $nf

          puts “running nam…”

          exec nam out.nam &

          exit 0

}

$ns run