Experiment-2
Using Free Open Source Software tools for network simulation – I Preliminary usage of the tool ns3 Simulate telnet and ftp between N sources – N sinks (N = 1, 2, 3). Evaluate the effect of increasing data rate on congestion.
Objectives
- Get a basic understanding of the way objectives interact in ns.
- Lay the foundations for more complicated simulations.
- Create a script that simulates the simplest topology
Network:
Figure 2.1
#Create NS Object :
set ns [new Simulator]
#Open the nam trace file
set nf [open out.nam w]
$ns namtrace-all $nf
#Define a ‘finish’ procedure
proc finish {} {
global ns nf
$ns flush-trace
#Close the trace file
close $nf
#Execute nam on the trace file
exec nam –a out.nam &
exit 0
}
#Create two nodes
set n0 [$ns node]
set n1 [$ns node]
#Create a duplex link between the nodes
$ns duplex-link $n0 $n1 1Mb 10ms DropTail
#Call the finish procedure after 5 seconds of simulation time
$ns at 5.0 “finish”
#Run the simulation
$ns run
#Execute a ns-2 script:
ns example1a.tcl
PART-B : To attach traffic from node 0 to node 1
set ns [new Simulator]
#open Trace Files
set f [open out.tr w]
$ns trace-all $f
set nf [open out.nam w]
$ns namtrace-all $nf
#define “finish” procedure
proc finish {} {
global ns
$ns flush-trace
#Execute the nam animation file
exec nam out.nam &
exit 0
}
#creating Node
set n0 [$ns node]
set n1 [$ns node]
#creating link and Queue
$ns duplex-link $n0 $n1 1Mb 10ms DropTail
#create UDP agent and attach it to nod 0
set udp0 [new Agent/UDP]
Figure 2.2
$ns attach-agent $n0 $udp0
#Adding Traffic to link
#create cbr traffic source and attach it to udp0
set cbr0 [new Application/Traffic/CBR]
Figure 2.3
$cbr0 set packetSize_ 500
$cbr0 set interval_ 0.005500
$cbr0 attach-agent $udp0
#Adding Traffic to link ; create null agent (a traffic sink) and attach it to node n1
set null0 [new Agent/Null]
Figure 2.4
$ns attach-agent $n1 $null0
#connect traffic source with the traffic sink
$ns connect $udp0 $null0
#schedule event for CBR agent
$ns at 0.5 “$cbr0 start”
$ns at 4.5 “$cbr0 stop”
$ns at 5.0 “finish”
#start ns
$ns run
#stop ns
exit 0
Figure 2.6
