This master’s thesis delves into the possibilities of the open-source Private Branch Exchange Asterisk, elaborates on its features and compares it with several other distros. The term SIP stack is explained here with the mention of two of its representatives. Further in the thesis, the security risks of the VoIP technology are explained, and specific attacks are described and then realized. As a part of the testing process, the possibilities of a custom module and its following implementation are explored, as well as the portability between the individual distros and its proper functioning.

Wireless networks are currently the frequent access connection to the local network or the Internet. Until 2005 there was no support in the 802.11 standard priority data and the use of multimedia services in these networks is problematic. Thesis deals with the standard IEEE 802.11 standard and quality of service support including IEEE 802.11e. They discussed methods of access to transmission medium, differences in the MAC sublayer, the reader issues in the transmission of priority data and the requirements for these data. In Opnet Modeler was created wireless network with access points and stations on which they are carried out simulations at different strain of transmitted data. It studied the difference in the use of DCF and EDCF method, used in the network with QoS support. In particular, it examined the behavior of priority voice and video data in both networks. The focus is on key parameters such as throughput, dropping data, packet loss, delay, jitter and the size of broadcasting front. The measured data are analyzed, and differences in the network without the support and promoting the quality of services are compared and evaluated. Part of this work is the role of laboratory in the Opnet Modeler.

Master’s thesis is trying to create opensource IM application for communication in Jabber network. In nowadays it is getting more and more popularity as at providers, so mainly at end users. In first half of thesis are explained basics of whole issues and in second half is described resulting application, which has been created by using of object oriented programming language Java. Java is very extended between programmers for her simplicity and great support. Thanks this is available a many external libraries and extensions. Application has been written on Smack library in version 3.04 and VoIP module on JMF (Java Media Framework). Graphic interface has been created by using of standard Java visual components (javax.swing).

The main task of this master’s thesis is to simulate the routing protocol AODV (Adhoc On-Demand Distance Vector Routing) to the Network Simulator ns-3 environment, and to realize a model of MANET (Mobile Ad-hoc Network) network with the support of Quality Of Service (QoS). Further implement the protocol AODV in real devices and the involvement of such nodes in the simulation process using the simulator ns-3. This work provides the theoretical basics: it deals with the primary characteristics of MANET, describes in detail the routing protocols MANET with support of QoS, provides information about the Network Simulator ns-3 simulation environment, describes in detail the existing implementation solutions of the protocol AODV in to real devices and provides information about the methods of involvement real devices to the simulation.

This thesis consists of theoretical and practical parts. The theoretical part contains an analysis of the problems of wireless networkssolutions individual standards and methodologies to ensure quality of service. In the practical part using the OPNET Modeler, a number of different simulation models and their evaluation. It is a model of individual standards, support mobility and interference effects on quality of service.

This master thesis deals with implementing triple-play services and providing it’s quality of services in heterogenous comunnication networks. The aim of thesis is to apply the- oretical methods in real case and existing network infrastructure. Practical part aims to create technical solution to prioritize network traffic based on classification of required services. The technical solution is created with conditions of being possible to add more functions and to provide scalability.

The aim of this thesis is to install and to configure three Open source PBXes Asterisk, Freeswitch and YATE. Furthermore, the aim is to realize the performance test and stability tests on three different HW configurations with the tester Spirent Abacus 5000. The scripts in bash were created to monitor PBX performance. Another part of the study is to analyze and to compare PBX security and to compare the Open Source PBX with a proprietary PBX Alcatel-Lucent OXE.

This Master's thesis deals with entrepreneurial intention of Invia.cz s.r.o. company. Aim of the thesis is extension of company. Based on analysis of current condition of copany, There is also offered specific design and realization of new created call center, that can help to festen the position of company on tourism market.

The main goal of this master's thesis is to apprise of principles of Cisco One Platform Kit based on software defined networks and with monitoring techniques in that type of networks. The focus is concentrated on monitoring the quality of Voice over IP communication. Next part of this thesis is a proposal and implementation of the extensible monitoring environment OneMon on the Cisco One Platform Kit. It is possible to extend OneMon environment using specific analyzers to monitor various types of network traffic. The part of this master's thesis is also implementation of VoIP traffic analyzer for SIP and RTP protocols. This analyzer provides information about phone calls and their quality in a monitored segment of a computer network.

This thesis deals with voice encryption in wireless communication. First, the necessary theoretical base about mobile telephone network is presented and followed by a description and comparison of existing voice encryption methods in wireless communication. After that, modern cryptographic algorithms are briefly described and a method based on voice over Internet protocol is proposed. This method is implemented as an Android application.