Network Simulator 2 (NS2) : Monitoring & Examples For NS2

6. Example on NS2

NS workbench is used in following examples to create scenarios and generate TCL scripts, which are then run in NS2 to generate trace file and NAM file

To use NS workbench you will need Java Sdk installed on your system then download ns-bench jar file and execute it to start ns workbench

Example 1:

The network consists of five nodes n0 to n4. In this scenario, node n0 sends constant bit-rate (CBR) traffic to node n3, and node n1 transfers data to node n4 using a file transfer protocol (FTP). These two carried traffic sources are carried by transport layer protocols User Datagram Protocol (UDP) and Transmission Control Protocol (TCP), respectively. In NS2, the transmitting object of these two protocols are a UDP agent and a TCP agent, while the receivers are a Null agent and a TCP sink agent, respectively.

Network created by ns workbench is shown below

Then Generate the TCL script and save it. Script generated is given below:

# Creating New Simulator
set ns [new Simulator]

# Setting up the traces
set f [open outEx1.tr w]
set nf [open outEx1.nam w]
$ns namtrace-all $nf
$ns trace-all $f

proc finish {} {

     global ns nf f
     $ns flush-trace
     puts "Simulation completed."
     close $nf
     close $f
     exit 0
}

#
#Create Nodes
#

set n0 [$ns node]
      puts "n0: [$n0 id]"
set n1 [$ns node]
      puts "n1: [$n1 id]"
set n2 [$ns node]
      puts "n2: [$n2 id]"
set n3 [$ns node]
      puts "n3: [$n3 id]"
set n4 [$ns node]
      puts "n4: [$n4 id]"

#
#Setup Connections
#

$ns duplex-link $n0 $n2 100Mb 5ms DropTail
$ns duplex-link $n2 $n4 54Mb 10ms DropTail
$ns duplex-link $n1 $n2 100Mb 5ms DropTail
$ns duplex-link $n2 $n3 54Mb 10ms DropTail
$ns queue-limit $n2 $n3 40
$ns simplex-link $n3 $n4 10Mb 15ms DropTail
$ns simplex-link $n4 $n3 10Mb 15ms DropTail


#
#Set up Transportation Level Connections
#

set tcp0 [new Agent/TCP]
$ns attach-agent $n1 $tcp0

set udp1 [new Agent/UDP]
$udp1 set dst_addr_ Unicast
$udp1 set fid_ 1
$ns attach-agent $n0 $udp1

set null0 [new Agent/Null]
$ns attach-agent $n3 $null0

set sink0 [new Agent/TCPSink]
$ns attach-agent $n4 $sink0

#
#Setup traffic sources
#

set ftp0 [new Application/FTP]
$ftp0 attach-agent $tcp0

set cbr0 [new Application/Traffic/CBR]
$cbr0 set rate_ 2Mb
$cbr0 set packetSize_ 1000
$cbr0 attach-agent $udp1
$ns connect $udp1 $null0
$udp1 set fid_ 0
$ns connect $tcp0 $sink0
$tcp0 set fid_ 1

#
#Start up the sources
#

$ns at 0.05 "$ftp0 start"
$ns at 0.1 "$cbr0 start"
$ns at 60.0 "$ftp0 stop"
$ns at 60.5 "$cbr0 stop"
$ns at 61.0 "finish"
$ns run
					

Then to run the script in NS2 start Cygwin and change directory path to folder you saved your TCL script in and then use ns command to run the script.