<p>Peer-to-Peer (P2P) computing is a recent hot topic in the areas of networking and distributed systems. Work on P2P computing was triggered by a number of ad-hoc systems that made the concept popular. Later, academic research efforts started to investigate P2P computing issues based on scientific principles. Some of that research produced a number of structured P2P systems that were collectively referred to by the term ``Distributed Hash Tables'' (DHTs). However, the research occurred in a diversified way leading to the appearance of similar concepts yet lacking a common perspective and not heavily analyzed. In this thesis we present a number of papers representing our research results in the area of structured P2P systems grouped as two sets labeled respectively ``Designs'' and ``Analyses''.</p><p>The contribution of the first set of papers is as follows. First, we present the principle of distributed k-ary search (DKS) and argue that it serves as a framework for most of the recent P2P systems known as DHTs. That is, given the DKS framework, understanding existing DHT systems is done simply by seeing how they are instances of that framework. We argue that by perceiving systems as instances of the DKS framework, one can optimize some of them. We illustrate that by applying the framework to the Chord system, one of the most established DHT systems. Second, We show how the DKS framework helps in the design of P2P algorithms by two examples: (a) The DKS(n;k;f) system which is a system designed from the beginning on the principles of distributed k-ary search. (b) Two broadcast algorithms that take advantage of the distributed k-ary search tree.</p><p>The contribution of the second set of papers is as follows. We account for two approaches that we used to evaluate the performance of a particular class of DHTs, namely the one adopting periodic stabilization for topology maintenance. The first approach was of an intrinsic empirical nature. In that approach, we tried to perceive a DHT as a physical system and account for its properties in a size-independent manner. The second approach was of a more analytical nature. In this approach we applied the technique of Master equations, which is a widely used technique in the analysis of natural systems. The application of the technique lead to a highly accurate description of the behavior of structured overlays.</p><p>Additionally, the thesis contains a primer on structured P2P systems that tries to capture the main ideas that are prevailing in the field and enumerates a subset of the current hot and open research issues.</p>

<p>There have been remarkable growths in wireless communication networks in</p><p>recent years; this is because of its merits over the wired networks such as</p><p>Mobility and convenience. Wireless networks transmit the signal over the</p><p>open air via radio waves of different frequencies, this makes it to be</p><p>vulnerable to several attacks and anybody on the street can easily intercept the</p><p>wireless data or inject new data into the entire network. There has been</p><p>existence of wired equivalent privacy (WEP) protocol (IEEE 802.11i), which</p><p>was designed for wireless network security. There were concerns of security</p><p>vulnerabilities in WEP; this made it necessary for the implementation of</p><p>another solution to overcome the weaknesses of the previous wireless</p><p>network security. The IEEE 802.1X (port-based network admission control)</p><p>which is defined on Extensible Authentication protocol (EAP) provides</p><p>effective and efficient admission control to wireless and other networks</p><p>devices [8].</p><p>Our thesis investigates the efficiency of NAC (IEEE 802.1X) as a security</p><p>solution, access different vendor solutions, protocols supported and look into</p><p>the inter-operability of these various vendors. In as much as we support the</p><p>premise of NAC being an excellent solution, we will also make brilliant</p><p>recommendations in this thesis to be considered for future refinements of this</p><p>security solution as well as deployment scenarios for the university network.</p>

