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This thesis deals with predicting the latency between two network nodes, such as the two stations, two servers or server and station. The main reason for adoption of effective latency prediction techniques is the elimination of network load caused by unnecessary repeated transmissios or by direct measurement of the latency. Of the many proposed methods of latency estimation, this thesis is focused on methods using artificial coordinate systems with primary focus on the Vivaldi algorithm. Characteristics of the latency prediction methods and properties of various coordinate systems used in practice are evaluated. The issue of the number of dimensions of space defined only by the latency matrix between nodes is also mentioned. Furthermore, some other systems, based on logical clustering of nearby nodes, are mentioned. Description of simulation software VivaldiMonitor developed as part of the thesis is included. The primary purpose is analysis of the behavior of overlay networks implementing Vivaldi algorithm with less than a few hundred nodes. The Vivaldi algorithm is assessed by several simulations carried out using the aforementioned software.

Dans les prochaines années, l’Internet des objets (IoT) constituera l’une des applications générant le plus de données. Actuellement, les données de l’IoT sont stockées dans le Cloud. Avec l’augmentation du nombre d’objets connectés, la transmission de la grande quantité de données produite vers le Cloud génèrera des goulets d’étranglement. Par conséquent, les latences seront élevées. Afin de réduire ces latences, le Fog computing a été proposé comme un paradigme étendant les services du Cloud jusqu’aux périphéries du réseau. Il consiste à utiliser tout équipement localisé dans le réseau (ex. routeur) pour faire le stockage et le traitement des données. Cependant, le Fog présente une infrastructure hétérogène. En effet, ses équipements présentent des différences de performances de calcul, de capacités de stockage et d’interconnexions réseaux.Cette hétérogénéité peut davantage augmenter la latence du service. Cela pose un problème : le mauvais choix des emplacements de stockage des données peut augmenter la latence du service. Dans cette thèse, nous proposons une solution à ce problème sous la forme de quatre contributions : 1. Une formulation du problème de placement de données de l’IoT dans le Fog comme un programme linéaire. 2. Une solution exacte pour résoudre le problème de placement de données en utilisant CPLEX, un solveur de problème linéaire. 3. Deux heuristiques basées sur le principe de “diviser pour régner” afin de réduire le temps du calcul de placement. 4. Une plate-forme expérimentale pour évaluer des solutions de placement de données de l’IoT dans le Fog, en intégrant la gestion du placement de données à iFogSim, un simulateur d’environnement Fog et IoT. / In the coming years, Internet of Things (IoT) will be one of the applications generating the most data. Nowadays, IoT data is stored in the Cloud. As the number of connected objects increases, transmitting the large amount of produced data to the Cloud will create bottlenecks. As a result, latencies will be high and unpredictable. In order to reduce these latencies, Fog computing has been proposed as a paradigm extending Cloud services to the edge of the network. It consists of using any equipment located in the network (e.g. router) to store and process data. Therefore, the Fog presents a heterogeneous infrastructure. Indeed, its components have differences in computing performance, storage capacity and network interconnections. This heterogeneity can further increase the latency of the service. This raises a problem: the wrong choice of data storage locations can increase the latency of the service. In this thesis, we propose a solution to this problem in the form of four contributions: 1. A formulation of the IoT data placement problem in the Fog as a linear program. 2. An exact solution to solve the data placement problem using the CPLEX, a mixed linear problem solver. 3. Two heuristics based on the principle of “divide and conquer” to reduce the time of placement computation. 4. An experimental platform for testing and evaluating solutions for IoT data placement in the Fog, integrating data placement management with iFogSim, a Fog and IoT environment simulator.

