Distributed applications built on top of Structured Overlay Networks (SONs) operate based on certain self-* behaviors of the underlying Peer-to-Peer network. Among those, self-organization and self-healing are the two most prominent and assumed properties. The operating environment of distributed systems continues to be more inhospitable with the advance and demand of new technologies; for example in case of mobile and ad hoc networks Churn (node turnover) can be extremely high due to node mobility, frequent disconnects/reconnects and configuration changes. Also, in such dynamic environments, the system may face high Churn (node turnover) and Network partition in a frequent manner. The situation becomes worse if the self-healing behavior of underlying SON is not complete and well defined. This implies the following non-trivial questions: Can the maintenance mechanism of a SON heal the damage to the structure due to harshness of the operating environment and reverse it back? What are the pre-conditions; in other words, what properties the healing mechanism should possess in order to achieve reversibility against stressful environments? Existing literature lacks such assessment and verification study of the self-healing property of a SON. In this thesis, we investigate both the behavior and design of a system that operate in inhospitable environments. This work is relevant to systems with both peaks of high stress (e.g. partitions, churn, network dynamicity etc.) and continuous high stress. We evaluate existing overlay maintenance strategies, namely Correction-on-Change, Correction-on-Use, Periodic Stabilization, and Ring Merge. We define the reversibility property of a system as its ability to repair itself to its original state. We propose a new strategy, called Knowledge Base, to improve conditions for reversibility against inhospitable environments. By means of simulations, we demonstrate reversibility for overlay networks with high levels of partition and churn. We make general conclusions about the ability of the maintenance strategies to achieve reversibility. Identification of Phase Transitions in a SON can provide useful information about the properties of each state of the system. Also, this enables to find the critical points in the operating space and parameters influencing them. The applications running on top of the SON can potentially utilize this knowledge to adapt its operation accordingly in different system states. In this thesis, a representative ring-based SON, namely Beernet is chosen and extended to achieve reversibility. The resulting overlay, Beernet++ exhibits reversible phase transitions under churn. We analyze the critical points observed during such transitions. We present the behavior of Beernet++ for high level of churn and network partitioning, along with their interaction. / <p>QC 20150929</p>

Conventional wisdom suggests that in order to build a secure system, security must be an integral component in the system design. However, cost considerations drive most system designers to channel their efforts on the system's performance, scalability and usability. With little or no emphasis on security, such systems are vulnerable to a wide range of attacks that can potentially compromise confidentiality, integrity and availability of sensitive data. It is often cumbersome to redesign and implement massive systems with security as one of the primary design goals. This thesis advocates a proactive approach that cleanly retrofits security solutions into existing system architectures. The first step in this approach is to identify security threats, vulnerabilities and potential attacks on a system or an application. The second step is to develop security tools in the form of customizable and configurable plug-ins that address these security issues and minimally modify existing system code, while preserving its performance and scalability metrics. This thesis uses overlay network applications to shepherd through and address challenges involved in supporting security in large scale distributed systems. In particular, the focus is on two popular applications: publish/subscribe networks and VoIP networks. Our work on VoIP networks has for the first time identified and formalized caller identification attacks on VoIP networks. We have identified two attacks: a triangulation based timing attack on the VoIP network's route set up protocol and a flow analysis attack on the VoIP network's voice session protocol. These attacks allow an external observer (adversary) to uniquely (nearly) identify the true caller (and receiver) with high probability. Our work on the publish/subscribe networks has resulted in the development of an unified framework for handling event confidentiality, integrity, access control and DoS attacks, while incurring small overhead on the system. We have proposed a key isomorphism paradigm to preserve the confidentiality of events on publish/subscribe networks while permitting scalable content-based matching and routing. Our work on overlay network security has resulted in a novel information hiding technique on overlay networks. Our solution represents the first attempt to transparently hide the location of data items on an overlay network.

