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Performance-enhancing mechanisms in the World Wide Web primarily exploit repeated requests to Web documents by multiple clients. However, little is known about patterns of shared document access, particularly from diverse client populations. The principal goal of this paper is to examine the sharing of Web documents from an organizational point of view. An organizational analysis of sharing is important, because caching is often performed on an organizational basis; i.e., proxies are typically placed in front of large and small companies, universities, departments, and so on. Unfortunately, simultaneous multi-organizational traces do not currently exist and are difficult to obtain in practice.

Proxy caches are increasingly used around the world to reduce bandwidth requirements and alleviate delays associated with the World-Wide Web. In order to compare proxy cache performances, objective measurements must be made. In this paper, we define a space of proxy evaluation methodologies based on source of workload used and form of algorithm implementation. We then survey recent publications and show their locations within this space. 1 Introduction Proxy caches are increasingly used around the world to reduce bandwidth and alleviate delays associated with the World-Wide Web. This paper describes the space of proxy cache evaluation methodologies and places current research within that space. The primary contributions of this paper are threefold: 1) definition and description of the space of evaluation techniques; 2) appraisal of the di#erent methods within that space; and 3) a survey of cache evaluation techniques from the research literature. In the next section we provide backgro...

User-perceived retrieval latencies in the World Wide Web can be improved by pre-loading a local cache with resources likely to be accessed. A user requesting content that can be served by the cache is able to avoid the delays inherent in the Web, such as congested networks and slow servers. The difficulty, then, is to determine what content to prefetch into the cache. This work explores machine learning algorithms for user sequence prediction, both in general and specifically for sequences of Web requests. We also consider information retrieval techniques to allow the use of the content of Web pages to help predict future requests. Although history-based mechanisms can provide strong performance in predicting future requests, performance can be improved by including predictions from additional sources. While past researchers have used a variety of techniques for evaluating caching algorithms and systems, most of those methods were not applicable to the evaluation of prefetching algorithms or systems. Therefore, two new mechanisms for evaluation are introduced. The first is a detailed trace-based simulator, built from scratch,

The last decade has seen a super-exponential growth of the World Wide Web. The demand of bandwidth has been consistently increasing faster than the resource. Researchers have looked for alternative solutions to improve response time and reduce bandwidth consumption in the Internet. Caching has been well accepted as a viable method for ease the ever growing bandwidth need and also to improve the speed of information delivery. However, single point caching has limitation regarding scalability. Cooperative caching, where cache servers support each other in serving requests for cached objects, has emerged as an approach to overcome the limitation. This survey looks at dierent studies done on cooperative caching. The studies have been grouped together according to their approaches to achieve cooperation. Cooperative caching architectures can be divided into two major categories, hierarchical and distributive. Both approaches have their advantages and disadvantages. There is also...

While several mechanisms for maintaining consistency in single proxy caches exist today, not as much research has addressed ways in which such techniques may be extended to a cluster of proxy caches. If such techniques are not developed and deployed carefully, the overheads involved in maintaining cache consistency in large-scale systems such as Content Distribution Networks (CDNs) increases by several orders of magnitude with increase in the number of proxies. The goal of developing such algorithms is therefore to come up with ways by which consistency guarantees can be provided while keeping network and server resource usage low. In this paper, we present efficient ways to maintain cache consistency in CDNs using leases. We address the following issues: (i) Selection of a leader proxy, via which updates and/or invalidates may be propagated to other proxies (ii) The effects of co-operation between proxy caches (iii) Eager vs. Lazy renewal of leases (iv) Policies for intelligent dissemination of updates and/or invalidates. (v) Means of adapting to changing server and network loads and yet providing consistency guarantees. (vi) Multi-level hierarchical proxy organization and (vii) The scalability achieved with increasing number of independent proxy clusters. 1

Abstract Nowadays, on-demand delivery of continuous media is becoming increasingly commonplace. At the same time, wireless networks are appearing everywhere in different forms, and handheld devices become more and more powerful and widespread. Nevertheless, the traditional approach used for streaming cannot scale efficiently and is not appropriate for mobile clients. In this article, we go into more detail in describing the orchestration layer of the MoVie project, SysMoVie. We describe more deeply the localization mechanism, which is based on the corba’s cosTrading service, and the clients’ mandataries which are intelligent agents. Keywords:VoD,mobility,corba,trader,mandatary 1

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We present the design and implementation of the #Ninja Jukebox", an infrastructural service that allows a community of users to build a distributed, collaborative music repository that delivers digital music to Internet clients, and that performs simple collaborative #ltering based on users' song preferences inferred by the service. The Jukebox, implemented in Java, was designed to allow rapid service evolution and recon#guration, simplicity in participation, and extensibility. We demonstrate that our careful use of a distributed component architecture enabled rapid prototyping of the service, and that our use of carefully designed, strongly typed interfaces enabled the smooth evolution of the service from a simple prototype to a more complex, mature system.