Cooperative Caching for Multimedia Streaming in Overlay Networks

Traditional data caching, such as web caching, only focuses on how to boost the hit rate of requested objects in caches, and therefore, how to reduce the initial delay for object retrieval. However, for multimedia objects, not only reducing the delay of object retrieval, but also provisioning reasonably stable network bandwidth to clients, while the fetching of the cached objects goes on, is important as well. In this paper, we propose our cooperative caching scheme for a multimedia delivery scenario, supporting a large number of peers over peer-to-peer overlay networks. In order to facilitate multimedia streaming and downloading service from servers, our caching scheme (1) determines the appropriate availability of cached stream segments in a cache community, (2) determines the appropriate peer for cache replacement, and (3) performs bandwidth-aware and availability-aware cache replacement. By doing so, it achieves (1) small delay of stream retrieval, (2) stable bandwidth provisioning during retrieval session, and (3) load balancing of clients' requests among peers

Smart PIN: utility-based replication and delivery of multimedia content to mobile users in wireless networks

Next generation wireless networks rely on heterogeneous connectivity technologies to support various rich media services such as personal information storage, file sharing and multimedia streaming. Due to users’ mobility and dynamic characteristics of wireless networks, data availability in collaborating devices is a critical issue. In this context Smart PIN was proposed as a personal information network which focuses on performance of delivery and cost efficiency. Smart PIN uses a novel data replication scheme based on individual and overall system utility to best balance the requirements for static data and multimedia content delivery with variable device availability due to user mobility. Simulations show improved results in comparison with other general purpose data replication schemes in terms of data availability

Efficiency of Tree-Structured Peer-to-Peer Service Discovery Systems

The efficiency of service discovery is a crucial point in the development of fully decentralized middlewares intended to manage large scale computational grids. The work conducted on this issue led to the design of many peer-to-peer fashioned approaches. More specifically, the need for flexibility and complexity in the service discovery has seen the emergence of a new kind of overlays, based on tries, also known as lexicographic trees. Although these overlays are efficient and well designed, they require a costly maintenance and do not accurately take into account the heterogeneity of nodes and the changing popularity of the services requested by users. In this paper, we focus on reducing the cost of the maintenance of a particular architecture, based on a dynamic prefix tree, while enhancing it with some load balancing techniques that dynamically adapt the load of the nodes in order to maximize the throughput of the system. The algorithms developed couple a self-organizing prefix tree overlay with load balancing techniques inspired by similar previous works undertaken for distributed hash tables. After some simulation results showing how our load balancing heuristics perform in such an overlay and compare to other heuristics, we provide a fair comparison of this architecture and similar overlays recently proposed.L’efficacité de la découverte de services est un point crucial du développement d’intergiciels de grille totalement décentralisés. Les travaux ayant pour but la résolution de ce problème ont généré un certain nombre d’approches pair-à-pair. le besoin de flexibilité et d’expressivité a donné lieu au développement d’architecture s’appuyant sur des arbres de préfixes(ou arbres lexicographiques). Ces overlays souffrent d’une maintenance couteuse et ne prennent pas en compte la nature hétérogène de la plate-forme physique sous-jacente et la popularité différente et changeante de chaque ressource enregistrée.Dans ce rapport, nous nous focalisons sur la réduction du cout de maintenance d’une telle architecture, basée sur un arbre de préfixes dynamique,tout en lui donnant la possibilité de s’adapter à l’hétérogénéité précitée par l’enrichissant de mécanismes de répartition de la charge qui adaptent dynamiquement la charge des nœuds dans le but de maximiser le débit sur service. Notre approche couple des travaux de répartition de la charge dans les DHTs avec un overlay en arbre de préfixes auto-organisant. Après des résultats de simulation mettant en évidence l’efficacité de notre heuristique, nous comparons notre approche avec les travaux s’appuyant sur des structures distribuées similaires

Distributed, Secure Load Balancing with Skew, Heterogeneity, and Churn

Numerous proposals exist for load balancing in peer-to-peer (p2p) networks. Some focus on namespace balancing, making the distance between nodes as uniform as possible. This technique works well under ideal conditions, but not under those found empirically. Instead, researchers have found heavytailed query distributions (skew), high rates of node join and leave (churn), and wide variation in node network and storage capacity (heterogeneity). Other approaches tackle these less-thanideal conditions, but give up on important security properties. We propose an algorithm that both facilitates good performance and does not dilute security. Our algorithm, k-Choices, achieves load balance by greedily matching nodes’ target workloads with actual applied workloads through limited sampling, and limits any fundamental decrease in security by basing each nodes’ set of potential identifiers on a single certificate. Our algorithm compares favorably to four others in trace-driven simulations. We have implemented our algorithm and found that it improved aggregate throughput by 20% in a widely heterogeneous system in our experiments.Engineering and Applied Science