The differences between networks of mobile operators can be in their achitecture or the optimization of each network. The architecture is standardized which means there will only be differences in the willingness of mobile operators to invest in newer network elements. Network optimization is more important. The way of optimization isn't strictly given and depends on how the operator deals with it. The most important attribute in optimization is balance. The operators try to achieve balance among three important parameters. Those are capacity, coverage and maintaining QoS. Optimization depends on RRM algorithms. The algorithms include various functions such as admission control, congestion control, handover control, power control, etc. These elements don’t only affect the optimization but also affect each other, because they cooperate with each other. For example, an incorrect admission control of the network leads either to frequent network congestion because of a large number of participants in the network (participants are dissatisfied with the services offered by the operator) or to low utilization of the network because of too few participants in the network (the operator is dissatisfied because he is losing the possible earnings). Neither of these posibilities is good for the mobile operator, therefore it is important that the admission control is well balanced.

This Master thesis is about multicast in mobile network 3rd generation UMTS(Universal Mobile Telecommunacitions System). UMTS network primary designs for data transfers and supports new services as real-time transfers of multimedia streams. This is reason why mobile network was equiped also with multicast service. When a lot of users want to receive same data (e.g. tv program) the network excessives load of transmission same data and the server have to keep connection to each user. Group 3GGP developed multicast service for UMTS, which name is MBMS (Multimedia Broadcast and Multicast Service). Thesis analyses function of this service in mobile network. First part describes basic principles of UMTS network and its structure. Next part focuses on change of main node (SGSN and GGSN) and of new node BM-SC(Broadcast-Multicast Service Center). This new node is main node for control of multicast transmission. BM-SC connects to server which provides multicast data for users and provisions individual phase of MBMS session. It was created new procedure which supports multicast session (e.g. Activate MBMS service). Next part focuses on GPRS Tunneling Protocol (GTP). This protocol is used for transfers control and user’s data in tunnels inside core network. This part describes structure of data and control messages. Last part analyzes multimedia transfers in UMTS with program Opnet Modeller.

This diploma thesis describes a possibility of application protocol implementation in OPNET Modeler simulation environment. It presumes that this application protocol is going to use TCP protocol for their communication on transport layer. The first part of thesis is focused on a description of TCP. It is a connection oriented, reliable and confirmed protocol which maintains sequence of transmitted data. This data is after receiving positively confirmed. In the second chapter are described the main functions of OPNET Modeler simulation environment. OPNET is hierarchical divided into four editors. Each editor has a specific function by creating a network and setting his behavior. There is also focused on the two lowest layers of OPNET Modeler and their components in detail, which are participating at usage TCP on transport layer to communication. Implemented applications communicate by sockets, which are created and destroyed on request. Communication is controlled by manager process, whose function is maintenance particular connections and redirect dataflow into relevant process. This manager put in action as well a process, which simulates a single TCP. In the practical part I made two applications: one is a client type and a second one is a server type. Both applications are using TCP on transport layer. The establishment of connection initiates a client, who is sending a request to the server for a data. Then server sends back data in desired quantity. After sending the entire data, client terminates the connection. The result of simulation is statistics, where we pictured the size of the transferred data, a number of transferred packets and other parameters typical for TCP.

These times the third generation cellular networks are getting in use increasingly and they dramatically exceed the parameters of second generation networks. Third generation networks are in contrast to older generations data-oriented, providing better maintenance in data and multimedia services. The most widespread third generation network is the UMTS, designed as succesor of GSM network. Master’s thesis is focused on parameters and communication protocols of radio interface of UMTS network. Parameters of radio interface affect the behaviour of mobile terminal through utilization of network services. This thesis describes individual protocols of radio interface and individual procedures, which the mobile terminal have to perform through its staying in the cell. Theoretical part of this thesis considers description of the UMTS network and individual procedures and parameters. Practical part is focused on measuring the radio interface and individual procedures in real UMTS networks. Some procedures are simulated in network simulation software. This thesis includes a lab task focused on this thema.

The diploma thesis gives the overall information about the field of wireless networks of standards 802.11 and Quality of Service (QoS). The practical measurements describe the reactions of multimedia dataflows in the networks 802.11a/b/g/n. The individual standards, offered services, access methods and the network architecture are analyzed in the theoretical part. In the following part there is written about QoS and its basic parameters. Moreover, the standard 802.11e and the question of QoS in the wireless networks are explained in a detailed way. The first part of the practical measurement is focused on the networks 802.11b/g/n. All main network statistics are measured when using the wireless stations and routers. The projection and implementation of the wireless network in the Opnet Modeler is included in the next part. The individual simulations WLAN in the Opnet Modeler are comparing the networks 802.11a/b/g. The analysis of the key QoS statistics is undertaken; the measured data are clearly displayed in the charts and schemes. The interpreted results are concluded and justified.

