Web Cache Prefetching Model

With the remarkable and exponential growth rate of Web information and users, how to reduce the user perceived access latency and improve the quality of service of the network is becoming a crucial problem, and Web prefetching and Web caching are the primary solutions. This paper has deeply studied the modeling of Web access characteristics, the integrated model for Web caching and prefetching.The concept, classification, structure of Web caching and prefetching and the working principle of integrated Web caching and prefetching system are described. A prefetch framework is proposed according to the user surfing procedure. Afterwards, Web surfing characteristics are discussed. Understanding the WWW traffic characteristics is the key to the effective design of Web caching and prefetching algorithm.Based on the Web access characteristics, the mathematical model of Web traffic is discussed, the integrated model of Web caching and prefetching is put forward. Then, the performance evaluation of the integrated Web caching and prefetching model (IWCPM) is made and discussed.The main research work of this thesis can be described as follows:1. This paper makes use of mathematical analytical approach to design and implement a Web LOG simulator: WEBGEN, in which the Web object popularity distribution, Web object size distribution and Web temporal locality are simulated. It not only can synthesize Web object access workload, but also has higher flexibility, and provide basis for further studying Web caching and prefetching.2. Previous studies in Web caching and prefetching mainly focus on improving replacement policies and building access models and evaluating the performance of such models in predicting future accesses. While these models are important, they lack the consideration of analysis based on integrated Web caching and prefetching system. Integrated Web caching and prefetching model (IWCPM) is presented and the performance evaluation of IWCPM is made. An improved PPM algorithm is discussed in detail in the discussion of the integrated model.3. A Web caching and prefetching simulator is designed and implemented. Experiments have been made based on IWCPM with the support of popularity-based prediction and pattern-based prediction mechanisms and four tipical replacement policies: GDSF, GDSize, LFU, and LRU. The experimental results illustrate the combination of Web prefetching and caching holds the promise of improving the QoS of Web systems. The corresponding application fields of popularity-based prediction and pattern-based prediction mechanisms are also presented in the paper.