The thesis is focused on implementation of aplication for secure telephone communication on data network. Application is developed for operating system Android. For call management is responsible signaling protocol SIP and for transfer of voice data is used protocol RTP. For security of call is first created cryptografic key for symetric cryptography. After generating key is established call, which is encrypted by symetric cipher AES. Encrypting between communicating sides is provided in application or on microSD card. Part of solution is measurement of speed of cryptographic primitives, which are used for secure call.

My master’s thesis is focused on designing and creating communication network, which provides communication between two independent networks through encrypted tunnel. My solution is based on routers formed by older personal computers with FreeBSD like a operating system. Between routers is created static encrypted tunnel by using IPSec protocol. Voice services provides packet oriented exchange Asterisk with support of signaling protocol SIP. This solution can be used eg. for connecting remote branch to headquarters of company and then can branch utilize shrared resources. To headquarters can connect also remote workers from their home. In this case are used SSL certificates to authentication of user. This scenario is very required today.

This diploma thesis is focused on the implementation of the technology VoIP in the remote branch offices of a big company. There are used the current WAN lines, which have been so far used only for transfer of data. Implementation of IP telephony is extending the utilization of those lines and at the same time the costs for running of the telephone services are reduced. There are described the models for proposal and also the proposal for solution of IP telephony for a specific company.

Subject of this thesis was the issue of effectiveness of wireless networks from the perspective of services. Become acquainted with WiFi network standard IEEE 802.11 with protocols and principles of WiFi networks and services. It should be focused on the quality of service QoS. In teoretical part of this thesis are described problems considering wireless networks, layer model and types of nets used in WiFi. Standard IEEE 802.11 is analysed in details including supplements and used packets. Special attention is paid to the quality of service QoS. Next are discussed the principles and application services as VoIP, videoconferencing, video streaming and others in WiFi network. On the basis of obtained knowledge is designed extensive WiFi network with assured supply of services. For modelling and simulation of wireless network is used software development environment Opnet Modeler. Model of wireless network is used to optimize and analyse this wireless communication network. In thesis are also simulated properties of data which are sensitive to delay. In last part of thesis is created a laboratory work, which contains a submission of task, detailed theory, wiring diagram, instructions for elaboration, guidelines for simulation and example of elaboration of task. Work is about comparison of network with used 802.11b and 802.11e standard, and support of quality of service QoS.

Issue of this diploma thesis is focused on analysis of audio codecs used within IP telephony. Attention of teoretical part is given mostly to audio codecs according to ITU-T recommendations, but also to signaling protocols used here. For practical part of analysis is chosen router Cisco 2821 and IP phones Cisco 7975G. Configuration is done over operating system Cisco IOS. Chosen signaling protocol is SCCP. For analysis itself are chosen 2 analysers – L-580FX and Fluke NetTool. These are used in combination with program Wireshark. Analysed parameters are latency, packet lost, bandwidth, jitter and mean opinion score. Measured values are presented in graphs and tables and they are discussed. Next output of the thesis is laboratory excercise, which deals with analysis of audio codecs.

The master’s thesis describes IMS (IP Multimedia Subsystem) in terms of IMS core ele- ments (functional description, different implementation, signaling etc.) Communication protocols SIP and DIAMETER, together with SNMP protocol, which is used for collecting data are briefly described in this thesis.Thesis is also describing various IMS projects to- gether with Open IMS project, for whom was this surveillance system designed. Next part deals with architecture design of surveillance system along with management options implemented in surveillance system for users and administrators. The main part of master’s thesis deals with the description of the surveillance system for the experimental school Open IMS network and describes the remote configuration of core elements and monitoring of network traffic, together with the monitoring servers performance. The most of the data in the designed surveillance system are processed into graphs, which are regularly updated. The final part of master’s thesis describes the configuration and implementation of monitoring tools MRTG and NfSen that were used in created web based surveillance system.

This master thesis deals with the problem of localization of the caller to the emergency line with focus on VoIP calls. It contains general description of the main active and passive geolocation methods, and explains their function. The paper analyzes market share of different VoIP clients and describes the program Skype. The focus of this work is to create an application for geolocation of the caller using analysis of VoIP transmission. The application gains IP address of the caller by capturing packets and displays his/her location on the map. The coordinates are obtained from the MaxMind GeoLite City database which been chosen by evaluating objective parameters as the most suitable for desired use.

This work explores, analyzes and rate infuence of VoIP attacks on open source pbx functionality. It describes how voice over IP attacks are achieved according to security standards. There are described concepts and basics of VoIP networks with orientation on facts necessary to understand analyzed actions and measurements in theoretical part. In practical part, there is described realization of attack tests according to instructions with first orientation on initial checking of testing device, pbx’s and security attack possibilities and then complex creation and testing of attack scenarios types such as fuzzing and denial of service attacks.

Diploma thesis is focused on the supporting of Quality of Services in wireless networks, especially in the Linux operation systems. The topic is connected not only with OS, but also with the wireless standard, which supports QoS in wireless networks called IEEE 802.11e. QoS is needed especially for time-consuming data transfers in real time. The theoretical part deals with the theoretical analysis of the issue of the QoS support. There are described parameters, which occurred in quality of services support. This section also deals with the division of services that are used to transmit data across computer networks. It also describes the QoS support in wireless networks according 802.11e, its implementation and methods of accessing a medium with a without possibility of traffic. This part is followed by a description of QoS support in UNIX operating systems. The chapter describes how is the QoS support designed in these operating systems. There are also characterized concrete tools which are used for control the data flow in the operating systems using Linux. At the end the theoretical part deals with different types of queues and methods used in linux OS. In the practical part of the thesis, there are various designed topologies and scenarios to verify the functionality of QoS support in wireless networks using a Unix system. These chapters show the results of different tests at selected transmission data streams that are sensitive to transmission time. There is also verified cooperation of QoS support between devices operating on the network and data link layers. The output of this work is to design a laboratory exercise for the subject Network Architecture. This exercise is focused on familiarization with the QoS support functionality in wireless networks and in Unix-like operating systems. This chapter also describes the devices and programs that are needed to measure this task. The last part of the chapter describes the procedure for the preparation of the measuring station. For this laboratory task, there is an inserted manual in the annex.

The master’s thesis presents routing protocols, SIP handshake, describes modern VoIP networks and its features. Thesis is primary focused on networks with integrated MPLS. The most known advantages and disadvantages were described of modern network based on such technology. Further, networks and a router with installed Cisco Call Manager Express 7.1 were configured, which is provided by CISCO. For recreating of fully working telephone network IP PBX10 has been used from SMC Networks. For connection between different phones within these integrated networks, SIP trunk was configured on SMC PBX10 as well as on router, which is connecting three configured Cisco IP phones. Each phone has its own number according to the dial plan. For calls from one network to another the special pattern has been established, so the number of each caller can be easily identified by added digit. On one of the CISCO routers was shown a configuration of MPLS and OSPF protocols. With an analyzer VePAL TX300e, the lab network has been measured to analyze QoS parameters of the network according to standard RFC 2544. Thesis also gives references to lab devices, which have been used accordingly to the work.