Taming The World Wide Web

From Web Measurements to Web Protocol Design

Prof. Azer Bestavros
Computer Science Department
Boston University

Friday, November 15, 1996
11 a.m. - 12 noon
Fuller Labs 320

This talk reports on a number of research projects undertaken by the Oceans Group at Boston University. These projects focus on using empirical performance measurements to design and tune new middleware services for the World Wide Web.

In the first part of this talk, the findings of a detailed study on the effectiveness of caching for the WWW will be presented. This study highlights the importance of locality of reference properties for large-scale distributed information systems. Next, the design and performance of various caching, dissemination and prefetching services that capitalize on these properties will be presented.

In the second part of this talk, I will present two complementary techniques for prefetching WWW documents. The first technique, termed speculative service, is server-initiated. It works by providing hints to clients based on analysis of server logs. The second technique is client-initiated. It works by allowing the client to build a Markov model of document access based on previous client access patterns and use that model to provide hints about future references. Using extensive trace simulations based on the logs of our departmental HTTP server logs and Mosaic client logs, we have evaluated the merits of each one of the above techniques. Our trace simulations suggest that client-initiated prefetching is very effective for frequently-traversed document sequences, whereas server-initiated prefetching is more effective for infrequently- traversed sequences. Based on these findings, we suggest an on-line heuristic that weighs the hints provided from both server and client agents based on dynamically-measured cache miss rates. Finally, I will overview our implementation of prototype HTTP server and browser software that include the above client-initiated and server-initiated prefetching capabilities.

Maintained by webmaster@wpi.edu
Last modified: Sep 27, 2006, 16:05 EDT