The ubiquity and speed of Internet access led over the past decade to an exponential increase in the use of thin clients and cloud computing, both taking advantage of the ability to remotely provide computing resources. The work investigates the role of remote display Protocol in behavioral biometric systems based on free-text keystroke dynamics. Authentication based on keystroke dynamics is easy in use, cheap, invisible for user and does not require any additional sensor.I n this project I will investigate how network characteristics affect the keystroke dynamics pattern in remote desktop scenario. Objectives: The aim of this project is to investigate the role of remote display Protocol in behavioral biometric system based on free-text keystroke dynamics, by measuring how network characteristics influence the computation of keystroke pattern in Virtual Desktop Infrastructure (VDI). Method: This thesis will answer all of its research question with the help of a Systematic Literature Review (SLR) and an Experiment. Literature review was conducted to gather information about the keystroke dynamics analysis, the applied algorithms and their performance; and to clarify the controlled changes of networking performance in VDI based scenario. Using the acquired knowledge, implemented keystroke dynamics pattern algorithm based on Euclidian distance statistical method, designed an experiment and performed a series of tests, in order to identify the influence of remote display protocol to keystroke pattern. Results: Through the SLR, keystroke dynamics analysis working structure is identified and illustrated, essential elements are summarized, and a statistical approach based on Euclidian distance is described; a technique to simulate and measure networklatency in VDI scenario is described including essential elements and parameters of VDI testbed. Keystroke analysis algorithm, dataset replication code and VDItestbed are implemented. The controlled experiment provided measurements of the metrics of the algorithm and network performance mentioned in objectives. Conclusions: During experimentation, I found that timing pattern in the keystroke dynamics data is affected by VDI in normal network conditions by 12% in average. Higher latency standard deviation, jitter, packet loss as well as remote display protocol overheads have a significant combined impact onto keystroke pattern. Moreover I found what maximum possible delay values does not affect keystroke pattern in a larger extent.

This thesis presents an evaluation of the performance, in terms of throughput and latency, of two Media Access Control (MAC) mechanisms in Underwater Acoustic Networks (UANs), using a model designed in the COTS simulation tool OPNET 10.5. The carrier sense multiple access with collision avoidance is the predominant approach for implementing the MAC mechanism in UANs. However, the underwater acoustic environment is characterized by extreme propagation delays and limited bandwidth, which suggests that an Aloha-like scheme may merit consideration. The performance of these two schemes was compared with respect to two topologies: tree and grid. The results showed that an Aloha-like scheme that does not segment messages outperforms the contention-based scheme under all load conditions, in terms of both throughput and latency, for the two topologies. This thesis is the first to establish that Aloha-like MAC mechanisms can be more than a limited alternative for lightly loaded networks; more specifically, they can be the preferred choice for an environment with large propagation delays. / Lieutenant Commander, Portuguese Navy

