Introduction to NS2
-Network Simulator-
-Prepared by Changyong Jung
Contents
Overview
How to Install
OTCL – The User Language
Event Scheduler
Packet
Simulation Example
Overview
 What is NS2?
- Event driven network simulator
- Developed at UC Berkely
- Implements network protocols
1) TCP, UPD
2) Traffic source mechanism: FTP, TELNET, Web, CBR and VBR
3) Router Queue management mechanism: Drop Tail, RED, CBQ
4) Routing Algorithm: Dijkstra, and etc…
5) Multicasting, Mac layer protocols for LAN
Overview
 Background on the ns Simulator
- based on two languages( an object-oriented
simulator (C++), and OTcl (object-oriented Tcl)
interpreter.
- has rich library of network and protocol object
- Compiled C++ hierarchy gives efficiency in
simulation and faster execution times.
- With OTcl script provided by user, a network
topology is simulated.
Overview
 Ns2 is event simulator where the advance of
time depends on the timing of events which are
maintained by a scheduler.
 Event – an object in C++ hierarchy.
unique ID, Scheduled time,
pointer to an object
 Scheduler – maintains ordered data structure
with the events to be executed and fires them
one by one, invoking the handler of the event.
How to Install
-Window XP-
Go to Website:
http://nsnam.isi.edu/nsnam/index.php/Running_Ns_and_Nam_Under_Windows_9x/2000/XP_Using_Cygwin
Read “Requirements and Installation Tips”
Carefully.
Download cygwin.exe from http://www.cygwin.com/
Click the “cygwin.exe”
How to Install
 Cygwin Installation
How to Install
How to Install
 Select browse for “cygwin” file( I selected as “default”)
How to Install
 Local package directory (I recommend c:\cygwin).
How to Install
 Select to Install all ( I recommend it)
 You can select “install”, “default”, “uninstall”, “install”, and “reinstall” behind the first
line “all”. If you select “install”, then all sub items will be automatically selected.
Otherwise you may lose some items.
How to Install
 Select download site
How to Install
Installing
How to Install
 Finishing Installing
How to Install
NS2 Installation
Download ns-allinone-2.29.2.tar.gz from
Website and Save it to the c:/cygwin
/usr/local
Unpack it: tar xvfz ns-allinone-2.29.2.tar.gz
Click on desktop icon “cygwin”
How to Install
How to Install
 Type “cd ..” to go to the upper folder(“cd” must be low case. And
there is one space between “d” and “.”)
 Type “cd ..” again.
How to Install
 “cd usr”, go to folder “usr”
 “cd local”, go to folder “local”
How to Install
 Find “install.exe”
How to Install
 Start to run the installation “./install”
How to Install
 Installing
How to Install
 Installing
How to Install
 Configure system variables and library paths
 After finishing installing, following window appears
How to Install
 Configure system variables
 Go to “My computer” and click “view system information”
How to Install
 Go to “advanced” Tab and Click “Environmental variables”
How to Install
How to Install
 Highlight “path” which is “system variable” box and press the “Edit”
button.
How to Install
How to Install
Add the following path separated with “;”
make sure to not change the existing path.
/usr/local/ns-allinone-2.29.2/bin
/usr/local/ns-allinone-2.29.2/tcl8.4.11/unix
/usr/local/ns-allinone-2.29.2/tk8.4.11/unix
How to Install
Go to cygwin and type the following
content
Export LD_LIBRARY_PATH=/usr/local/nsallinone-2.29/otcl-1.11
Export LD_LIBRARY_PATH=/usr/local/nsallinone-2.29/lib
Export TCL_LIBRARY_PATH=/usr/local/nsallinone-2.29/tcl8.4.11/library
How to Install
OTcl – The User Language
 NS2 is basically an OTcl interpreter with network
simulation object libraries
 Very simple syntax and easy integration with
other languages.
 Characteristics:
- fast development
- provide graphic interface
- compatible with many platforms
- flexible for integration
- easy to use
- free
OTcl – The User Language
Example
OTcl – The User Language
Proc: define a procedure, followed by an
procedure name and arguments
Set: assign a value to a variable
[expr …]: to make the interpreter calculate
the value of expression within the bracket
To assign to variable x the value that
variable a has, then write “set x $a”.
Put: prints out
OTcl – The User Language
Event Scheduler
 Main users of an event scheduler are network components that
simulate packet-handling delay or that need time
Event Scheduler
Two different types of event schedulers
- real time: for emulation which allow the
simulator to interact with a real network
- non-real time: three implementations are
available (Heap, List, Calendar). The
default is set as Calendar
Event Scheduler
 Example
...
set ns [new Simulator]
$ns use-scheduler Heap
...
...
set ns [new Simulator]
$ns use-scheduler Heap
$ns at 300.5 "complete_sim"
...
proc complete_sim {} {
...
}
Packet
NS2 packet is composed of a stack of
headers and optional dataspace.
Packet format is initialized when a
Simulator object is created. So, a network
object can access any header in the stack
of a packet it processes using
corresponding offset value.
Packet
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Click on desktop icon “cygwin”
Make sure to put the exe files under
C:\cygwin\usr\local
Do the following steps to execute
example.
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 However you will fail to run the “ns-simple.tcl” with the displayed
notice. This is because you did not open “XWin” yet
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 Open “Xwin” from “C:\cygwin\usr\X11R6\bin”. If everything is fine,
you will then get the following figures.
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 Yet you may get the following warning messages:
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 That means some components missed. You can then copy these
files from “C:\cygwin\bin” to “C:\cygwin\usr\X11R6\bin”
 After you open X11, you may still can not run “ns-simple.tcl”
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The following command can solve this
issue
export DISPLAY=:0.0
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 Run “ns-simple.tcl”
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 DONE !!!
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Thank You….
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Introduction to NS2 -Network Simulator-