ns-2 tutorial

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ns-2 tutorial
CSCI 5931 Network Security Instructor Dr. T.
Andrew Yang

• Karthik Sadasivam
• Banuprasad Samudrala

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Introduction

• Ns-2 is a discrete event simulator targeted at
  network research
• focused on modeling network protocols
• wired, wireless, satellite
• TCP, UDP, multicast, unicast
• web, telnet, ftp
• ad hoc routing, sensor networks
• infrastructure stats, tracing, error models, etc

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Goals of ns

• 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 comparision of similar protocols
• increase confidence in results
• models provide useful results in several
  situations
• multiple levels of detail in one simulator

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ns status

• platforms basically all Unix and Windows
• size about 200k loc each C and Tcl, 350 page
  manual
• user-base gt1k institutions, gt10k users
• releases about every 6 months, plus daily
  snapshots

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Components of ns

• ns, the simulator itself
• nam, the Network AniMator
• visualize ns (or other) output
• GUI input simple ns scenarios
• pre-processing
• traffic and topology generators
• post-processing
• simple trace analysis, often in Awk, Perl, or Tcl

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ns Software Structure C and Otcl

• Uses two languages
• C for packet-processing
• fast to run, detailed, complete control
• OTcl for control
• simulation setup, configuration, occasional
  actions
• fast to write and change
• pros trade-off running vs. writing speed,
  powerful/documented config language
• cons two languages to learn and debug in

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oTcl and C The Duality
C
otcl

• OTcl (object variant of Tcl) and C share class
  hierarchy
• TclCL is glue library that makes it easy to share
  functions, variables, etc.

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Installation and documentation

• http//www.isi.edu/nsnam/ns/
• download ns-allinone
• includes Tcl, OTcl, TclCL, ns, nam, etc.
• mailing list ns-users_at_isi.edu
• documentation (see url above)
• Marc Gries tutorial
• ns manual

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Steps to set up the simulation

• Initialize the simulator
• Define files for output (tracing)
• Set up the topology
• Set up the agents
• Set up the traffic between the nodes
• Start the simulation
• Analyze the trace files to compute the parameters
  of interest

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Example TCP
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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Script to start nam

• set nf open out.nam w
• ns namtrace-all nf
• proc finish
• global ns nf
• ns flush-trace
• close nf
• exec nam out.nam
• exit 0
• your code goes in here
• ns at 12.0 "finish" 12.0 is the simulation
  time in secs

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Screenshots
Project B.2
Project B.1
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References

• 1 slides by John Heidemann
• http//sce.cl.uh.edu/yang/teaching/csci5931netSecu
  ritySpr05/johnh_class_slides_sp2003.ppt
• 2 ns2 website http//www.isi.edu/nsnam/ns
• 3 ns-2 Tutorial http//www.isi.edu/nsnam/ns/tut
  orial/nsindex.html
• 4 Tcl/Tk tutorial http//hegel.ittc.ukans.edu/
  topics/tcltk/tutorial-noplugin/