Aquesta tesi recull la recerca al voltant de les pràctiques musicals mitjançant xarxes d'ordinadors realitzada al Grup de Tecnologia Musical de la Universitat Pompeu Fabra a Barcelona entre l'any 2001 i el 2005. Parteix del treball dut a terme durant la última dècada dins del camp del Treball Cooperatiu amb Ordinadors (Computer-Supported Cooperative Work, CSCW) el qual aporta els mecanismes de col·laboració els quals, des de un punt de vista musical, poden ser estudiats en diversos escenaris: composició, interpretació, improvisació i educació.La primera contribució d'aquest treball és un anàlisi exhaustiu i una classificació sistemàtica del Treball Cooperatiu amb Ordinadors per Aplicacions Musicals. Aquest anàlisi es va centrar en la identificació de propostes innovadores, models i aplicacions, amb un especial èmfasi en la natura compartida de la comunicació mitjançant internet. El concepte d'Entorns Sonors Compartits va ser presentat i implementat en una aplicació prototip anomenada Public Sound Objects (PSOs).La segona gran contribució d'aquesta tesi consisteix en l'estudi del possibles mètodes per reduir les interrupcions degudes als retards inherents en la comunicació musical entre xarxes molt allunyades. A partir de l'experimentació i avaluació al laboratori les tècniques Network Latency Adaptive Tempo i Individual Delayed Feed-Back van ser definides i implementades dins del prototip PSOs.Al llarg del desenvolupament del PSOs es van haver de resoldre altres problemes, com per exemple, el disseny d'interfícies en funció del comportament per a aplicacions amb interfícies desacoblades, la superació dels diversos sistemes de seguretat de les xarxes informàtiques i les possibilitats d'escalabilitat de diverses aplicacions d'àudio per a web.Durant l'elaboració d'aquesta tesi es van discutir diferents perspectives per resoldre problemes relacionats amb la pràctica musical mitjançant ordinadors, aplicant diferents punts de vista provinents de l'estudi psicosocial dels processos de col·laboració musical al món de la informàtica i de la tecnologia musical. / This dissertation derives from research on musical practices mediated by computer networks conducted from 2001 to 2005 in the Music Technology Group of the Pompeu Fabra University in Barcelona, Spain. It departs from work carried out over the last decades in the field of Computer-Supported Cooperative Work (CSCW), which provides us with collaborative communication mechanisms that can be regarded from a music perspective in diverse scenarios: Composition, Performance, Improvisation or Education.The first contribution originated from this research work is an extensive survey and systematic classification of Computer-Supported Cooperative Work for Music Applications. This survey led to the identification of innovative approaches, models and applications, with special emphasis on the shared nature of geographically displaced communication over the Internet. The notion of a Shared Sonic Environments was introduced and implemented in a proof-of-concept application entitled Public Sound Objects (PSOs).A second major contribution of this dissertation concerns methods that reduce the disrupting effect of network latency in musical communication over long distance networks. From laboratorial experimentation and evaluation, the techniques of Network Latency Adaptive Tempo and Individual Delayed Feed-Back were proposed and implemented in the PSOs prototype.Over the course of the PSOs development other relevant and inspirational issues were addressed, such as, behavioral-driven interface design applied to interface decoupled applications, the overcome of network technology security features and system scalability for various applications in audio web services.Throughout this dissertation conceptual perspectives of related issues to computer-mediated musical practices dissertation were widely discussed, conveying different standpoints ranging from a Psycho-Social study of collaborative music processes to the Computer Science and Music Technology point of view.

This Bachelor thesis presents an in-depth investigation into the effects of RogueAccess Point interference within Internet of Things networks. The study focuses onthe impact of rogue APs on the modulation and coding scheme indices, round triptime, and overall network performance. The presence of a rogue AP was found toshift devices from dual-stream to single-stream operation, causing a decrease in themodulation and coding scheme indices and data rates. Additionally, a significantincrease in round trip time was observed, emphasizing the detrimental impact ofrogue AP interference on network latency. The insights gained from this researchcontribute to a greater understanding of the challenges posed by rogue APinterference. This deeper comprehension paves the way for devising effectivestrategies to mitigate these impacts, thereby enhancing the reliability, security, andperformance of IoT networks. / Detta examensarbete presenterar en grundlig undersökning av effekterna avstörande åtkomstpunkter (Rogue Access Points) inom nätverk för Sakernas Internet(Internet of Things). Studien fokuserar på störande åtkomstpunkter inverkan påmodulations- och kodningsschemaindex (MCS), round trip time och denövergripande nätverksprestandan. När en störande åtkomstpunkt blev närvarandetvingades enheterna att omställa sig från att använda dubbelströmsoperation tillenkelströmsoperation, vilket ledde till en minskning av MCS-index ochdatahastigheter. Dessutom observerades en betydande ökning av RTT, vilketbetonar den skadliga inverkan av störande åtkomstpunkt interferens pånätverkslatens. De insikter som vunnits bidrar till en större förståelse för deutmaningar som störande åtkomstpunkter interferens medför. Denna djupareförståelse banar väg för att utforma effektiva strategier för att mildra dessa effekter,vilket i sin tur förbättrar tillförlitligheten, säkerheten och prestanda för IoT-nätverk.