USENIX Symposium on Internet Technologies and Systems, 1997
The Measured Access Characteristics of World-Wide-Web Client Proxy Caches
Bradley M. Duska, David Marwood, and Michael J. Feeley
University of British Columbia
The growing popularity of the World Wide Web is placing tremendous
demands on the Internet. A key strategy for scaling the Internet to
meet these increasing demands is to cache data near clients and thus
improve access latency and reduce network and server load.
Unfortunately, research in this area has been hampered by a poor
understanding of the locality and sharing characteristics of
Web-client accesses. The recent popularity of Web proxy servers
provides a unique opportunity to improve this understanding, because
a small number of proxy servers see accesses from thousands of clients.
This paper presents an analysis of access traces collected from seven
proxy servers deployed in various locations throughout the Internet.
The traces record a total of 47.4 million requests made by 23,700
clients over a twenty-one day period. We use a combination of static
analysis and trace-driven cache simulation to characterize the
locality and sharing properties of these accesses.
Our analysis shows that a 2- to 10-GB second-level cache yields hit
rates between 24% and 45% with 85% of these hits due to sharing
among different clients. Caches with more clients exhibit more
sharing and thus higher hit rates. Between 2% and 7% of accesses are
consistency misses to unmodified objects, using the Squid and CERN
proxy cache coherence protocols. Sharing is bimodal. Requests for
shared objects are divided evenly between objects that are narrowly
shared and those that are shared by many clients; widely shared
objects also tend to be shared by clients from unrelated traces.
- View the full text of this paper in
HTML form and
- If you need the latest Adobe Acrobat Reader, you can download it from Adobe's site.
- To become a USENIX Member, please see our Membership Information.