CprE 543x ns2 Tutorial

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CprE 543x ns-2 Tutorial

• Zak Abichar, abicharz_at_iastate.edu
• Dept of Electrical and Computer Engineering
• Iowa State University
• Ames, IA 50011
• Based on a presentation by Polly Huang (2nd
  European ns-2 Workshop, April 2001)

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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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The VINT Project

• Virtual InterNet Testbed
• a common platform for network research
• focus on multi-protocol interactions and scale
• http//netweb.usc.edu/vint
• Follow-up projects
• SAMAN scenario and performance
• CONSER educational use

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Multi-state collaboration

• ATT 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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Platforms

• Most UNIX and UNIX-like systems
• FreeBSD or BSD
• Linux
• Sun Solaris
• HP, SGI
• Window 95/98/NT...
• Emulation only for FreeBSD for now

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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

• 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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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
Event Scheduler
ns-2
tclcl
Network Component
otcl
tcl8.0

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

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Installation

• Getting the code
• http//www.isi.edu/nsnam/ns/
• Installing ns-2
• http//csl.ee.iastate.edu/cpre543/ns2_howToInstal
  l.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

• 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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Hello World

• simple.tcl
• set 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.ht
  ml
• 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 tcl
k lt 5, pow 1.0 k lt 5, pow 1120.0 k lt 5, pow
1254400.0 k lt 5, pow 1404928000.0 k lt 5, pow
1573519360000.0 k gt 5, mod 0 k gt 5, mod 4 k gt
5, mod 0 k gt 5, mod 0 k gt 5, mod 4

• proc test
• set a 43
• set b 27
• set c expr a b
• set d expr expr a - b c
• for set k 0 k lt 10 incr k
• if k lt 5
• puts k lt 5, pow expr pow(d, k)
• else
• puts k gt 5, mod expr d k
• test

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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 Whats up, dude?
• set a new mom 34
• set b new kid 6
• a greet
• b greet

34 years old mom How are you doing? 6 years old
kid What's up?
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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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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
Network Topology
Traffic Generation

• set ns new Simulator
• set n0 ns node
• set n1 ns node

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
Transport Protocol
set tcp ns create-connection TCP n0 TCPSink
n1 0
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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 0
• r 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 0
• r 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 1
• r 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 1
• r 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 Excel
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Plot results in Excel
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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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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 connection
• set udp new Agent/UDP
• ns attach-agent n1 udp
• set null new Agent/Null
• ns attach-agent n3 null
• ns connect udp null
•  
• Setup a CBR over UDP connection
• set 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