Are CDNs worth it

What is a CDN (Content Delivery Network)?

Forwarding the request

Once the target server has been determined in the CDN, the second step is the technical forwarding of the request by the request routing system. There are several procedures for this "request redirection", which mainly differ in the location at which they are initiated - on the client, in the network or on the replica server.

The forwarding of the request from the client is an easy to implement method in which the client makes the selection of the replica server from a presented list. However, this has the disadvantage that the content delivery network has little influence on the assignment. The server-side is also easy to implement - and also comes with good information about the CDN HTTP 302 redirection. In this case, the outgoing server responds to the request with the HTTP status code, thereby informing the client of the appropriate replica server, which the client automatically contacts with a further request. The main disadvantage of this method is the duplication of the connections required.

The most common type of forwarding is that DNS-based request routing. Here, the client's request to a local DNS server is forwarded to a special DNS server within the content delivery network, which in turn returns the IP address of a replica server. The main disadvantage of this method is that repeated looking up in the domain name system delays access.