Content delivery network (or content distribution network) – is a complex system, which allows diversifying storage and delivery of content. Due to such systems online business all over the globe improve the quality of their websites and services. To reveal the essence of delivery network it is necessary to show how does a cdn work. Every content delivery system consists of a large number of servers located in multiple data-centers in different countries. Such servers form complex connections. The main features that characterize how does cdn work are technological closeness, bandwidth and speed of communications. Content distribution system uses its servers to deliver content to users faster. When specific company decides to work with a delivery company, it copies cdn data and places it on multiple delivery servers. After that, instead of loading large data from the edge server, every user can deal with technologically close delivery servers.
Technological closeness includes such characteristics as geographical closeness, bandwidth (available ports on a way to end-user) and speed of connections. Every time when a new request from user arrives, distribution system decides which server or servers are technologically the closest for this request due to above characteristics. Normally, delivery company uses caching principle to organize storage on delivery servers effectively. Caching involves storage of only popular content data. For example, when the first request arrives to distribution system, it decides can this request be satisfied. If there is no needed data in delivery servers yet, request will be forwarded to the edge server. After that delivery servers will copy the requested information. That means that every first specific request is always satisfied only be the edge server, but the others – by distribution servers.
There are two different ways how to build a cdn – focused on number of pops (points of presence) or focused on the increasing of capacity and speed of connections. Most of the biggest delivery companies have a big number of pops, but still improve the quality of connections. For example Amazon CloudFront and CDNsun have 52 and 85 pops all over the globe, respectively. However, several companies decide to have small number of pops and improve their quality. These companies are completely competitive to others. Most of popular delivery companies propose two ways how to setup a cdn. First way is to use several presets, the other – is to set up all the settings manually. There is no consensus about how to use cdn. Presets greatly simplify customizer’s job. Meanwhile, some important things can be tuned only manually – for example several security features. Often cdn can be set and powered within ten-twenty minutes. User may choose data, which he wants to deliver from distribution servers, and methods of protection. He also can make changes in settings in any moment. Thus, content distribution network is a complex tool for online-businesses, which can be simply used and set for every specific company.