Overlay networks have recently gained popularity as a viable alternative to overcome functionality limitations of the Internet (e.g., lack of QoS, multicast routing). They offer enhanced functionality to end-users by forming an independent and customizable virtual network over the native network. Typically, the routing at the overlay layer operates independent of that at the underlying native layer. There are several potential problems with this approach because overlay networks are selfish entities that are chiefly concerned with achieving the routing objective of their own users. This leads to complex cross-layer interactions between the native and overlay layers, and often tends to degrade the achieved performance for both layers. As overlay applications proliferate and the amount of selfish overlay traffic surges, there is a clear need for understanding the complex interactions and for strategies to manage them appropriately. Our work addresses these issues in the context of "service overlay networks", which represent virtual networks formed of persistent nodes that collaborate to offer improved services to actual end-systems. Typically, service overlays alter the route between the overlay nodes in a dynamic manner in order to satisfy a selfish objective. The objective of this thesis is to improve the stability and performance of overlay routing in this multi-layer environment. <br><br> We investigate the common problems of functionality overlap, lack of cross-layer awareness, mismatch or misalignment in routing objectives and the contention for native resources between the two layers. These problems often lead to deterioration in performance for the end-users. This thesis presents an analysis of the cross-layer interaction during fault recovery, inter-domain policy enforcement and traffic engineering in the multi-layer context. Based on our characterization of the interaction, we propose effective strategies that improve overall routing performance, with minimal side-effects on other traffic. These strategies typically 1) increase the layer-awareness (awareness of information about the other layer) at each layer, 2) introduce better control over routing dynamics and 3) offer improved overlay node placement options. Our results demonstrate how applying these strategies lead to better management of the cross-layer interaction, which in turn leads to improved routing performance for end-users.

Τα δίκτυα αισθητήρων είναι μια εξειδικευμένη κατηγορία κατανεμημένων δικτύων, η οποία τα τελευταία χρόνια έχει συγκεντρώσει το ενδιαφέρον της ερευνητικής κοινότητας, λόγω του ευρύτατου πεδίου εφαρμογών της. Τα δίκτυα αυτά αποτελούνται από συσκευές που διαθέτουν αισθητήρες (sensors) και ενδεχομένως μηχανισμούς δράσης (actuators) και είναι διασκορπισμένες στο χώρο, με δυνατότητα επικοινωνίας μεταξύ τους και επεξεργασίας σε ένα βαθμό της πληροφορίας που διακινούν στο δίκτυο. Στόχος των δικτύων αυτών είναι η παρακολούθηση της εξέλιξης ενός φαινόμενου, ή η ανίχνευση περιβαλλοντικών συνθηκών και η αποστολή των δεδομένων που συλλέγονται σε έναν κεντρικό κόμβο, το κέντρο ελέγχου. Οι δυνατότητες των συσκευών είναι κατά κανόνα περιορισμένες, λόγω του μικρού μεγέθους τους, του χαμηλού κόστους τους και ενίοτε του αναλώσιμου ρόλου τους. Οι εφαρμογές των δικτύων αυτών ποικίλουν, από εφαρμογές στην επιστήμη γεωργίας ακριβείας, στην πυρανίχνευση και την παρακολούθηση συνθηκών περιβάλλοντος σε κτιριακές εγκαταστάσεις, μέχρι εφαρμογές ανίχνευσης κίνησης των εχθρικών μονάδων σε πεδίο μάχης, ή παρακολούθησης φαινόμενου που εξελίσσεται σε δυσπρόσιτη περιοχή. Μερικές από τις βασικές προκλήσεις που προκύπτουν σε αυτά τα δίκτυα, λόγω της φύσης τους, είναι η βέλτιστη διαχείριση των ενεργειακών πόρων κάθε κόμβου, η αποδοτική συνδυαστική επεξεργασία των διακινούμενων μηνυμάτων και η αξιόπιστη δρομολόγηση της πληροφορίας που συλλέγεται προς το κέντρο ελέγχου, καθώς και η δυναμική και αυτόνομη οργάνωση του δικτύου. Η εξέλιξη των δικτύων αισθητήρων σε συνδυασμό με την επιθυμία υλοποίησης περίπλοκων και περισσότερο ολοκληρωμένων εφαρμογών, οδήγησε σε δίκτυα που περιέχουν ετερογενείς κόμβους, όπως για παράδειγμα κόμβους με διαφορετική αρχιτεκτονική, διαφορετικούς αισθητήρες, με διαφορετικές