The Media Layers of the OSI (Open Systems Interconnection) Reference Model: A Tutorial

The Media Layers of the open systems interconnection (OSI) reference model convert bits to packets. It is a very important aspect of network communication and consists of various networking protocols. At the lowest level the physical layer deals with Media, Signal and Binary Transmission of Bits. Then there is the Data Link layer which deals with media access control (MAC) and logical link control (LLC) Physical Addressing of Frames, for example Ethernet. Finally, there is the Network layer which deals with Path Determination and IP Logical addressing of Packets. This article gives a review of these Media Layers and will contribute to adding knowledge for a networking novice while consolidating concepts for an experienced professional or academic

Multipath Communication in QKD Networks

Táto diplomová práca sa zaoberá technológiou Quantum Key Destribution (QKD) a simuláciou tejto technológie pomocou simulátora QKDNetSim. Teoretická časť práce obsahuje úvod do problematiky kvantovej distribúcie kľúčov, ktorá sa nespolieha na matematické problémy ako konvenčne používaná kryptografia ale na zákonitosti kvantovej mechaniky. Praktická časť práce popisuje rozšírenie simulátoru QKDNetSim o viaccestnú komunikáciu a následnú implementáciu. Záver práce sa venuje popisu a experimentálnemu overeniu viaccestnej komunikácie v simuláciách následne zhodnoteniu dosiahnutých výsledkov.This diploma thesis deals with Quantum Key Destruction (QKD) technology and the simulation of this technology using the QKDNetSim simulator. The theoretical part of the thesis contains an introduction to the issues of quantum key distribution, which does not rely on mathematical problems such as conventionally used cryptography but on the laws of quantum mechanics. The practical part of this thesis describes the extension of the QKDNetSim simulator by multipath communication and subsequent implementation. The conclusion of the work is devoted to the description and experimental verification of multipath communication in simulations and subsequent evaluation of the achieved results.440 - Katedra telekomunikační technikyvýborn

The new ecosystem of the digital age: Impact of blockchain technology on the accounting environment and financial statement fraud detection

The agency theory is an underlying framework for the installation of corporate governance roles in business enterprises. Their function to shield from financial statement fraud remains a shield with lacks that allow the occurrence of unsolved and intrinsic misbehaviour in business conduct. Technological developments have not been able to solve this issue, still waiting for a liberator from these well-known chains. One is seen in the use of Blockchain technology, the framework that builds trust among untrusting participants in networks such as Bitcoin or Ethereum. Since its mainstreaming popularity, researchers, corporations, and advocates foresee a great impact on the accounting industry that stems from the use of Blockchain. Taking this opportunity, this work investigates on these assumptions by reviewing literature on the domain, using case studies of former financial statement frauds to frame the fraudster’s profile, and applying it in the suggested scenario of blockchain-based accounting. By doing so, the use of permissioned blockchains raises doubt in a scenario that is shaped by management override activities, causing severe adversely affections to tiers in an ecosystem that trusts a technology and its “immutable” records.A teoria da agência é um quadro subjacente para a instalação de funções de governação empresarial em empresas comerciais. A sua função de protecção contra a fraude de declarações financeiras continua a ser um escudo com carências que permitem a ocorrência de comportamentos incorrectos não resolvidos e intrínsecos na conduta empresarial. Os desenvolvimentos tecnológicos não foram capazes de resolver esta questão, ainda à espera de um libertador destas bem conhecidas cadeias. Vê-se na utilização da tecnologia Blockchain, a estrutura que gera confiança entre os participantes não confiantes em redes como a Bitcoin ou a Ethereum. Desde a sua popularidade de mainstreaming, investigadores, empresas e defensores prevêem um grande impacto na indústria da contabilidade que resulta da utilização da Blockchain. Aproveitando esta oportunidade, este trabalho investiga estes pressupostos através da revisão da literatura sobre o domínio, utilizando estudos de caso de antigas fraudes em demonstrações financeiras para enquadrar o perfil do fraudador e aplicando-o no cenário sugerido de contabilidade baseada em cadeias de bloqueio. Ao fazê-lo, a utilização sugerida de cadeias de bloqueio autorizadas levanta dúvidas num cenário que é moldado por actividades de substituição da gestão, causando graves afecções negativas a camadas num ecossistema que confia numa tecnologia e nos seus registos "imutáveis"