NS2 Tutorial

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NS-2 Tutorial

• Presented by
• Lap Kong Law
• lklaw_at_cs.ucr.edu

2
Problem

• Impossible to carry real experiments
• Difficult to find a location
• Wireless experiments take huge space (in the
  order of km).
• Difficult to arrange experiments
• Hard to manage a large number of nodes.
• High equipment cost
• Feasibility study is costly
• The cost of implementing a real system to study
  the feasibility is very high
• Not flexible
• Difficult to change parameters

So, we use NS-2!
3
Roadmap

• Introduction to NS-2
• Installation
• NS-2 Architecture
• Mobile Networking in NS-2
• Example simulation script
• Trace file Analysis
• Visualization
• Cautions
• Other Simulators

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Introduction to NS-2

• NS-2 stands for Network Simulator ver. 2
• Discrete event simulator
• Packet Level
• Link layer and up
• Provide substantial support on
• TCP, Routing, Multicast protocols on both wired
  and wireless networks
• Began in 1989 as a variant of the REAL network
  simulator
• In 1995, NS development was supported by DARPA in
  VINT project
• Supported and contributed by
• DARPA, NSF, ACIRI and many researchers
• Latest version 2.26
• Released on Feb 28, 2003

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Installation

• Download NS-2
• http//www.isi.edu/nsnam/ns/ns-build.html
• Recommend the all-in-one package
• Install NS-2
• ./configure make in OTcl TclCL directory
• ./configure make in ns directory
• ./validate
• Get an account with HUGE space available

6
NS-2 Architecture

• Object-oriented (C, OTcl)
• Scalability Extensibility
• Data / Control Separation
• Split C / OTcl object
• C for data
• Define packet action
• OTcl for control
• Periodic or triggered action
• Each object defined in TCL script is an instance
  of class written by C language

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Mobile Networking in NS-2

• MobileNode inherits from Node object
• MobileNode consists of
• Link Layer (LL)
• ARP module connected to LL
• Interface priority queue (IFq)
• MAC layer (MAC)
• Network Interface (netIF)

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Mobile Networking in NS-2

• Support four Ad-hoc Routing Protocols
• Destination Sequence Distance Vector (DSDV)
• Dynamic Source Routing (DSR)
• Temporally ordered Routing Algorithm (TORA)
• Adhoc On-demand Distance Vector (AODV)
• MAC layer protocols
• 802.11
• Preamble TDMA
• Radio Propagation Model
• Friss-space attenuation at near distance
• Two Ray Ground at far distance
• Antenna
• Omni-directional antenna

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Mobile Networking in NS-2

• Basic steps to do simulation
• Build your simulation script (.tcl)
• Create scenario
• Generating traffic pattern
• Run simulation
• Analyze trace file
• Visualize your simulation

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Example Simulation Script
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Example Scenario

• For large topologies, the node movement are
  defined in a separated file for convenience (and
  also for flexibility)
• You can find some examples of node movement files
  in the /tcl/mobility/scene/ directory
• There is a generator (called setdest) for
  creating node movement. It is located in the
  /indep-utils/cmu-scen-gen/setdest/ directory
• Usage of the setdest tool
• ./setdest n ltnum_of_nodegt -p ltpause_timegt
• -s ltmax_speedgt -t ltsim_timegt -x ltmax_xgt -y
  ltmax_ygt
• gt ltscenario_filegt

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Example Traffic pattern

• Similarly, traffic patterns are also defined in a
  separated file.
• Examples can be found in the /tcl/mobility/scene/
  directory
• Traffic generator is located in
  /indep-utils/cmu-scen-gen/ and are called
  cbrgen.tcl
• Constant Bit Rate (CBR) or Transport Control
  Protocol (TCP)
• To create connections, run
• ns cbrgen.tcl -type cbrtcp -nn nodes
• -seed seed -mc connections -rate rate
• gt lttraffic pattern filegt

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Trace file Analysis

• Trace support for wireless simulations currently
  use cmu-trace objects
• Cmu-trace objects are of three types
• CMUTrace/Drop
• CMUTrace/Recv
• CMUTrace/Send
• Tracing packets sent by agents, routers, mac
  layers or interface queues

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Trace file Analysis

• Revised trace format
• ns use-newtrace
• Example

s -t 0.267662078 -Hs 0 -Hd -1 -Ni 0 -Nx 5.00 -Ny
2.00 -Nz 0.00 -Ne -1.000000 -Nl RTR -Nw --- -Ma
0 -Md 0 -Ms 0 -Mt 0 -Is 0.255 -Id -1.255 It
message -Il 32 -If 0 -Ii 0 -Iv 32
Event type s ? send r ? receive d ? drop f ?
forward
Next hop info Hs ? id for this node Hd ? id for
next hop towards the dest.

• Packet info for MAC level
• Packet info for Application level
• Consists of field leading with P
• ARP
• TCP
• CBR
• DSR

Packet info at IP level Is ? source
address.port Id ? dest. Address.port It ? packet
type Il ? packet size If ? flow id Ii ? unique
id Iv ? TTL value
Node property Ni ? node id Nx ? nodes x
coordinate Ny ? nodes y coordinate Nz ? nodes z
coordinate Ne ? nodes energy level
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Visualization

• Nam stands for Network Animator
• It is a Tcl/TK based animation tools for viewing
  network simulation traces
• Produce the nam trace file
• set namtrace open opt(nam) w
• ns namtrace-all-wireless namtrace ltmax_xgt
  ltmax_ygt

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Result Visualization

• Use Python!
• To extract the required information from the
  trace file.
• To produce output in particular formats that are
  easier to plot.
• GNUPlot
• Command-line driven program for producing 2D and
  3D plots.
• Generate beautiful plots.
• Matlab
• More advanced ploting functions.
• Various ploting libraries available for download.

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Cautions

• NS-2 is still under research and development
• Bugs in the software are still being discovered
  and corrected
• Users are responsible for verifying their
  simulation results that may be invalidated by
  bugs.
• Similarly, users are responsible for verifying
  that they are using the correct models in their
  simulations.

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Other Simulators

• OPNET (http//www.opnet.com)
• Commercial Software
• Support Windows and Unix
• Graphical Interface
• Not free
• GloMoSim (http//pcl.cs.ucla.edu/projects/glomosim
  )
• Simulation environment for wireless network
• Scalable to support thousands of nodes
• Using layered approach to build different
  simulation layers
• Free for educational users