The thesis deals with the principles of assurance quality of services in IP networks. The first part of the thesis describes specifications which are required by current applications for data network, and also illustrates the methods suitable for solving those requirements. The most attention is given to multimedia service VoIP whose development has not been finished from far. That theoretical knowledge implies in the second part of the thesis which analyzes the implementation of assurance QoS for the service VoIP within the standard 802.11, or more precisely, for wireless networks in general. The simulation of wireless networks within the program Opnet Modeler and the attest of the ability to assure QoS within both wireless networks and th...