Advanced Computer communication laboratory: NS2 Introduction

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Advanced Computer communication laboratoryNS-2
Introduction
Miriam Allalouf

• 2005-2006 - Semester B

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NS-2 lab Introduction

• Wild list of Network components
• Customers / Edge components / Home Equipment
• Service to be transferred
• Infrastructure Transportation cables/wires
• Switching components, Topology
• Routing, Connection kinds and Geographical span
• Protocol layers
• Addressing, Management and Traffic Management
• Human activities
• Infrastructure installation
• Provider and billing
• Network Administration
• Owners

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NS-2 lab Introduction

• Network Simulation and -
• Real-world experiments sometimes impossible
• Mathematical modeling can be painful
• Sometimes even painful and inaccurate
• -Simulation cannot replace real-world experiments
  
• -Processing delay, traffic pattern, Physical
  layer
• Scaling, Long Simulations
• Simulation sometimes misses the whole picture
• Specific layers, wrong assumption

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NS-2 lab Introduction

• NS-2 Goals
• Support networking research and education
• Protocol design, traffic studies, etc
• Protocol comparison
• Provide a collaborative environment
• Freely distributed, open source
• Share code, protocols, models, etc
• Allow easy comparison of similar protocols
• Helps to debug problems in a controlled
  environment
• Increase confidence in results
• More people look at models in more situations
• Experts develop models
• Multiple levels of detail in one simulator

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NS-2 lab Introduction

• ns-2 functionalities
• Focus on Internet technology (layers IP and up )
• Wired world
• Intra-Domain Routing DV, LS
• Transportation TCP and UDP the tool for TCP
  simulations
• Traffic sources and generator web, ftp, telnet,
  cbr, stochastic
• Queuing disciplines drop-tail, RED, FQ, SFQ, DRR
• QoS IntServ and Diffserv
• Emulation
• Wireless Not ideal for new link layer
  technologies
• CSMA/CD, 802.11 (?) - Contributed Modules
• Ad hoc routing and mobile IP
• Satellite nodes
• Link Loss Model
• Tracing, visualization

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NS-2 lab Introduction

• History
• 1989 REAL network simulator
• 1995 DARPA VINT project at LBL, Xerox PARC, UCB,
  and USC/ISI
• Present DARPA SAMAN project and NSF CONSER
  project
• Collaboration with other researchers including
  ACIRI

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NS-2 lab Introduction

• Help and Resources
• Course Home Page
• http//www.eng.tau.ac.il/miriama/ns2.htm
• NS-2
• http//www.isi.edu/nsnam/ns/
• http//www.isi.edu/nsnam/ns/tutorial/index.html
• TCL
• http//dev.scriptics.com/scripting
• Otcl tutorial
• http//www.isi.edu/nsnam/otcl/README.html

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NS-2 lab Introduction

• ns-2 Overview
• OTcl and C
• OTcl scripts and C mechanism implementation,
  timing critical code
• Open source
• Facilitates building upon other work
• Support via mailing list (frequently no answers)
• Huge and complicated code
• Semi-Poor documentation

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NS-2 lab Introduction

• Ns Status
• Periodical release (ns-2.29, February 2006)
• 200K LOC in C and Otcl,
• 100 test suites and 100 examples
• 371 pages of ns manual
• Daily snapshot (with auto-validation)
• Stability validation
• http//www.isi.edu/nsnam/ns/ns-tests.html
• Platform support
• FreeBSD, Linux, Solaris, Windows and Mac
• User base
• 1000 institutes (50 countries), gt10000 users
• About 300 posts to ns-users_at_isi.edu every month

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NS-2 lab Introduction

• Ns Components
• Ns, the simulator itself
• Nam, the network animator
• Visualize ns (or other) output (files .nam)
• Nam editor GUI interface to generate ns scripts
• Pre-processing
• Traffic and topology generators
• Post-processing
• Generates Output files
• Simple trace analysis, often in Awk, Perl, or Tcl

