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Summary
Cache: A Scalable Wide-Area Web Cache Sharing Protocol
Li Fan, Pei Cao, and Jussara Almeida (University of Wisconsin-Madison) Andrei Z. Broder (Digital Equipment Corporation) The
sharing of caches among Web proxies is an important technique to reduce
Web traffic and alleviate network bottlenecks. Nevertheless it is not widely
deployed due to the overhead of existing protocols. In this paper we propose
a new protocol called "Summary Cache"; each proxy keeps a summary of the
URLs of cached documents of each participating proxy and checks these summaries
for potential hits before sending any queries. Two factors contribute to
the low overhead: the summaries are updated only periodically, and the
summary representations are economical { as low as 8 bits per entry. Using
trace-driven simulations and a prototype implementation, we show that compared
to the existing Internet Cache Protocol (ICP), Summary Cache reduces the
number of inter-cache messages by a factor of 25 to 60, reduces the bandwidth
consumption by over 50%, and eliminates between 30% to 95% of the CPU overhead,
while at the same time maintaining almost the same hit ratio as ICP. Hence
Summary Cache enables cache sharing among a large number of proxies.
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