Skip to main content

What is a CDN? Everything you need to know about content delivery networks

Deliver your content faster all over the world

What is a CDN?
(Image: © Shutterstock)

CDN stands for content delivery network. You can think of a CDN as a network of servers that are tuned for delivering content. These servers are placed strategically all across the globe with the intention of accelerating the delivery of web content. By some estimates, a majority of the Internet traffic is served by CDNs.

How do CDNs work?

The goal of the CDN is to reduce the time between when the request for a web page is submitted and when it fully renders on the web browser. The CDN helps cut down this time by reducing the physical distance between the request and the content. 

So for instance consider that a visitor from the UK wants to access a web page from a web server in the US. The request for the content and the data will have to cross the Atlantic ocean, which will result in a noticeable delay. CDNs however reduce the delay by storing a version of the US website in a server in the UK, and serving this version to the UK visitor much faster. 

The multiple servers placed in strategic geographical locations around the world are known as Points of Presence (PoPs). These PoPs typically contain several caching servers that host identical copies of the participating websites, which they serve to a user when requested. So when a user requests a participating website, it is the PoPs nearest to the visitor that respond to the request in a fraction of the time it would have taken had the content been served by the original web server. 

In addition to redirecting the request to a PoP and serving the cached content, a CDN will also communicate with the original server in case it needs to deliver any content that has not been previously cached or is in fact generated dynamically.

While CDNs are most commonly used for delivering static content, it isn’t the only type of content that you can transmit using CDNs. These days CDNs deliver all types of multimedia content including high definition video, and audio, and also help facilitate software downloads be it apps, games, and even OS updates. Potentially any data that can be digitized and isn’t generated dynamically can be delivered through a CDN. 

Benefits of using CDNs

The obvious advantage CDNs offer to website owners who have regular visitors from multiple geographic locations, is that their content will be delivered faster to these users as there is less distance for it to travel. 

In addition to accelerating the delivery of content, CDNs offer various other advantages. For starters it reduces IT infrastructure costs since you no longer need to acquire servers across the globe. CDNs typically cost a fraction of the amount and are also easier to deploy and manage than a fleet of worldwide servers.

In the same vein, CDNs give website owners the ability to easily scale up or down as per their traffic requirements. They also do load balancing in that respect, since they help take the load off the original server by handling incoming traffic. By redirecting users to replicated content helps reduce network congestion, which gives visitors a better user experience. 

Many CDN providers also have the ability to detect and thwart distributed denial-of-service (DDos) attacks, thereby protecting your original server, while at the same time ensuring uninterrupted access to your content. 

Since CDNs charge for their services based on the amount of data delivered (usually per GB), they collect and provide data analytics that could be useful to the content creators. Depending on the type or metadata collected by the CDNs, website owners can use the data analytics to improve their content and identify gaps in their outreach strategy. 

One of the indirect advantages of using CDNs is the improved SEO ranking. This comes about since one of the factors that search engines take into account while ranking a website is page load times. Search engines will rank faster websites higher than slower websites with high bounce rates. 

How to choose a CDN?

Like with all the web infrastructural services, there’s no dearth of CDN providers to choose from. We’d suggest you start out by making a list of your requirements based on the type of content you want to deliver via CDNs, the geographies you want to cover, the amount of bandwidth you’d need, and your budget. 

Next you need to shortlist the CDN providers based on a few general considerations before finding the best one that meets your requirements. The whole idea of using a CDN is to deliver content faster, which is why you should make sure the CDN you select is faster than your original server. 

Look out for CDNs that are tuned to deliver the type of content you host. For instance, while most CDNs will deliver all kinds of data, there are specialized ones that have optimized their network to deliver a specific type of content, particularly Full HD and 4K streaming video. Some of the reputable CDN providers will also employ extra caching layers to reduce the load on your original server. 

A CDNs scalability is also an important factor, especially for websites that experience occasional spikes in traffic. The best CDN shouldn’t just offer infinite scalability but should also allow some amount of automation to the process to keep up with the traffic.

Besides these content delivery features, also keep an eye out for the amount of time CDNs take to propagate your content throughout their network. Similarly, it’s also important to make note of the time it takes for a CDN to purge a file in case you need to take down a piece of content.