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NS-2 lab Introduction

• Ns-2 A discrete Event Simulation
• Model world as events
• Simulator has list of events
• Process take next one, run it, until done
• Each event happens in an instant of virtual
  (simulated) time, but takes an arbitrary amount
  of real time
• Ns uses simple model single thread of control gt
  no locking or race conditions to worry about
  (very easy)

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NS-2 lab Introduction

• Ns-2 is a discrete event driven simulation
• Physical activities are translated to events
• Events are queued and processed in the order of
  their scheduled occurrences
• Time progresses as the events are processed

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Event Driven Simulation
NS-2 lab Introduction
Event Queue
Simulation Finished!
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Using ns
NS-2 lab Introduction
Problem
Result analysis
Simulation model
Modify ns
Setup/run simulation with ns
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NS-2 lab Introduction

• Using ns Simulation Model Components
• Network core functions - building blocks
  (protocols, nodes, events, etc..)
• C , OTCL implementation
• Network configuration (build network topology,
  generate communication events, etc..)
• Testing different configurations needs to be fast
  (without recompilation)
• Use script language TCL

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Basic tcl
NS-2 lab Introduction

• proc test args body
• 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
• tclgt test

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Basic otcl
NS-2 lab Introduction

• Class mom
• 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
• a set age_ 45
• set b new kid
• b set age_ 15
• a greet
• b greet
• 45 years old mom How are you doing?
• 15 years old kid What's up, dude?

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NS-2 lab Introduction

• Creating Event Scheduler
• Create event scheduler
• set ns new Simulator
• Schedule events
• ns at lttimegt lteventgt
• lteventgt any legitimate ns/tcl commands
• ns at 5.0 finish
• Start scheduler
• ns run

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Hello World Example
NS-2 lab Introduction

• Batch mode
• simple.tcl
• set ns new Simulator
• ns at 1 puts \Hello World!\
• ns at 1.5 exit
• ns run
• swllow 74 ns simple.tcl
• Hello World!
• swllow 75

• Interactive mode
• swallow 71 ns
• set ns new Simulator
• _o3
• ns at 1 puts \Hello World!\
• 1
• ns at 1.5 exit
• 2
• ns run
• Hello World!
• swallow 72

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NS-2 lab Introduction

• NS Models
• Traffic models and applications
• Web, FTP, telnet, constant-bit rate, real audio
• Transport protocols
• unicast TCP (Reno, Vegas, etc.), UDP
• Multicast SRM
• Routing and queueing
• Wired routing, ad hoc rtg and directed diffusion
• queuing protocols RED, drop-tail, etc
• Physical media
• Wired (point-to-point, LANs), wireless (multiple
  propagation models), satellite

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NS-2 lab Introduction

• NS-2 programming
• Create the event scheduler
• Turn on tracing
• Creating network
• Computing routes and Setup routing
• Creating transport connections - agents
• Creating traffic applications
• Transmit application-level data
• Inserting errors
• Monitoring

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NS-2 lab Introduction

• Packet Switching

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NS-2 lab Introduction

• Creating Network
• Nodes
• set ns new Simulator
• set n0 ns node
• set n1 ns node
• Links Queuing
• Set mylink ns duplex-link n0 n1 ltbandwidthgt
  ltdelaygt ltqueue_typegt
• ltqueue_typegt DropTail, RED, CBQ, WFQ, SFQ, DRR
• Set myqueue mylink queue
• mylink set parameter value
• For defaults ns/tcl/lib/ns-default.tcl

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NS-2 lab Introduction

• Computing Routes
• Unicast
• ns rtproto lttypegt
• lttypegt Static, Session, DV, cost, multi-path
• Multicast
• Simulator set EnableMcast_ 1
• Simulator set NumberInterfaces_ 1
• ns mrtproto lttypegt
• lttypegt CtrMcast, DM, dynamicDM, pimDM

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NS-2 lab Introduction

• Creating Connection agents
• UDP
• set src new Agent/UDP
• set rcv new Agent/Null
• ns connect src rcv
• TCP
• set tcp new Agent/TCP
• set tcpsink new Agent/TCPSink
• ns connect tcp tcpsink

