CprE 543x – ns-2 Tutorial

CprE 543x – ns-2 Tutorial

Zak Abichar, [email protected] Dept of Electrical and Computer Engineering

Iowa State UniversityAmes, IA 50011

Based on a presentation by Polly Huang (2nd European ns-2 Workshop, April 2001)

mailto:[email protected]

2

Tutorial Goals

• overview/intro/essentials/getting started

• tcl/otcl/ns-2 fundamentals

• designing a simulation

• examples

3

Outline

• Introduction– The project, the software, the philosophy– Software architecture– Installation and getting started– About extending ns-2

• tcl/otcl/ns-2 fundamentals– Programming tcl/otcl

• Running a ns-2 simulation– Simulation design– Example scripts

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Multi-state collaboration

• AT&T Research

• Lawrence Berkeley National Laboratory

• UC Berkeley

• USC/ISI

• Xerox PARC

• ETH TIK (Swiss Federal Institute of Technology)

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Project Goal

• To support collaborative simulation effort– promote sharing

• incorporate recent simulation models

– increase confidence in results• establish regression test suite

– establish common reference• current and periodic availability of source code

• Base software is ns-2

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ns-2

• Discrete event simulator

• Packet level

• Link layer and up

• Wired and wireless

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Development Status

• Columbia NEST• UCB REAL• ns-1• ns-2

– 100K lines of C++ code– 70K lines of otcl support code– 30K lines of test suites– 20K lines of documentation

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Usage and Releases• Users from approximately

– 600 institutes – 50 countries

• Releases– periodic official releases– nightly snapshots (probably compiles and

works, but buyers beware)– available from USC/ISI or UK mirror

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Words of Caution

• While we have considerable confidence in ns, ns is not a polished and finished product, but the result of an ongoing effort of research and development. In particular, bugs in the software are still being discovered and corrected.

• Users of ns are responsible for verifying for themselves that their simulations are not invalidated by bugs.

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Preliminary for NS-2

• Ability to write correct programs

• Familiarity with object-oriented programming

• Patience to debug NS source code when needed

– Simple usage will not need NS source code debugging

– More complex simulations may need modification to NS source code

• Debugging skills

– NS uses C++ and Otcl

– User scripts are in Otcl

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What you can do using NS-2

• Simulate different scenarios with existing protocols (TCP/UDP)

• Wired Routing protocols - Distance Vector and Link State (with the link state patch)

• Ad-Hoc Routing protocols - DSR, AODV, TORA• MAC protocols - 802.3, 802.11 (Wireless MAC)• Scheduling disciplines - DropTail, RED, WFQ,

DRR, LQD etc.• Different traffic characterizations - Poisson,

Exponential, Pareto etc.

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What you can do using NS-2

• Modify NS-2 to implement your own versions of the above protocols or even code totally new protocols

• Measurement of Statistics: – Throughput, Delay, Jitter etc.– Queue Monitoring, Drops at Queues.– Literally all that you will need to know with your

simulations.

• Graphic visualization - using “nam” (Network Animator)

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The downside

• Cannot capture all the nuances of the real world networks.

• Very large scale simulations take a lot of time – they may not be feasible

• Still in the research phase, and there may be many more bugs lurking out there

• Documentation not adequate• No fancy user interface – often perceived as

“unfriendly” (at least by people who are new to ns-2)

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Outline




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Object-Oriented

+ Reusability

+ Maintainability

– Careful planning ahead

– Performance

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C++ and otcl Separation

• C++ for data– per packet action

• otcl for control– periodic or triggered action

+ Compromize between composibility and speed

– Learning & debugging

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otcl and C++: The Duality

C++

otcl

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tcl Interpreter With Extents

• otcl: Object-oriented support• tclcl: C++ and otcl linkage• Discrete event scheduler• Data network components

tcl8.0

otcl

tclcl

ns-2EventScheduler

Netw

orkC

omponent

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Installation

• Getting the code:– http://www.isi.edu/nsnam/ns/

• Installing ns-2– http://csl.ee.iastate.edu/~cpre543/

ns2_howToInstall.htm

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About extending ns-2

• Implement new functionalities not covered in ns-2– Essential for researchers

– Implementing and evaluating new protocols and schemes

• Requires the understanding of the internal architecture– Not that hard

• Need more information?

