Simulation is a very important modern technology in the world. It is being applied to different fields such as science, engineering, or other application for different purposes. To predict the behaviour of the system can be used different variables. Computer simulation can be used to assist the modelling and analysis of the system. The application of simulation into networking area such as network traffic simulation, however, is relatively new.
Specifically the computer assisted simulation technologies are being applied in the simulation of networking algorithms or systems by using software engineering for network simulation,.
For instance, the network simulations can put more importance on the performance or validity of a distributed protocol rather than the visual or real-time visibility simulation’s features. People are used network simulators in different areas like academic researchers, industrial developers, and Quality Assurance (QA) to verify, design, simulate, and analyze the performance of different networks protocols. Apart from they can be used to evaluate the effect of the different parameters on the protocols.
A network simulator will consist of a wide range of networking technologies and protocols generally. So, it can be helped the users to build complex networks from basic building blocks like clusters of nodes and links. One can design different network topologies using various types of nodes for instances end-hosts, hub, network bridges, routers, optical link-layer devices, and mobile units with their help.
Presently the most popular simulators for wireless networks.NS2 and OPNET.WSN has two kinds of simulation software Commercial and Non commercial. NS2 and OMNET++ is the most famous in non commercial software and OPNET is well known commercial software. This section will make comparison of OPNET vs NS2 and OMNET++.
Network Simulator2 (NS2):
The network simulator (NS2) is one of the most popular open source network simulators. Originally, NS is a discrete event simulator targeted at networking research. In NS, there is a lack of user interface. NS is more difficult to learn. NS is less generic and less configurable than OPNET. There is a clearer animation with OPNET. It has more system functions and assistance of OPNET is done better.
2. OMNET++ Simulator:
OMNET++ and NS2 is also a public-source and component-based network simulator with GUI supports . OMNET++ has generic and flexible architecture that makes it successful also in other areas like the IT systems, hardware architectures, queuing networks, or even business processes as well. The main application area of OMNET++ is the simulation of communication networks. However its design quite open, which enables also other target applications. OMNET++ has a sophisticated GUI support and common used models are available like IPv4, IPv6, Ethernet, MPLS etc. OMNET is free for academic and non profit use .However; a license must be obtained for commercial use. OMNET++ has own network definition language NED which the functionality is coded by using C++ classes. OMNET++ is available for UNIX System (like) as well as windows supporting Visual C++6.0, Visual Studio. NET2003, CygWin
3. OPNET Simulator:
Commercial software and some non commercial software don’t provide source code of the simulation kernel. OPNET only provides the source code of the protocol models.NS2 and OMNET++ is fully open sourced. NS2 and OMNET++are not paid for the license and user can learn these logical architecture, thus OMNET++ and NS2 is better than OPNET in this project in simulation library. The simulation library of NS2 provides less function. The simulation library of OPNET is based on C/C++, on the other hand OMNET is a C++ class library. In this features, OMNET++’s function are much more power full than NS2.
OPNET provides its full-feature software packages. This full features free software assists to qualifying universities worldwide for academic research and teaching. OPNET Modeler offers several distinct advantages over NS-2/3 and Other simulation software :
Extensive Model Library with Source Code: 800+ protocol and vendor device models available with source code, including specialized models such as UMTS, MANET, MPLS, WIMAX and more Advanced Modeling and Simulation: Discrete Event, Analytical, and Hybrid technologies for high-fidelity, scalable simulations
Technical Support: the world-class technical supports are available at a significantly discounted price.
FREE Training: OPNET standard training is available free of charge to University Program participants and free lab manuals for popular textbooks downloadable from OPNET web site .
3.1 Main features of OPNET:
OPNET has three main functions inherently: modelling, simulating, and analysis. OPNET provides intuitive graphical environment to create all kinds of models of protocols for modelling. It uses three different advanced simulations technologies for simulating and can be used to address a wide range of studies. The results of simulation and data could be analyzed and displayed easily for analysis. OPNET can generate user friendly graphs, charts, statistics, and even animation for users ‘ convenience.
According to the OPNET whitepaper, OPNET’ s detailed features include:
1. Fast discrete event simulation engine
2. Lot of component library with source code
3. Object-oriented modeling
4. Hierarchical modeling environment
5. Scalable wireless simulations support
6. 32-bit and 64-bit graphical user interface
7. Customizable wireless modeling
8. Discrete Event, Hybrid, and Analytical simulation
9. 32-bit and 64-bit parallel simulation kernel
10. Grid computing support
11. Integrated, GUI-based debugging and analysis
12. Open interface for integrating external component libraries
OPNET have good efficient and tracing is an important issue in wireless networks. . OPNET and NS2, OMNET++, both have strong programmability. OPNET has lots of protocol models including TCP/IP .ATM, Ethernet, etc. But it is so expensive to get the license. NS2 has a large number of protocol models but mostly centred on TCP/IP.OPNET is so expensive although it has some facilities such as free training and free lab manuals and you can also download free software from the OPNET web site. NS2’s protocol model is excessively unitary. Additionally, NS2 doesn’t allow hierarchical models, it greatly limit NS2 use in WSN. OPNET allows hierarchical models with arbitrarily deep nesting.
A significant difference between OMNET++ and OPNET is OPNET models always use fixed topology .But OMNET++ has graphical editor which is allowed customized topology and parameterized topology. In network topology and hierarchical models, OMNET++ is better than NS2 and NS2 is insufficient in this ability.
OMNET++ offers three tools for debugging purposes: automatic, animation, module output windows and project inspectors. OPNET has the lack of graphical runtime environment although it has a powerful command line simulation debugger .In NS2 environment; NS2 is very slow in WSN simulation which limits its use. In network simulation, NS2’s performance of debugging and tracing is not very good.NS2 needs a long time and a lot of memories to simulate.
The only way to see which simulator models a scenario best or is more accurate is to make comparisons. The question which simulator is the best in specific situation is important for developers. But since most simulators are not easy to learn and handle and therefore the time to adjust to it is long, most developers are familiar to only one simulator. Because of this fact, the finding of differences between simulators is not happening during daily work. Developers just do not realize that the result they gain are sometimes not as precise or useful as expected.
As you can see, comparisons on the accuracy of network simulator are interesting for both developers of simulators and their users. They could help to improve the simulators as well as the algorithm developed with them.
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