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NS-2 lab Introduction

• Agents - More
• TCP ?? TCPsink
• one-way Tahoe implementation
• other flavors TCP/Reno, TCP/NewReno, TCP/Sack1,
• TCP/Vegas
• two-way use FullTCP at both sides
• TCP-friendly connectionless protocols
• RAP lt-gt RAP Rate Adaptation Protocol (rate-based
  AIMD Slow Start)
• TFRC lt-gt TFRCSink
• TCP Friendly Rate Control protocol (based on TCP
  throughput-equation)

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NS-2 lab Introduction

• Creating Traffic applications
• Use app on Top of agent
• app start
• app stop
• FTP
• set ftp new Application/FTP
• ftp attach-agent tcp
• Telnet
• set telnet new Application/Telnet
• Web
• set session new httpSession ns ltnumPagesgt
  ltclientNodegt
• Traffic generator
• set cbr new Application/traffic/cbr

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NS-2 lab Introduction

• Inserting Errors
• Creating Error Module
• set loss_module new ErrorModel
• loss_module set rate_ 0.01
• loss_module unit pkt
• loss_module ranvar new RandomVariable/Uniform
• loss_module drop-target new Agent/Null
• Inserting Error Module
• ns lossmodel loss_module n0 n1

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NS-2 lab Introduction

• Tracing
• Trace packets on all links
• ns trace-all open test.out w
• lteventgt lttimegt ltfromgt lttogt ltpktgt ltsizegt--ltflowidgt
  ltsrcgt ltdstgt ltseqnogt ltuidgt
• 1 0 2 cbr 210 ------- 0 0.0 3.1 0 0
• - 1 0 2 cbr 210 ------- 0 0.0 3.1 0 0
• r 1.00234 0 2 cbr 210 ------- 0 0.0 3.1 0 0
• Uid packet id
• Trace packets on all links in nam-1 format
• ns namtrace-all open test.nam w
• Beware of large output files

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NS-2 lab Introduction

• Visualization Tools
• nam-1 (Network AniMator Version 1)
• xgraph

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Example TCP
NS-2 lab Introduction
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
set tcp new Agent/TCP set tcpsink new
Agent/TCPSink ns attach-agent n0 tcp ns
attach-agent n1 tcpsink ns connect tcp
tcpsink
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Example Nam
NS-2 lab Introduction
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 tf open out.tr w ns trace-all
tf
Define a 'finish' procedure proc finish
global ns nf tf ns flush-trace
Close the trace files close nf
close tf Execute nam on the trace file
exec nam out.nam exit 0 ns at
5.0 "finish Run the simulation ns run
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Summary Generic Script Structure
NS-2 lab Introduction

• set ns new Simulator
• Turn on tracing
• Create topology
• Setup packet loss, link dynamics
• Create routing agents
• Create
• - multicast groups
• - protocol agents
• - application and/or setup traffic sources
• Post-processing procs
• Start simulation

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NS-2 lab Introduction

• Compare to Real World
• More abstract (much simpler)
• No addresses, just global variables
• Connect them rather than name lookup/bind/listen/a
  ccept
• Easy to change implementation
• Set tsrc2 new agent/TCP/Newreno
• Set tsrc3 new agent/TCP/Vegas

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NS-2 lab Introduction

• Getting Started
• Cygwin install only using the Install (not
  the default) In case of already installed
  cygwin - ask me how!
• ns-2 version ns-allinone_2.28 installation over
  cygwin
• C/cygwin/home/user
• .bashrc file contains the following
• export NS_HOME/home/user/ns-allinone-2.28
• export LD_LIBRARY_PATHNS_HOME/otcl1.9NS_HOM
  E/lib
• export TCL_LIBRARYNS_HOME/tcl8.4.5/library
• export PATH NS_HOMENS_HOME/binNS_HOME/
  tcl8.4.5/unixNS_HOME/tk8.4.5/unix/PATH
• Use the C/cygwin/home/user/my_ns directory for
  your stuff
• Read sections I-V in the Marc Greis tutorial.
• http//www.isi.edu/nsnam/ns/tutorial/index.html
• Run ns examples described in these sections that
  are located in
• NS_HOME/ns-2.28/ns-tutorial/examples/