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Outline




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Hello World

simple.tclset ns [new Simulator]

$ns at 1 “puts \“Hello World!\””

$ns at 1.5 “exit”

$ns run

% ns simple.tcl

Hello World!

%

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Fundamentals

• tcl

• otcl– ftp://ftp.tns.lcs.mit.edu/pub/otcl/doc/tutorial.html

• ns-2– http://www.isi.edu/nsnam/ns/ns_doc.ps.gz

– http://www.isi.edu/nsnam/ns/ns_doc.pdf

– http://www.isi.edu/nsnam/ns/doc/index.html

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Basic tclproc test {} {

set a 43

set b 27

set c [expr $a + $b]

set d [expr [expr $a - $b] * $c]

for {set k 0} {$k < 10} {incr k} {

if {$k < 5} {

puts “k < 5, pow= [expr pow($d, $k)]”

} else {

puts “k >= 5, mod= [expr $d % $k]”

}

}

}

test

k < 5, pow = 1.0k < 5, pow = 1120.0k < 5, pow = 1254400.0k < 5, pow = 1404928000.0k < 5, pow = 1573519360000.0k > 5, mod = 0k > 5, mod = 4k > 5, mod = 0k > 5, mod = 0k > 5, mod = 4

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Basic otcl

Class mom

mom instproc init {age} {

$self instvar age_

set age_ $age

}

mom instproc greet {} {

$self instvar age_

puts “$age_ years old mom: How are you doing?”

}

Class kid -superclass mom

kid instproc greet {} {

$self instvar age_

puts “$age_ years old kid: What’s up, dude?”

}

set a [new mom 34]

set b [new kid 6]

$a greet

$b greet34 years old mom: How are you doing?6 years old kid: What's up?

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Outline




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NS input & output

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Running a Simulation

• Design your simulation • Build NS-2 scripts• Run simulation program• Analyze trace files• Visualize your simulation (Animation)

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Design your simulation

• Goal and expected results• Network topology

– Node– Link

• Specify Agents– Protocol

• Traffic• Simulation Scenario

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A simulation example

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A TCL script example

set ns [new Simulator]

set n0 [$ns node]

set n1 [$ns node]

n0 n1

set ftp [new Application/FTP]$ftp attach-agent $tcp$ns at 0.2 "$ftp start"$ns at 1.2 ”exit"

$ns run$ns duplex-link $n0 $n1 1.5Mb 10ms DropTail

set tcp [$ns create-connection TCP $n0 TCPSink $n1 0]

Network Topology

Transport Protocol

Traffic Generation

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Run simulation program

• Usage: ns file.tcl• If the C++ source codes are modified, re-compilation

is required

• What ns-2 does:– Read the tcl file– Run the simulation program– Create trace files– NAM (network animator) input files– Statistics (you may need to write post processing scripts)

