Transmission Control Protocol (TCP) designed to deliver seamless and reliable end-to-end data transfer across unreliable networks works impeccably well in wired environment. In fact, TCP carries the around 90% of Internet traffic, so performance of Internet is largely based on the performance of TCP. However, end-to-end throughput in TCP degrades notably when operated in wireless networks. In wireless networks, due to high bit error rate and changing level of congestion, retransmission timeouts for packets lost in transmission is unavoidable. TCP misinterprets these random packet losses, due to the unpredictable nature of wireless environment, and the subsequent packet reordering as congestion and invokes congestion control by triggering fast retransmission and fast recovery, leading to underutilization of the network resources and affecting TCP performance critically. This thesis reviews existing approaches, details two proposed systems for better handling in networks with random loss and delay. Evaluation of the proposed systems is conducted using OPNET simulator by comparing against standard TCP variants and with varying number of hops.

No description available.

The Web, being the most popular component of the Internet, has been transformed from a static information-serving medium into a fully interactive platform. This platform has been used by developers to create web applications rivaling traditional desktop systems. Designing, developing and evaluating these applications require new or modified methodologies, techniques and tools because of the different characteristics they exhibit. This dissertation discusses two important areas for developing and evaluating these applications: security and data mining. In the security area, a survey using a process similar to the Goal Question Metric approach examines the properties of web application vulnerabilities. Using results from the survey, a white-box approach to identify web applications vulnerabilities is proposed. Although the approach eliminates vulnerabilities during the development process, it does not protect existing web applications that have not utilized the approach. Hence, an Anomaly-based Network Intrusion Detection System, called AIWAS, is introduced. AIWAS protects web applications through the analysis of interactions between the users and the web applications. These interactions are classified as either benign or malicious; malicious interactions are prevented from reaching the web applications under protection. In the data mining area, the method of reliability estimation from server logs is examined in detail. This examination reveals the fact that the session workload is currently obtained using a constant Session Timeout Threshold (STT) value. However, each website is unique and should have its own STT value. Hence, an initial model for estimating the STT is introduced to encourage future research on sessions to use a customized STT value per website. This research on the STT leads to a deeper investigation of the actual session workload unit. More specifically, the distributional properties of the session workload are re-examined to determine whether the session workload can be described as a heavy-tailed distribution. / Software Engineering and Intelligent Systems

No description available.

Dairy farming as one part of agriculture has thousands of year’s history. The increasingdemands of dairy products and the rapid development of technology bring dairyfarming tremendous changes. Started by first hand milking, dairy farming goes throughvacuum bucket milking, pipeline milking, and now parlors milking. The automatic andtechnical milking system provided farmer with high-efficiency milking, effective herdmanagement and above all booming income.DeLaval Automatic Milking Rotary (AMRTM) is the world’s leading automatic milkingrotary system. It presents an ultimate combination of technology and machinerywhich brings dairy farming with significant benefits. AMRTM technical milking capacityis 90 cows per hour. However, constrained by farm management, cow’s condition andsystem configuration, the actual capacity is lower than technical value. In this thesis, anoptimization system is designed to analyze and improve AMRTM performance. The researchis focusing on cow behavior and AMRTM robot timeout. Through applying knowledgediscover from database (KDD), building machine learning cow behavior predictionsystem and developing modeling methods for system simulation, the optimizing solutionsare proposed and validated. / Mjölkproduktion är en del av vårt jordbruks tusenåriga historia. Med ökande krav påmejeriprodukter tillsammans med den snabba utvecklingen utav tekniken för det enormaförändringar i mjölkproduktionen. Mjölkproduktion började inledningsvis med handmjölkningsedan har mjölkproduktionsmetoder utvecklats genom olika tekniker och gettoss t.ex. vakuum mjölkning, rörledning mjölkning, fram till dagens mjölkningskarusell.Nu har det automatiska och tekniska mjölkningssystem försedd bönder med högeffektivmjölkning, effektiv djurhållningen och framför allt blomstrande inkomster.DeLaval Automatic Milking Rotary (AMRTM) är världens ledande automatiska roterandemjölkningssystemet. Den presenterar en ultimat kombination av teknik och maskinersom ger mjölkproduktionen betydande fördelar. DeLaval Automatic Milking Rotarytekniska mjölknings kapacitet är 90 kor per timme. Den begränsas utav jordbruksdrift,tillståndet hos kor och hantering av systemet. Det gör att den faktiska kapaciteten blirlägre än den tekniska. I denna avhandling undersöks hur ett optimeringssystem kan analyseraoch förbättra DeLaval Automatic Milking Rotary prestanda genom fokusering påkors beteenden och robot timeout. Genom att tillämpa kunskap från databas (KDD), skapamaskininlärande system som förutsäger kors beteenden samt utveckla modelleringsmetoderför systemsimulering, ges lösningsförslag av optimering samt validering.

