Silesian University of Technology, Poland

Biography: Tadeusz Czachorski 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 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 co-responsible for the work package concerning analytical, numerical and simulation methods to model performance of the Internet. He took part in Future Internet Engineering project and currently his institute coordinates a European project H2020 on safe and secure Internet of Things. 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. In 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" and member of IFIP General Assembly. 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 quality of service, traffic control mechanisms and related problems.

Speech Title: Models of traffic control in large Internet topologies

Abstract: Transient state queueing models help us to understand better the dynamics of internet transmissions and the performance of traffic control algorithms. Fluid flow approximation, due its simplicity is popular and frequently used -- but even it, if applied to large topologies, is time and space consuming. The alternative approaches as Markov chains or diffusion approximation lead to much more complex computations. Fluid flow approximation is based on first-order differential equations, and its algorithm is based on iterative calculations on large mutually interdependent structures. In consequence, the bottleneck of the method lies not in numerical computations but in storing and selection of data. This is why we use an approach in which a database (SAP HANA) and its language are used to implement the method. The model logic is represented by ETL (Extract, Transform and Load) customizable and user-friendly processes. The numerical examples are based on a real topology having over 100 000 nodes. We may investigate and compare this way various TCP control algorithms as Vegas or Reno, as well as the influence of the introduction of energy aware algorithms to routers.