What is a CDN and How It Works?

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Content Delivery Networks (CDN) are a crucial part of the internet’s infrastructure and are directly responsible for bringing you content in all forms including images, text, videos and more. Quite a few people use CDN without understanding what they actually are or what’s happening behind the scenes.

Whether we know it or not, each of us interacts with CDNs on a day to day basis. Whether you’re reading a blog on some site, watching a video on YouTube or shopping on an e-commerce store it’s highly likely that you’re using a CDN. Before we get into how a CDN works it’s important that you understand exactly what a CDN is and how it’s used to bring you content.

What is a CDN and How It Works?

What Is A CDN (Content Delivery Network)?

Performance and reliability are extremist important factors for every web services. How fast a site performs and loads content directly impacts the customer retention, satisfaction, and profitability. This means that every web service wants to make sure that their content and services are readily available to everyone. This is where a Content Delivery Network (CDN) comes in the picture.

A content delivery network is a platform of servers optimized to deliver web content which includes traditional media such as videos and articles along with a variety of applications.

This network of servers is spread across a massive number of network and physical locations to make sure that any user that wants access to specific content receive it quickly and securely.  Basically, a CDN acts as an intermediary between the origin server of the content and the user.

How A CDN Works?

If a content server doesn’t use a CDN then it has to respond to every user request on its own which can drastically increase the latency of the server due to the high amount of traffic which results in slower data delivery to all users. By caching content on a CDN, you don’t just reduce the load on the origin server but also make the experience much better for the end user since they’ll be accessing a server that is closer to their physical location.

CDN operate by storing cached versions of your content throughout multiple geographic locations around the world which are referred to as points of presence or PoPs.

These PoP contain multiple caching servers that deliver content to users based on the server closest to their location. For example, if someone from Japan was to view content from a US site the time it would take the content to open from the origin server would take much longer compared to a CDN server based in Japan or a server based in another Asian country. But not all CDN providers are created equal. If you’re looking for a professional CDN service then what you need to look for is a CDN service providers that offers a large network of PoP and server capabilities.

Here is an example of how a CDN works:

  1. The developer for a site called “newsite.com” signs up with CDN service provider like EdgeCast CDN. The CDN provider will give the site developer a URL for the CDN
  2. The developer uses the URL provided by the CDN service provider to configure their site to load static assets from the URL. This can be easily done using WordPress plugins as well.
  3. When a user opens content on newsite.com, the page will reference the CDN URL to draw static assets to provide content for the user.
  4. The CDN automatically directs the incoming users request to the nearest CDN server.
  5. The browser downloads assets from a nearby CDN server to increase page load speed and reduces the load on the origin server.
  6. The CDN server updates the assets it stores with new content for future use from the origin server.

What To Look For In A CDN Service Provider?

The speed provided by a CDN server and the locations of a CDN server are by far the two most important things that you should look for in any CDN service.

Established CDN services like EdgeCast CDN have PoP servers across the world and their server speeds and reliability are comparatively some of the finest you can find. For years, CDN services have been supporting the internet from delivering content for almost all kinds of sites to users at reliable speeds on a massive scale.


Adithya Shetty is the creator of The Blog Metrics, a site that is dedicated to WordPress, blogging, and marketing since 2013. He's a Minimalist who loves to read and write.