Content Delivery Network

A Content Delivery Network ( CDN), or also known as Content Distribution Network, is a network of locally distributed and connected through the Internet server are delivered with the content (especially large media files ).

CDN nodes are distributed in many places and often on many backbones. They work together to create as economically as possible to serve requests (requests) of end- users for content (content).

In the background (transparent), the data is kept in the network ( caching) that the respective delivery either as quickly as possible is ( performance optimization ) or as little bandwidth consumed (cost optimization), or both.

Large CDNs entertain thousands of nodes with tens of thousands of servers.

Operation

The CDN initially consists of an origin server on which the content provider stores the contents to be distributed, a large number of replica servers that hold the copies of such content, and a distribution system that distributes the content on the replica servers. For the redirection of user queries on the individual Replica server a request- routing system is responsible, which relies on various key figures on these servers, which are supplied to it by the accounting system.

When a client sends a request to the CDN, then the request routing system selects an appropriate replica server. When selecting it relates indicators of their current load (for example, CPU usage, number of active connections ) and the network connection between client and server (for example, geographical distance, latency, transfer rate ), rare on the identity of the client ( for example, distinction between standard and premium users ) with one, put to him by the accounting system.

After selecting the server, the user query must now be diverted. The procedure is most often used for DNS -based Request Routing. It requests the client to a CDN provided by DNS servers are passed which returns the IP address of the Replica server. Alternatively, can be used where the 302 status code causes the redirection to another Web server as well as the method HTTP transmission protocol.

Selection of CDN providers

  • Akamai
  • Amazon Web Services ( CloudFront )
  • CDNetworks
  • CloudFlare
  • Coral
  • Host Europe
  • Level 3 Communications
  • Limelight Networks
  • NTT Europe ( NTTEO )

Open Source Projects

  • MirrorBrain
Transparency (human–computer interaction) Cache (computing) Client (computing) Akamai Technologies KDDI Coral Content Distribution Network NTT Europe Ltd
201146
de