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USENIX Symposium on Internet Technologies and Systems, 1997
Exploring the Bounds of Web Latency Reduction from Caching and Prefetching
Thomas M. Kroeger and Darrell D. E. Long
University of California, Santa Cruz
Jeffrey C. Mogul
Digital Equipment Corporation
Abstract
Prefetching and caching are techniques commonly used in I/O
systems to reduce latency. Many researchers have advocated the
use of caching and prefetching to reduce latency in the Web. We
derive several bounds on the performance improvements seen from
these techniques, and then use traces of Web proxy activity taken
at Digital Equipment Corporation to quantify these bounds.
We found that for these traces, local proxy caching could reduce
latency by at best 26%, prefetching could reduce latency by at
best 57%, and a combined caching and prefetching proxy could
provide at best a 60% latency reduction. Furthermore, we found
that how far in advance a prefetching algorithm was able to
prefetch an object was a significant factor in its ability to
reduce latency. We note that the latency reduction from caching
is significantly limited by the rapid changes of objects in the
Web. We conclude that for the workload studied caching offers
moderate assistance in reducing latency. Prefetching can offer
more than twice the improvement of caching but is still limited in
its ability to reduce latency.
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