What is CDN?
A CDN is a network of distributed servers, separated geographically, aimed at ease, and speed up delivery of the content of a website to its visitors. CDN service, which stands for Content Delivery Network, can effectively boost the transmission speed of the content from the origin webpage to the visitor by reducing the distance between the location of request and response. This remarkably improves the content delivery process. A website can benefit from quicker, cheaper, and more reliable transfer of contents from its origin server to its visitors, especially as the types of contents that are being delivered using CDN cover a wide variety of assets from images and videos to HTML pages.
The geographical distribution of servers, which is the main characteristic of a CDN, offers a variety of benefits for the websites. This is the reason why CDN is becoming more and more popular every day. Some of the most popular websites in the world, like Netflix, Twitter, Facebook, and Amazon, are now delivering their content through these networks.
In addition to improving the websites’ load time, using CDN can help websites reduce bandwidth costs, as the origin server needs to provide a lesser amount of data due to the caching processes. CDNs can also prevent hardware failures or similar problems from interrupting website functions. With geographically distributed servers, it ensures a redundancy level, leading to better availability of the website. Protection against different types of malicious attacks is another benefit of content delivery networks. Utilizing some security improvements, CDNs improve the security of the websites against various issues like DDoS attacks.
How does a CDN work?
As mentioned before, a content delivery network consists of geographically separated servers. The distance between these servers can be as long as a continent. CDN servers are placed in physical locations known as PoPs, which stands for Points of Presence. These are data centers built in strategic points all around the world that together shape an extensive network of servers. These data centers are equipped with cutting-edge devices and software optimizations to provide high levels of security and availability. Placing servers in PoPs helps CDNs avoid latency and reduce costs at the same time. Each PoP includes caching servers that store a cached version of the website contents. This means that when you use CDN services, there will be as many cached versions of your websites as there are PoPs, which brings you a high level of redundancy as well as all the benefits a CDN offers. When a visitor sends a request for a specific resource on your website using the browser, the content will be delivered from the closest cache server to the request. This prevents the request from being transferred all the way to reach the origin server and fetch the content back to the visitor. As an example, if a visitor from Japan wants to watch a video uploaded on a website whose origin server is located in Denmark, he will experience a considerable latency. Using a content delivery network, the request will be transferred to the closest PoP to Japan, which is in South Korea, and will be responded by the caching server containing the cached version of that website. This will remarkably reduce the loading time and bandwidth costs.