This is a bachelor thesis regarding the performance differences for hosting a web-application in a virtualized environment. We compare virtual machines against containers and observe their resource usage in categories such as CPU, RAM and disk storage in idle state and perform a range of computation experiments in which response times are measured from a series of request intervals. Response times are measured with the help of a web-application created in Python. The experiments are performed under both normal and stressed conditions to give a better indication in to which virtualized environment outperform the other during different scenarios. The results show that virtual machines and containers remained close to each other in response times during the first request interval, but the containers outperformed virtual machines in terms of resource usages while in idle state, they had less of a burden on the host computer. They were also significantly more rapid in terms of response times. This is also most noticeable during stressed conditions in which the virtual machine almost doubled its sluggishness.

V informatice je pojem entropie obvykle znám jako nahodný proud dat.  Tato práce krátce shrnuje metody generovaní nahodných dat a popisuje generátor náhodnych čísel, jež je obsažen v jádře operačního systému Linux.  Dále se práce zabývá určením bitové rychlosti generování nahodných dat tímto generátorem ve virtualizovaném prosředí, které poskytují různé hypervizory.  Práce popíše problémy nízkého výkonu generátory nahodných dat ve virtualním prostředí a navrhne postup pro jejich řešení.  Poté je nastíňena implementace navržených postupů, které je podrobena testům a její vysledky jsou porovnány s původním systémem. Systém pro distribuci entropie může dále vylepšit množství entropie v sytémovém jádře o několik řádu, pokud je připojen k vykonému generátoru nahodných dat.

The thesis is focused on the new IT trend – virtualization. Below are described the types of virtualization, as well as different implementations of it. In the following chapters there will be described the TCP and ICMP protocols, as well as the SSH services. The last part of this work is dedicated to measurements where there will be highlighted the advantages and disadvantages of virtualization.

The master’s thesis deals with Domain Name System (DNS) and its practical use. It describes hierarchy of domain names, resource record types, protocol used, as well as DNSSEC extension. The most utilized implementations of authoritative and recursive DNS servers are presented. Virtualization, containers and other tools with potential use in labs are described. Two lab scenarios in virtualized environment with instructions for students were designed and developed in this thesis.

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 theses explains the Evolution Packet System (EPS) and subsystem IP Multimedia Subsystem (IMS). It also informs how these systems cooperate and through which interfaces the main data and signals between these two technologies are transfered. The thesis includes practical section, in which installation and configuration of sections of the IMS system including its "core", and application and medial server. For verification of the functionality of the system, two dissimilar clients are installed, and emulator WAN is applied for simulation of Internet. The product of the theses is the design of the laboratory exercise drafted in such a way that it can be solved by students less knowledgeable of the issues.