The OPNET IT GURU has been in existence for years and designed to be used for the industry and the academics. The simulation software is now in version 10.0 and equipped with abundant features such as: modeling networlc topology and traffic, application impact assessment, and server capacity planning.
Chen, Jen-Chung Victor
"Review of the OPNET IT GURU Software,"
Journal of International Information Management: Vol. 13
, Article 7.
Available at: http://scholarworks.lib.csusb.edu/jiim/vol13/iss4/7