A Causal-Based Consistent Update Approach for Software-Defined Networks

Software-Defined Network (SDN) is a network paradigm that has been recently introduced. Unlike traditional networks, e.g. IP networks, SDNs separate the network control logic from forwarding devices, and delegate network management tasks to a logically-centralized entity called the controller. However, SDN is still a distributed and asynchronous system. In fact, during forwarding policy updates, any network entity may trigger update events at any time, e.g. the sending of messages or data packets, while they are prone to arbitrary and unpredictable transmission delays. Moreover, the absence of an agreed and common temporal reference results in a broad combinatorial range space of event order. An out-of-order execution of events may lead to invariant violations, e.g. forwarding loops and forwarding blackholes, referred to as inconsistent updates. Some works tackle the issue of inconsistent updates by imposing global time references; however, they do not compromise consistency during updates as clocks of entities cannot be perfectly synchronized. Other solutions lie on performing updates on different rounds, i.e. steps, while each update step guarantees consistency. These solutions compromise consistency during updates; however, performing updates over different steps may congest the communication canals between the controller and the forwarding devices, leading to bandwidth overhead. In this dissertation, we propose a causal-based consistent update approach that ensures the connectivity update properties: transient forwarding loop-free and transient forwarding blackhole-free. This is achieved by defining a formal model of the two connectivity invariant violations as a specification of the Happened-Before relation of Lamport. Based on this model, network update policies are introduced by establishing causal dependencies between relevant update events. These update policies are reflected by an update mechanism oriented towards transient connectivity inconsistency-free SDN updates. To prove the correctness of the update mechanism, it was demonstrated that it is sufficient to ensure the transient forwarding loop-free and the transient forwarding blackhole-free properties. In terms of findings, the formal modelisation of the two connectivity update properties defines the root cause of their triggering and capture the conditions under which they may occur

Analyse des conditions de rupture des conduites d’adduction d’eau potable en polyéthylène, sous l’effet d’écoulement transitoire, en présence d’un défaut

The efficiency of potable water distribution systems has been recently the subject of much research. Leakages or a ruptures, occurring in pipes, are quite a frequent phenomenon in urban areas. In order to minimize long-term risks of leakage, about 60% of potable water networks are built or renewed with the third generation of polyethylene pipe, PE100. It is a material with various features, which makes it a widely used material in the water supply networks. However, under transient conditions and with a surficial defect in the pipe, a failure occurs. To investigate this issue, our study is divided into two main parts. The first part is studying the dynamic effect of the viscoelastic material under transient flow conditions using a developed mathematical model. We have demonstrated that the viscoelastic behavior of PE100 plays a primordial role in the damping of water hammer and resonance phenomenon. In case of presence of coupling junction, a study of the fluid structure interaction is mandatory to correctly define the natural frequencies of a piping system. In the second part, we have investigated the crack behavior of PE100 pipes with defects. Using the experimental tests and finite elements results, we have demonstrated that the concept of elastic-plastic fracture mechanics, the J-Integral, define with reasonable accuracy the behavior of cracked PE100-pipe. At the end, we sought to determine the J-Integral with a semi-empirical model in order to define a relationship between the crack initiation pressure, the dimension of semi-elliptical surface cracks and the geometry of the pipeLe problème du rendement de la distribution des eaux potables a récemment fait l’objet de nombreux travaux de recherche. En effet, les ruptures des canalisations et les fuites sont des phénomènes assez fréquents en milieu urbain. Afin de réduire au maximum les risques de fuite à long terme, près de 60 % des réseaux d’eau potable sont construits ou renouvelés avec des conduites en polyéthylène de troisième génération, PE100. De par ses caractéristiques, c’est un matériau de choix pour les réseaux d’adduction d’eau. Mais la présence d’un défaut superficiel peut générer la rupture de la conduite sous l’effet d’écoulement transitoire. Afin d’étudier ce problème, notre étude est décomposée en deux parties. La première est consacrée à l’étude de l’effet dynamique du comportement viscoélastique du matériau sur l’écoulement transitoire à l’aide d’un modèle mathématique que nous avons développé dans cette thèse. Nous avons démontré que le comportement viscoélastique du PE100 joue un rôle primordial dans l’amortissement du phénomène du coup de bélier et de résonance. En cas de présence de couplage de jonction, l’étude de l’interaction fluide-structure est nécessaire pour définir correctement les fréquences propres d’un système de conduites. Ensuite, dans la seconde partie, nous avons étudié le comportement à la fissuration des conduites en PE100 présentant un défaut. A l’aide d’essais expérimentaux et de modélisations par éléments finis, nous avons démontré que le concept de la mécanique élasto-plastique de rupture, l’intégrale J, peut définir avec une précision acceptable le comportement à la fissuration d’une conduite en PE100. Nous avons cherché à déterminer l’intégrale J à l’aide d’un modèle semi-empirique afin de définir une relation entre la pression d’amorçage de fissure, la taille de défaut (fissure semi-elliptique) et la géométrie de la conduit

