Comparative actinopterygian fish taphonomy of laminated fossil Lagerstätten: case studies from the late Mesozoic of Eurasia

Laminated fossil Lagerstätten such as Plattenkalks offer a unique insight into ancient palaeo-biodiversity due to the exceptional quality of fossil preservation. Through the integrated use of qualitative, as well as quantitative taphonomical analyses of their fossil content, in combination with microfacial and geochemical investigations, the palaeoenvironmental conditions of such fossil Lagerstätten can be reconstructed. By comparing taphonomic features observed in various laminated fossil Lagerstätten, common palaeoenvironmental features which are a prerequisite for exceptional fossil preservation can be deduced. As a template for comparative taphonomy, the Upper Jurassic Wattendorf Plattenkalk of Southern Germany was chosen. Biostratinomic features of actinopterygian fish specimens, mainly of the genus Tharsis were recorded. Frequency of different grades of preservational features such as bending of the spinal column, skeletal articulation and overall completeness of the fish fossils was noted. By means of Euclidean cluster analysis, percentages of the occurrence of these features per bedding plane were grouped into clusters with similar patterns. Four different taphofacies W-A to W-D, representing various combinations of preservational features could be identified. These taphofacies indicate four energy regimes represented in the depositional environment of the Wattendorf Plattenkalk. The transition from taphofacies W-A to taphofacies W-D marks the development from only slight environmental disturbance to conditions of higher disturbance affecting the fish carcasses. At the beginning of Plattenkalk deposition, cyclic changes of the palaeoenvironment prevailed with periodic high disturbance, probably caused by storm-induced flows. In the upper part of the Plattenkalk unit, taphofacies indicative of higher disturbance dominate, suggesting a change from stable to less stable environmental conditions in the Plattenkalk basin resulting in cession of the typical Plattenkalk sedimentation. The Wattendorf Plattenkalk yielded three distinct modes of soft tissue preservation. In some fish fossils, connective tissues preserved as francolite can be observed. Soft-tissues were also preserved in acicular pyrite in a specimen of ?Palaeohirudo sp.. This modification requires slight amounts of oxygen. The third type of soft-tissue preservation is impregnation of internal voids in bones left by osteocytes and blood vessels by amorphic pyrite. Analysis of the micro- and ultrafacies of the Plattenkalk unit show rare layers of abundant coccoliths that co-occur with well-preserved fish fossils. This hints at occasional coccolithophorid blooms that might have caused fish kills. Abundant remnants of microbial mats had a positive and stabilising effect on fossil preservation. Changes in the water energy deduced from the taphonomic analysis are corroborated by microfacies analysis. Geochemical investigations of the Plattenkalk unit yielded additional palaeoenvironmental parameters for the genesis of Plattenkalks. An analysis of crystal size distribution of pyrite framboids showed anoxic conditions in the water column and in the sediment of the Wattendorf basin. Stable isotope ratios of calcitic skeletal elements of belemnites, brachiopods and bivalves found in the Plattenkalk unit show a clear thermal gradient in the water column of the Plattenkalk basin ranging from 9°C to 24°C. Combining the results of the various taphonomic, sedimentological and geochemical analyses, reconstruction of the palaeoenvironmental conditions influencing the sedimentation and early genesis of the Wattendorf Plattenkalk is possible. Based on the palaeoenvironmental information of the Wattendorf Plattenkalk gained by taphonomic analysis, these results were compared with the preservational features of actinopterygian fishes of two other laminated fossil Lagerstätten. Using quantitative taphonomy on fish specimens from the Upper Jurassic Nusplingen Plattenkalk lagerstätte of Southwestern Germany, again four different taphofacies could be established. Taphofacies N-A to taphofacies N-D show a gradual increase in extrinsic forces acting upon fish carcasses. Distribution of the taphofacies throughout the Plattenkalk succession shows only obscure cyclic changes. Low-energy taphofacies N-A to N-C prevail. High-energy taphofacies N-D, though, corresponds well with rarely occurring coarse sediment beds, colonisation horizons and scavenger activity and indicates an oxygenation of the whole water body. To test the method of quantitative taphonomic analysis on a continental depositional systems, actinopterygian fish specimens of the genus Lycoptera from the lacustrine Dawangzhangzi Bed of the Lower Cretaceous Yixian Formation of northwestern China were investigated. Euclidean cluster analysis established two taphofacies Y-A and Y-B. Taphofacies Y-A represents the lowest-energy conditions also observed in the other two fossil Lagerstätten. Taphofacies Y-B corresponds to the taphofacies W-B and N-B. Exceptionally good articulation was again likely caused by an abundance of microbial mats in a stagnant water body under inhospitable an anoxic conditions. Identification of mass mortality events of Lycoptera suggests that these conditions became on occasion widespread and even reached the uppermost part of the water column. Comparison of the preservational features of all three fossil Lagerstätten yielded common features required for exceptional fossil preservation. The presence of microbial mats is an important stabilising and encasing mechanism of carcasses. Inhospitable bottom waters caused by anoxic conditions exclude bioturbation and scavenging. The genesis of Plattenkalks is not restricted to tropical palaeoclimates. Slight wave activity and oxygen in the sediment and lower water column are not necessarily detrimental to exceptional fossil preservation and may even facilitate certain kinds of soft-tissue preservation

