World-Wide Web Cache Consistency
James Gwertzman
Microsoft Corporation
Margo Seltzer
Harvard University
Abstract
The bandwidth demands of the World Wide Web continue to grow at a
hyper-exponential rate. Given this rocketing growth, caching of web
objects as a means to reduce network bandwidth consumption is likely
to be a necessity in the very near future. Unfortunately, many Web
caches do not satisfactorily maintain cache consistency. This paper
presents a survey of contem- porary cache consistency mechanisms in
use on the Internet today and examines recent research in Web cache
consistency. Using trace-driven simulation, we show that a weak cache
consistency protocol (the one used in the Alex ftp cache) reduces
network bandwidth consumption and server load more than either
time-to-live fields or an invalidation protocol and can be tuned to
return stale data less than 5% of the time.
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