#Create a simulator object
set ns [new Simulator]
#Open a trace file
set nt [open lab1.tr w]
$ns trace-all $nt
#Open a nam trace file
set nf [open lab1.nam W]
$ns namtrace-all $nf
# Create the nodes.
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]
#Assign color to the packets.
$ns color 1 Red
$ns color 2 Blue
#Label the nodes
$n0 label "Source/udp0"
$n1 label "Source/udp1"
$n2 label "Router"
$n3 label "Destination/Null"
#Create links, vary bandwidth to check the number of packets dropped.
$ns duplex-link $n0 $n2 10Mb 30ms DropTail
$ns duplex-link $n1 $n2 10Mb 30ms DropTail
$ns duplex-link $n2 $n3 1Mb 30ms Drop?Tail
# Set the queue size between the nodes
$ns set queue-limit $n0 $n2 10
$ns set queue-limit $n1 $n2 10
$ns set queue-limit $n2 $n3 5
#Create and attach UDP agent to n0, n1 and null agent to n3.
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 $n1 $udp1
set cbr1 [new Applicatin/traffic/CBR]
$cbr1 attach-agent $udp1
set null3 [new Agent/Null]
$ns attach-agent $n3 $null3
#Set udp0 packets to red color and udp1 packets to blue color
$udp0 set class_1
$udp1 set class_2
#Connect the agents.
$ns connect $udp0 $null3
$ns connect $udp1 $null3
#Set the packet size to 500
$cbr1 set packetSize_ 500Mb
#Set the data rate of the packets. if the data rate is high then packets drops are high
$cbr1 set interval_ 0.005
#Finish Procedure
proc finish {} {
global ns nf nt
$ns flush-trace
exec nam lab1.nam &
close $nt
close $nf
exit0
}
$ns at 0.1 "$cbr0 start"
$ns at 0.1 "cbr1 start"
$ns at 10.0 "finish"
$ns run AWK FILE:
BEGIN{
count=0;
}
{
if($1==”d”)
count++;
}
END{
printf (“No. of packets dropped is= %d\n”, count);
}