Traffic simulation is an important tool for modelling the operations of dynamic traffic systems and helps analyse the causes and potential solutions of traffic problems such as congestion and traffic safety. Microscopic simulation models provide a detailed representation of the traffic process, which makes them most suitable for evaluation of complicated traffic facilities and Intelligent Transportation Systems that often consist of complex traffic management, safety and information systems. Macroscopic and mesoscopic models on the other hand, capture traffic dynamics in lesser detail, but are faster and easier to apply and calibrate than microscopic models. Therefore they are most suitable for modelling large networks, while microscopic models are usually applied to smaller areas. The objective of this thesis is to combine the strengths of both modelling approaches and diminish their individual weaknesses by constructing a hybrid mesoscopic-microscopic model that applies microscopic simulation to areas of specific interest, while simulating a surrounding network in lesser detail with a mesoscopic model. Earlier attempts at hybrid modelling have concentrated on integrating macroscopic and microscopic models and have proved difficult due to the large difference between the continuous-flow representation of traffic in macroscopic models and the detailed vehicle-and driver-behaviour represented in microscopic models. These problems are solved in this thesis by developing a mesoscopic vehicle-based and event-based model that avoids the (dis)aggregation problems of traffic flows at the inter-model boundaries. In addition, this thesis focuses on the general problems of consistency across the entire hybrid model. The requirements are identified that are important for a hybrid model to be consistent across the models at different levels of detail. These requirements vary from network and route-choice consistency to consistency of traffic dynamics across the boundaries of the micro- and mesoscopic submodels. An integration framework is proposed that satisfies these requirements. This integration framework has been implemented in a prototype hybrid model, MiMe, which is used to demonstrate the correctness of the solutions to the various integration issues. The hybrid model integrates MITSIMLab, a microscopic traffic simulation model, and Mezzo, the newly developed mesoscopic model. Both the hybrid model and the new Mezzo model are applied in a number of case studies, including a network in the North of Stockholm, which show their validity and applicability. The results are promising and support both the proposed integration architecture and the importance of integrating microscopic and mesoscopic models. / QC 20100520

As computing devices and wireless connectivity become ubiquitous, new usage scenarios emerge, where wireless communication links between mobile devices are established in an ad-hoc manner. The resulting wireless ad-hoc networks differ from classical computer networks in a number of ways, lack of permanent access to the global network and heterogeneous structure being some of them. Therefore, security services and mechanisms that have been designed for classical computer networks are not always the optimal solution in an ad-hoc network environment. The research is focused on analyzing how standard security services that are available in classical networks can be provided in an ad-hoc wireless network environment. The goal is to design a security system optimized for operation in ad-hoc wireless networks that provides the same security services – authentication, access control, data confidentiality and integrity, non-repudiation – currently available in classic wired networks. The first part of the thesis is the design and implementation of a security platform based on generic secure objects. The flexible and modular nature of this platform makes it suitable for deployment on devices that form ad-hoc networks – ranging from Java-enabled phones to PDAs and laptops. We then investigate the problems that appear when implementing in ad-hoc networks some of the security technologies that are standard building blocks of secure systems in classical computer networks. Two such technologies have been found to present problems, namely the areas of certification and access control. In a series of articles, we have described the problems that appear and devised solutions to them by designing protocols, techniques and extensions to standards that are optimized for usage in the ad-hoc network environment. These techniques, together with the functionality provided by the underlying security platform, are used to implement all standard security services – confidentiality, authentication, access control, non repudiation and integrity, allowing to integrate ad-hoc networks into the existing security infrastructure. / QC 20101001

WEB 2.0

<p>The purpose of this report is to answer the question:</p><p>How do you create a media player that can stream music for a website?</p><p>We started the work by searching the web and reading books about the subject</p><p>and found several technologies to use to stream media files over the internet.</p><p>We decided upon using the http protocol and created the media player itself in</p><p>Macromedia Flash.</p><p>The website is mostly developed with PHP, JavaScript and CSS templates and</p><p>the websites design was created with Macromedia Dreamweaver and Adobe</p><p>Photoshop. We also created an administrative system for the media player with</p><p>PHP programming.</p><p>The website contains a simple guestbook; the guestbook makes use of a</p><p>database created with MySQL.</p><p>Our work resulted in a webpage with a fully functional media player that</p><p>streams audio files together with a corresponding administrative system for it.</p>

