When it is needed to predict the behaviour of a communication system and this system does not yet exist, a technique that can be used is to build a mathematical model and to process it using someone of the existing tools in order to obtain an estimation of the system performance. Many of these tools are based on the queuing network theory.

In consequence, this tutorial starts briefly reviewing the variables describing the performance. Then a presentation of how it is done the abstraction allowing the transformation of a real system into a queuing network model and where to find the data needed to compute the model. The core of the tutorial contains the presentation of the main techniques (analytical, numerical and simulation) used to process the queuing network in order to obtain the performance estimations. This presentation will have, beside their theoretical foundation, an important set of significant examples. Special importance will be given to the application domain of the different techniques.

Finally a short presentation of the main techniques used to characterize the traffic crossing different types of networks.

1. Introduction
2. Concept of Queue
3. Concept Queuing Network?
4. Numerical Techniques
5. Analytic Solutions
6. Approximate Solutions of Queuing Networks
7. Decomposition-Aggregation Methods
8. Diffusion Methods
9. Iterative Methods
10. Simulation Techniques
11. Traffic Characterization