επεξεργαστικές και επικοινωνιακές ικανότητες ή και κόμβους με δυνατότητες κίνησης ή επιτέλεσης εργασιών (actuators) σε απόκριση εντολών που λαμβάνουν από το κέντρο ελέγχου. Επιπρόσθετα, σε πολλές εφαρμογές διαφαίνεται η ανάγκη για διασύνδεση πολλαπλών δικτύων αισθητήρων και διάδοση της πληροφορίας που συλλέγουν μέσω του διαδικτύου προς απομακρυσμένους εξυπηρετητές με αυξημένες επεξεργαστικές ικανότητες, προς βάσεις δεδομένων, συσκευές pda ή κινητά τηλέφωνα, σταθμούς εργασίας τελικών χρηστών και άλλες συσκευές. Δημιουργείται με αυτόν τον τρόπο ένα ευρύτερο ετερογενές δίκτυο επικάλυψης (overlay sensor network), η διαχείριση και αποδοτική χρήση του οποίου απαιτεί νέες αρχιτεκτονικές οργάνωσης των επιμέρους δικτύων, προσαρμοσμένα πρωτόκολλα διάδοσης πληροφορίας και πλατφόρμες που διευκολύνουν τον προγραμματισμό των δικτύων αυτών. Για το λόγο αυτό η επιστημονική κοινότητα επικεντρώνει το ενδιαφέρον της στο σχεδιασμό ειδικών περιβαλλόντων λογισμικού που μεσολαβούν ανάμεσα στον προγραμματιστή εφαρμογών και τα ετερογενή δίκτυα αισθητήρων, τα οποία ανήκουν στην κατηγορία των middleware. Τα περιβάλλοντα αυτά αναλαμβάνουν να διαχειριστούν θέματα χαμηλού επιπέδου ή και ανώτερων επιπέδων στα δίκτυα αισθητήρων, που δεν θα έπρεπε να απασχολούν τον προγραμματιστή κάθε φορά που επιθυμεί να υλοποιήσει μια εφαρμογή. Απώτερος σκοπός είναι να παρέχουν υπηρεσίες υψηλού επιπέδου και ομοιογενείς λογικές αφαιρέσεις πάνω στα ετερογενή δίκτυα, ενώ είναι επιθυμητή η αποδοτική λειτουργία τους σε παγκόσμια κλίμακα όπου πολλά γεωγραφικά διάσπαρτα δίκτυα συνεργάζονται για να παρέχουν τις υπηρεσίες τους με οργανωμένο και καλά ορισμένο τρόπο. Η δική μας συνεισφορά στην έρευνα του πεδίου αυτού, έγκειται πρώτα στη μελέτη ήδη διαθέσιμων προτάσεων middleware για τον προγραμματισμό και τη διασύνδεση πολλαπλών και ετερογενών δικτύων αισθητήρων, με σκοπό τον εντοπισμό των θεμάτων και προβλημάτων που αντιμετώπισαν κατά το σχεδιασμό τους, την ανάλυση της αρχιτεκτονικής τους και την αξιολόγηση της απόδοσής τους. Επιθυμώντας να δώσουμε τη δική μας πρόταση στο πεδίο των middleware για δίκτυα αισθητήρων και αξιοποιώντας τα συμπεράσματά μας από την μελέτη των άλλων προτάσεων, σχεδιάσαμε και υλοποιήσαμε το middleware σύστημα ShareSense II. Το σύστημα ShareSense II προέρχεται από τον επανασχεδιασμό τού αρχικού και απλούστερου ShareSense και ενσωματώνει το middleware jWebDust επεκτείνοντας κατά ένα τρόπο την αρχιτεκτονική του, ώστε να υποστηρίζει δίκτυα επικάλυψης (overlay sensor networks) μεγάλης κλίμακας. Η πλατφόρμα του ShareSense II σχεδιάστηκε για να παρέχει λογική αφαίρεση των δικτύων αισθητήρων, ώστε ο προγραμματιστής να μπορεί εύκολα να ρυθμίσει τις υπηρεσίες που παρέχει ένα δίκτυο επικάλυψης, να διαχειρίζεται τις λειτουργίες των επιμέρους δικτύων, να μπορεί να προγραμματίσει δυναμικά τη συμπεριφορά τους και να καθορίσει τον τρόπο παρουσίασης της χρήσιμης πληροφορίας που αποκομίζει από αυτά, στον τελικό χρήστη. Βασιζόμενοι στην ευέλικτη υποδομή των peer-to-peer δικτύων, προτείνουμε μια λύση για τη διασύνδεση πολλαπλών ετερογενών δικτύων αισθητήρων με συσκευές και σταθμούς εργασίας πάνω από το διαδίκτυο. Δώσαμε έμφαση στην επεκτασιμότητα της αρχιτεκτονικής ως προς τις υποστηριζόμενες υπηρεσίες και τύπους δικτύων, την αξιοποίηση και τη συνεργασία με υπάρχοντα middleware που διαχειρίζονται κάποια επιμέρους δίκτυα και την παροχή χρήσιμων διεπαφών για την εύκολη υλοποίηση πρακτικών εφαρμογών. Υλοποιήσαμε, τέλος, μια εφαρμογή η οποία στηρίζεται στην πλατφόρμα του ShareSense II για να τεκμηριώσουμε την επάρκεια της αρχιτεκτονικής του συστήματός μας και να εντοπίσουμε τα σημεία όπου απαιτείται βελτίωσή της. Η εφαρμογή χρησιμοποιεί το περιβάλλον του Google Earth για την παρακολούθηση των επιμέρους δικτύων που συμμετέχουν στο σύστημα, επιτρέποντας παράλληλα τη δυναμική υποβολή ερωτημάτων και την αντιστοίχιση των δικτύων σε τρισδιάστατα μοντέλα κτιρίων και άλλων περιοχών, ώστε να είναι άμεση και εύληπτη η παρουσίαση της πληροφορίας στον τελικό χρήστη. / Sensor networks are a special case of distributed networks, which in the recent years have become increasingly interesting to the scientific community, due to their wide range of applications. These networks are comprised of devices that have sensors attached to