What is CDN & How does it Work? Content Delivery Networks

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What is CDN, How CDN Works, Explain CDN

If you have been browsing the internet, chances are, you almost definitely encountered a CDN being used by one of the websites you have visited. Many popular websites such as Reddit, Spotify, Netflix, Twitch, Stack Overflow, GitHub, Hulu, HBO Max, Quora, PayPal, Vimeo, Shopify, Stripe & more make use of CDN but what exactly is a CDN, how does a CDN work and why would a website want to use a CDN? This is a question many people have and in this blog post, we will be tackling these questions and breaking it down to make them easy and simple to understand.

What is a CDN (Content Delivery Network)?

A Content Delivery Network, commonly abbreviated to CDN refers to a widely distributed group of servers that are placed in many locations and sometimes even worldwide. These distributed groups of servers work together to provide fast delivery of various content such as images, website files, and more. When you use a CDN, the content of your website isn’t just stored on the origin server where your website is hosted, instead, copies are also cached (stored) across the group of servers.

The CDN is responsible for the quick transfer of web assets that are required for loading a website’s content such as HTML pages, javascript files, CSS stylesheets, and media files such as images or videos. The CDN thus offloads the bandwidth strain on your origin server to elsewhere – normally the server that is closest to the user who is trying to load your website. The use of CDN services has been continuously rising and these days, CDNs are responsible for serving most of a website’s traffic.

Another lesser-known advantage of using a CDN is DDoS Mitigation. DDoS or ‘Distributed Denial of Service’ attacks are malicious attempts that are aimed to disrupt the normal traffic of a targeted server or service by overwhelming or flooding the target with large volumes of Internet traffic.

Let’s break that down a bit. Let’s say you have a small server that is perfect for your small website which serves on average 100 users per day. In this case, you probably wouldn’t be expecting a large number of simultaneous users as that is far from the norm. When your small website becomes the target of a DDoS attack, you will notice a sudden spike in the traffic and within minutes you are now seeing traffic of over 10 000 simultaneous users. This sudden flooding of your server to render your website unavailable is called a DDoS attack.

These attacks involve overloading the server where your website is hosted with fake traffic and you can be a victim regardless of your size. A popular incident is a DDoS attack on GitHub which occurred in 2018. This was the largest DDoS recorded in human history! This attack had a throughput of 1.3 Terabytes per second, transmitting 126.9 million packets per second. Luckily for GitHub, they had been utilizing a DDoS protection service that was able to mitigate the attack.

Because of the nature of a CDN and how it redistributes traffic when needed, it makes for a fantastic defense against DDoS attacks. If your website happens to be the target of a DDoS attack, a CDN will help to ensure that the requests don’t reach the origin server and render your site completely unavailable. If a server is hit with more traffic than it can handle, it simply sends the traffic to other servers.

Can A CDN Replace The Need For Having A Web Host?

As mentioned above, a CDN is responsible for the quick transfer of website files which include HTML Files, CSS files, and javascript files so if this is the case, then surely I can get rid of my web hosting provider and switch to a CDN Provider which will be cheaper right? This is a common question that many people wonder about when learning about what a CDN is.

The answer is NO. While a CDN can improve a website’s global performance considerably, it is still no replacement for a high-quality web hosting service. With that being said, a CDN can help you relieve some of the strain placed on your hosting server by caching files and this would improve the user experience and performance of your website while also saving you from bandwidth costs.

Benefits of A CDN:

  • Significantly Improved Loading Times
  • Reduced Bandwidth Usage & Strain On Origin Server
  • Increased Content Availability
  • Improved Website Security

Significantly Improved Loading Times: When a user visits your website, he/she will be served with content from a CDN server that is closest to the user. This is especially helpful if you have a high-traffic site with users from all around the world. Because your site content is stored on servers close to them (instead of another continent, or country), the load time will be significantly faster compared to if the user was served from the origin server located on a whole different continent.

A faster website means more users will stick around for longer. In a study conducted by the Financial Times Technology Department which had a test group and control in which the test group would have a 5-second delay added to each page load time, the findings were as follows: The first-second delay resulted in a 4.9% drop in the number of articles a visitor read. The three-second delay resulted in a 7.9% drop. From these findings, we see that visitors read less when delays occur. It is therefore imperative that your website performance is as good as possible.

