A Content Delivery Network or CDN refers to the geographically distributed series of servers that act in the middle of a central/origin server and end-users, virtually reducing the distance that data needs to travel to reach various locations. As a result, CDNs enable much faster delivery of content among users, promising better reliability, while reducing the amount of bandwidth used.
As an example, let’s say site X is hosting a US-based server for its video content. Viewers that want to access the videos are spread throughout the world. Without a CDN, all viewers, no matter where they are located in the world, would have to directly request the video content from the central server in the USA. The server would then have to provide content to each individual viewer.
In this case, the users will experience marked differences in access speed, stability and video quality depending on their physical distance with the central server. The farther away they are, the higher the latency, the slower the loading times and the worse experience they are likely to have with the said content. CDNs resolve this issue by having local nodes, also called edge servers or Points of Presence (PoP), in various locations so that users can access content through a node that is geographically closest to them.
These nodes replicate and store content from the central server, which means loading and latency times are significantly lowered and this approach also reduces traffic to/from the main server. Although CDNs can’t replace the provision of web hosting, it helps in caching content which improves website and platform performance.
Some of the platforms that use CDNs today are video hosting sites such as YouTube and Netflix, music streaming services like Spotify and Joox, dynamic and interactive webpages and lots more. So, if you’re wondering how these sites/services are able to serve millions or even billions of global users while still providing a smooth and lag-free experience, chances are, they are using a CDN.
CDNs not only enable fewer downtimes due to reduced network traffic, but they also provide security capabilities that can be useful in mitigating traffic attacks.