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 Therefore simulator!
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 NAM – Network AniMator
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 C++
objects
Pure OTcl
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
> 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
something's burning!

11. A simulation Instantiate a simulator object Create nodes links
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 Mark Greis’ tutorial ns manual
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