How Does a CDN Work? We Explain All

How Does a CDN Work? We Explain All

In MicroMarketMonitor’s recent report, it was noted that the North American content delivery network market is expected to grow from $1.95 billion in 2013 to $7.83 billion in 2019. One significant factor driving this growth is end user interaction with online content.

The interaction between a user and online content is far more complex today than it was a few years ago. Today’s users are much more likely to be streaming a longer video from a mobile phone or accessing a SaaS portal when working from home. These are far more complex experiences that did not exist five or so years ago. Given the expected growth of the CDN market in the coming years, this post will define exactly what a CDN is and how it operates.

A content delivery network, also called a CDN, improves the performance, security and reliability of a website.Since the start of the internet, websites have evolved in how they deliver content to the end user. In the example below, you will see the CDNetworks’ Twitter stream. Highlighted in red, is what is known as static content. The CDNetworks logo and profile descriptions are basic graphics and HTML text that rarely change. Highlighted in yellow, is what is known as dynamic content. The Twitter stream represents content that is always changing and moving.

It is the growing popularity of dynamic online experiences, like Twitter, that are driving the growth of CDNs.

How CDNs Work:

A CDN has Points of Presence (PoPs) or data centers that are situated around the world. Within each PoP are thousands of servers. Both the PoPs and servers help accelerate the speed at which content is delivered to the end user.

Below, is a representation of how a web page works without a CDN. An end user requests a page in which all the page’s components (images, HTML, dynamic content) are retrieved from the website’s server or origin, which could be anywhere in the world. In the example below, you can see the user is in North America, while the origin that holds the content requested is all the way across the globe.

Below are images that represent how a web page loads content using a CDN. A CDN caches all files locally (images, HTML, etc.) in the local PoP they have established. As a result, when an end user requests a web page, it loads faster. If the CDN does not have an image or file that is requested by the user, it will load from the origin as needed.

A CDNs approach changes for sites that have dynamic content. CDNs that support dynamic content create a “super highway” to accelerate the delivery of content across a longer distance. An individual ISP cannot provide this. In the image below, you can see the “super highway” helping to facilitate the delivery of dynamic content from the origin to the end user.

Lastly, a CDN should protect itself and all the data it stores as well as a website’s origin from any data breaches or internet hackers. The most common data threat are various forms of distributed denial of service (DDoS) attacks. A CDN has proper techniques for preventing, detecting and correcting different forms of DDoS attacks. Prevention measures such as HTTP load balancing, have an always-on approach, making sites less vulnerable to attacks. Detection systems within a CDN look for suspicious behavior and highlight the need for additional investigation and action. An example of a detection might be a traffic surge in which case the CDN provider has systems in place to automatically notify those responsible for the website. Corrective measures such as secured DNS will block out unwanted requests while continuing to allow trustworthy requests to continue being served.

Final Thoughts

At the end of the day, A CDN helps provide the end user with the best experience possible when interacting with a website’s content. Below are some additional CDN resources:

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