REAL a modular network simulator featuring a java GUI http://www.cs.cornell.edu/skeshav/real/overview.html

Parsec a C-based simulation language for sequential and parallel execution of discrete-event simulation models http://may.cs.ucla.edu/projects/parsec/

x-sim The x-kernel protocol framework can be used as a complete simulation environment for TCP/IP networks. http://www.cs.arizona.edu/xkernel/

NIST ATM/HFC Network Simulator http://www.hsnt.nist.gov/misc/hsnt/prd_atm-sim.html

cnet 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. http://www.cs.uwa.edu.au/pls/cnet/

SSFNet 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. http://www.ssfnet.org/

OMNeT++ 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). http://www.hit.bme.hu/phd/vargaa/omnetpp.htm

ns2 network simulator 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. http://www.isi.edu/nsnam/ns/

Scalable Networks Network simulator designed from the outset for maximum speed and scalability, with real-time simulation as an achievable goal. http://www.scalable-networks.com

BRITE Tool for generation of realistic internet topologies, with export to several network simulators (currently ns2, JavaSim, and SSFNet). http://www.cs.bu.edu/brite/

Akaroa 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. http://www.cosc.canterbury.ac.nz/research/RG/net_sim/simulation_group/akaroa/

J-Sim A component-based, compositional simulation environment. http://www.j-sim.org/

Solutions Consulting Provides SerialPort package in Java, enabling serial port communication for serial devices. Also offers consulting services specializing in hardware/sofware interface design. http://www.sc-systems.com/