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ns or the network simulator (also popularly called ns-2, in reference to its current generation) is a discrete event network simulator. It is popular in academia for its extensibility (due to its open source model) and plentiful online documentation. ns is popularly used in the simulation of routing and multicast protocols, among others, and is heavily used in ad-hoc networking research. ns supports an array of popular network protocols, offering simulation results for wired and wireless networks alike. It can be also used as limited-functionality network emulator.
ns is licensed for use under version 2 of the GNU General Public License.
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Design
ns was built in C++ and provides a simulation interface through OTcl, an object-oriented dialect of Tcl. The user describes a network topology by writing OTcl scripts, and then the main ns program simulates that topology with specified parameters.
The NS2 makes use of flat earth model in which it assumes that the environment is flat without any elevations or depressions. However the real world does have geographical features like valleys and mountains. NS2 fails to capture this model in it.
Many researchers have proposed the additions of new models to NS2. Shadowing Model in NS2 attempts to capture the shadow effect of signals in real life, but does that inaccurately. NS2's shadowing model does not consider correlations: a real shadowing effect has strong correlations between two locations that are close to each other. Shadow fading should be modeled as a two dimensional log-normal random process with exponentially decaying spatial correlations.
History
ns began development in 1989 as a variant of the REAL network simulator. By 1995, ns had gained support from DARPA, the VINT (Virtual Inter Network Testbed) project at LBL, Xerox PARC, UCB, and USC/ISI.[1].
ns is now developed in collaboration between a number of different researchers and institutions, including SAMAN (supported by DARPA), CONSER (Collaborative Simulation for Education and Research)(through the NSF), and ICIR (formerly ACIRI). It is currently maintained by volunteers. Long-running contributions have also come from Sun Microsystems and the UCB Daedelus and Carnegie Mellon Monarch projects, cited by the ns homepage for wireless code additions.
ns-3
Generation 3 of ns has begun development as of July 1, 2006 and is projected to take four years.[2]. It is funded by the institutes like University of Washington, Georgia Institute of Technology and the ICSI Center for Internet Research with collaborative support from the Planète research group at INRIA Sophia-Antipolis. Currently ns-3 is in development phase. It is an event based network simulator.
See also
References
- ^ "The Network Simulator - ns-2." Information Sciences Institute. The University of Southern California. 13 July 2006 <http://www.isi.edu/nsnam/ns/>.
- ^ "Ns-3." The Nsnam Wiki. 2 July 2006. Information Sciences Institute. <http://nsnam.isi.edu/nsnam/index.php/Ns-3>.
Further reading
- T. Issariyakul and E. Hossain, Introduction to Network Simulator NS2, Springer, Nov. 2008, ISBN 978-0-387-71759-3 ([Slides])
External links
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