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Subsections

5 Conclusions

  Caching Web proxies are an effective and low-cost tool for reducing bandwidth demands and document fetch latencies in the Internet. In a 25-day trace from Digital Equipment Corporation Web proxies, almost 70% of recorded references are to static objects shared with other users. The percentage of references to shared documents grows with larger numbers of users. This motivates the design of large-scale shared caches to exploit sharing of Internet documents among members of large communities.

Large-scale caches are most effectively built as distributed systems. Besides being more scalable, individual caching servers participating in a collective cache can be placed close to their users, improving access times and reducing the network traffic for document accesses that hit in the cache.

This paper addresses a key issue for distributed Internet caches: how should individual caching servers share directory information to capture the largest percentage of shared document references as hits at the lowest cost? We presented trace analyses and results from trace-driven execution of collective cache prototypes to evaluate a range of directory alternatives on the basis of cost, hit ratios, hit penalties, miss penalties, and network traffic.

While our analysis is not yet complete, we present sufficient evidence to conclude the following:

Acknowledgments

We extend our sincere appreciation to Jeff Mogul, Tom Kroeger, Carlos Maltzahn, and Digital Equipment Corporation for providing sanitized access traces from DEC proxies. We also thank Pei Cao, Fred Douglis, Mike Feeley, and David Marwood for their valuable insights and feedback on this paper. Thanks also go to Peter Danzig for providing details on commercial Harvest and NetCache.


next up previous
Next: References Up: Directory Structures for Scalable Previous: 4 Alternatives for Managing
Syam Gadde
11/14/1997