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Analyze trace file

• Use some scripts like awk or Perl, to filter the trace file

• Use Excel, xplot or xgraph to plot the results

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Raw trace file+ 0.001 2 0 tcp 1000 ------- 0 2.0 1.0 0 0- 0.001 2 0 tcp 1000 ------- 0 2.0 1.0 0 0r 0.0028 2 0 tcp 1000 ------- 0 2.0 1.0 0 0+ 0.0028 0 1 tcp 1000 ------- 0 2.0 1.0 0 0- 0.0028 0 1 tcp 1000 ------- 0 2.0 1.0 0 0r 0.009884 0 1 tcp 1000 ------- 0 2.0 1.0 0 0+ 0.009884 1 0 ack 40 ------- 0 1.0 2.0 0 1- 0.009884 1 2 ack 40 ------- 0 1.0 2.0 0 1r 0.013128 1 0 ack 40 ------- 0 1.0 2.0 0 1+ 0.013128 0 2 ack 40 ------- 0 1.0 2.0 0 1- 0.013128 0 2 ack 40 ------- 0 1.0 2.0 0 1r 0.01416 0 2 ack 40 ------- 0 1.0 2.0 0 1+ 0.01416 2 0 tcp 1000 ------- 0 2.0 1.0 1 2- 0.01416 2 0 tcp 1000 ------- 0 2.0 1.0 1 2

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Open trace.out in Exceltype time src node next dest protocol size flags flowid src addr dest addr seq # ns seq #+ 0.001 2 0 tcp 1000 ------- 0 2.0 1.0 0 0- 0.001 2 0 tcp 1000 ------- 0 2.0 1.0 0 0r 0.0028 2 0 tcp 1000 ------- 0 2.0 1.0 0 0+ 0.0028 0 1 tcp 1000 ------- 0 2.0 1.0 0 0- 0.0028 0 1 tcp 1000 ------- 0 2.0 1.0 0 0r 0.009884 0 1 tcp 1000 ------- 0 2.0 1.0 0 0+ 0.009884 1 0 ack 40 ------- 0 1.0 2.0 0 1- 0.009884 1 2 ack 40 ------- 0 1.0 2.0 0 1r 0.013128 1 0 ack 40 ------- 0 1.0 2.0 0 1+ 0.013128 0 2 ack 40 ------- 0 1.0 2.0 0 1- 0.013128 0 2 ack 40 ------- 0 1.0 2.0 0 1r 0.01416 0 2 ack 40 ------- 0 1.0 2.0 0 1+ 0.01416 2 0 tcp 1000 ------- 0 2.0 1.0 1 2- 0.01416 2 0 tcp 1000 ------- 0 2.0 1.0 1 2

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Plot results in Excel

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Outline




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A Simulation Example

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TCL Script Step 1#Create a simulator object

set ns [new Simulator]

#Open the NAM trace file

set nf [open out.nam w]

$ns namtrace-all $nf

#Open the general trace file

Set f [open out.tr w]

$ns trace-all $f

# has denotes a one line commentns holds the name of the new simulation

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TCL Script Step 2

#Create four nodes

set n0 [$ns node]

set n1 [$ns node]

set n2 [$ns node]

set n3 [$ns node]

#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 20ms DropTail

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TCL Script Step 3

#Set Queue Size of link (n2-n3) to 10

$ns queue-limit $n2 $n3 10

#Setup a TCP connection

set tcp [new Agent/TCP]

$ns attach-agent $n0 $tcp

set sink [new Agent/TCPSink]

$ns attach-agent $n3 $sink

$ns connect $tcp $sink

#Setup a FTP over TCP connection

set ftp [new Application/FTP]

$ftp attach-agent $tcp

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TCL Script Step 4

#Setup a UDP connectionset udp [new Agent/UDP]$ns attach-agent $n1 $udpset null [new Agent/Null]$ns attach-agent $n3 $null$ns connect $udp $null

#Setup a CBR over UDP connectionset cbr [new Application/Traffic/CBR]$cbr attach-agent $udp$cbr set packet_size_ 1000$cbr set rate_ 1mb

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TCL Script Step 5

#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"

#Call the finish procedure after 5 seconds of simulation time

$ns at 5.0 "finish"

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TCL Script Step 6

#Define a 'finish' procedure

proc finish {} {

global ns nf

$ns flush-trace

#Close the NAM trace file

close $nf

#Execute NAM on the trace file

exec nam out.nam &

exit 0

}

#Run the simulation

$ns run

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CprE 543x – ns-2 Tutorial