This paper addresses two unresolved issues about web caching. The first issue is whether web requests from a fixed user community are distributed according to Zipf's law [22]. Several early studies have supported this claim [9], [5], while other recent studies have suggested otherwise [16], [2]. The ;econd issue relates to a number of recent studies on the characteristics of web proxy traces, which have shown that the hit-ratios and temporal locality of the traces exhibit certain asymptotic properties that are uniform across the different sets of the traces [43, [XO], [71, [XO], [XS]. In partlc- ular, the question is whether these properties are inherent to web accesses or whether they are simply an artifact of the traces. An answer to these unresolved issues will facili- tate both web cache resource planning and cache hierarchy design

While algorithms for cooperative proxy caching have been widely studied, little is understood about cooperative-caching performance in the large-scale World Wide Web environment. This paper uses both trace-based analysis and analytic modelling to show the potential advantages and drawbacks of inter-proxy cooperation. With our traces, we evaluate quantitatively the performance-improvement potential of cooperation between 200 small-organization proxies within a university environment, and between two large-organization proxies handling 23,000 and 60,000 clients, respectively. With our model, we extend beyond these populations to project cooperative caching behavior in regions with millions of clients. Overall, we demonstrate that cooperative caching has performance benefits only within limited population bounds. We also use our model to examine the implications of future trends in Web-access behavior and traffic.

Data mining algorithms have been the focus of much research recently. In practice, the input data to a data mining process resides in a large data warehouse whose data is kept up-to-date through periodic or occasional addition and deletion of blocks of data. Most data mining algorithms have either assumed that the input data is static, or have been designed for arbitrary insertions and deletions of data records.

Placeshifting systems stream videos from the home to a single remote user using the limited upstream capacity of the home broadband link. We analyze the behavior of two placeshifting systems each using two types of broadband networks. We show that the duration between packets did not depend on the way that the servers were sending the packets through the bottleneck link. Even though both of these systems used TCP, the duration between packets did not follow the round trip times either. Instead, it depended on the particular broadband network. Our analysis shows how the bottlenecked first mile network leads to predictable packet delivery at the remote client. Paradoxically, it also leads to shorter periods and a single packet within each data burst. We discuss the limitations imposed by this behavior on a client side energy saving mechanism. We also describe techniques that allow the placeshifting servers to better operate with client side WNIC energy saving mechanisms.

Clustering support with a single-system image for large-scale Web servers is important to improve the system scalability in processing a large number of concurrent requests from Internet, especially when those requests involve resource-intensive dynamic content generation. This paper proposes scheduling optimization for a Web server cluster with a master/slave architecture which separates static and dynamic content processing. Our experimental results show that the proposed optimization using reservation-based scheduling can produce up to a 68% performance improvement.

The benefits of using caches for reducing traffic in backbone trunk links and for improving web access times are well-known. However, there are some known problems with traditional web caching, namely, maintaining freshness of web objects, balancing load among a number of caches and providing protection against cache failure. This paper investigates in detail the advantages and disadvantages of a distributed architecture of caches which are coordinated through a central controller. In particular, the performance of a set of independent caches is compared against the performance of a set of coordinated distributed caches using extensive simulation. The conclusion is that a distributed architecture of coordinated caches consistently provides a better hit ratio, improves response time, provides better freshness, achieves load balancing, and increases the overall traffic handling capacity of a network while paying a small price in terms of additional control traffic. In particular...

Web traffic has been increasing and evolving rapidly in recent years. It is important to measure the volume and characteristic of such dominant traffic to understand large-scale user access pattern and analyze performance of Web applications. Among the common methods of Web measurements, the passive way using packet monitoring is more advantageous since it provides comprehensive information and is transparent to end-users. However, the throughput of current packet monitoring system is limited by the bandwidth of network adapters. Computational capacity and buffer size are also potential performance bottlenecks for monitoring high-speed links. This paper proposes a cluster-based online monitoring system, which generates rich logs by packet sniffing for Web analysis in a cluster environment. Powered by cluster computing technologies, the system achieves high performance and availability. Other techniques, such as online reconstruction in memory and kernel packet filter, are also adopted to improve the system performance. The experimental results indicate that it is feasible to trace in high-speed links with the cluster-based system. 1.

The web is emerging as the primary data dissemination and e-commerce mechanism. Users access the Internet from a wide variety of devices with different resource constraints in terms of their processing, storage, network and display capabilities. Users are not only accessing the Internet from traditional desktops, but they are also using mobile devices such as palmtops and laptops as well as newer consumer devices such as webtops and navigation systems. Popular web ...

The bene ts of using caches for reducing trac in backbone trunk links and for improving web access times are well-known. However, there are some known problems with traditional web caching, namely, maintaining freshness of web objects, balancing load among a number of caches and providing protection against cache failure. This paper investigates in detail the advantages and disadvantages of a distributed architecture of caches which are coordinated through a central controller. In particular, the performance of a set of independent caches is compared against the performance of a set of coordinated distributed caches using extensive simulation and analytical modeling. The conclusion is that a distributed architecture of coordinated caches consistently provides a better hit ratio, improves response time, provides better freshness, achieves load balancing, and increases the overall trac handling capacity of a network while paying a small price in terms of additional control trac. In particular, we have observed up to 40% improvement in hit ratio, 70% improvement in response time, 60% improvement in freshness and 25% improvement in trac handling capacity of a network with caches.