This document provides an introduction and overview of Network Simulator 2 (NS2). It discusses the history and goals of NS2, the languages and protocols it supports, and how to work with and extend NS2. It describes how to create simple simulations using Tcl scripts, including defining nodes, links, traffic sources and sinks. It also provides an example of simulating wireless networks in NS2 using scripts to define node movement and the DSDV routing protocol.

1. Introduction to
Network Simulator v 2 (ns2)
Presented By:
Dr. Sharad Sharma, Professor, MMDU, Mullana

2. Outline
NS2 Overview
Working with NS2
Extending NS2

3. NS2 OVERVIEW

4. History
NS was developed by UC Berkeley
Maintained by USC Berkeley
Popular simulator in scientific
environment
Other popular network simulators
-Qualnet
-GloMoSim
-OPNET etc.

5. Help & Resources
NS main web page:
 http://www.isi.edu/nsnam/ns/
 Tutorials:
http://www.isi.edu/nsnam/ns/tutorial/index.html
 http://www.isi.edu/nsnam/ns/ns-tutorial/
 NS Manual:
 http://www.isi.edu/nsnam/ns/ns-
documentation.html

6. Supporting OS: Most UNIX and UNIX
like systems
-Linux
-SunOS
-Solaris
(Windows)
-95/98/2000/NT/ME
Some work, some do not

7. NS2 Goals
To support networking research and
education
-Protocol design, traffic studies, etc.
-Protocol comparison
-New architecture designs are also
supported

8. 2 Languages
TCL-Tool command language (Front
end design) . It is easy to code but runs
slowly
C++ (Back end support). It is fast to
run but slower to code and change

9. C++ is used mainly for the creation of
objects. It is fast to run but slower to
change, making it suitable for detailed
protocol implementation.
OTcl is used as a front-end to setup the
simulator, configure objects and
schedule events. It runs much slower
but can be changed very quickly and
interactively, making it ideal for
simulation configuration.

10. Protocols/Models Supported by NS2
Wired Networking
-Routing:Unicast, Multicast, and
Hierarchical Routing, etc.
-Transportation:TCP, UDP, others.
-Traffic sources:web, ftp, telnet, cbr, etc.
-Queuing disciplines:Drop-tail, RED, etc.

11. Protocols/Models Supported by NS2
Ad hoc routing and mobile IP
-Routing Protocol:AODV, DSDV, DSR,
etc.
-MAC layer Protocol:TDMA, CDMA, IEEE
Mac 802.x, etc.
-Physical layers:Different channels,
directional antenna
Sensor Networks

12. Working with
NS2
-Let‟s start at the very beginning,
a very nice place to start,
when you sing, you begin with A,B,C,
when you simulate, you begin with the
topology,………

13. Tools
NAM (Network Animator-Visualized
trace tool)
Xgraph-Output (Bandwidth, Cumulative
Packet Loss, Queue Size, etc.)
Trace Files (Tracing on different links)

14. Steps in Writing a Simulation Script
Create the event scheduler
Turn on tracing
Create network
Setup routing
Create transport connection
Create traffic
Transmit application-level data

15. A Simple Simulation
0
1
2 3
2Mbps,10ms
2Mbps,10ms
1.7Mbps,20ms

16. A Simple Simulation
It can be done with a simple Tcl script.
set ns [new Simulator] ;#Create a simulator object
$ns color 1 Blue ;#Define different colors(NAM)
$ns color 2 Red
set nf [open out.nam w] ;Create trace files for simulation
$ns namtrace-all $nf
set tf [open trace.tr w]
$ns trace-all $tf
proc finish {} { ;Define a „finish‟ procedure
global ns nf tf ;nf-nam trace,tf-ns2 trace file
$ns flush-trace

17. A Simple Simulation
#Close the NAM trace file
close $nf
#Close the ns2 trace file
close $tf
exit 0
}
#Create four nodes
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]

18. A Simple Simulation
#Create links between the nodes
$ns duplex-link $n0 $n2 2Mb 10ms Droptail
$ns duplex-link $n1 $n2 2Mb 10ms Droptail
$ns duplex-link $n2 $n3 1.7Mb 10ms Droptail
#Set Queue Size of link (n2-n3) to 10
$ns queue-limit $n2 $n3 10
#Give node position (for NAM)
$ns duplex-link-op $n0 $n2 orient right-down
$ns duplex-link-op $n1 $n2 orient right-up
$ns duplex-link-op $n2 $n3 orient right

