Professor Dr.- Ing. Christian Grimm has been working for more than ten years with measuring and modelling of data traffic in packet switched networks. In his PhD thesis he investigated complex methods for the traffic modelling in the World Wide Web. At present he is head of the division for research and development and new network services at the regional computing centre for lower saxony. Since 2003 he has an assistant professorship (Juniorprofessur) in computer networks at the faculty of electrical engineering and computer sciences at the university of Hannover. Professor Dr. rer.nat. Georg Schlüchtermann finished his study in Mathematics in 1984. He habilitated 1994 at the Ludwig-Maximilians-Universität in functional analysis. Since 2001 he is apl. professor at the faculty for mathematics, computer sciences and statistics at the university of Munich. He is lecturing in the fields of traffic theory, mathematical modelling in mobile communication and finance mathematics.