Nowadays, users of mobile devices are growing. The users expect that they could communicate constantly using their mobile devices while they are also constantly moving. Therefore, there is a need to provide disconnection tolerance of transactions in the mobile devices’ platforms and its synchronization management. System on Mobile Devices (SyD) is taken as one of the examples of mobile devices’ platforms. The thesis studies the existing SyD architecture, from its framework into its kernel, and introduces the proxy module enhancement in SyD to handle disconnection tolerance, including its synchronization. SyD kernel has been extended for the purpose of enabling proxy module. SyDSync has been constructed for synchronization with the proxy. The timeout has been studied for seamless proxy invocation. A Camera application that tries to catch a stolen vehicle has been simulated for the practical purpose of using the proxy module extension.

A Mobile Ad hoc Network (MANET) is a collection of wireless mobile nodes forming a temporary network without the need for base stations or any other pre–existing network infrastructure. In a peer-to-peer fashion, mobile nodes can communicate with each other by using wireless multihop communication. Due to its low cost, high flexibility, fast network establishment and self-reconfiguration, ad hoc networking has received much interest during the last ten years. However, without a fixed infrastructure, frequent path changes cause significant numbers of routing packets to discover new paths, leading to increased network congestion and transmission latency over fixed networks. Many on-demand routing protocols have been developed by using various routing mobility metrics to choose the most reliable routes, while dealing with the primary obstacle caused by node mobility. ¶ In the first part, we have developed an analysis framework for mobility metrics in random mobility model. Unlike previous research, where the mobility metrics were mostly studied by simulations, we derive the analytical expressions of mobility metrics, including link persistence, link duration, link availability, link residual time, link change rate and their path equivalents. We also show relationships between the different metrics, where they exist. Such exact expressions constitute precise mathematical relationships between network connectivity and node mobility. ¶ We further validate our analysis framework in Random Walk Mobility model (RWMM). Regarding constant or random variable node velocity, we construct the transition matrix of Markov Chain Model through the analysis of the PDF of node separation after one epoch. In addition, we present intuitive and simple expressions for the link residual time and link duration, for the RWMM, which relate them directly to the ratio between transmission range and node speed. We also illustrate the relationship between link change rate and link duration. Finally, simulation results for all mentioned mobility metrics are reported which match well the proposed analytical framework. ¶ In the second part, we investigate the mobility metric applications on caching strategies and hierarchy routing algorithm. When on-demand routing employed, stale route cache information and frequent new-route discovery in processes in MANETs generate considerable routing delay and overhead. This thesis proposes a practical route caching strategy to minimize routing delay and/or overhead by setting route cache timeout to a mobility metric, the expected path residual time. The strategy is independent of network traffic load and adapts to various non-identical link duration distributions, so it is feasible to implement in a real-time route caching scheme. Calculated results show that the routing delay achieved by the route caching scheme is only marginally more than the theoretically determined minimum. Simulation in NS-2 demonstrates that the end-to-end delay from DSR routing can be