How do CDN (Content Delivery Networks) server work?

Question

There are many CDN (Content Delivery Networks) for hosting mainly static content. How do they work? How they handle http requests?

Answer 1

Short answer: CDN's take your data and place it on many different servers around the world so that high traffic content can be delivered to the end user as quickly as possible.

Long answer: CDN's distribute your file(s) to multiple edge locations and assign a URI to it. When a request is made the CDN evaluates the location of the request and routes it to the edge location that will provide the lowest latency and best connection speed for the requester. The file is then transferred directly from the edge location's server to the user that requested it.

For more info: http://developer.yahoo.net/blog/archives/2007/04/high_performanc_1.html

Answer 2

Please check http://aws.amazon.com/cloudfront/ you would find all answers here. Let me know if you need more information.

Answer 3

theandym has a great answer for CDNs like Akami where distributing the content is the way to make it more widely available with reduced lag. There are CDNs (read low budget like Internap) who keep the content in a more centralized location and stream through cashing servers located on the edge. An end user's request for content is routed to the nearest 'super-pop' or a location where the actual location is stored. Following this the requested content returns to the end user through a 'cashing server' physically located nearer to the end user. This has the effect of the first request having the standard lag of a long distance request but subsequent requests being as fast as if the content were more regionally distributed. The advantage of this setup is that the content can be taken off line. Once your movie has had it's run you can take the trailers down and stop paying for the bandwidth. This method works far better with media and other highly 'bandwidth intensive' type files. It is also cheaper for the CDN as they do not have to rent as much datacenter space in remote parts of the globe.

Answer 4

CDN works mainly for sites concerned about loading speed and possibly no downtime. CDN works like it copies the entire static content and places it at different servers globally,so that on request by an user the content is provided from the nearest server as quickly as possible. And about the http request.Like you live in US, California,mountain view,your internet connection has a unique ip address which helps the CDN servers determines your location and then accordingly the nearest servers servers you.A server in CDN is mainly targetted to some locations only.Like CDN server in US is marked to serve only in US and nearby places till the coverage of other CDN server starts.