Java Modelling Tools is a suite of scientific tools for performance analysis and modelling using queueing theory and colored stochastic Petri nets. Models are solved either with analytical, asymptotic or simulation methods; workload characterization tools are also included in the suite.
See the project website for more details: http://jmt.sf.net
Pretty Damn Quick (PDQ) analytically solves queueing network models of computer and manufacturing systems, data networks, etc., written in conventional programming languages. Generic or customized reports of predicted performance measures are output.
Simulator of G/G/k queue systems used in computer networks.
QueueSimulator is a free software which aims to simulate primarily
G/G/k queueing systems that are used in computer networks. But
it can be used to simulate practically any stable queue system.