Exploiting Metadata of Absent Objects for Proxy Cache Consistency

Jooyong KIM  Hyokyung BAHN  Kern KOH  

Publication
IEICE TRANSACTIONS on Communications   Vol.E84-B   No.5   pp.1406-1412
Publication Date: 2001/05/01
Online ISSN: 
DOI: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Network
Keyword: 
proxy,  cache,  consistency,  metadata,  World Wide Web,  

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Summary: 
Caching at the Web proxy server plays an important role in reducing the response time, the network traffic, and the load of Web servers. Many recent studies have proposed and examined the replacement and consistency policies for the proxy cache, which plays a central role in the performance of caching components. For better performance, they exploit various metadata of Web objects, such as the reference count, reference time, and modification time information of past behaviors, to estimate the re-reference likelihood and freshness of the objects. However, all of these known to the authors use the metadata only when the actual object is in the cache. We observed from various proxy traces that about 20-30% of clients' requests incurred only the validity checks of cached objects without transferring actual objects from the proxy server. In this case, only the metadata are necessary at the proxy server. This paper proposes a proxy cache consistency policy that uses the metadata even for absent objects. These include the time information of evicted objects from the cache and those out of the header-only replies from Web servers. Trace-driven simulations with public proxy cache traces show that our policy reduces the response time and the number of connections to Web servers significantly.