OPNET Modeler® accelerates the R&D process for analyzing and designing communication networks, devices, protocols, and applications. Users can analyze simulated networks to compare the impact of different technology designs on end-to-end behavior. Modeler incorporates a broad suite of protocols and technologies, and includes a development environment to enable modeling of all network types and technologies including:

* VoIP
* TCP
* OSPFv3
* MPLS
* IPv6
* Others

Key Features:
* Fastest discrete event simulation engine among leading industry solutions
* Hundreds of protocol and vendor device models with source code (complete list)
* Object-oriented modeling
* Hierarchical modeling environment
* Discrete Event, Hybrid, and optional Analytical simulation
* 32-bit and 64-bit fully parallel simulation kernel
* Grid computing support for distributed simulation
* Optional System-in-the-Loop to interface simulations with live systems
* Open interface for integrating external object files, libraries, and other simulators
* Integrated, GUI-based debugging and analysis

HomePage: http://www.opnet.com