A content delivery network is a group of proxy servers and data centres in different geographical locations, the purpose of which is to deliver fast and reliable internet content at high speeds. This cuts down the bandwidth needed for high-traffic sites, avoids service interruption and increases security. As the worldwide web has become more congested, CDNs are an effective means of easing that congestion.

The slow loading of internet content is a serious problem in an environment where users expect instant access. Apart from the inconvenience for the user, a slow speed tends to reflect badly on the company which owns the site and can negatively affect SEO. A CDN enables the rapid transfer of assets including videos, images, JavaScript files and HTML pages. 

The use of CDNs has become widespread and most of the busiest sites such as Amazon, Netflix and Facebook serve their customers in this way.

A CDN is definitely not a substitute for web hosting. In fact CDN providers pay ISPs for hosting their servers in their data centres. 

How Does it Work?

A CDN places servers at the key points of exchange between different networks, known as Internet exchange points (IXPs). These are the junctions at which the pathways of different internet providers meet to allow the free flow of traffic between them. By placing CDNs at these crucial intersections, web owners can lower costs and reduce the time it takes to deliver data.

The reduction in loading time is achieved by the simple expedient of shortening connections between user and data centre. Instead of having to communicate directly with a server on the other side of the world, site visitors access it via a local substation. The effect is beneficial because it reduces the likelihood of users navigating away from a non-responsive site. 

The twin challenge facing every site owner is to attract visitors and to make them stay. By using caching, a CDN lowers hosting costs by reducing the amount of data that needs to be provided by the originating server.

Another significant advantage of a CDN is its ability to protect a site from traffic spikes, hardware failures, malicious attacks or anything else that may bring websites down. It does this by balancing the load across multiple servers and if necessary rerouting traffic through an alternative data centre.