What are Content Delivery Networks?
A content delivery network or content distribution network (CDN) is a large distributed system of proxy servers deployed in multiple data centers via the Internet. The goal of a CDN is to serve content to end-users with high availability and high performance. CDNs serve a large fraction of the Internet content today, including web objects (text, graphics and scripts), downloadable objects (media files, software, documents), applications (e-commerce, portals), live streaming media, on-demand streaming media, and social networks.
Content providers such as media companies and e-commerce vendors pay CDN operators to deliver their content to their audience of end-users. In turn, a CDN pays ISPs, carriers, and network operators for hosting its servers in their data centers. Besides better performance and availability, CDNs also offload the traffic served directly from the content provider's origin infrastructure, resulting in possible cost savings for the content provider. In addition, CDNs provide the content provider a degree of protection from DoS attacks by using their large distributed server infrastructure to absorb the attack traffic. While most early CDNs served content using dedicated servers owned and operated by the CDN, there is a recent trend to use a hybrid model that uses P2P technology. In the hybrid model, content is served using both dedicated servers and other peer-user-owned computers as applicable.
How content is load balanced.
Content is load balanced (traffic controlled) and uses geo-steering configuration, which directs traffic to the nearest origin based on region. For example: European clients to our Berlin datacenter, East Coast US clients to our New York datacenter, and Oceanic clients to our Singaporean datacenter and South African clients to their nearest datacenter depending on the origin of your IP Address.
Of course, all of these approaches can be combined: load-balancing can occur across multiple locations in a specific region, failing over to the next-nearest datacenter should the first (or second) fail. Failure modes are fine-tuned, given a pool of five servers, we can sustain two unhealthy ones, but a third failure might be the trigger to steer traffic to our next data center, allowing content to be delivered quickly and efficiently around the world in seconds.