The Hong Kong University of Science and Technology
Department of Computer Science


PhD Thesis Defence

"Caching and Replication Schemes on the Internet"

By

Mr. Athanasios Loukopoulos


Abstract

With the proliferation of the Internet, clients abandoning their
connections due to excessive downloading delays translates directly to
profit losses. Hence, minimizing the latency perceived by end-users has
become the primary performance issue comparing to more traditional ones,
such as server utilization. In this thesis we first survey research on the
two more widely used techniques to improve Web responsiveness namely,
proxy caching and server replication/mirroring. We argue on their
complimentary roles for decreasing client perceived response time and
proceed by illustrating the main topics that affect their successful
deployment on the Internet. Concerning replication we turn our focus on
allocation issues namely, what to store where. We formulate the problem as
a constrained optimization one and provide fast heuristics that achieve
good solution quality both when the access patterns remain static and when
they change in time. Moreover, we investigate the potential of minimizing
the page retrieval delays by downloading the various page components in
parallel from multiple servers. Of particular interest is the case of
multimedia repositories which we examine in more details. In proxy caching
we identify two significant limitations of current schemes. The first one
is the inability to cache dynamic pages carrying query results. We use an
active caching framework that enables caching such pages at current Web
proxies. Intuitively, the benefits are expected to be higher in the case
of computationally expensive queries. Therefore, we turn our attention to
On Line Analytical Processing (OLAP) queries that often involve
aggregations of millions of rows. Such queries are typically issued by
decision makers towards the Data Warehouse of an enterprise. Finally, we
motivate the need for adaptive strategies that organize proxies in
dynamically reconfigured cooperative groups. Two cases are distinguished,
depending on whether the neighborhood relations are symmetric or not. We
formulate the problem as a second level caching and experimentally prove
the viability of our framework.


Date:				Wednesday, 28 August 2002

Time:				2:00p.m.-4:00p.m.

Venue:				Room 4480
				Lifts 25-26

Chairman:			Prof. Anne S. Tsui (MGTO)

Main Supervisor:		Dr. Ishfaq Ahmad (COMP)

Committee Members:		Dr. Dimitris Papadias (Supervisor)
				Dr. Brahim Bensaou
				Dr. Bo Li
				Prof. Khaled Ben Letaief (ELEC)
				Dr. Francis C.M. Lau (Comp. Sci. & Inf. Sys., HKU)


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