them and possibly even actuators, and are scattered in a field, being able to comminucate with each other and process -to a certain degree- information that they forward in the network. Among the goals of these networks are the monitoring of physical phenomena, the detection of special events or conditions and consequently the communication of the acquired information towards a control center. These devices usually have strict constraints on their capabilities due to their small size, their low production cost and quite often their expendable role. The applications of these networks vary, from applications in the precision agriculture field, fire detection and monitoring environmental conditions in buildings and offices, to applications for the detection of enemy units' movements in the battlefield or observing a physical phenomenon in a inaccessible location. Some of the important challeges that emerge for these networks are the optimal management of the power resources of each node, the efficient aggregation of the in-network messages and the reliable routing of information acquired towards the control center, as well as the autonomous and adaptive network operation. The evolution in the sensor netorks research in combination with the desire to implement even more sophisticated applications, has led to highly heterogeneous networks, where nodes belong to different architectures, they use various sensor models, and they have different processing and communicating capabilities. Additionally, in many applications there is the need to interconnect multiple sensor networks and to distribute the information collected locally towards remote servers, databases, pda devices or cell phones, workstations and other end user devices. Thus, a new type of networks, the overlay networks, emerges. The administration and effecient usage of these networks require new management architectures for the local networs, adaptive protocols for the distribution of information and new software platforms that simplify application programming. Following these developments, the scientific community has focused in designing middleware software for the sensor networks. Such software have the role of managing low level or intermediate level issues, that should not burden a programmer every time s/he needs to design and implement a new application. The main goal of middleware is to provide high level services and unified logical abstractions over heterogeneous sensor networks, and to perform well in a global scale where multiple geographically disparate networks cooperate to provide services in an organized and well defined manner. Our contribution to this field, is foremost to study the state of the art middleware projects for overlay sensor networks, in an effort to understand the issues and problems that were faced during their design, to analyze their architecure and evaluate their performance. We have used the results of this study to design and implement a new middleware architecture, which we have named ShareSense II. Our middleware comes from the redesign and expansion of its simpler predecessor, the original ShareSense middleware, and also integrates the jwebdust middleware, bringing the services of that middleware to the large scal overlay networks. The ShareSense II platfrom was designed to provide logical abstractions for sensor networks, so that the programmer is able to tweak their services, maange the resources of the local networks and build flexible applications. For our overlay netowrk we have embedded an efficient peer-to-peer infrastructure that performs well in networks with frequent and temporary node disconnections and large scale applications. Finally, we implemented an application that uses the ShareSense II middleware, in order to show the benefits of our design and also locate the parts of the architecture that need further optimization. Our application uses the Google Earth software to monitor geographically disparate networks that participate in ShareSense II, allowing the online issuing of queries, as well as matching 3d models of buildings (and other areas) to local networks, in order to display information to the end user in an interesting and exciting way.

