AnyLogic - AnyLogic has changed simulation modeling and expanded its application into complex business environments. The unmatched flexibility of multimethod modeling allows users to capture the complexity of virtually any system, at any level of detail.

MATSim - MATSim is an open-source framework for implementing large-scale agent-based transport simulations.

ns-3 - a discrete-event network simulator for internet systems

Simulation of Urban MObility (SUMO) - "Simulation of Urban MObility" (SUMO) is an open source, highly portable, microscopic and continuous road traffic simulation package designed to handle large road networks. SUMO is licensed under the Eclipse Public License V2.

NetSim - NetSim software was created to simulate various Cisco systems. Cisco software is known around the world as being one of the best network, routing and switch systems for businesses and private use. Read more about NetSim.

Paessler Multi Server Simulator - Paessler Multi Server Simulator is inexpensive and robust software that helps you power massive-scale testing.