A content delivery network is an environment containing a network of systems. The systems will contain objects, files etc...Once a client from UK connects to a CDN, the system near to the UK location will provide data. The same thing will happen for a client from Japan, i.e.system near to Japan will provide data. So this will improve the network bandwidth as clients are getting data from different systems rather than a centralized mechanism. How this can be used in a developer perspective? Yes, we have ajax with support of CDN.
By taking advantage of the Microsoft Ajax CDN, you can significantly improve the performance of your Ajax applications. The contents of the Microsoft Ajax CDN are cached on servers located around the world. In addition, the Microsoft Ajax CDN enables browsers to reuse cached JavaScript files for Web sites that are located in different domains. In VS2010 we have an attribute for ScriptManager named "EnableCdn="true". This will make the script libraries to be loaded from CDN. Follow this link for more information

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