During a recent engagement I needed to use queuing theory based modelling to examine the performance of a system. Searching the Internet I found the JMT open source tools:
These tools provide a strong set of analytical and simulation capabilities that are designed for computer system modelling. They provide an integrated set of tools with a graphical user interface, meaning that the learning curve necessary to use the tools and understand the models will not be too steep. If you need to apply queuing theory models to a piece of performance analysis these tools are well worth looking at.
Sarquol Ltd 