remarkably reduced by our caching scheme. By using overhead analysis model, we demonstrate that the minimum routing overhead can be achieved by increasing timeout to around twice the expected path residual time, without significant increase in routing delay. ¶ Apart from route cache, this thesis also addresses link cache strategy which has the potential to utilize route information more efficiently than a route cache scheme. Unlike some previous link cache schemes delete links at some fixed time after they enter the cache, we proposes using either the expected path duration or the link residual time as the link cache timeout. Simulation results in NS-2 show that both of the proposed link caching schemes can improve network performance in the DSR by reducing dropped data packets, latency and routing overhead, with the link residual time scheme out-performing the path duration scheme. ¶ To deal with large-scale MANETs, this thesis presents an adaptive k-hop clustering algorithm (AdpKHop), which selects clusterhead (CH) by our CH selection metrics. The proposed CH selection criteria enable that the chosen CHs are closer to the cluster centroid and more stable than other cluster members with respect to node mobility. By using merging threshold which is based on the CH selection metric, 1-hop clusters can merge to k-hop clusters, where the size of each k-hop cluster adapts to the node mobility of the chosen CH. Moreover, we propose a routing overhead analysis model for k-hop clustering algorithm, which is determined by a range of network parameters, such as link change rate (related to node mobility), node degree and cluster density. Through the overhead analysis, we show that an optimal k-hop cluster density does exist, which is independent of node mobility. Therefore, the corresponding optimal cluster merging threshold can be employed to efficiently organise k-hop clusters to achieve minimum routing overhead, which is highly desirable in large-scale networks. ¶ The work presented in this thesis provides a sound basis for future research on mobility analysis for mobile ad hoc networks, in aspects such as mobility metrics, caching strategies and k-hop clustering routing protocols.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-04-04T21:30:07Z No. of bitstreams: 1 DIÓGENES GALDINO GONDIM - DISSERTAÇÃO PPGCC 2014..pdf: 1586466 bytes, checksum: 3b6e47836d1098cd946a0d8486669b23 (MD5) / Made available in DSpace on 2018-04-04T21:30:07Z (GMT). No. of bitstreams: 1 DIÓGENES GALDINO GONDIM - DISSERTAÇÃO PPGCC 2014..pdf: 1586466 bytes, checksum: 3b6e47836d1098cd946a0d8486669b23 (MD5) Previous issue date: 2014-08-04 / A maioria dos sistemas operacionais oferecem suas próprias estratégias de gerenciamento de energia, mas é muito difícil modificar ou ampliar as políticas de energia sem acesso ao código fonte. Várias arquiteturas em gerenciamento dinâmico de energia já foram propostas na literatura, mas elas não são integradas com o sistema operacional subjacente. Neste trabalho, é proposto um arcabouço de software para o desenvolvimento de aplicações gerenciadoras de energia ao nível de usuário, com a flexibilidade arquitetural de se adaptar a diferentes políticas e de se integrar às políticas de gerenciamento do sistema operacional. Para validar o arcabouço, é descrito um estudo de caso mostrando sua viabilidade, demonstrando que a aplicação resultante oferece redução no consumo de energia. / Most operating systems implement their own power management techniques, but it is hard to modify or hack their power policies without the source code. Many dynamic power management architectures have been proposed in the literature, but they are not integrated with the underlying OS power manager. In this work, we proposed a software framework for user-level power management, with a flexible architecture to be adapted to different policies and integrated with OS power managers and validated its feasibility with a case study.

