Network Simulation using OPNET

Network managers and researchers design certain topologies, protocols and
algorithms, the effectiveness of which can be decided by simulation. The
proposed designs cannot be directly fielded with existing infrastructure without
testing of compatibility with it.

The network simulator provides a test bed by simulating the real world
network. A number of network simulation tools are available in the market like
NS-2, GloMoSim, QualNet, NetSim, OPNET, etc.

About OPNET

OPNET is a graphical user interface (GUI) based network simulation tool which is
simple to install and use. It comes with a good documentation and is available
for installation on Windows.

We reviewed the OPNET IT Guru academic edition for network simulation and
analysis. The user interface would be found self explanatory by those having
basic knowledge of computer networking. OPNET's GUI provides an easy way to
develop models for network, different hardware devices and protocols. This tool
supports most of the network types and technologies like LAN, ATM, Frame Relay,
WAN, Wireless Networks etc. It allows designing scenarios based on these
technologies and simulating them. It also provides outputs in form of plots and
simulation data.

OPNET uses a wizard to help you choose the devices you want to use in your network design.

For the purpose of simulation it provides various models of different type of
network devices like hubs, bridges, switches, routers and servers from many
network vendors like Cisco, Nortel, 3Com, Bay Networks, Cabletron, HP, Juniper,
Lucent, NEC and many more.

It also allows to drag and drop in the workspace and use printers,
workstations, different types of links like 1000BaseX, 1000BaseT, 100BaseT, 10G,
Fast Ethernet, OC links, SONET etc available in its library for network
designing.

Getting started

The OPNET IT Guru academic edition of the software can be freely downloaded
and installed after online registration with OPNET.

The size of the setup file is 50.3 MB. During installation it requires online
activation of the license.

A detailed step-wise process of installation is available at

www.opnet.com/itguru-acaemic/instructions.html.

Designing network scenarios

For the purpose of demo we would be first creating a WAN with a centralized
server and analyse its performance based on CPU utilization, link utilization,
etc.

Object Palette displays all the models of products available in OPNET's library for the selected technologies and vendors

Start OPNET, open a new project and give a suitable name for the project and
scenario. Create an empty scenario and select a suitable network scale among
World, Enterprise, Campus, Office, Logical, maps. We would select 'enterprise'.

Then select the required technologies and vendors. This will lead to the
display of all products related to the technology and the vendor available in
OPNET's library. Drag and drop the products and links from object palette into
workspace to design the network.

A generated network scenario

This way we can complete one scenario. This network can be analysed for
various parameters like CPU utilisation, bandwidth utilization, throughput, etc.

Performance analysis

Performance analysis can be seen in two ways — one using plot and another
through result data table. Here we generated another scenario of a similar WAN
simulated above but with distributed cache servers and compared the performance
of the server in these two scenarios.

A comparative graph on point to point throughput for two scenarios.

Conclusion

It was just a demo on simulation of a WAN; however there are many more
simulation scenarios like load balancing, advanced web modeling, QoS is
possible. By using a virtual network environment, we can simulate and diagnose
difficult problems more effectively. We can change different parameters and
analyse their effect on the network before it is implemented so as to enhance
the performance.

A number of scenarios can be generated with respect to change of load and
failure analysis can be performed. The tool gives better understanding of the
working and performance of  a network.

Nirav Shah, Sumit Goswami, IIT Kharagpur