In todays society, the internet is all around us and use it in our everyday life. From checking the schedule to signing on to your bank. This has made it so that data is traveling all around us, from our walls filled with cables to the air in wireless form. But data takes time to travel from computer to computer, and it has the problem that data is not saved just on its own. It can be lost or it can be corrupted. This means that we need safeguards in place for the data. Go-Back-N is a protocol that makes it so that data always gets to the recipient by resending data that has been lost. But it takes time. Also, the sender can't send as much data as it wants. There needs to be a window where a certain amount of data can be sent and accepted before  the sender can send out more. But what is the relation between the delay and window size? In this thesis, we look at the relationship between them and how it effect the protocol if the delay is turned down, or the window size is increased.

Cílem bylo navrhnout dva simulační scénáře v prostředí NS-3. První scénář obsahuje ARQ (Automatic Repeat Request) metody v TCP (Transmission Control Protocol). Je v něm porovnání Stop-and-Wait, Go-Back-N a Selective-Repeat metod. Teoretická část obsahuje TCP a ARQ. Druhý scénář je o způsobech přenosu zpráv. Vytvořený scénář převážně s komutací paketů a buněk a teoretické základy jsou obsaženy v práci. Je v něm porovnání metod komutací s různou velikostí paketu/buňky, počtem uzlů a důsledek zpoždění v každé metodě. Scénáře jsou ve formě laboratorní úlohy s instrukcemi k vypracování.

The goal of this thesis was to design two complex scenarios with focus on different kinds of transmission in packet-switched networks. First scenario is about ARQ (Automatic Repeat Request) protocols. It consists of introduction to Stop-and-Wait, Go Back N and Selective Repeat protocols and their comparison. Second scenario compares unicast, multicast, broadcast and anycast transmission methods. Both scenarios use applications which can simulate particular methods or protocols. These applications along with virtual environments are used for demonstration of characteristics of these methods/protocols.

The diploma thesis aimed at the study of the topic of communication protocols and several transmission modes, as well as ARQ (Automatic Repeat Request) mechanisms. Subsequently, the task was to design and describe individual scenarios for their simulation. As a part of solving the mentioned task, it was necessary to create an application that allows the emulation of the behaviour of communication protocols without the need for a transmission in the real network a nd the requirements for the edition of the source code. The application was created in the Microsoft Visual Studio 2017 development environment using the C# programming language and .NET framework and it consists of a library and a graphical interface. The output of the solution is the application of a mode simulator of the data transmission in the network with two scenarios with the prepared input situations in the frame of graphical environment together with instructions, additional tasks and sample solutions. The program allows the simulation of the behaviour of communication protocols between the client and the server without the need for a transmission in a real network. In conclusion, the simulator of data transfer was created in the form of the desktop application which contains two scenarios. The first scenario is used to simulate ARQ mechanisms and the second one is active in the simulation of commutation of messages, circuits, packets or cells.