Failure analysis of drinking water polyethylene pipe under the effect of transient flow in the presence of a defect

Le problème du rendement de la distribution des eaux potables a récemment fait l’objet de nombreux travaux de recherche. En effet, les ruptures des canalisations et les fuites sont des phénomènes assez fréquents en milieu urbain. Afin de réduire au maximum les risques de fuite à long terme, près de 60 % des réseaux d’eau potable sont construits ou renouvelés avec des conduites en polyéthylène de troisième génération, PE100. De par ses caractéristiques, c’est un matériau de choix pour les réseaux d’adduction d’eau. Mais la présence d’un défaut superficiel peut générer la rupture de la conduite sous l’effet d’écoulement transitoire. Afin d’étudier ce problème, notre étude est décomposée en deux parties. La première est consacrée à l’étude de l’effet dynamique du comportement viscoélastique du matériau sur l’écoulement transitoire à l’aide d’un modèle mathématique que nous avons développé dans cette thèse. Nous avons démontré que le comportement viscoélastique du PE100 joue un rôle primordial dans l’amortissement du phénomène du coup de bélier et de résonance. En cas de présence de couplage de jonction, l’étude de l’interaction fluide-structure est nécessaire pour définir correctement les fréquences propres d’un système de conduites. Ensuite, dans la seconde partie, nous avons étudié le comportement à la fissuration des conduites en PE100 présentant un défaut. A l’aide d’essais expérimentaux et de modélisations par éléments finis, nous avons démontré que le concept de la mécanique élasto-plastique de rupture, l’intégrale J, peut définir avec une précision acceptable le comportement à la fissuration d’une conduite en PE100. Nous avons cherché à déterminer l’intégrale J à l’aide d’un modèle semi-empirique afin de définir une relation entre la pression d’amorçage de fissure, la taille de défaut (fissure semi-elliptique) et la géométrie de la conduiteThe efficiency of potable water distribution systems has been recently the subject of much research. Leakages or a ruptures, occurring in pipes, are quite a frequent phenomenon in urban areas. In order to minimize long-term risks of leakage, about 60% of potable water networks are built or renewed with the third generation of polyethylene pipe, PE100. It is a material with various features, which makes it a widely used material in the water supply networks. However, under transient conditions and with a surficial defect in the pipe, a failure occurs. To investigate this issue, our study is divided into two main parts. The first part is studying the dynamic effect of the viscoelastic material under transient flow conditions using a developed mathematical model. We have demonstrated that the viscoelastic behavior of PE100 plays a primordial role in the damping of water hammer and resonance phenomenon. In case of presence of coupling junction, a study of the fluid structure interaction is mandatory to correctly define the natural frequencies of a piping system. In the second part, we have investigated the crack behavior of PE100 pipes with defects. Using the experimental tests and finite elements results, we have demonstrated that the concept of elastic-plastic fracture mechanics, the J-Integral, define with reasonable accuracy the behavior of cracked PE100-pipe. At the end, we sought to determine the J-Integral with a semi-empirical model in order to define a relationship between the crack initiation pressure, the dimension of semi-elliptical surface cracks and the geometry of the pip

