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An Introduction to NS and NAM: Network Simulation and Animation Tools

This document introduces NS (Network Simulator) and NAM (Network Animator), fundamental tools for simulating and analyzing network protocols and behavior. NS is an event-driven simulator implemented in C++ with OTcl as its interface for command and configuration. The document covers basic Tcl and OTcl commands, organization of simulations, and provides demonstrations for both wired and wireless networks. It also discusses the importance of simulation in testing, time, and cost efficiency, especially in mobile computing. Ideal for understanding network simulation frameworks and their applications.

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An Introduction to NS and NAM: Network Simulation and Animation Tools

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  1. Introduction to NS Srinath Perur

  2. This introduction… • Why NS • NS and NAM • Basic Tcl • Basic OTcl • Organization of a simulation • Demos of wired and wireless simulations

  3. Why NS? • Preliminary testing/validation in field • Time, effort, money • Internet scale testing • Mobile computing – hardware, etc. • Slow to modify Therefore simulator! • NS • Easily available • Widely accepted

  4. NS and NAM • NS – Network Simulator • Event driven simulator • Implemented in C++ • OTcl for command and configuration interface • NAM – Network AniMator • Graphical representation of NS output

  5. C++ and OTcl Separation • C++ for “data” • Per packet action • OTcl for control • Periodic or triggered action • Compromise between composibility and speed • Learning and debugging

  6. OTcl and C++: The Duality Pure OTcl objects Pure C++ objects C++/OTcl split objects C++ OTcl ns

  7. Basic Tcl %ns > puts “Hello!” > Hello! >set a 5 > set b 4 >set c [expr $a + $b] >puts “The sum of $a and $b is $c”

  8. Basic Tcl >proc print_list {list}{ set count 0 foreach element $list { incr count puts $element } return $count } >set list1 {a, b, c} > set num_elements [print_list $list]

  9. Basic OTcl > Class Bun > set abun [new Bun] abun > $abun info class Bun > Bun info instances abun > Bun instproc init {args} { $self instvar toasted set toasted 0 eval $self next $args }

  10. Basic OTcl > Bun instproc toast {} { $self instvar toasted incr toasted if {$toasted>1} then { error "something's burning!" } return {} } > $abun toast > $abun toast something's burning!

  11. A simulation • Instantiate a simulator object • set global properties for simulation • Create nodes • create agents at nodes, set their properties • links • connecting nodes, set their properties

  12. References • ns web pages • http://www.isi.edu/nsnam/ns/ • Mark Greis’ tutorial • recommended for starting • ns manual • ns workshop slides • ns mailing list archive • OTcl tutorial • Look at IT-605/IT-644 resources page

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