socialmedian: ETags - Roles in Web Application to Cloud Computing

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ETags - Roles in Web Application to Cloud Computing

Source: The Byte Scrolls

Nov 03, 2009

Summary

A web server returns a value in the response header known as ETag (entity tag) helps the client to know if there is any change in content at a given URL which requested.When a page is loaded in the browser, it is cached.It knows the ETag of that page.The browser uses the value of ETag as the value of the header key "If-None-Match".The server reads this http header value and compares with the ETag of the page.If the value are same ie the content is not changed, a status
code 304 is returned ie. 304:Not Modified. These HTTP meta data can be very well used for predicting the page downloads thereby optimizing the bandwidth used.But a combination of a checksum (MD5) of the data as the ETag value and a correct time-stamp of modification could possible give quality result in predicting the re-download. An analysis of the effectiveness of chosing the value of ETag is described in this paper.

According to http://www.mnot.net/cache_docs/

A resource is eligible for caching if: