Content Delivery Networks explains: The unknown backbones of many websites

On June 8, 2021, many major web services stopped working for several hours, including the community site Reddit, the streaming provider Spotify and the short message service Twitter. The GitHub code repository was affected by outages, as were the websites of the New York Times, the Guardian, the Bloomberg news agency and even the Amazon website. What happened? Fastly’s services were down. A software update resulted in a global crash.

Very few users should have heard of Fastly by then. Many surfers regularly receive content from this provider. The company is one of the world’s largest operators of a so-called content delivery network, or CDN for short. Such services are actually supposed to improve the performance and availability of websites. To do this, they operate data centers with proxy servers that are distributed all over the world and bring content closer to users. Website operators store data-intensive content such as video (streams) or images on CDNs, for example. Not infrequently, however, CDNs also deliver complete websites.

Over the past 10 years, many web presences have been converted to use CDNs, unnoticed by surfers. “There isn’t much left of the pre-CDN world,” Geoff Huston told the c’t. He must know. As chief scientist at the Asia Pacific Network Information Center, the Internet registry for the Asia and Pacific region, he is one of the most avid surveyors of network traffic.