Explaining Content Delivery Networks and Why Big Websites Crash Together

You don’t hear much about content-delivery networks, or CDNs, until they stop delivering. A global outage of major websites on June 8 that lasted about an hour was caused by problems at the San Francisco-based Fastly Inc. It took down websites including the New York Times, Bloomberg News, Reddit Inc. and even the U.K. government.

It’s a kind of bridge between a website or app and a user, helping to push data quickly around the internet on behalf of some of the most popular online companies. CDN providers do that by hosting multiple servers and directing people who call up a web page to the nearest one geographically, rather than sending them back to the origin. Say a company’s website is based in the U.S. and gets traffic from France, it’s possible a CDN provider has a server in France that will direct users there. This allows for faster and more reliable delivery of web content.