1. Department of Systems and Computer Networks , Wroclaw University of Science and Technology, Faculty of Information and Communication Technology, Wybrzeze Wyspanskiego 27, 50-370 Wrocław, Poland , joanna.klikowska@pwr.edu.pl
2. Department of Systems and Computer Networks , Wroclaw University of Science and Technology, Faculty of Information and Communication Technology, Wybrzeze Wyspanskiego 27, 50-370 Wrocław, Poland , michal.wozniak@pwr.edu.pl