Tenue en service des joints soudés (influence des paramètres géométriques)

LILLE1-BU (590092102) / SudocSudocFranceF

An Efficient Service Selection Approach with Time-Dependent QoS

International audienceIn advanced service-oriented computing, complex applications are usually specified as abstract business processes. The execution of these applications requires the selection of a set of services to invoke abstract business tasks. With the growing number of alternative services of each business task that differ in their QoS, the selection of the best combination of services that satisfies business process constraints and end-to-end users' requirements becomes a complex decision problem. Current selection approaches consider only static QoS and ignore the fact that QoS values can depend on temporal properties. In this paper, we propose a novel service selection approach considering time-dependent QoS attributes. The proposed approach introduces two search space reduction mechanisms that combine QoS and temporal constraints. The application of these mechanisms improves the performance of the selection process which is demonstrated by experimental results

Modélisation et analyse expérimentale du procédé de soudage par friction

Cette étude contribue à la modélisation numérique du soudage par friction pour l'identification des paramètres de soudage. La modélisation repose sur le calcul de la quantité de chaleur générée par frottement et sur la répartition spatiale de la chaleur en tenant compte de la variation des propriétés thermiques et physiques du matériau. Des essais de soudage par friction nous ont permis d'étudier l'effet du temps de friction sur la propagation de la chaleur et sur la taille de la zone affectée thermiquement

Time-aware selection approach for service composition based on pruning and improvement techniques

International audienceIn service-oriented environments, abstract business processes can be implemented by concrete services to build complex applications. Given global user constraints, service selection allows to identify the best combination of services with respect to the business constraints. Generally, the selection problem is challenging, but it is particularly complex when dealing with QoS (quality of service) values, which can change during the time associated with temporal constraints. Indeed, these constraints make the selection problem heavily constrained, which can present a barrier for enabling effective service selection. Unlike static QoS values which have been deeply studied in the existing service selection approaches, time-dependent QoS associated with temporal constraints are insufficiently taken into consideration. Moreover, existing approaches cannot handle heavily constrained problems and usually do not provide strategies to detect the source of failure in order to enhance the selection problem in case there is no solution. In this paper, we introduce a new service selection approach, while considering time-dependent QoS values associated with temporal constraints. First, pruning techniques are proposed. The aim of the pruning process is twofold: (1) it allows for reducing the search space and thus, enhancing the efficiency of the selection process; (2) it allows for improving the selection problem by detecting at earlier stages the possible causes of failure, even before the selection process. Second, based on the pruning phase, improvement techniques are proposed to identify possible actions for finding a solution. Third, an exact and an approximate service selection algorithms under several constraints are given. Finally, we demonstrate the effectiveness of our approach through experimental results

A comprehensive survey on intra and inter organizational agreements

International audienceWith the continued growth of Service Oriented Architectures (SOA), cross-organizational enterprise collaboration is needed to satisfy complex client needs. To define dependencies between collaborative enterprises and guarantee the required Quality of Service (QoS) at different layers of the SOA, agreements present an effective solution. In fact, using agreements at different layers of SOA gives a clear specification and control of the agreed service levels between different stakeholders involved in the composition. In this context, aggregation functions that allow the management of composite agreements from the atomic ones at the same layer and translation techniques to detect dependencies between agreements at multiple layers are needed. In this paper, we give a survey on intra and inter organizational agreements for enterprise collaborations. We start by presenting the motivation of this paper and give an overview of agreements lifecycle and categories. Then, we give a state of the art of agreements composition approaches. After that, we highlight the techniques used to manage dependencies between agreements composition and we finish this paper by giving a synthetic view of existing works