A content delivery network (CDN) or content distribution network is a geographically distributed network of proxy servers and corresponding data centers. CDNs provide high availability and performance ("speed") through geographical distribution relative to end users, and arose in the late 1990s to alleviate the performance bottlenecks of the Internet as it was becoming a critical medium. Since then, CDNs have grown to serve a large portion of Internet content, including text, graphics and scripts, downloadable objects (media files, software, and documents), applications (e-commerce, portals), live streaming media, on-demand streaming media, and social media services.
CDNs are a layer in the internet ecosystem. Content owners such as media companies and e-commerce vendors pay CDN operators to deliver their content to their end users. In turn, a CDN pays Internet service providers (ISPs), carriers, and network operators for hosting its servers in their data centers.
