1.Implement three nodes point to point network with duplex links between them.
Set
the queue size, vary the bandwidth and find the number of packets dropped.
#Create Simulator
set ns [new Simulator]
#Open Trace file and NAM file
set ntrace [open prog1.trw]
$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 $namfile
#Execute the nam animation file
exec nam prog1.nam & #Show the number of packets dropped exec echo "The number of packet
drops is " & exec grep -c "^d" & exit 0
}
#Create 3 nodes
set n0 [$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
AWK File:
BEGIN {
count=0;
}
{
if ($1==” d”)
count++;
}
END {
printf(“no. of packets dropped is %d\n”,count);
}
Command:
awk -f lab1.awk prog1.tr
The no. of packets dropped is 8.