Reduced Bandwidth Usage & Strain On Origin Server: Bandwidth costs for website hosting are a primary expense for websites. By utilizing caching and other optimizations, CDNs are able to greatly reduce the amount of data that an origin server must provide which therefore reduces the hosting costs for website owners.

Increased Content Availability: Due to CDN’s distributed nature, a CDN can handle more traffic and withstand hardware failure better than multiple origin servers. These hardware failures if occur can interrupt normal website function.

Improved Website Security: A CDN may improve security by providing ⦁ DDoS mitigation, improvements to security certificates, and other optimizations.

What To Look For In A Quality CDN Provider?

Choosing a quality CDN provider can sometimes be as difficult as choosing a web host. There are many CDN providers out there with each making big claims and boosting their stats and performance. To make things worse, there are countless blogs out there with each recommending a different provider. Blogs aside, even people you meet may suggest a particular CDN provider which makes this task a lot more daunting.

Choosing a quality CDN provider can sometimes be as difficult as choosing a web host. There are many CDN providers out there with each making big claims and boosting their stats and performance. To make things worse, there are countless blogs out there with each recommending a different provider. Blogs aside, even people you meet may suggest a particular CDN provider which makes this task a lot more daunting.

Luckily for you, we will be making your life a lot easier by providing you with a tool that allows you to compare CDN providers side by side and view their performance in your target location. For example, if you are a company operating in Australia then you pretty much wouldn’t or shouldn’t be too concerned with a CDN Providers’ speed in the United States. Instead, it would make more sense to look for a CDN provider that offers a significant performance gain within your target region as that is where you expect most of your traffic to originate from.

Meet CDNPerf – The Most Reliable CDN Comparison Tool

CDNPerf is a website that assists you to find the fastest and most reliable CDN for free based on billions of tests. This tool allows you to set a bunch of parameters to narrow your search down such as search based on continent or country as well as compare providers based on uptime or performance in the region.

This makes the task of finding a quality CDN provider a lot easier for you. For example, if we were to look for the best CDN provider for the Australian Region based on real statistics, we could use CDNPerf and set the country to Australia. From here we view a provider’s performance in the last 30 days, the previous month, or even a specific month. From here we can start narrowing our list of possible providers until we find statistics that we’re happy with.

Features of A Good CDN Provider?

So now we have a CDN Provider in mind. The next task is to research the provider to get a better idea of what features are included & what makes them ‘The Best Provider’ for us.

A Good CDN Provider Offers The Following:

  • A global network
  • DDoS protection
  • Customization
  • Excellent Customer Support

A global network: The wider the distribution of your CDN Provider, the faster your content will reach your visitors – with minimum delay and almost no buffering. As we mentioned before, a CDN will serve your visitor from the server close to them. As we mentioned before, some CDN Providers have a lot more nodes in some regions than other providers and therefore if your target audience is only in a specific country or region, your selected CDN Provider should at least have servers near to where your users are.

DDoS protection: Many CDN Providers do have integrated DDoS protection, not all of them do so it’s worth checking if the CDN provider you have in mind offers this.

Customization: No 2 websites are built the same way with the same requirements. Often times you might find that you may need some customizations made to suit your needs and therefore it is important that you ensure your CDN provider allows you to change the settings to suit your site.

Excellent Customer Support: The last thing you’d ever want is to find yourself with a provider that takes days to respond to emails or support tickets. Every hour of downtime is a loss of revenue so therefore you should not settle for anything less than 24/7 customer support.


A CDN is one of the most effective ways of ensuring your visitors get an exceptional browsing experience on your website. The difference between the number of sales a fast-performing website receives per day compared to a slow website can be quite alarming. The last thing your customers online would want is to be waiting minutes for a webpage to load. Google recommends that your site load in under 2 seconds. Studies show that a slow webpage leads to users going away and visiting a different site.

It is for this reason that you should take great care to ensure that you make an informed decision when it comes to your website and business. Simply going for what everyone else is using just isn’t enough. Spending a few extra minutes to research is always a good method to ensure you make the best decisions and gain the greatest performance advantages over your competitors.

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