Tadeusz Czachórski received M.Sc., Ph.D., D.Sc. degrees in informatics respectively in 1972, 1979, 1988, and professor title in 1999. Currently he is a professor at the Silesian University of Technology (Division of Computer Systems Theory and Design) and the director of the Institute of Theoretical and Applied Informatics of Polish Academy of Sciences, IITiS PAN, Gliwice. He spent more than five years at several French universities and research institutes (IRISA Rennes, University of Versailles, ISEM Orsay Paris-Sud, Paris-Nord, National Institute of Telecommunication) and still maintains scientific cooperation with these centres. He also participated in Next Generation Internet European project concerning such issues as multiservice-multimedia, mobility, services convergence, quality of service and variable connectivity, where he was coresponsible for the work package concerning analytical, numerical and simulation methods to model performance of the Internet. Currently he is a member of Polish project Future Intenet Engineering. He is a member of programme committees of some periodic international and national conferences, e.g. Heterogeneous Networks HET-NETS, European Workshop on Performance Engineering EPEW, Polish Teletraffic Symposium, Computer Networks, Internet in the Information Society, currenly also International Symposium on Modeling, Analysis and Simulation of Computer and Telecommunication Systems (MASCOTS) and COMPSAC. 1990 - 2007 he was scientific secretary of the Committee of Informatics of Polish Academy of Sciences, 2007 - 2011 vice-president of this committee, currently member of presidium and head of the section of computer networks and distributed systems of the committee. Chair of IFIP Technical Committee TC5 "Information Technology and Applications". His scientific interests include mathematical methods and software related to modelling and performance evaluation of wide area computer networks, especially the Internet. The methods include Markov chains, diffusion approximation and fluid flow approximation. They are used to study qualiy of service, traffic control mechanisms and related problems.