Gestion des accès massifs des équipements dans les réseaux NB-IoT : une stratégie basée sur l'apprentissage par renforcement

International audienc

Climate forecasts in disaster management: Red Cross flood operations in West Africa, 2018

In 2008, the International Federation of Red Cross and Red Crescent Societies (IFRC) used a seasonal forecast for West Africa for the first time to implement an Early Warning, Early Action strategy for enhanced flood preparedness and response. Interviews with disaster managers suggest that this approach improved their capacity and response. Relief supplies reached flood victims within days, as opposed to weeks in previous years, thereby preventing further loss of life, illness, and setbacks to livelihoods, as well as augmenting the efficiency of resource use. This case demonstrates the potential benefits to be realised from the use of medium-to-long-range forecasts in disaster management, especially in the context of potential increases in extreme weather and climate-related events due to climate variability and change. However, harnessing the full potential of these forecasts will require continued effort and collaboration among disaster managers, climate service providers, and major humanitarian donors

Using seasonal climate forecasts to guide disaster management: the Red Cross experience during the 2008 West Africa floods

In 2008, the seasonal forecast issued at the Seasonal Climate Outlook Forum for West Africa (PRESAO) announced a high risk of above-normal rainfall for the July–September rainy season. With probabilities for above-normal rainfall of 0.45, this forecast indicated noteworthy increases in the risk of heavy rainfall. When this information reached the International Federation of Red Cross and Red Crescent Societies (IFRC) West and Central Africa Office, it led to significant changes in the organization’s flood response operations. The IFRC regional office requested funds in advance of anticipated floods, prepositioned disaster relief items in strategic locations across West Africa to benefit up to 9,500 families, updated its flood contingency plans, and alerted vulnerable communities and decision-makers across the region. This forecast-based preparedness resulted in a decrease in the number of lives, property, and livelihoods lost to floods, compared to just one year prior in 2007 when similar floods claimed above 300 lives in the region. This article demonstrates how a science-based early warning informed decisions and saved lives by triggering action in anticipation of forecast events. It analyses what it took to move decision-makers to action, based on seasonal climate information, and to overcome traditional barriers to the uptake of seasonal climate information in the region, providing evidence that these barriers can be overcome. While some institutional, communication and technical barriers were addressed in 2008, many challenges remain. Scientists and humanitarians need to build more common ground

A new fireworm (Amphinomidae) from the Cretaceous of Lebanon identified from three-dimensionally preserved myoanatomy

© 2015 Parry et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. The attached file is the published version of the article

Context-aware media services delivery in heterogeneous environments for future media networks