The Master´s Thesis describes laboratory exercises for Advanced communication technology subject. Exercises are created in Opnet IT Guru aplication. Each exercise has detailed instructions according to which can be realized whole exercise. Each exercise also contains individual task, where are checked knowledge gained from studies of example exercise. Exercises are based on issues of routing in autonomous systems, protocol BGP, protocols TCP and UDP and issues of QoS in IP networks.

Recent research supports the eventual convergence of wireless LAN (WLAN) and cellular systems in order to achieve the IMT-2000 (3G) requirement for 2 Mbps indoor capacities. The WLAN access point can be enhanced to either incorporate or supplant the transmission and packet data capabilities in the cellular network. This research used OPNET™ to design, implement, and test a network system level simulation environment to allow investigators to study the issues and trade-offs for interworking the infrastructure-based WLAN technologies into 3G mobile subscriber cellular systems. The specific contribution of this research was to augment the current OPNET™ model library by creating an enhanced user equipment node (UW) and an enhanced WLAN access point node (UWLAN_AP). The UW was augmented with the capability to selectively gain network access through either a UMTS Node-B or through a 3G-aware WLAN access point. The UWLAN_AP was made 3G-aware by augmenting it with the capability to process UMTS control messages in order to build an access control table to support UMTS authentication and access control. Together, the UW and UWLAN_AP create a simulation framework for interworking the WLAN technology into UMTS as an alternate radio access network for supporting "hot spots." This research is the foundation to allow investigators to identify signaling and data transfer mechanisms that leverage the capabilities of WLAN while supporting cellular service provisioning and accountability requirements for current and future systems. / Master of Science

Internet Protocol version 6 (IPv6) is being adopted in networks around the world as the Internet Protocol version 4 (IPv4) addressing space reaches its maximum capacity. Although there are IPv6 applications being developed, there are not many production IPv6 networks in place in which these applications can be deployed. Simulation presents a cost effective alternative to setting up a live test bed of devices to validate specific IPv6 environments before actual physical deployment. OPNET Modeler provides the capability to simulate the IPv6 protocol and System-in-the-Loop, an add-on module, allows for real communication traffic from physical devices to be converted and sent over the simulated network. This research has developed a campus framework, modeled after the Virginia Tech Blacksburg campus, to verify and validate standard and custom IPv6 applications. Specifically, the framework was used to test MT6D, a custom IPv6 security application developed in the Virginia Tech IT Security Lab (ITSL) as well as test Voice over IP (VoIP) as a somewhat bandwidth demanding benchmarking standard application. The work presented shows that simulation helped to identify potential issues within the applications and verified the results after fixes were applied. It also reveals challenges and shortcomings of OPNET Modeler's IPv6 implementation and presents potential solutions to these problems. / Master of Science