O gerenciamento das redes de comunicações modernas frequentemente requer que operadores de diferentes domínios administrativos interajam uns com os outros de modo a realizar uma tarefa de gerenciamento de maneira cooperativa. Nesse contexto, pode-se observar que há distribuição tanto na execução das ações como na tomada das decisões pelos operadores participantes da sessão de gerenciamento. As soluções tradicionais de gerenciamento de redes praticamente não oferecem suporte algum ao gerenciamento baseado na cooperação entre humanos, pois foram concebidas levando em consideração um único domínio administrativo sendo gerenciado por um único operador ou por um grupo de operadores pertencentes a uma mesma organização. Visando solucionar esse problema, é introduzido nesse trabalho o uso de tecnologias peer-to-peer (P2P) em soluções de gerenciamento de redes de modo a permitir o gerenciamento baseado na cooperação entre humanos. Nessa abordagem, operadores de rede usam ferramentas híbridas que, ao mesmo tempo, gerenciam os seus domínios locais e fazem parte de um sistema P2P de gerenciamento. A proposta de gerenciamento apresentada foi implementada através de uma ferramenta chamada ManP2P, a qual combina funcionalidades de gerenciamento de redes e trabalho cooperativo. / Modern networks not rarely require human operators from different administrative domains to interact with one another in order to accomplish a management task in a cooperative fashion. In this scenario one observes that not only management actions are executed in a distributed way, but also the management decisions are cooperatively taken by all autonomous operators participating in a management session. Traditional management solutions fail to support human centered cooperative management because they were conceived considering a single administrative domain being managed by a single operator or by a group of operators belonging to the same organization. In order to address this issue, we introduce in this paper the use of peer-to-peer (P2P) technologies in network management solutions to enable human-centered cooperative management. In this approach, network operators use hybrid tools that both manage their local domains and are peers of an overlay management system. We have implemented the proposed management approach through a tool called ManP2P, which combines network management and groupware functionalities.

O gerenciamento das redes de comunicações modernas frequentemente requer que operadores de diferentes domínios administrativos interajam uns com os outros de modo a realizar uma tarefa de gerenciamento de maneira cooperativa. Nesse contexto, pode-se observar que há distribuição tanto na execução das ações como na tomada das decisões pelos operadores participantes da sessão de gerenciamento. As soluções tradicionais de gerenciamento de redes praticamente não oferecem suporte algum ao gerenciamento baseado na cooperação entre humanos, pois foram concebidas levando em consideração um único domínio administrativo sendo gerenciado por um único operador ou por um grupo de operadores pertencentes a uma mesma organização. Visando solucionar esse problema, é introduzido nesse trabalho o uso de tecnologias peer-to-peer (P2P) em soluções de gerenciamento de redes de modo a permitir o gerenciamento baseado na cooperação entre humanos. Nessa abordagem, operadores de rede usam ferramentas híbridas que, ao mesmo tempo, gerenciam os seus domínios locais e fazem parte de um sistema P2P de gerenciamento. A proposta de gerenciamento apresentada foi implementada através de uma ferramenta chamada ManP2P, a qual combina funcionalidades de gerenciamento de redes e trabalho cooperativo. / Modern networks not rarely require human operators from different administrative domains to interact with one another in order to accomplish a management task in a cooperative fashion. In this scenario one observes that not only management actions are executed in a distributed way, but also the management decisions are cooperatively taken by all autonomous operators participating in a management session. Traditional management solutions fail to support human centered cooperative management because they were conceived considering a single administrative domain being managed by a single operator or by a group of operators belonging to the same organization. In order to address this issue, we introduce in this paper the use of peer-to-peer (P2P) technologies in network management solutions to enable human-centered cooperative management. In this approach, network operators use hybrid tools that both manage their local domains and are peers of an overlay management system. We have implemented the proposed management approach through a tool called ManP2P, which combines network management and groupware functionalities.

