CDNs

CDN stands for content delivery network. You probably get content delivered from them all the time.

What makes them different from normal servers that deliver content to your browsers and devices is that they have this distributed network that, depending on the quality of the CDN, makes sure there is a server to deliver that content that's geographically close to your computer, no matter where you are.

At the very least, a CDN usually has servers on your side of the world. Even just having a server on your continent is a big improvement than the case in which the content is available on only a cluster of servers that are all on the other side of the world.

They get all over the world by paying ISPs to host their servers in the ISPs' data centers.

There's many ways in which CDNs get you to the closest server, but DNS is the way I know about. CDNs have domain name servers just like your domain registrar has domain name servers. When your registrar's DNS is asked to resolve yourdomain.com to an IP address, it just points to the server you told it about.

When a CDN's DNS answers a request to resolve a domain name, it figures out where you are, network-wise, and what the closest server with your requested content is. Then, it gives you the IP address for that. Your web browser or other client downloads the content from that IP address.

As far as I know, the DNS has just a single IP address, so if it takes a long time for you to get to that, the experience will seem slow no matter what.

#cdn #server