CDN (Content Delivery Network) is a system of servers networked together across the internet, that cooperate transparently to deliver content to end users, most often for a purpose of improving performance, scalability and cost efficiency.
- Identifying the geographic location of the end user: The system can direct each user to the physical server that is closest to them, amongst the many servers in the network. This operation greatly shortens the response time of serving the website to the end user based on basic principles of physics – the information on the internet arrives faster when it has to cover a shorter physical distance.
- Keeping a local copy on servers distributed in the network: In order to display the site’s files as quickly as possible, local copies are kept on the servers, so that repeated user queries from a specific area will be displayed from the files kept as local copies on the server closest to them. The copies are updated according to the definitions of the source server.
- Monitoring of all of the network servers: In order to meet the high loads and verify the full redundancy and maximal uptime, all of the servers in the network, are continuously monitored. This enables uniform load-balancing and gives the option to present files that have very high traffic and no less importantly than that, to withstand large peaks in traffic that typically a single server has great difficulty handling.
Who needs CDN?
- Sites that appeal to client audiences located in several countries – instead of setting up multiple servers in multiple countries in order to provide fast access to the content, it is possible to use one or two servers located somewhere and serve the rest of the clients through the CDN network.
- Sites that stream large amounts of media (banners, pictures, clips and more) – there is great importance to seamlessly streaming the media without interference or stops.
- Companies that maintain applications in various places around the world (such as forecast companies) and that want to direct surfers from specific countries to different applications and still receive a short response time.
Advantages of the CDN:
- Serving clients from different countries in the world by using only a single source-server. All clients from all regions receive the content at speeds very similar to those from the source-server, regardless of their physical distance from it.
- It is possible to server a lot more clients on a single source-server.
- The traffic volume possible is unlimited.
- Redundancy – Despite there being only a single source server, local copies are kept on all servers in the network. Therefore if the source-server crashed the files are still “live” on the end-servers. Additionally the large number of servers ensures continuous access to the site files even if some of them fail for whatever reasons.
- Control of client routing based on their geographic location – it is possible to block surfers from specific countries or direct them to specific servers.