Program no 1.

Write a TCL script to simulate the network described below  Consider a small network with five nodes n0, n1, n2, n3, n4, forming a star topology. The node n4 is at the center. Node n0 is a TCP source, which transmits packets to node n3 (a TCP sink) through the node n4. Node n1 is another traffic source, and sends UDP packets to node n2 through n4. The duration of the simulation time is 10 seconds.

TCL Script:

set ns [new Simulator]
set namfile [open ex_01.nam w]
$ns namtrace-all $namfile

set tracefile [open ex_01.tr w]  

$ns trace-all $tracefile

set n0 [$ns node] 

set n1 [$ns node] 

set n2 [$ns node] 

set n3 [$ns node] 

set n4 [$ns node]

$ns duplex-link $n0 $n4 1Mb 10ms DropTail 

$ns duplex-link $n1 $n4 1Mb 10ms DropTail 

$ns duplex-link $n4 $n3 1Mb 10ms DropTail 

$ns duplex-link $n4 $n2 1Mb 10ms DropTail

set tcp [new Agent/TCP] 

$ns attach-agent $n0 $tcp 

set sink [new Agent/TCPSink] 

$ns attach-agent $n3 $sink  

$ns connect $tcp $sink

set ftp [new Application/FTP] 

$ftp attach-agent $tcp

set udp [new Agent/UDP] 

$ns attach-agent $n1 $udp

set null [new Agent/Null] 

$ns attach-agent $n2 $null

$ns connect $udp $null

$udp set class_ 1 

$ns color 1 Blue

$tcp set class_ 2 

$ns color 2 Red

set cbr [new Application/Traffic/CBR] 

$cbr set packetsize_ 500 

$cbr set interval_ 0.005 

$cbr attach-agent $udp

$ns at 0.0 "$cbr start" 

$ns at 0.0 "$ftp start" 

$ns at 9.0 "$cbr stop" 

$ns at 9.0 "$ftp stop"

proc finish {} {              

global ns namfile tracefile          

$ns flush-trace        

close $namfile        

close $tracefile        

exec nam ex_01.nam &        

exit 0 

}

$ns at 10.0 "finish" 

$ns run