UBC Theses and Dissertations

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UBC Theses and Dissertations

Proxy-based adaptive push-pull web caching Gao, Mulong

Abstract

Although the volume of Web traffic on the Internet is staggering, a large percentage of the traffic is redundant — multiple users at any given site request much of the same content. This means that a significant percentage of the W A N infrastructure carries identical content (and identical requests for it) day after day. Web caching performs the local storage of Web content to serve these redundant user requests more quickly, without sending the requests and the resulting content over the WAN. There are two major categories of Web caching mechanisms: client pull and origin server or parent proxy push. This thesis investigates a proxy-based, adaptive push-pull mechanism to enhance user experience by selecting some of the most frequently accessed objects to push to a proxy instead of letting the proxy request it later. Web servers or parent proxies collect the objects access frequency for specific proxies rather than on a global scope. Web servers or parent proxies adopt a push policy to distribute hot objects to cooperating proxies; other objects are pulled by the proxies as usual. As time moves, frequently requested objects may become cold in one region and become hot in another region; Web servers and caching proxies can thus learn the change pattern and adjust their distribution policy accordingly, avoiding pushing objects to proxies which may not request those objects in the near future. By using the adaptive push-pull distribution mechanism, the most frequently updated and accessed objects, which form the major chunk of Internet traffic, are pushed to proxies, saving many If-Modified-Since GET requests. Hence, Web traffic is more productive and user perceived latency is reduced.

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