Content delivery network — What is a CDN?

A CDN, or content delivery network, is a network or collection of servers in locations all over the world. Also known as a content distribution network, a CDN can refer to many types of content delivery services, such as load balancing and video streaming.

A CDN’s network of servers allows companies to deliver content from their websites and mobile applications to people more quickly and efficiently, based on their geographic location. In short, a CDN moves data and applications closer to the end user — increasing speed, enhancing security, and improving the user experience.

What are the benefits of a CDN?

There are many benefits of a content delivery network, from improved user experience to increased security to lower costs.

Reduced page load time CDNs eliminate the need for data to travel over long distances because they deliver content from servers that are close to the end user. As a result, CDNs dramatically decrease the amount of time it takes to load a webpage, including those with high-bandwidth, media-rich content. For many businesses, this improvement in the user experience translates into better brand reputation and more efficient sales.

Improved availability No more frustrating error messages; CDNs allow websites and apps to be “always on” for the end user. If an origin server goes down, the CDN can continue serving whatever content was last in cache to users from POPs, points of presence, that are geographically and strategically distributed for peak performance.

Increased scalability CDNs allow businesses to scale on demand. While web traffic is typically consistent for most of the year, events like Black Friday sales or breaking news events can cause traffic to surge, sometimes unexpectedly. In an effort to preserve the user experience, companies traditionally have had to buy or rent enough servers to account for the peak times. This means, for the rest of the year, they may be paying for wasted storage.

In contrast, CDNs allow companies to normalize their server spend and buy a more reasonable amount of space. When a traffic surge does occur, companies can send it to be served from a distributed POP instead of from the origin. This scalability happens on demand; as soon as a company needs more capacity, they get it. In addition, load balancing allows servers to distribute the requests over the network for more optimal routing decisions and greater resilience.

Increased security Content delivery networks provide extra layers of security. First, CDNs are more resistant to certain types of cybersecurity threats because traffic is routed through POPs. For example, CDNs protect your website against Distributed Denial-of-Service (DDoS) attacks, which overload origin servers with fake traffic to slow down or even crash websites. A CDN’s large, high-bandwidth, globally distributed network is able to absorb that traffic and prevent it from hitting the customer’s origin server.

Second, CDNs assist with data encryption. Because data moving across the internet is vulnerable, it must be encrypted using protocols such as Transport Layer Security (TLS) and Secure Socket Layer (SSL) so that only the intended recipient can decode and read the information. CDNs can help protect a site by providing TLS and/or SSL certificates that ensure a high standard of authentication and encryption.

In addition, CDNs can help protect your websites and apps through a Web Application Firewall (WAF). WAFs offered by CDNs will analyze and channel traffic to and from a website, blocking application layer (Layer 7) threats. They examine every HTTP request and act as a shield to block suspicious traffic, only allowing secure traffic through. This is seamless to the user, and prevents threats such cross-site scripting (XSS) and SQL injection attacks. CDNs can also help protect against bots, which are software programs that perform automated tasks and can be used for malicious attacks. CDNs can use detection technology to quickly identify and neutralize bot threats.

Reduced bandwidth costs Lastly, CDNs can help save companies money on bandwidth. By rerouting traffic from the origin server to the CDN’s servers, CDNs reduce spend on origin infrastructure and egress costs. If content is held in cache by a CDN, there are fewer reasons to travel back to the origin.

Who needs a CDN?

Businesses with an online presence stand to benefit from a content delivery network, including ecommerce platforms, digital publishers, social media sites, and entertainment websites:

• A CDN can benefit large ecommerce platforms by handling heavy traffic, regulating seasonal and unexpected traffic spikes, and increasing security around transactions. These platforms span a range of industries, including retail and hospitality.


• Similarly, digital publishers with large global readerships can use CDNs to handle traffic, page downloads, transactions, and other demands.


• A CDN is also ideal for entertainment websites (like streaming sites that deliver real-time, high-definition content) where users have come to expect a predictable, high-quality experience.


• Financial services providers enhance their users’ experiences by using CDNs to cache APIs so they can serve highly dynamic content, like stock prices. -


• Social media sites, which experience high traffic volumes and feature rich multimedia content, can use a CDN to enhance and regulate the user experience.


• High tech companies use CDNs to deliver insights and analysis they can act on to constantly improve the user experience — a CDN that provides real-time analytics and streaming logs provides actionable insights they can use to differentiate themselves.

These are just a few examples of businesses that benefit from CDNs. Your business might need a CDN if your site experiences a lot of traffic or uses a lot of bandwidth — or both.

Example use case: A CDN in action

Let’s look at a use-case example to understand how a CDN provides a quicker and more efficient way of serving content to users.

Take an end user visiting a favorite news website. Once they type in the URL to initiate communication between the browser and the news site server where the webpage is hosted (the origin), the back-and-forth communication between the user’s browser and the origin goes through a number of steps: first relaying the DNS lookup, then routing, then a TCP and TLS handshake, and finally the HTML transmission, along with various files like CSS, JavaScript, and videos or images on the news site.

Now, let’s say the user is in San Francisco, and the news site server is in New York. Remember that all the communication between the user’s browser and the news site server happens over real wires and cables. So, the physical distance between San Francisco and New York adds time, or “latency,” to the browsing experience. Imagine if our user was in Australia and the communication had to travel back and forth between Australia and New York! As you might predict, that distance would dramatically increase latency, degrading the user experience.

In contrast, let’s picture this scenario again – this time, using a CDN.

We know that the closer the user is to the news site server, the faster the experience will be. CDNs put servers physically closer to end users — thereby speeding up load times.

With this knowledge, the news site has opted to “cache” — meaning, temporarily store — its content on CDNs. Now, instead of going back and forth between New York and San Francisco, the user’s browser can communicate with a server much closer to home. And for the user over in Australia, their browser can connect to a POP in that part of the world, for example, Sydney.

And because cached content is only stored temporarily, CDNs also purge, or remove and update, content constantly. Companies don’t have to worry about serving their users outdated content; the most up-to-date content is delivered automatically. As a result, not only will our user’s article load significantly faster, but they’ll also see the latest headlines as the day unfolds. A CDN has dramatically enhanced the user experience — and, we might presume, the loyalty to visit that news site again and again.

Get started with a CDN

This is just one of countless examples of how a content delivery network can add value — optimizing web performance and enhancing a user’s online experience, resulting in enhanced brand reputation and loyalty. Indeed, by increasing performance, availability, scalability, and security, all while reducing costs, CDNs are a win-win for many types of businesses.