1. VTU COMPUTER NETWORK LAB | READ NOW
VTU COMPUTER NETWORK LAB
Program – 1:- Implement three nodes point–to–point networks with duplex links between them. Set the queue size, vary the bandwidth, and find the number of packets dropped.
Program Code
#Create Simulator set ns [new Simulator] #Open Trace file and NAM file set ntrace [open prog1.tr w] $ns trace-all $ntrace set namfile [open prog1.nam w] $ns namtrace-all $namfile #Finish Procedure proc Finish {} { global ns ntrace namfile #Dump all the trace data and close the files $ns flush-trace close $ntrace close $namfile #Execute the nam animation file exec nam prog1.nam & #Show the number of packets dropped exec echo "The number of packet drops is " & exec grep -c "^d" prog1.tr & exit 0 } #Create 3 nodes set n0 [$ns node] set n1 [$ns node] set n2 [$ns node] #Label the nodes $n0 label "TCP Source" $n2 label "Sink" #Set the color $ns color 1 blue #Create Links between nodes #You need to modify the bandwidth to observe the variation in packet drop $ns duplex-link $n0 $n1 1Mb 10ms DropTail $ns duplex-link $n1 $n2 1Mb 10ms DropTail #Make the Link Orientation $ns duplex-link-op $n0 $n1 orient right $ns duplex-link-op $n1 $n2 orient right #Set Queue Size #You can modify the queue length as well to observe the variation in packet drop $ns queue-limit $n0 $n1 10 $ns queue-limit $n1 $n2 10 #Set up a Transport layer connection. set tcp0 [new Agent/TCP] $ns attach-agent $n0 $tcp0 set sink0 [new Agent/TCPSink] $ns attach-agent $n2 $sink0 $ns connect $tcp0 $sink0 #Set up an Application layer Traffic set cbr0 [new Application/Traffic/CBR] $cbr0 set type_ CBR $cbr0 set packetSize_ 100 $cbr0 set rate_ 1Mb $cbr0 set random_ false $cbr0 attach-agent $tcp0 $tcp0 set class_ 1 #Schedule Events $ns at 0.0 "$cbr0 start" $ns at 5.0 "Finish" #Run the Simulation $ns run