What is a CDN (content delivery network)?

Forwarding requests

Once the target server has been determined in the CDN, the second step in this processes consists of forwarding the requests through the request routing system. There are many different methods for this ‘request redirection’ process. Most of them vary from one another in that they are directed from different locations: from the client, in the network, or on the replica server.

Directing the request from the client is a relatively simple method to carry out, and the client also has a large selection of replica servers at their disposal. The disadvantage here is that the content delivery network has very little influence in allocating the client to the right server. The serverside HTTP-302 redirection status code is also easy to implement and is equipped with useful information on the CDN. In this case, the exit server replies to the request with the status code mentioned above, and through this informs the client about the best suited replica server, which is then automatically contacted through a further request. Doubling the required connections is the main disadvantage of this process.

The most popular forwarding method is known as DNS-based request routing. Requests placed by clients on a local DNS server are forwarded to a special DNS server within the content delivery network, which in turn returns the IP address of a replica server. The biggest disadvantage of this process is that constantly looking up information in the domain system leads to access delays.   

Thanks to a global network of servers scattered across the globe, customers benefit from quicker loading times and smaller burdens on bandwidths. But operators also have some considerable advantages with CDNs: by forwarding queries, not only are server occupancy rates minimized, cached data is also more secure. This is because security breaches, like DDoS attacks, don’t reach the exit servers at first. Requirements for protecting cached data include keeping user names and passwords out of the CDN, as this increases the chances of a successful attack. Assigning a custom domain for the outsourced CDN content is well worth the work, since this prevents attacks from spreading onto other parts of the website. Here’s a summary of all the advantages of a CDN:

•    Static elements like HTML pages, images, stylesheets, documents, or client-side scripts are buffered in the replica server’s cache and needn’t be requested from your webserver any longer. This spares your server from overuse and also shortens the loading time for users. All of this leads to lower bounce rates and good search engine rankings.
•    The limited usage of the server as well as all involved applications protects your server from overuse and other potential threats, such as outages. This has a positive effect on the hardware needed for hosting.
•    Server operators can decide which static elements clients in the content delivery network are supposed to download. For example, should you only wish to store images from your blog, they can then be loaded alongside the rest of the page, ensuring a faster overall loading time.
•    When it comes to streaming videos and music, websites benefit from delivery with CDNs, as large sums of data need to be processed over a short period of time. This also counts for live-streams.
•    Spikes in traffic and increasing visitor numbers are easy to overcome with a CDN. The request routing system’s search for replica servers with free capacity is especially worthwhile when working with files that are available for download. It’s also beneficial for those operating online stores.
•    CDNs don’t only cut down on loading times, they also limit the bandwidth usage that is connected with the information request of your content.
•    The security of your server, data, and used applications increases by using a CDN. This is because attacks can be detected and dealt with early in the game.