Working with NS2

Presentation on-
Working with Network
Simulator 2
Presented By-
Chanchal
Agarwal
Id-47043
M.Tech 1st year

Hello World - Interactive Mode
chanchal>ns
% set ns [new Simulator]
_o3
% $ns at 1 “puts “Hello World!””
1
% $ns at 1.5 “exit”
2
% $ns run
Hello World!
chanchal>

Hello World - Batch Mode
simple.tcl
set ns [new Simulator]
$ns at 1 “puts “Hello World!””
$ns at 1.5 “exit”
$ns run
chanchal> ns simple.tcl
Hello World!
chanchal>

Tcl and OTcl
 TCL- Tool Command Language and pronounced
as "Tickle“.
 TCL is a scripting programming language -
similar to PERL or Python.
 Very good for quick and dirty jobs
 Object TCL (OTCL) is an object oriented
extension of TCL. OTcl is written in C++.
 OTCL's library of objects can
be extended by adding object definitions in
the C++ source code

NS-2 Design
 To use NS-2, a user programs should be in the
OTcl script language.
 An OTcl script will do the following.
 Initiates an event scheduler.
 Sets up the network topology using the network
objects.
 Tells traffic sources when to start/stop
transmitting packets through the event
scheduler.

 Depending on the user’s purpose for an OTcl
simulation script, simulation results are stored as
trace files, which can be loaded for analysis by
an external application:
1. A NAM trace file (file.nam) for use with the
Network Animator Tool.
2. A Trace file (file.tr) for use with XGraph or
TraceGraph.

Languages Used in NS-2
 Split-Language programming is used .
Scripting Language (Tcl - Tool Command
Language and pronounced ‘tickle’)
System Programming Language (C/C++)
 Ns is a Tcl interpreter to run Tcl Scripts .
 By using C++/OTcl, the network simulator is
completely Object-oriented.
 TclCL is the language used to provide a linkage
between C++ and OTcl.

NAM
 NAM- Network Animator.
 Provides a visual interpretation of the network
created.
 Can be executed directly from a Tcl script.
 Presents information such as throughput,
number packets on each link.
 Provides a drag and drop interface for creating
topologies.

Trace Files
 Syntax For Creating A Trace File
# Open the trace file
set nf [open out.tr w]
$ns trace-all $nf
# Define finish procedure
proc finish {} {
global ns nf
$ns flush-trace
close nf
exit 0 }

Creating Network
 Nodes
set n0 [$ns node]
set n1 [$ns node]
 The following creates 5 nodes, with handles n0-n4
for {set i 0} {$i<5} {incr i} {Set n($i) [$ns node] }
 To set the colour of a node, the following code is used.
$n0 color <colour>
where <colour> is black, red, blue, seaGreen.
n0 n1

Creating Network
 Links and queuing
$ns duplex-link $n0 $n1 <bandwidth> <delay>
<queue_type>
1. <bandwidth>: 1000b, 1kb, 0.001Mb, …
2. <delay>: 1ms, 0.001s, …
3. <queue_type>: DropTail, RED, CBQ, FQ,
SFQ, DRR.
n0 n1

Creating Connection – Agents
 UDP
1. set src [new Agent/UDP]
2. set rcv [new Agent/Null]
3. $ns attach-agent $n0 $src
4. $ns attach-agent $n1 $rcv
5. $ns connect $src $rcv
 TCP
1. set tcp [new Agent/TCP]
2. set tcpsink [new Agent/TCPSink]
3. $ns attach-agent $n0 $src
4. $ns attach-agent $n1 $rcv
5. $ns connect $tcp $tcpsink

Traffic Applications
 The OTcl code to implement a CBR traffic
source in a simulation is as follows:
1. set my_cbr [new Application/Traffic/CBR]
2. $my_cbr attach-agent $udp
3. $ns at <time> “$my_cbr start”
 Parameters:
1. start: starts sending packets according to
the configuration parameters
2. stop: stops sending packets

 Configuration parameters:
1. PacketSize_: constant size of packets
generated e.g. 48
2. rate_: sending rate e.g. 64kb
3. interval_: (optional) interval time between
packets e.g. 0.05
4. random_: Flag to introduce noise in the
departure times, default is off, 1 for on
5. maxpkts_: the maximum number of packets
to send e.g. 1000

 Two simulation applications exist to send traffic on top of a TCP object:
Application/FTP and Application/Telnet.
File Transfer Protocol (FTP- for simulating bulk data transfer)
1. set ftp [new Application/FTP]
2. $ftp attach-agent $tcp
3. $ns at <time> “$ftp start”
Parameters
1. attach-agent: attaches an Application/FTP agent to an agent
2. start: start the Application/FTP to send data .
3. stop: stop sending data.
4. produce n: where n is the counter of packets to be sent .
5. producemore n: where n is the new increased value of packets to be sent .
6. send n: similar to producemore, but sends n bytes instead of packets .

 Telnet
1. OTcl code for using Telnet in a simulation:
2. set telnet [new Application/Telnet]
3. $telnet attach-agent $tcp
Parameters
1. start; start producing packets.
2. stop: stop producing packets.
3. attach-agent: attaches a Telnet object to an
agent.

Example-2
#Create a simulator object
#Open the namtrace 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 out.nam &
exit 0
}

Example-2
#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

Example-3
#Create a simulator object
#Define different colors for data flows (for NAM)
$ns color 0 Blue
#Open the namtrace 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 out.nam &
exit 0
}

Example-3
#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
#Give node position (for NAM)
$ns duplex-link-op $n0 $n1 orient right-down
#Create a UDP agent and attach it to node n0
set udp0 [new Agent/UDP]
$ns attach-agent $n0 $udp0
# Create a CBR traffic source and attach it to udp0
set cbr0 [new Application/Traffic/CBR]
$cbr0 set packetSize_ 500
$cbr0 set interval_ 0.005
$cbr0 attach-agent $udp0

Example-3
#Create a Null agent (a traffic sink) and attach it to node n1
set null0 [new Agent/Null]
$ns attach-agent $n1 $null0
#Connect the traffic source with the traffic sink
$ns connect $udp0 $null0
#Schedule events for the CBR agent
$ns at 0.5 "$cbr0 start"
$ns at 4.5 "$cbr0 stop"
#Call the finish procedure after 5 seconds of simulation time
$ns at 5.0 "finish"
#Run the simulation
$ns run

Working with NS2

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