Depending on the type of your PhD research work, you can use a variety of network simulator softwares that are available in the market. Network simulators are particularly useful in academic research work as it is expensive and time-consuming to test your project over real-time network of computers and data connectors.

There are a number of network simulators, including the popular ones like OPNET, NS2/NS3, and OMNeT++. Network simulators can be classified on basis of the following criteria:

• Commercial use or Open source

For commercial software such as OPNET and QualNet, researchers have to pay for the license and cannot modify the source code. Advantages include regular updates and fixes and documentation set for easy learning. Open source software such as NS2/NS3 and OMNeT++ are free for downloads and are very flexible. Open source network simulators are more popular in academic circles.

• Ease of use

GUI-based simulators such as OPNET and OMNeT++ provide a visual interface to the user, making it easier to understand the working. Alternatively, simulators with text-based interfaces are easier to customize for your project requirements.

For your convenience, OPNET simulator allows you to model, simulate, and analyse networks. Additional features include user-friendly graph and chart generation, statistics, and even animation.

• Programming features

Simulators with strong programming features provide a highly-customizable framework to design your own network simulating application for testing. NS2 uses C++ object-oriented language with Tcl script language. This programming code allows you to write your own event scheduler and network component objects, thus reducing the network packet and event processing time. NS3 that uses C++ with Python scripting is an open source simulator that is aimed particularly for research work.

The strength of OMNeT++ is in its component-based architecture with a number of modules assembled using reusable software components. Besides this, OMNeT++ can run on both Windows-based and Linux-based systems.

• Performance

For a network comprising of 400 to 2000 nodes, among NS2, NS3, and OMNeT++, NS2 uses the highest amount of memory with NS3 utilizing the lowest amount of memory. With a gradual increase in nodes, there is a corresponding increase in memory consumption among all the network simulators. With respect to the computational time, NS2 shows a rapid increase in time with increase in nodes. NS3 is the most efficient in computation time and scalability as compared to the other simulators.