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Caching Description

Following is a diagram that describes the flow of data between the end users, Akamai caching servers and origin.www.upenn.edu.

Requesting a page

In this example, End User A requests a page from www.upenn.edu. End User A is connected to the closest Akamai caching server, Akamai Edge caching server A. The Akamai Edge caching server A doesn't have a copy of the requested page so it goes back to origin.www.upenn.edu, the server that actually resides at Penn, gets a copy of the requested page, and serves the copy of the page back to End User A.

End User D requests that same page and happens to be connected again to Akamai Edge caching server A. Akamai Edge caching server A now has a copy of the page and serves it up to End User D without having to go back to origin.www.upenn.edu to get a copy of the page.

Updating web pages

The following examples explains what users will see if you update a web page and there is a 5-minute cache on that page.

If you update a page on origin.www.upenn.edu at 10:00am and End User B requests a copy of that page from Akamai Edge caching server B at 10:01am, End User B will see your changes because Akamai Edge caching server B does not have a copy of your page and has to go to origin.www.upenn.edu to get a copy of it.

End User D requests that same page from Akamai Edge caching server A at 10:01am. Akamai Edge caching server A already has a copy of the page and the cache on that copy is not set to expire until 10:04am so End User D will not see your changes. If End User A requests the same page at 10:05am from Akamai Edge caching server A, Akamai Edge caching server A will go back to origin.www.upenn.edu to get a new copy of the page and will pick up the changes that you made at 10:00am.

A detailed explanation of the service is available from the Akamai web site.

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