O gerenciamento das redes de comunicações modernas frequentemente requer que operadores de diferentes domínios administrativos interajam uns com os outros de modo a realizar uma tarefa de gerenciamento de maneira cooperativa. Nesse contexto, pode-se observar que há distribuição tanto na execução das ações como na tomada das decisões pelos operadores participantes da sessão de gerenciamento. As soluções tradicionais de gerenciamento de redes praticamente não oferecem suporte algum ao gerenciamento baseado na cooperação entre humanos, pois foram concebidas levando em consideração um único domínio administrativo sendo gerenciado por um único operador ou por um grupo de operadores pertencentes a uma mesma organização. Visando solucionar esse problema, é introduzido nesse trabalho o uso de tecnologias peer-to-peer (P2P) em soluções de gerenciamento de redes de modo a permitir o gerenciamento baseado na cooperação entre humanos. Nessa abordagem, operadores de rede usam ferramentas híbridas que, ao mesmo tempo, gerenciam os seus domínios locais e fazem parte de um sistema P2P de gerenciamento. A proposta de gerenciamento apresentada foi implementada através de uma ferramenta chamada ManP2P, a qual combina funcionalidades de gerenciamento de redes e trabalho cooperativo. / Modern networks not rarely require human operators from different administrative domains to interact with one another in order to accomplish a management task in a cooperative fashion. In this scenario one observes that not only management actions are executed in a distributed way, but also the management decisions are cooperatively taken by all autonomous operators participating in a management session. Traditional management solutions fail to support human centered cooperative management because they were conceived considering a single administrative domain being managed by a single operator or by a group of operators belonging to the same organization. In order to address this issue, we introduce in this paper the use of peer-to-peer (P2P) technologies in network management solutions to enable human-centered cooperative management. In this approach, network operators use hybrid tools that both manage their local domains and are peers of an overlay management system. We have implemented the proposed management approach through a tool called ManP2P, which combines network management and groupware functionalities.

This thesis presents the design and evaluation of content-based publish/subscribe systems for efficient content dissemination and sharing of dynamic and large-scale networked applications. The rapid development of network technologies and the continuous investment in network infrastructure have realized a ubiquitous platform for sharing information. However, there lacks efficient protocol and software that can utilize such resource to support novel networked applications. In this thesis, we explore the possibility of content-based publish/subscribe as an efficient communication substrate for dynamic and large-scale networked applications. Although content-based publish/subscribe has been used extensively in many small-to-medium scale systems, there is no Internet-scale applications that utilize this technology. The research reported in this thesis investigates the technical challenges and their solutions of applying content-based publish/subscribe in various applications in mobile networks and Internet. We apply content-based publish/subscribe in the interest-driven information sharing for smartphone networks. We design efficient approximate content matching algorithms and data structures. We study how to construct optimal overlay publish/subscribe overlay networks. We propose architecture designs that make Internet content-based publish/subscribe robust. We also design a name resolution system that enables content discovery in the Internet. These techniques are evaluated comprehensively in realistic simulation studies, and some of them are further evaluated on PlanetLab testbed with prototype implementations. / Computer and Information Science

