Building Internet caching systems for streaming media delivery

The proxy has been widely and successfully used to cache the static Web objects fetched by a client so that the subsequent clients requesting the same Web objects can be served directly from the proxy instead of other sources faraway, thus reducing the server\u27s load, the network traffic and the client response time. However, with the dramatic increase of streaming media objects emerging on the Internet, the existing proxy cannot efficiently deliver them due to their large sizes and client real time requirements.;In this dissertation, we design, implement, and evaluate cost-effective and high performance proxy-based Internet caching systems for streaming media delivery. Addressing the conflicting performance objectives for streaming media delivery, we first propose an efficient segment-based streaming media proxy system model. This model has guided us to design a practical streaming proxy, called Hyper-Proxy, aiming at delivering the streaming media data to clients with minimum playback jitter and a small startup latency, while achieving high caching performance. Second, we have implemented Hyper-Proxy by leveraging the existing Internet infrastructure. Hyper-Proxy enables the streaming service on the common Web servers. The evaluation of Hyper-Proxy on the global Internet environment and the local network environment shows it can provide satisfying streaming performance to clients while maintaining a good cache performance. Finally, to further improve the streaming delivery efficiency, we propose a group of the Shared Running Buffers (SRB) based proxy caching techniques to effectively utilize proxy\u27s memory. SRB algorithms can significantly reduce the media server/proxy\u27s load and network traffic and relieve the bottlenecks of the disk bandwidth and the network bandwidth.;The contributions of this dissertation are threefold: (1) we have studied several critical performance trade-offs and provided insights into Internet media content caching and delivery. Our understanding further leads us to establish an effective streaming system optimization model; (2) we have designed and evaluated several efficient algorithms to support Internet streaming content delivery, including segment caching, segment prefetching, and memory locality exploitation for streaming; (3) having addressed several system challenges, we have successfully implemented a real streaming proxy system and deployed it in a large industrial enterprise

Cooperative Caching of Dynamic Content on a Distributed Web Server

In this technical report we propose a new method for improving the average response time of Web servers by cooperatively caching the results of requests for dynamic content. The work is motivated by our recent study of access logs from the Alexandria Digital Library server at UCSB, which demonstrates that approximately a 30 percent decrease in average response time could be achieved by caching dynamically generated content. We have developed a distributed Web server called Swala, in which the nodes cooperatively cache the results of CGI requests. We use a two-level cache table consistency protocol and a replicated global cache directory to maximize the system performance and minimize overhead in responding to dynamic Web requests. Our experiments show that the single-node performance of Swala without caching is comparable to the Netscape Enterprise server, that considerable speedups are obtained using caching, and that the cache hit rate is substantially higher with cooperative cache t..

Proxys Internet avancés

Since the 90's, the Internet has tremendously evolved in terms of number and diversity of available services. In this trend, proxies are playing a central role and are spread all over the net. Today, the only functionality of proxies is to speed content access through caching only considering statistics based on use made by a user group, all together. Nowadays, evolutions are focusing on two main trends: specific infrastructures that do not comply anymore with the Web universality or individual applications like filtering. We propose to make proxies evolve from simple passive intermediaries to an open platform with advanced caching functionalities stressing on maintaining a high level of compatibility with existing paradigms. We ground our developments on two qualities already available in proxies, widely spread over the Net: the privileged position (plesiocentrism) within the network infrastructures and the perceptivity we extend to new dimensions, more specifically semantic (engnose). In a first step, we elaborate a new Web resources indexation binding to the documents a semantic space, based on the absolute position defined from the URL and a relative position defined with the links that connect those resources. We extend the usage statistics to those new dimensions to build up a topological space that take into account the localization of the documents and the user browsing into that space. We present algorithms and functionalities to build, maintain and take advantage of this topology. With the aim of accelerating web browsing, we use this statistical space to implement a prefetching system based on Markov's model. To extend the proxy perceptivity upstream to the users, we propose a mechanism to maintain a session, based on proxy-cookies. Therefore, we propose two new HTTP directives similar to those used for cookies. This paradigm also allows us to install personalized services with the support of the interaction concept and user profile. This last one allows us to tackle with mobility problems and to install proxies independently of physical network infrastructures. In a second move, we study how the proxy could take into account new dimensions in the semantic web and ontology context. The new technologies emerging like XML and annotations bring new information. That information can easily be processed by a computer system. As for the annotations, they considerably enrich the available informations in the proxy's perception through the classification or resources in ontology. We underline the opportunity for proxys, regarding their situation, to integrate functionalities of annotation server. We demonstrate what can be acquired that way and advantages to be won with the engnose definition as a new proxy quality that become perceptive to web disseminated knowledge. We present a new cache management based on virtual multi-level cache. We present an algorithm able to switch automatically to the correct domain regarding the ontological value of currently visited resources. Last, to demonstrate the validity of our propositions, we define the I3 platform (Intelligent Interactive Intermediaries): an architecture that supports all the various mechanisms presented above, but preserving integration with a minimum of impact on existing infrastructures. We define the concept of proxlet that is an intermediary agent generalization and allow the development of new user services. We demonstrate the value of our proposition by presenting opportunities brought by our platform. We take advantage of the interaction allowed by the session concept to implement functionalities also made possible by an advanced cache model based on topology, semantic and ontology. This platform allows the implementation of services such as browsing help, mobility filtering and service integration