Content Delivery Networks (CDNs)
Content Delivery Networks are operated to support the distribution of content from content owners to content consumers. A typical business model is that content owners contract one or multiple CDNs' service commercially.
The typical CDN consists of thousands of servers placed in geographically distributed data centers. Content consumers are directed to suitable server instances based on parameters such as their location (geographical and/or topological), server utilization, and policy rules. This redirection may be based on DNS, anycast routing, or HTTP redirects.
Prominent examples of CDNs are Akamai Technologies
and Limelight Networks
. With Akamai, many content servers are placed directly in Internet Service Provider (ISP) premises, so that connectivity to those ISPs' customers stays "on-net". Most other CDNs have servers in their own or contracted facilities, and reach content consumers through transit and peering agreements.
- 18 Nov 2008