What is a CDN?
A quick tour of content delivery networks: what they are, why they exist, and where they're headed as the internet stretches into orbit.
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The short version
A CDN, short for content delivery network (sometimes content distribution network), is a geographically distributed network of proxy servers and the data centers that house them [Source 1]. The whole point is to put copies of content physically closer to the people requesting it, so pages load faster and stay available even when traffic spikes.
If you've ever wondered why a video from halfway around the world starts playing in under a second, this is usually why.
Why they exist
CDNs showed up in the late 1990s to deal with performance bottlenecks on the early internet, right as it was turning into critical infrastructure [Source 1]. Since then they've expanded well past static files. Today they serve text, graphics, scripts, downloadable objects, applications, live and on-demand streaming media, and social media services [Source 1].
Basically: if it travels over HTTP and a lot of people want it, a CDN is probably involved.
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