La généralisation de l’usage de l’Internet, ces dernières années, a été marquée par deux tendances importantes. Nous citerons en premier, l’enthousiasme de plus en plus grand des utilisateurs pour les services médias. Cette tendance est particulièrement accentuée par l’avènement des contenus générés par les utilisateurs qui amènent dans les catalogues des fournisseurs de services un choix illimité de contenus. L’autre tendance est la diversification et l’hétérogénéité en ressources des terminaux et réseaux d’accès. Seule la valeur du service lui-même compte aujourd’hui pour les utilisateurs et non le moyen d’y accéder. Cependant, offrir aux utilisateurs un accès ubiquitaire à de plus en plus de services Internet, impose des exigences très rigoureuses sur l’infrastructure actuelle de l’Internet. En effet, L’évolution de l’Internet devient aujourd’hui une évidence et cette évolution est d’autant plus nécessaire dans un contexte de services multimédias qui sont connus pour leur sensibilité au contexte dans lequel ils sont consommés et pour générer d’énormes quantités de trafic. Dans le cadre de cette thèse, nous nous focalisons sur deux enjeux importants dans l’évolution de l’Internet. A savoir, faciliter le déploiement de services médias personnalisés et adaptatifs et améliorer les plateformes de distribution de ces derniers afin de permettre leur passage à l’échelle tout en gardant la qualité de service à un niveau satisfaisant pour les utilisateurs finaux. Afin de permettre ceci, nous introduisons en premier, une nouvelle architecture multi environnements et multi couches permettant un environnement collaboratif pour le partage et la consommation des services médias dans un cadre des réseaux média du futur. Puis, nous proposons deux contributions majeures que nous déployons sur la couche virtuelle formés par les Home-Boxes (passerelles résidentielles évoluées) introduite dans l’architecture précédente. Dans notre première contribution, nous proposons un environnement permettant le déploiement à grande échelle de services sensibles au contexte. Deux approches ont été considérées dans la modélisation et la gestion du contexte. La première approche est basée sur les langages de balisage afin de permettre un traitement du contexte plus léger et par conséquent des temps de réponse très petits. La seconde approche, quant à elle est basée sur les ontologies et les règles afin de permettre plus d’expressivité et un meilleur partage et réutilisation des informations de contexte. Les ontologies étant connues pour leur complexité, le but de cette proposition et de prouver la faisabilité d’une telle approche dans un contexte de services multimédias par des moyen de distribution de la gestion du contexte. Concernant notre deuxième contribution, l’idée et de tirer profit des ressources (disque et connectivité) des Home-Boxes déjà déployées, afin d’améliorer les plateformes de distribution des services médias et d’améliorer ainsi le passage à l’échelle, la performance et la fiabilité de ces derniers et ce, à moindre coût. Pour cela, nous proposons deux solutions pour deux problèmes communément traités dans la réplication des contenus : (1) la redirection de requêtes pour laquelle nous proposons un algorithme de sélection à deux niveaux de filtrage, un premier filtrage basé sur les règles afin de personnaliser les services en fonction du contexte de leur consommation suivi d’un filtrage basé sur des métriques réseaux (charges des serveurs et délais entre les serveurs et les clients) ; et (2) le placement et la distribution des contenus sur les caches pour lesquels on a proposé une stratégie de mise en cache online, basée sur la popularité des contenus.Users’ willingness to consume media services along with the compelling proliferation of mobile devices interconnected via multiple wired and wireless networking technologies place high requirements on the Future Internet. It is a common belief today that Internet should evolve towards providing end users with ubiquitous and high quality media services and this, in a scalable, reliable, efficient and interoperable way. However, enabling such a seamless media delivery raises a number of challenges. On one hand, services should be more context-aware to enable their delivery to a large and disparate computational context. On another hand, current Internet media delivery infrastructures need to scale in order to meet the continuously growing number of users while keeping quality at a satisfying level. In this context, we introduce a novel architecture, enabling a novel collaborative framework for sharing and consuming Media Services within Future Internet (FI). The introduced architecture comprises a number of environments and layers aiming to improve today’s media delivery networks and systems towards a better user experience. In this thesis, we are particulary interested in enabling context-aware multimedia services provisioning that meets on one hand, the users expectations and needs and on another hand, the exponentially growing users’ demand experienced by these services. Two major and demanding challenges are then faced in this thesis (1) the design of a context-awareness framework that allows adaptive multimedia services provisioning and, (2) the enhancement of the media delivery platform to support large-scale media services. The proposed solutions are built on the newly introduced virtual Home-Box layer in the latter proposed architecture.First, in order to achieve context-awareness, two types of frameworks are proposed based on the two main models for context representation. The markup schemes-based framework aims to achieve light weight context management to ensure performance in term of responsiveness. The second framework uses ontology and rules to model and manage context. The aim is to allow higher formality and better expressiveness and sharing. However, ontology is known to be complex and thus difficult to scale. The aim of our work is then to prove the feasibility of such a solution in the field of multimedia services provisioning when the context management is distributed among the Home-Box layer. Concerning the media services delivery enhancement, the idea is to leverage the participating and already deployed Home-Boxes disk storage and uploading capabilities to achieve service performance, scalability and reliability. Towards this, we have addressed two issues that are commonly induced by the content replication: (1) the server selection for which we have proposed a two-level anycast-based request redirection strategy that consists in a preliminary filtering based on the clients’ contexts and in a second stage provides accurate network distance information, using not only the end-to-end delay metric but also the servers’ load one and, (2) the content placement and replacement in cache for which we have designed an adaptive online popularity-based video caching strategy among the introduced HB overlay

