NS2 Programs

                        Network Simulator is a piece of hardware or software that simulates and predicates the behavior of a network without the presence of an actual network. Network Simulator Version 2 (NS2) is an event driven network simulator, developed by UC Berkely in 1995. It supports several algorithms for the routing and queuing of network packets. Similar to internet it can set up packet traffic and measure various network parameters. Simulators are heavily used in the ad-hoc networking research and support several network protocols, offering simulation results for wired as well as wireless networks.

                        NS2 is based on two languages, an object oriented simulator written in C++ and an OTCL interpreter. NS2 has a rich library network and protocol objects. It can be implemented in most UNIX systems as well as Windows. Most of the NS2 code is in C++ and uses TCL as its scripting language. OTCL adds object orientation to TCL.

                        In NS2, the events are scheduled in a global event queue according to their time of execution. When a simulation is run, the simulator removes events from the head of the queue, moves the simulator time to that of the currently removed events and executes it. When done, it continues to the next and so on. Each simulation is defined by a scenario that contains a number of predefined events that define the scenario. NS 2 scenarios are implemented in TCL scripts that contain the command to initialize the simulator and to create the nodes and their configuration. Each simulation run generates a trace file containing all the data packets that are sent between the nodes during the course of the scenario. By analyzing this trace file, it is possible to determine the performance effect of parameter variations, various routing protocols, etc. A simulation can be very useful since it is possible to scale the networks easily and therefore to eliminate the need for time consuming and costly real world examples. While the simulator is a powerful tool, it is important to remember that the ability to do predictions in the real world is dependent on the accuracy of the models in the simulator.

                        One of the major problems that anyone faces while dealing with NS-2 is its installation. The following section provides you with the installation guides:

Installing ns-2.35 in Ubuntu 12.04 LTS

As you know Ubuntu 12.04 launched on 26th April 2012 and it is a Long Term Support OS. To install ns2 in Ubuntu 12.04, it refers the same step as done in 11.10 OS.  For new users, here are the steps to install ns2.35:

Step 1: Download NS-2.35 from http://www.isi.edu/nsnam/ns/

Step 2: Go to terminal (Alt + t) and install the necessary updates using the command

“sudo apt-get update”  (without Quotes)

Step 3: Install the ns2 required libraries using the command

“sudo apt-get install build-essential autoconf automake libxmu-dev” (without quotes)

Step 4: Untar the downloaded ns-allinone-2.35.tar.gz file using the command

“tar zxvf ns-allinone-2.35.tar.gz”

Step 5: Execute the commands one by one as given below

cd ns-allinone-2.35

./install

(You get the PATH information if the installation was successful, upon succeeding set the PATH
    in the relevant file .bashrc)

Step 6: To set environment variables: (add the following lines in .bashrc file)

export PATH=$PATH:/home/username*/ns-allinone-2.35/bin:/home/username*/
   ns-allinone-2.35/tcl8.5.10/unix:/home/username*/ns-allinone-2.35/tk8.5.10/unix

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/home/username*/
   ns-allinone-2.35/otcl-1.14

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/home/username*/
   ns-allinone-2.35/lib

export TCL_LIBRARY_PATH=$TCL_LIBRARY_PATH:/home/username*/
   ns-allinone-2.35/tcl8.5.10/library

(Notes*: Replace the username with your own)

Step 7: Finally execute the command:

source .bashrc

===================================================

Notes: Type ns and see a  % symbol indicates that the installation of ns2 is successful and also try the command  nam so that a network animator will be opened. If you try to install ns2 which comes along with the synaptic package manager, you cannot write new modules and recompile it. In that case, you need to use the above method of installation.