Proxy caching is a key technique to reduce transmission cost for on-demand multimedia streaming. The effectiveness of current caching schemes, however, is limited by the insufficient storage space and weak cooperations among proxies and their clients, particularly considering the high bandwidth demands from media objects. In this paper, we propose COPACC, a cooperative proxy-and-client caching system that addresses the above deficiencies. This innovative approach combines the advantages of both proxy caching and peer-to-peer client communications. It leverages the client-side caching to amplify the aggregated cache space and rely on dedicated proxies to effectively coordinate the communications. We propose a comprehensive suite of distributed protocols to facilitate the interactions among different network entities in COPACC. It also realizes a smart and cost-effective cache indexing, searching, and verifying scheme. Furthermore, we develop an efficient cache allocation algorithm for distributing video segments among the proxies and clients. The algorithm not only minimizes the aggregated transmission cost of the whole system, but also accommodates heterogeneous computation and storage constraints of proxies and clients. We have extensively evaluated the performance of COPACC under various network and end-system configurations. The results demonstrate that it achieves remarkably lower transmission cost as compared to pure proxy-based caching with limited storage space. On the other hand, it is much more robust than a pure peer-to-peer communication system in the presence of node failures. Meanwhile, its computation and control overheads are both kept in low levels. Keywords: Media Streaming, Proxy caching, Peer-to-Peer caching, Media segmentat ion and Resource allocation I.

A hierarchical storage system achieves scalable storage in providing on-demand video services. In such a system, video files are stored in a tertiary level (such as a library or jukebox), and transferred to a secondary level (such as magnetic disks) from which it is streamed to the users. In this paper, we study the design of such a system for interactive applications in which a movie has to be completely transferred (or "staged") to the secondary level before it is displayed to its user; thereby incurring some user delay. We specify the required storage and bandwidth to meet a delay goal, given application characteristics. We have developed an accurate and yet simple model for the system, which greatly facilitates the design process and allows us to extract important performance characteristics of the system. We provide some design examples, and study the influence of video popularity. Keywords---Hierarchical storage systems, interactive video services, tertiary storage, secondary st...

Video-on-demand (VOD) refers to video services in which users can request any video program from a server at any time. VOD has important applications in entertainment, education, information, and adverstising, such as movie-on-demand, distance learning, home shopping, interactive news, etc. In order to provide VOD services accommodating a large number of video titles and concurrent users, a VOD system has to be scalable --- scalable in storage and scalable in streaming capacity. Our goal is to design such a system with low cost, low complexity, and offering high level of service quality (in terms of, for example, user delay experienced or user loss rate). Storage scalability is achieved by using a hierarchical storage system, in which video files are stored in tertiary libraries or jukeboxes and transferred to a secondary level (of magnetic or optical disks) for display. We address the design of such a system by specifying the required architectural parameters (the bandwidth and storag...

AbstractÐIn designing cost-effective video-on-demand (VOD) servers, efficient resource management and proper system sizing are of great importance. In addition to large storage and I/O bandwidth requirements, support of interactive VCR functionality imposes additional resource requirements on the VOD system in terms of storage space, as well as disk and network bandwidth. Previous works have used ªdata sharingº techniques (such as batching, buffering, and adaptive piggybacking) to reduce the I/O demand on the storage server. However, such data sharing techniques complicate the provision of VCR functions and diminish the amount of benefit that can be obtained from data sharing techniques. The main contribution of this paper is a simple, yet powerful, analytical modeling approach which allows for analysis, system sizing, resource allocation, and parameter setting for a fairly general class of ªdata sharingº techniques which are used in conjunction with the providing of VCR-type functionality. Using this mathematical model, we can determine the proper amount of resources to be allocated for normal playback as well as for service of VCR functionality requests while satisfying predefined system performance requirements. To illustrate the usefulness of our model, we focus on a specific data sharing scheme which combines the use of batching, buffering, and adaptive piggybacking, as well as allows for the use of VCR functions. We show how to utilize this mathematical model for system sizing and resource allocation purposesÐthat is, how to distribute the available resources between the service of normal playback and VCR functionality requests under various workloads and resource price ratios, so as to obtain the lowest system cost. Index TermsÐVideo-on-demand, data sharing techniques, resource allocation, system sizing. 1

Abstract not found

Until now, true video-on-demand can only be achieved using a dedicated data flow for each service request. This bruteforce approach is prohibitively expensive. Using multicast can significantly reduce the system cost. This solution, however, must delay services in order to serve many requests as a batch. In this paper, we consider a third alternative called Patching. In our technique, an existing multicast can expand dynamically to serve new clients. Allowing new clients to join an existing multicast improves the efficiency of the multicast. Furthermore, since all requests can be served immediately, the clients experience no service delay and true video-on-demand can be achieved. A significant contribution of this work, is making multicast work for true video-on-demand services. In fact, we are able to eliminate the service latency and improve the efficiency of multicast at the same time. To assess the benefit of this scheme, we perform simulations to compare its performance with that ...

de nationalité espagnole acceptée sur proposition du jury: Prof. Roger D. Hersch, directeur de thèse Prof. Karl Aberer, rapporteur