Context-aware media services delivery in heterogeneous environments for future media networks

La généralisation de l’usage de l’Internet, ces dernières années, a été marquée par deux tendances importantes. Nous citerons en premier, l’enthousiasme de plus en plus grand des utilisateurs pour les services médias. Cette tendance est particulièrement accentuée par l’avènement des contenus générés par les utilisateurs qui amènent dans les catalogues des fournisseurs de services un choix illimité de contenus. L’autre tendance est la diversification et l’hétérogénéité en ressources des terminaux et réseaux d’accès. Seule la valeur du service lui-même compte aujourd’hui pour les utilisateurs et non le moyen d’y accéder. Cependant, offrir aux utilisateurs un accès ubiquitaire à de plus en plus de services Internet, impose des exigences très rigoureuses sur l’infrastructure actuelle de l’Internet. En effet, L’évolution de l’Internet devient aujourd’hui une évidence et cette évolution est d’autant plus nécessaire dans un contexte de services multimédias qui sont connus pour leur sensibilité au contexte dans lequel ils sont consommés et pour générer d’énormes quantités de trafic. Dans le cadre de cette thèse, nous nous focalisons sur deux enjeux importants dans l’évolution de l’Internet. A savoir, faciliter le déploiement de services médias personnalisés et adaptatifs et améliorer les plateformes de distribution de ces derniers afin de permettre leur passage à l’échelle tout en gardant la qualité de service à un niveau satisfaisant pour les utilisateurs finaux. Afin de permettre ceci, nous introduisons en premier, une nouvelle architecture multi environnements et multi couches permettant un environnement collaboratif pour le partage et la consommation des services médias dans un cadre des réseaux média du futur. Puis, nous proposons deux contributions majeures que nous déployons sur la couche virtuelle formés par les Home-Boxes (passerelles résidentielles évoluées) introduite dans l’architecture précédente. Dans notre première contribution, nous proposons un environnement permettant le déploiement à grande échelle de services sensibles au contexte. Deux approches ont été considérées dans la modélisation et la gestion du contexte. La première approche est basée sur les langages de balisage afin de permettre un traitement du contexte plus léger et par conséquent des temps de réponse très petits. La seconde approche, quant à elle est basée sur les ontologies et les règles afin de permettre plus d’expressivité et un meilleur partage et réutilisation des informations de contexte. Les ontologies étant connues pour leur complexité, le but de cette proposition et de prouver la faisabilité d’une telle approche dans un contexte de services multimédias par des moyen de distribution de la gestion du contexte. Concernant notre deuxième contribution, l’idée et de tirer profit des ressources (disque et connectivité) des Home-Boxes déjà déployées, afin d’améliorer les plateformes de distribution des services médias et d’améliorer ainsi le passage à l’échelle, la performance et la fiabilité de ces derniers et ce, à moindre coût. Pour cela, nous proposons deux solutions pour deux problèmes communément traités dans la réplication des contenus : (1) la redirection de requêtes pour laquelle nous proposons un algorithme de sélection à deux niveaux de filtrage, un premier filtrage basé sur les règles afin de personnaliser les services en fonction du contexte de leur consommation suivi d’un filtrage basé sur des métriques réseaux (charges des serveurs et délais entre les serveurs et les clients) ; et (2) le placement et la distribution des contenus sur les caches pour lesquels on a proposé une stratégie de mise en cache online, basée sur la popularité des contenus.Users’ willingness to consume media services along with the compelling proliferation of mobile devices interconnected via multiple wired and wireless networking technologies place high requirements on the Future Internet. It is a common belief today that Internet should evolve towards providing end users with ubiquitous and high quality media services and this, in a scalable, reliable, efficient and interoperable way. However, enabling such a seamless media delivery raises a number of challenges. On one hand, services should be more context-aware to enable their delivery to a large and disparate computational context. On another hand, current Internet media delivery infrastructures need to scale in order to meet the continuously growing number of users while keeping quality at a satisfying level. In this context, we introduce a novel architecture, enabling a novel collaborative framework for sharing and consuming Media Services within Future Internet (FI). The introduced architecture comprises a number of environments and layers aiming to improve today’s media delivery networks and systems towards a better user experience. In this thesis, we are particulary interested in enabling context-aware multimedia services provisioning that meets on one hand, the users expectations and needs and on another hand, the exponentially growing users’ demand experienced by these services. Two major and demanding challenges are then faced in this thesis (1) the design of a context-awareness framework that allows adaptive multimedia services provisioning and, (2) the enhancement of the media delivery platform to support large-scale media services. The proposed solutions are built on the newly introduced virtual Home-Box layer in the latter proposed architecture.First, in order to achieve context-awareness, two types of frameworks are proposed based on the two main models for context representation. The markup schemes-based framework aims to achieve light weight context management to ensure performance in term of responsiveness. The second framework uses ontology and rules to model and manage context. The aim is to allow higher formality and better expressiveness and sharing. However, ontology is known to be complex and thus difficult to scale. The aim of our work is then to prove the feasibility of such a solution in the field of multimedia services provisioning when the context management is distributed among the Home-Box layer. Concerning the media services delivery enhancement, the idea is to leverage the participating and already deployed Home-Boxes disk storage and uploading capabilities to achieve service performance, scalability and reliability. Towards this, we have addressed two issues that are commonly induced by the content replication: (1) the server selection for which we have proposed a two-level anycast-based request redirection strategy that consists in a preliminary filtering based on the clients’ contexts and in a second stage provides accurate network distance information, using not only the end-to-end delay metric but also the servers’ load one and, (2) the content placement and replacement in cache for which we have designed an adaptive online popularity-based video caching strategy among the introduced HB overlay