<p>This thesis presents the design, implementation, and evaluation of Flow Java, a programming language for the implementation of concurrent programs. Flow Java adds powerful programming abstractions for automatic synchronization of concurrent programs to Java. The abstractions added are single assignment variables (logic variables) and futures (read-only views of logic variables).</p><p>The added abstractions conservatively extend Java with respect to types, parameter passing, and concurrency. Futures support secure concurrent abstractions and are essential for seamless integration of single assignment variables into Java. These abstractions allow for simple and concise implementation of high-level concurrent programming abstractions.</p><p>Flow Java is implemented as a moderate extension to the GNU GCJ/libjava Java compiler and runtime environment. The extension is not speci c to a particular implementation, it could easily be incorporated into other Java implementations.</p><p>The thesis presents three implementation strategies for single assignment variables. One strategy uses forwarding and dereferencing while the two others are variants of Taylor's scheme. Taylor's scheme represents logic variables as a circular list. The thesis presents a new adaptation of Taylor's scheme to a concurrent language using operating system threads.</p><p>The Flow Java system is evaluated using standard Java benchmarks. Evaluation shows that in most cases the overhead incurred by the extensions is between 10% and 50%. For some pathological cases the runtime increases by up to 150%. Concurrent programs making use of Flow Java's automatic synchronization, generally perform as good as corresponding Java programs. In some cases Flow Java programs outperform Java programs by as much as 33%.</p>

No description available.

Shifting the design entry point up to the system level is the most important countermeasure adopted to manage the increasing complexity of SoCs. The reason is that decisions taken at this level, early in the design cycle, have the greatest impact on the final design in terms of performance, energy efficiency and silicon area occupation. However, taking decisions at this level is very difficult, since the design space is extremely wide, and it has so far been mostly a manual activity. Efficient system-level estimation tools are therefore necessary to enable proper design-space exploration and the development of system-level synthesis tools. Proposing an efficient approach to system-level estimation is the main contribution of this thesis. The approach consists of three layers. The bottom layer relies on building a library of IP energy and performance models, where each IP functionality is pre-characterized. Characterization is done only once at the gate level, which gives high accuracy to the approach. The implementation of an energy and performance model for a Leon3 processor is reported as an example. The impact that the IP-to-IP communication infrastructure has over individual IP properties is also taken into account, for bus-based and NoC-based architectures. The intermediate layer is where the actual estimation takes place. At this level, applications are run and profiled on a development host (a common PC). This allows us to create a trace of the executed source code, which is then mapped to the assembly code of the target architecture. This operation allows a trace of target instructions to be indirectly built and confers high speed on the whole methodology. Once the target trace is inferred, energy and performance figures can be extracted by using the IP models from the bottom layer. To make the whole process possible, changes are made to the GNU GCC compiler. Estimation is shown for a few common image/video codec applications. The top layer is a refinement layer that accounts for the presence of caches and for the fact that multiple applications normally run concurrently, share the same resources and are controlled by an operating system. Statistical models are built to account for the impact of each of these components. An MPSoC hosting up to 15 processors and using both fixed-priority and round robin bus arbitration is used for modeling bus contention. The RTEMS operating system is taken as a reference to model the OS impact. Validation for each layer is also carried out. The results show that the approach is within 15% of gate-level accuracy and exhibits an average speed-up of <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Csim" />30X compared to transaction-level modeling (TLM). / QC 20110315

<p>Examensarbetet, 15 poäng har utförts på högskolan i Kalmar. Input Soft AB är ett företag som är beläget i Strängnäs. Uppdraget för projektarbetet bestod av att utforma en webbbaserad givarservice till Myrorna. Myrorna använder idag fleetIT som är ett program utvecklat av Input Soft AB för registrering/hämtning av gåvor till Myrorna. Denna webbaserade givarservice förenklar och effektiviserar arbetet för Myrorna genom att användarna själva går in via Internet och registrerar sina gåvor istället för som idag då registreringen sköts helt av personalen i Sätra. Teknikerna som använts är ASP-dotnet och en nexus databas som är integrerad med fleetIT Systemet. Server Applikationen kommer att ligga på Myrornas egen server och vara kopplat till fleetIT systemet.</p>