The transformation of the legacy electric grid to Smart Grid (SG) poses numerous challenges in the design and development of an efficient SG communications network. While there has been an increasing interest in identifying the SG communications network and possible SG applications, specific research challenges at the network protocol have not been elaborated yet. This dissertation revisited each layer of a TCP/IP protocol stack which basically was designed for a wired network and optimized their performance in IEEE 802.11s-based Advanced Metering Infrastructure (AMI) communications network against the following challenges: security and privacy, AMI data explosion, periodic simultaneous data reporting scheduling, poor Transport Control Protocol (TCP) performance, Address Resolution Protocol (ARP) broadcast, and network interoperability. To address these challenges, layered and/or cross-layered protocol improvements were proposed for each layer of TCP/IP protocol stack. At the application layer, a tree-based periodic time schedule and a time division multiple access-based scheduling were proposed to reduce high contention when smart meters simultaneously send their reading. Homomorphic encryption performance was investigated to handle AMI data explosion while providing security and privacy. At the transport layer, a tree-based fixed Retransmission Timeout (RTO) setting and a path-error aware RTO that exploits rich information of IEEE 802.11s data-link layer path selection were proposed to address higher delay due to TCP mechanisms. At the network layer, ARP requests create broadcast storm problems in IEEE 802.11s due to the use of MAC addresses for routing. A secure piggybacking-based ARP was proposed to eliminate this issue. The tunneling mechanisms in the LTE network cause a downlink traffic problem to IEEE 802.11s. For the network interoperability, at the network layer of EPC network, a novel UE access list was proposed to address this issue. At the data-link layer, to handle QoS mismatch between IEEE 802.11s and LTE network, Dual Queues approach was proposed for the Enhanced Distributed Channel Access. The effectiveness of all proposed approaches was validated through extensive simulation experiments using a network simulator. The simulation results showed that the proposed approaches outperformed the traditional TCP/IP protocols in terms of end to end delay, packet delivery ratio, throughput, and collection time.

Le droit traite principalement l’abstention sous l’angle de la faute d’abstention, mais éprouve des difficultés à appréhender l’abstention du titulaire d’une prérogative qui nécessite une nouvelle approche. Refus temporaire, et non exprimé, de jouir immédiatement des effets de sa prérogative pour les retenir jusqu’au moment le plus opportun, l’abstention crée une situation équivoque. N’ayant ni la clarté d’un exercice actif, ni celle d’une renonciation, elle génère en effet imprévisibilité et insécurité juridique. Cette dernière est d’ailleurs exacerbée par les interprétations erronées dont l’abstention fait l’objet et par l’aggravation dans le temps des conséquences qui touchent celui qui la subit. Ainsi, à défaut de statut légalement défini de l’abstention, il est impératif de se saisir de la problématique d’imprévisibilité de l’abstention du titulaire d’une prérogative pour tenter de l’atténuer, tout en mettant en relief sa légitimité. L’encadrement du comportement de celui qui s’abstient dans le temps est la solution qui s’impose. Ainsi, à compter de la fin d’un délai raisonnable, laps de temps préservant sa liberté au sein du délai imparti, il doit respecter le standard de l’agent raisonnable. À défaut, sa responsabilité pourrait être engagée sans que cela n’exclue la responsabilisation de celui qui subit l’abstention. / French law is usually understanding the abstention as the abstention fault. However, the abstention of the holder of a prerogative can not be analyzed this way and requires a new juridical approach. Abstention creates an equivocal situation by being a refusal, silent and temporary, to immediately enjoy the effects of a prerogative in order to retain them until the most appropriate moment. By being unclear unlike an active exercise or a real renunciation, it generates indeed unpredictability and a lack of legal safety. This insecurity is, moreover, exacerbated by erroneous interpretations of abstention and by the aggravation of the consequences affecting the one who suffers from it with the passing time. As a result, due to the absence of a legal status of abstention, it is imperative to take up the unpredictability problem of the abstention of the holder of a prerogative in order to attempt to mitigate it, while highlighting its legitimacy. The appearing necessary solution finds its way in the regulation of the behavior of the one abstaining in time. Consequently, from the end of a reasonable period, preserving his liberty within the time limit, he has to respect the standard of a reasonable agent. Failing that, his liability could be incurred. This would not exclude the accountability of the person who suffers from abstention.