Flexible User Profile Management for Context-Aware Ubiquitous Environments

International audienceWith the important advent of multimedia services and the ubiquity of computing environments, the concept of context-awareness in services access and provisioning is getting crucial. Services, especially the multimedia ones, must perform automatically actions/operations to adapt the delivered content to the user expectations and his environment capabilities, thus ensuring the best quality of experience. To facilitate the adaptation process, we introduce a flexible context-sensitive user profile model that gathers static and dynamic data characterizing the user and his operational context. An efficient framework for managing and delivering the user profile is also proposed. A context-dependent user profile instance is created for each application according to its adaptation process needs. This paper also presents some implementation issues of the developed prototype together with an IPTV streaming use case

Gestion des accès massifs des équipements dans les réseaux NB-IoT : une stratégie basée sur l'apprentissage par renforcement

International audienc

Context-aware media services delivery in heterogeneous environments for future media networks

La généralisation de l usage de l Internet, ces dernières années, a été marquée par deux tendances importantes. Nous citerons en premier, l enthousiasme de plus en plus grand des utilisateurs pour les services médias. Cette tendance est particulièrement accentuée par l avènement des contenus générés par les utilisateurs qui amènent dans les catalogues des fournisseurs de services un choix illimité de contenus. L autre tendance est la diversification et l hétérogénéité en ressources des terminaux et réseaux d accès. Seule la valeur du service lui-même compte aujourd hui pour les utilisateurs et non le moyen d y accéder. Cependant, offrir aux utilisateurs un accès ubiquitaire à de plus en plus de services Internet, impose des exigences très rigoureuses sur l infrastructure actuelle de l Internet. En effet, L évolution de l Internet devient aujourd hui une évidence et cette évolution est d autant plus nécessaire dans un contexte de services multimédias qui sont connus pour leur sensibilité au contexte dans lequel ils sont consommés et pour générer d énormes quantités de trafic. Dans le cadre de cette thèse, nous nous focalisons sur deux enjeux importants dans l évolution de l Internet. A savoir, faciliter le déploiement de services médias personnalisés et adaptatifs et améliorer les plateformes de distribution de ces derniers afin de permettre leur passage à l échelle tout en gardant la qualité de service à un niveau satisfaisant pour les utilisateurs finaux. Afin de permettre ceci, nous introduisons en premier, une nouvelle architecture multi environnements et multi couches permettant un environnement collaboratif pour le partage et la consommation des services médias dans un cadre des réseaux média du futur. Puis, nous proposons deux contributions majeures que nous déployons sur la couche virtuelle formés par les Home-Boxes (passerelles résidentielles évoluées) introduite dans l architecture précédente. Dans notre première contribution, nous proposons un environnement permettant le déploiement à grande échelle de services sensibles au contexte. Deux approches ont été considérées dans la modélisation et la gestion du contexte. La première approche est basée sur les langages de balisage afin de permettre un traitement du contexte plus léger et par conséquent des temps de réponse très petits. La seconde approche, quant à elle est basée sur les ontologies et les règles afin de permettre plus d expressivité et un meilleur partage et réutilisation des informations de contexte. Les ontologies étant connues pour leur complexité, le but de cette proposition et de prouver la faisabilité d une telle approche dans un contexte de services multimédias par des moyen de distribution de la gestion du contexte. Concernant notre deuxième contribution, l idée et de tirer profit des ressources (disque et connectivité) des Home-Boxes déjà déployées, afin