15.1. Types of CDNs

CDNs can be classified according to two properties, their relationships with ISPs whose networks they use, and their relationships with their customers and the mechanism for delivering client requests to CDN servers.

The relationship between a CDN and ISPs may take several forms. A CDN may be a stand-alone company not affiliated with any particular ISP. Instead, it partners with multiple ISPs and deploys its servers in as many ISPs as possible. We refer to such a CDN as a multi-ISP CDN. CDN servers of a multi-ISP CDN are colocated with ISP points of presence or with entry points into ISP backbones, typically on the LAN with their access routers. For this reason, multi-ISP CDNs are said to follow a colocation model. An advantage ...

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