Les réseaux de capteurs sans fils sont de plus en plus utilisés dans des applications de surveillance de grands systèmes (feux de forêt, gaz dans les galeries minières, éthologie, ...). Une caractéristique de ces applications est que la topologie du réseau va être dynamique : soit les capteurs sont géographiquement mobiles (dispersion d'une nappe de pétrole), soit les conditions environnementales évoluent et modifient les capacités de communication des capteurs entre eux. Aussi, d'un système connexe, on peut évoluer vers un système clustérisé qui présente une rupture de la connectivité globale, et donc du système d'information. Une solution consiste à utiliser un (ou des) collecteur(s) des mesures (par exemple un robot mobile) qui va rétablir une connectivité discrète pour reconstituer à des échéances fixes un système d'information cohérent. Nous avons proposé un algorithme de clustering du réseau de capteurs sans fils adapté à la dynamique de sa topologie. La métrique choisie prend en compte la densité et la mobilité des noeuds, ainsi que leur énergie résiduelle. Ensuite, nous avons conçu un protocole de couche session permettant au collecteur de reconstruire le contexte de communication avec les clusters précédemment visités, sachant qu'ils ont pu évoluer en nombre, dispersion, fusion, ... Pour ce faire, il faut générer dynamiquement une trajectoire optimale du collecteur, en se basant sur un modèle d'estimation de la topologie, en prenant en compte les exigences applicatives (fréquence et volume des informations remontées). Pour la validation de l'algorithme de clustering et du protocole de couche session proposés, nous avons défini un modèle de noeud capteur que nous avons intégré à l'environnement de simulation Opnet / Wireless sensor networks are increasingly used in applications for monitoring large systems (forest fires, gas in the mine galleries, ethology, ...). A characteristic of these applications is that the topology of the network will be dynamic, either the sensors are geographically mobile (dispersion of an oil slick) or environmental conditions change and modify the communication capabilities of these sensors. Also, from a connex system, we can move to a clustered system that presents a discontinuity of the global connectivity, and therefore of the information system. One solution is to use one (or more) collector (s) that will restore a discrete connectivity at fixed deadlines to reconstruct a coherent information system. We have proposed a clustering algorithm of the wireless sensor network which is adapted to the dynamics of its topology. The chosen metric takes into account the density and the mobility of nodes and their remaining energy. Then we designed a session-layer protocol allowing the collector to reconstruct the context of communication with the previously visited clusters, knowing that they have evolved in number, splitting, merging, ... To do this, it is necessary to dynamically generate the trajectory of the collector, on the basis of a model of the topology, taking into account the application requirements (frequency and volume of the collected information). For the validation of the proposed clustering algorithm and the session-layer protocol, we defined a sensor model we have integrated in the Opnet simulation environment

Šiuo metu yra sukurta nemažai priemonių aptikti įvairiausias DDoS atakas, tačiau siekiant sustabdyti arba bent sušvelninti DDoS atakų poveikį yra nuveikta labai nedaug. Yra labai sunku pasirinkti tinkamą DDoS atakos atrėmimo metodą. DDoS atakų atrėmimo metodų analizė galėtų padėti pasirinkti tinkamiausią metodą. „BGP DDoS Diversion“ atakų atrėmimo metodas yra vienas efektyviausių ir mažiausiai kaštų reikalaujantis metodas. Šis metodas įgyvendinamas panaudojant BGP protokolą. Ataka yra atremiama kuomet BGP protokolo pagalba yra paskelbiama tik dalis tinklo. DDoS atakos duomenų srautas tokiu atveju yra nukreipiamas į paskelbtą tinklo dalį, o kita tinklo dalis lieka nepažeista atakos. Interneto paslaugų teikėjai naudodami „BGP DDoS Diversion“ atrėmimo metodą gali apsaugoti savo tinklą nuo visiško nepasiekiamumo. Šiame tyrime buvo išnagrinėti DDoS atakų atrėmimo metodai. Išsamiai analizei buvo pasirinktas „BGP DDoS Diversion“ atrėmimo metodas. Metodo analizei buvo pasirinkta virtuali terpė. Sudaryti virtualią terpę buvo pasirinkta OPNET tinklų modeliavimo programa. Panaudojant OPNET modeliavimo įrangą, buvo sukurtas virtualus tinklas, veikiantis Interneto tinklo pagrindu. Sukurtame tinkle buvo įgyvendintas „BGP DDoS Diversion“ atakų atrėmimo metodas. Šiame darbe yra pateikta minėto atrėmimo metodo veikimo charakteristikų analizė. / Nowadays there are lot of ways how to detect various types of DDoS attacks, but in order to stop, or at least to mitigate the impact of such DDoS attacks not enough work is done. It is very difficult to choose the right DDoS mitigation method. The research of DDoS attacks mitigation can provide a good manual how to choose the most appropriate method. „BGP DDoS Diversion“ method is one of the most effective and least cost to deliver DDoS mitigation method. This method is implemented using BGP protocol. BGP diversion mechanism is used to announce a specific part of the provider‘s network to (a part of) the Internet. Announcing a specific part of this network will divert the DDoS traffic and thereby prevent other parts of the provider‘s network becoming unreachable. This gives the provider the ability to continue providing services of the rest of his custumers. This research was based on analyzing the DDoS mitigation methods. For the better analyzes the „BGP DDoS Diversion“ method was chosen. To analyze this method the virtual environment was the best way to accomplish this task. OPNET modeler software was chosen to create the virtual environment. Using OPNET the virtual network was created. Virtual network was based on Internet network standards. „BGP DDoS Diversion“ method was implemented and tested in the virtual network. This research provides the detail analyzes of „BGP DDoS Diversion“ method.