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> >>>> METHODOLOGY
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Why Is Caching Important?
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Caching is the process of storing Web elements (pages, files, images) on an ISP or corporate proxy server, or on a PC hard drive. The use of caching makes serving information on the Internet more efficient in terms of reducing bandwidth costs and server utilization, as the most popular information is always served form the "edge of the network"- the shortest, and hence fastest, route to the end-user. The use of caching has proliferated because it reduces bottlenecks. The Internet Caching Resource Center (www.caching.com) estimates that caching can reduce the need for bandwidth by at least 35 percent.
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There are three primary forms of caching:
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| Browser Cache:
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Assigns a section of your computer's hard drive to store objects that you've seen. Pages served out of a local browser cache are displayed with use of the "Back" or "Forward" buttons on your browser. Fairly simple rules determine whether the copy of an object in the browser cache is still "fresh," or whether it needs to retrieve a new copy form the origin server.
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| Proxy Cache:
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Works on the same principle as the browser cache, but on a much larger scale. Corporations or ISPs that want to reduce their consumption of Internet bandwidth deploy proxy caches. Because the cache is shared by a large number of users, there are a large number of shared page requests (objects that are requested by a number of clients). Page request rates of 50 percent efficiency or greater are not uncommon for pages served out of a proxy cache.
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| Content Delivery Service:
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Collects data from servers at the center of a network and intelligently stores these data on other servers that are closer to users; therefore helping content providers deliver their information more efficiently and with greater reliability. Akamai and CacheFlow are caching service companies.
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Why Caching Is Used on the Internet:
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| To reduce latency
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Because a user's request for a page is satisfied from cache, which is closer to the end user than the origin server, it takes less time for the end user to get the object and display it than it would without a cache. This makes Web sites seem more responsive.
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| To reduce traffic
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Because each object is requested from the server once, it reduces the amount of bandwidth used by an end user and the ISP. The site also uses less bandwidth and requires fewer servers to satisfy the requests for their content.
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Impact of Caching on Log Files
Web site owners reap the benefits of reduced bandwidth and infrastructure costs that amass by pushing content to the edge of the network. However, the trade-off is that they can no longer trust the veracity of their log files for measuring traffic. If a request made by an end-user is satisfied by a page served from a cache, then the origin server is oblivious to the transaction. The page is then not recorded, and the server log file does not have an accurate view of what pages were consumed by end users. ISP and corporate proxy caches account for up to 15 percent of total pages viewed. If log files are missing this much traffic, any reports they do produce are dramatically skewed and inaccurate. Such misleading information may lead to critical miscalculations and consequently poor business decisions.
Impact of Local Browser Caching
LiveAnalysis is the only clear GIF technology that can measure pages served out of a local browser cache, while adhering to the stringent privacy concerns that impact commercial applications of the Internet. Pages that are served out of local browser cache can account for up to 37 percent of a site's total page impressions. If a site is uninformed about these pages, then it is impossible to accurately track a visitor's clickstream.
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| For more information, please email us at support@liveanalysis.com or call us at 1 914 251 9230 |
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