PROXY BASED WEB CACHE CONSISTENCY FOR ENHANCING NETWORK EXECUTION

With the exponential growth of the Internet, the World Wide Web (WWW) has become the most widely used tool for access and dissemination of commercial educational, and news information on the internet. The success of the WWW is largely due to its cap ability of providing quick and easy accesses to a large variety of information form sites all over the world. The retrieval latency of the WWW is however sensitive to overload conditions of the network which agonizes web users. Caching data copies at client Sites (including web proxies) is regarded as a good technique for reducing both the network traffic and the server load, thus improving retrieval latency of web documents. Use of proxy caches in the World Wide Web is beneficial to the end user, network administrator, and server administrator since it reduces the amount of redundant traffic that circulates through the network. In addition, end users get quicker access to documents that are cached. However, the use of proxies introduces additional issues that need to be addressed. The existing consistency protocols used in the web are proving to be insufficient to meet the growing needs of the Internet population. For example, too many messages sent over the network are due to caches guessing when their copy is inconsistent. Many decisions must be made when exploring World Wide Web coherency, such as whether to provide consistency at the proxy level (client pull) or to allow the sever to handle it (server push). What tradeoffs are inherent for each of these decisions? The relevant usage of any method strongly depends upon the conditions of the network (e.g., document types that are frequently requested or the state of the network load) and the resources available (e.g., disk space and type of cache available). One goal of this dissertation is to study the characteristics of document retrieval and modification to determine their effect on proposed consistency mechanisms. A set of effective consistency policies is identified from the investigation. The main objective of this dissertation is to use these findings to design and implement a consistency algorithm that provide improved performance over the current mechanisms. Optimistically, we want an algorithm that provides strong consistency. However, we do not want to further degrade the network or cause undue burden on the server to gain this advantage. We propose a system based on the notion of soft-state and based on server push. In this system, the proxy would have some influence on what state information. Our results show that an average of 20% control message savings by limiting how much polling occurs with the current Web cache consistency mechanism, Adaptive Client Polling.