Akaroa is a package for supporting the Multiple Replications In Parallel (MRIP) simulation technique to harness the computing power of a network of inexpensive workstations. Integration exists with the Ptolemy Classic, ns2 and OMNeT++ simulators.

Tool for generation of realistic internet topologies, with export to several network simulators (currently ns2, JavaSim, and SSFNet).

A network simulator with a GUI and targeted at undergraduate teaching. Enables experimentation with various data-link layer, network layer, routing and transport layer networking protocols.

A component-based, compositional simulation environment.

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.

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).

a C-based simulation language for sequential and parallel execution of discrete-event simulation models

a modular network simulator featuring a java GUI

Network simulator designed from the outset for maximum speed and scalability, with real-time simulation as an achievable goal.

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.

The x-kernel protocol framework can be used as a complete simulation environment for TCP/IP networks.