  Different kinds of models are used to study various natural and technical
phenomena. Usually, the researcher is limited to using a certain kind of model
approach, not using others (or even not realizing the existence of other model
approaches). The authors believe that a complete study of a certain phenomenon
should cover several model approaches. The paper describes several model
approaches which we used in the study of the random early detection algorithm
for active queue management. Both the model approaches themselves and their
implementation and the results obtained are described.
