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Wednesday, July 15, 2009

Web Pre-Fetching





Nearly two decades ago with the introduction of the "World Wide Web" (WWW), much of the world's economy, culture, business, etc all were e ected heavily by WWW and will continue to do so. Due to the fast development of internet services, heterogeneous network connectivity, real-world distances, congestion in networks or servers and a huge amount of network traffic, now it is becoming "World Wide Wait" and can contribute to this less-than-speedy web experiences.

According to the 8-second rule if the web page load-time exceeds eight seconds (now it is said to be 8 ± 2 seconds), users are unlikely to wait, or stick around, for its completion. So it is becoming an essential issue to reduce World Wide Web user-perceived latency. Though the caching gives a solution to this the bene t of caching is limited due to the rapid changes of network resources. The maximum hit rate achievable by any caching algorithm is just 40% - 50%. Therefore the need for a better solution led people to think of a way to bring the web resources to the client side in advance so that the clients' requests can be responded locally. This is what we call "Web Pre-Fetching".

The goal of "Web Pre-Fetching" is to improve the quality of the Internet Services by reducing the World Wide Web user-perceived latency. In other words, reduce the web page loading time by pre-loading the local cache by pre-fetching the web resources in advance and serve the requests through the local cache.

In web prefetching the web resources/objects are prefetched from the web servers in advance that the user is likely to access in the next moment. So that the next requests can be handle locally and therefore the user would not experience any delay in page loading. Nowadays in most web con gurations, a proxy server exists between client browsers and web servers. Therefore most web pre-fetching is caching proxy servers so that those proxy servers can serve clients requests. However, even caching browsers is also possible (e.g.Link prefetching).

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