PEPSY-QNS is the Performance Evaluation and Prediction SYstem for Queueing NetworkS. Its main purpose is to calculate performance values for queueing networks.


  1. Contents
  4. What do you need?
  5. Getting more information

PEPSY-QNS at a glance

The following paragraphs describe which networks and node-types PEPSY-QNS can handle. In addition to this a short characterization of the available analysis methods and a list of the performance measures that are calculated is given.

Queueing Networks

Network types that PEPSY-QNS can handle:
with one or more job-classes. Routing is given by visit ratios or transition probabilities. A change of a jobs class going through the network is not possible.

Node types that can be used:
The service process is defined by its first and second moment - the service rate and the squared coefficient of variation.

Analysis methods

Until now there are more than 50 different analysis methods implemented and available to PEPSY-QNS.

Calculated performance measures

The table of results that has the same format for all methods contains the following perfomance values: The results are shown for each node
  1. for every job class separately and
  2. summary over all job classes.
These values are listed for each job class for the overall network:

How to work with PEPSY-QNS

PEPSY-QNS has two different user interfaces. The first and more simple way to work with it only needs the standard UNIX(TM) environment and ASCII-Terminals. The second and more comfortable way is to use the X-Windows front end called XPEPSY.


Working with XPEPSY


Starting the work with XPEPSY when the queueing network is available resulting from the modelling phase - as it has to be when using the "normal" PEPSY.

This is the greeting window of XPEPSY

Creating the queueing network

The main window of XPEPSY contains the working area. Here you have to place your queueing-systems and to define the transition paths. Using the Graphical Editor Menu you can select the current edit mode, e.g. create node or delete object.

After the layout of the network is done, the parameters of the nodes have to be specified. This is done in the Node Data Dialog.

After you specified all parameters that are needed, save the queueing network model and change to the Analysis Mode to perform the analysis.

Choosing the analysis method

When switching to the Analysis Mode the Analysis Menu appears and the feasible methods are listed in it. The methods shown up are selected out of the internal database by comparing the networks characteristics with the possibilities of the algorithms. For any method that is not able to analyze the network the reason why can be queried.

Performing the analysis

Now it is very simple to perform the analysis. Select the method and simply click on the "Analyze"-button and the program will start the calculations. They will be shown up a few seconds later in a results window. You can continue by selecting further algorithms to compare their results to the ones you've got already or go back to the Graphical Editor to change your model for case study purposes.

What do you need?

The program system is available for any UNIX(TM) system. PEPSY-QNS has been installed successfully on HPUX, SunOS, IRIX, AIX, Ultrix, SORIX and some other architectures, as well as on several LINUX distributions.

For the installation of the graphical front-end XPEPSY you need the X-Window-System (at least revision 4) and the Motif widget-set (version 1.2 or higher).

Getting more information...


The On-Line-Help-System coming with PEPSY-QNS can be used during the work with the basic system or the XPEPSY. The texts are converted and available here.


Kirschnick, M.: XPEPSY-Handbuch; Universität Erlangen-Nürnberg; Institut für Mathematische Maschinen und Datenverarbeitung IV; Tech. Report; Sep. 1993; German: (compr. Postscript, ~141kB).

Bolch, G., Kirschnick, M.: PEPSY-QNS - Performance Evaluation and Prediction SYstem for Queueing NetworkS; Universität Erlangen-Nürnberg; Institut für Mathematische Maschinen und Datenverarbeitung IV; Tech. Report TR-I4-92-21; Oct. 1992; German: (compr. Postscript, ~266kB).

Bolch, G., Kirschnick, M.: PEPSY-QNS - Ein Programmsystem zur Leistungsanalyse von Warteschlangennetzwerken; In: Walke, B., Spaniol, O. [Eds.]: Messung, Modellierung und Bewertung von Rechen- und Kommunikationssystemen; Kurzberichte und Werkzeugvorstellungen zur 7.ITG/GI-Fachtagung Aachen, 21.-23. Sep. 1993; Aachener Beiträge zur Informatik (Bd. 2), Verlag der Augustinus Buchhandlung, Aachen 1993, pp. 216-220.

Kirschnick, M.: The Performance Evaluation and Prediction SYstem for Queueing NetworkS - PEPSY-QNS; University of Erlangen-Nuremberg; Institut für Mathematische Maschinen und Datenverarbeitung IV; Tech. Report TR-I4-94-18; Jun. 1994; (compr. Postscript, 60kB).


For further information contact via mail, email or telephone/fax Dr. G. Bolch or S. Kösters.

Done by Matthias Roessler with changes by Stephan Kösters