Les systèmes pair-à-pair (P2P) sont utilisés par des millions d'usagers tous les jours. Dans beaucoup de cas, un usager souhaite communiquer, échanger du contenu ou des services à travers différents systèmes P2P. Cela requiert de la coopération entre les différents systèmes P2P, ce qui est très souvent difficile ou même impossible à obtenir, à cause des raisons suivantes; in primis, l'absence d'une infrastructure de routage entre les réseaux, ce qui rend la communication étanche et, in secundis, l'incompatibilité des protocoles et des opérations des susdits systèmes. L'objectif principal de cette thèse est celui de permettre la coopération entre systèmes P2P. La thèse introduit un cadre de coopération rétro-compatible entre systèmes P2P hétérogènes constitué de deux parties. La première est un cadre de routage intra-réseaux permettant à des réseaux hétérogènes de communiquer. La deuxième est une application coopérative, conçue à l'aide et au travers du cadre de routage, dont l'objectif est celui de résoudre les incompatibilités protocolaires des systèmes P2P sous-jacents. A cause des différences intrinsèques des domaines d'applications - dans la description du cadre de coopération - la thèse se focalise essentiellement sur les principes fondateurs de la construction du cadre de coopération. Comme étude de cas de notre cadre de coopération, on présente une solution complète permettant une coopération entre des réseaux P2P spécialisés dans l'échange des fichiers pouvant s'appliquer aux réseaux P2P actuels. La solution proposée serait composée par une application de coopération, devant fonctionner à l'aide d'un protocole d'échange de fichiers inter-réseaux (IFP), et qui devrait être à la base du cadre de routage inter-protocolaire. A travers des expérimentations en taille réelle, on montre l'efficacité du cadre de routage inter-réseaux ainsi que l'efficacité de la solution proposée, pour permettre la coopération entre réseaux d'échange des fichiers P2P. Pendant l'étude des protocoles de routages inter-réseaux, on a observé que l'interconnexion des systèmes P2P pourrait donner une réponse à des problématiques communes aux systèmes P2P, comme le passage à l'échelle, la localisation, la tolérance aux pannes, et l'auto-organisation. Notre conviction est qu'un système possédant toutes ces caractéristiques pourrait être à la base de la conception de plusieurs systèmes ''cyber-physiques'' (CPS). En fait, dans la deuxième partie de la thèse, on présente une étude de cas d'usage de notre architecture d'interconnexion des réseaux P2P appliquée à un cas typique de CPS, notamment les réseaux d'électricité intelligents. Dans cette étude de cas, une collection des ''tables de hachage distribuées'' et organisées de façon hiérarchique est à la base d'une infrastructure de communication entre de compteurs d'électricité intelligents (AMI). L'analyse et les expérimentations montrent le passage à l'échelle et l'efficacité de communication de l'architecture proposée.

<p>This Ph.D. thesis addresses topics related to overlay networks, their de_nition,<br />formalization and applications. Descriptions of the Chord and Synapse protocols using<br />the ASM formalism is presented, and both a high-level and a re_ned proof of the<br />correctness of the Chord formalization is given. A probabilistic assessment of the<br />exhaustiveness of the Synapse protocol is performed. An updated version of the<br />Proposal of metadata schemata for movable cultural heritage as well as a Proposal of<br />metadata schemata for describing collections are provided. Based of the Chord protocol, a Distributed catalog of digitized collections of Serbian cultural herigate is implemented.</p> / <p>Doktorska disertacija se bavi temama vezanim za prekrivajuće mreže, njihovom<br />definicijom, formalizacijom i primenama. Dati su opisi Chord i Synapse protokola<br />kori&scaron;ćenjem ASM formalizma, kao i dokaz korektnosti formalizacije Chord protokola<br />na visokom nivou, kao i njegovo profinjenje. Izvr&scaron;ena je verovatnosna ocena uspe&scaron;nosti pretrage pomoću Synapse protokola. Predstavljena je ažurirana verzija Predloga sheme meta podataka za pokretna kulturna dobra, kao i Predlog sheme meta podataka za opis kolekcija. Implementiran je Distribuirani katalog digitalizovanih kolekcija kulturne ba&scaron;tine Srbije zasnovan na Chord protokolu.</p>