19. A Simple Simulation
#Monitor the queue for link (n2-n3,for NAM)
$ns duplex-link-op $n2 $n3 queuePos 0.5
#Setup a TCP connection:from node 0 to node 3
set tcp [new Agent/TCP]
$ns attach-agent $n0 $tcp
set sink [new Agent/TCPSink]
$ns attach-agent $n3 $sink
$ns connect $tcp $sink
$tcp set fid_ 1

20. A Simple Simulation
#Setup a FTP over TCP connection
set ftp [new Application/FTP]
$ftp attach-agent $tcp
$ftp set type_ FTP ;fro NAM
#Setup a UDP connection:from node 1 to node 3
set udp [new Agent/UDP]
$ns attach-agent $n1 $udp
set null [new Agent/Null]
$ns attach-agent $n3 $null
$ns connect $udp $null
$udp set fid_ 2

21. A Simple Simulation
#Setup a CBR over UDP connection
set cbr [new Application/Traffic/CBR]
$cbr attach-agent $udp $cbr
set type_ CBR $cbr ;used by NAM
set packet_size_ 1000 $cbr
set rate_ 1mb $cbr
set random_ false ;generating traffic periodically
#Schedule events for the CBR and FTP agents
$ns at 0.1 “$cbr start”
$ns at 1.0 “$ftp start”
$ns at 4.0 “$ftp stop”
$ns at 4.5 “$cbr stop”

22. A Simple Simulation
#Detach tcp and sink agents
$ns at 4.5 “ns detach-agent $n0 $tcp ; $ns detach-agent $n3
$sink”
#Call the finish procedure after 5 seconds
$ns at 5.0 “finish”
#Run the simulation
$ns run

23. The Trace File
Turn on tracing on specific links
$ns_ trace-queue $n0 $n1
Each line in the trace file is in the format
<event> <time> <from> <to> <pkt-type>
<pkt-size> <flags> <fid> <src.port>
<dst.port> <seq> <unique pkt id>
Trace example:
+ 1 0 2 cbr 210--------------0 0.0.3.1 0 0
Event: s send, r receive, + enqueue, -
dequeue, d drop, f forward

31. A wireless Simulation
Scenario
2 mobile nodes
moving within 500mX500m flat
topology
using DSDV ad hoc routing protocol
TCP traffic

32. Step 1
# Define Global Variables
# create simulator
set ns_ [new Simulator]
# create a topology in a 500m x 500m area
set topo [new Topography]
$topo load_flatgrid 500 500

33. Step 2
# Define standard ns/nam trace
# ns trace
set tracefd [open demo.tr w]
$ns_ trace-all $tracefd
# nam trace
set namtrace [open demo.nam w]
$ns_ namtrace-all-wireless $namtrace
500 500

34. Step 3
# Create God
set god [create-god 2]
God: store an array of the smallest number of hops
required to reach one node to an other
Optimal case against which to compare routing
protocol performance
Automatically generated by scenario file

35. Step 4
# Define how a mobile node should be created
$ns_ node-config
-adhocRouting DSDV
-llType LL
-macType Mac/802_11
-ifqLen 50
-ifqType Queue/DropTail/PriQueue
-antType Antenna/OmniAntenna
-propType Propagation/TwoRayGround
-phyType Phy/WirelessPhy
-channelType Channel/WirelessChannel
-topoInstance $topo
-agentTrace ON
-routerTrace OFF
-macTrace OFF

36. Step 5
Single Node
# Create a mobile node, attach it to the channel
set node_(0) [$ns_ node]
# disable random motion
$node_(0) random-motion 0
Set of Nodes
Use “for” loop to create 2 or more nodes:
for {set i < 0} {$i < 2} {incr i} {
set node_($i) [$ns_ node]
$node_($i) random-motion 0
}

37. Step 6
Node Movement
$node_(0) set X_ 200.00
$node_(1) set X_ 100.00
$node_(0) set Y_ 400.00
$node_(1) set Y_ 350.00
$node_(0) set Z_ 0.00
$node_(1) set Z_ 0.00
$ns_ at 10 $node_(0) setdest 400.00 300.00
5.00
$ns_ at 12 $node_(1) setdest 300.00 150.00
10.00

38. Extending NS2

39. Creating New Components
Extending ns in Otcl
source your changes in your simulation
scripts
Extending ns in C++
Change Makefile (if created new files)
make depend
recompile

44. Thanks.
Any Query?
.
.
.
Demo