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Introduction to Content Delivery Network

By Tina Yew, March 16, 2005

Most Web sites online today has followed the traditional internet infrastructure, where files are stored on centralized servers. Despite the use of load balancers or multiple servers, users still need to query a central hub in order to obtain any information. Under this structure, users all over the world are required to line-up and ping this central location, before they can access any Web site files.

Content Delivery Networks restructures the path that clients use to access Web site files by caching content, and distributing it to multiple servers throughout the world. For example, a visitor may demand content from www.foo.com/bar.html. Once the central server receives this request, bar.html is pushed onto the cache closest to the visitor. As this content is downloaded onto the cache, other users close by may access the same content by accessing this cache, rather than making a long visit the central hub. The shorter path saves users time required to load the Web page. Theoretically, the use of bandwidth is also more efficient, as the same file accessed over and over again by different users from the same area will stem from the cache closer to the users. On the other hand, the centralized model will incur each file request separately and bandwidth to the central hub is multiplied. Thus, the benefits of CDN is dependent on the geographic location of the servers and its visitors.

The difference between CDNs and mirroring is that mirroring replicates the server in its entirety, constantly, whereas caching only occurs when a visitor requests for a file. Only the file requested is cached, rather than the entire server.

Whether your Web site will benefit from a CDN infrastructure is dependent on several factors. CDN is most suitable for Web sites with a global reach and have high traffic. Also, the CDN model deployed will be dependent on how your Web site is built, for example, whether it contains dynamically generated or streaming content. We recommend you to speak with your hosting provider for the model that is best suited for your individual site.

Resources: PowerMedium

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