d améliorer les plateformes de distribution des services médias et d améliorer ainsi le passage à l échelle, la performance et la fiabilité de ces derniers et ce, à moindre coût. Pour cela, nous proposons deux solutions pour deux problèmes communément traités dans la réplication des contenus : (1) la redirection de requêtes pour laquelle nous proposons un algorithme de sélection à deux niveaux de filtrage, un premier filtrage basé sur les règles afin de personnaliser les services en fonction du contexte de leur consommation suivi d un filtrage basé sur des métriques réseaux (charges des serveurs et délais entre les serveurs et les clients) ; et (2) le placement et la distribution des contenus sur les caches pour lesquels on a proposé une stratégie de mise en cache online, basée sur la popularité des contenus.Users willingness to consume media services along with the compelling proliferation of mobile devices interconnected via multiple wired and wireless networking technologies place high requirements on the Future Internet. It is a common belief today that Internet should evolve towards providing end users with ubiquitous and high quality media services and this, in a scalable, reliable, efficient and interoperable way. However, enabling such a seamless media delivery raises a number of challenges. On one hand, services should be more context-aware to enable their delivery to a large and disparate computational context. On another hand, current Internet media delivery infrastructures need to scale in order to meet the continuously growing number of users while keeping quality at a satisfying level. In this context, we introduce a novel architecture, enabling a novel collaborative framework for sharing and consuming Media Services within Future Internet (FI). The introduced architecture comprises a number of environments and layers aiming to improve today s media delivery networks and systems towards a better user experience. In this thesis, we are particulary interested in enabling context-aware multimedia services provisioning that meets on one hand, the users expectations and needs and on another hand, the exponentially growing users demand experienced by these services. Two major and demanding challenges are then faced in this thesis (1) the design of a context-awareness framework that allows adaptive multimedia services provisioning and, (2) the enhancement of the media delivery platform to support large-scale media services. The proposed solutions are built on the newly introduced virtual Home-Box layer in the latter proposed architecture.First, in order to achieve context-awareness, two types of frameworks are proposed based on the two main models for context representation. The markup schemes-based framework aims to achieve light weight context management to ensure performance in term of responsiveness. The second framework uses ontology and rules to model and manage context. The aim is to allow higher formality and better expressiveness and sharing. However, ontology is known to be complex and thus difficult to scale. The aim of our work is then to prove the feasibility of such a solution in the field of multimedia services provisioning when the context management is distributed among the Home-Box layer. Concerning the media services delivery enhancement, the idea is to leverage the participating and already deployed Home-Boxes disk storage and uploading capabilities to achieve service performance, scalability and reliability. Towards this, we have addressed two issues that are commonly induced by the content replication: (1) the server selection for which we have proposed a two-level anycast-based request redirection strategy that consists in a preliminary filtering based on the clients contexts and in a second stage provides accurate network distance information, using not only the end-to-end delay metric but also the servers load one and, (2) the content placement and replacement in cache for which we have designed an adaptive online popularity-based video caching strategy among the introduced HB overlay.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF