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To model a real world process or system, simulators have been used. In telecommunication networks and computer networking, researchers use simulators to validate their protocols and algorithms. The most widely used simulator in the networking research community is Network Simulator NS-2. The network simulator NS-2 is an open source discrete event simulator which was incepted in 1989, in which the core backend libraries are developed in C++ programming language. NS-2 was further supported by Defense Advanced Research Project Agency (DARPA), USA under the VINT project. It is also used for education purposes for better understanding of the underlying network behavior. Additionally, it is also used for validating new and existing network related algorithms and protocols. These networks range from ZigBee, LANs, IEEE 802.11 to Vehicular Ad-Hoc Networks. Also, it is worth noted that new simulators or support in existing simulators are required whenever new technology is introduced. For example, when Cognitive Radio Network (CRN) was introduced, NS-2 existed at that time. Thus in order to simulate CRN, either a new simulator or CRN support in existing simulators is required. Since NS-2 is an open source simulator, therefore the community has contributed a lot for providing support of new technologies in NS-2 including CRN. While on the other hand, in commercialized simulators, only the company can provide support for new technologies and most of the time, they take extra charges for such support. Thus, this is one of the foremost benefits of NS-2 as being open source besides its widely adoption among the researchers.
Key Terms in this Chapter
C++: A famous general purpose programming language. C++ is hybrid in nature i.e., it combines both the features of functional language as well as object oriented programming. C++ was developed by BjarneStroustrup in 1979 at Bell Labs. A standard library is also available in C++ which is called as standard template library.
Perl: A general purpose, high level programming language designed by Larry Wall. It has been widely used as UNIX based scripting language. Additionally, it is very powerful in extracting the results by parsing the trace files.
Trace File: A file that contains event logs during a simulation process. For instance, when the network simulation run, some events happens such as packet drops and packet reception by different nodes in the network. These events there then logged in the text file and this text is normally called as trace file.
Computer Simulator: A software program that models the real life or hypothetical situation in order to study how system works. Famous computer network simulators are NS-2, NS-3, GloMoSim, OMNeT++, QualNet, and OPNET.
Tool Command Language (TCL): A scripting language which has been widely used in the programming of embedded systems platforms.
Defense Advanced Research Project Agency (DARPA): A military based US research agency responsible for funding new technologies useful for military. One of its major projects is the world's first operational packet switch network named as ARPANET. ARPANET was the first network which implemented TCP/IP.