15.2. Delivering Requests to a CDN

Before deciding how to deliver content to clients, a CDN must first decide how to make clients send their requests to its network rather than the customer's origin server. We refer to mechanisms that achieve this as request-delivery mechanisms.

Hosting CDNs do not face the request-delivery issue because they have control over their customers' origin servers and usually also control the DNS servers for their customers' domain names. Relaying CDNs commonly use various DNS tricks for request delivery, but details vary in different CDN types.

Relaying CDNs with first hit at CDN use a DNS outsourcing technique illustrated in Figure 15.4. Consider a company called firm-x that signs up with such a CDN for delivery ...

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