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ns2 network simulator - http://www.isi.edu/nsnam/ns/
Ns is a discrete event simulator targeted at networking research. Ns provides substantial support for simulation of TCP, routing, and multicast protocols over wired and wireless (local and satellite) networks. |
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Scalable Networks - http://www.scalable-networks.com/
Network simulator designed from the outset for maximum speed and scalability, with real-time simulation as an achievable goal. |
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http://www.omnetpp.org/ - http://www.omnetpp.org/
OMNeT++ is an open-source, component-based simulation package built on C++ foundations. It offers a C++ simulation class library and GUI support (graphical network editing, animation). |
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http://www.cs.cornell.edu/skeshav/real/overview.html - http://www.cs.cornell.edu/skeshav/real/overview.html
a modular network simulator featuring a java GUI |
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http://www.ssfnet.org/ - http://www.ssfnet.org/
SSF (Scalable Simulation Framework) is a public-domain standard for discrete-event simulation of large, complex systems in Java and C++. Several SSF implementations and a large number of open-source protocol models and other components exist. |