What Is a CDN, and Why Do Companies Use Them?

Services you probably use every day, from Netflix to Amazon, rely on something called a CDN, or Content Distribution (sometimes “Delivery”) Network. So what are these special computer networks for, and why are they so important?

The Internet Is a Real Place

It’s easy to think of web content such as Netflix steaming episodes or your Google Drive files being “out there” in the cloud. However, every bit of data has to live somewhere on a physical storage device, inside a network-connected computer.

If you try to access a website on the other side of the planet, it will take much longer to load than one on a website hosted in your city or country. The further data packets have to travel, the more likely they are to hit a bottleneck as they pass through interconnections or they could simply get lost. In that case, they have to be sent again.

Nuts and bolts of internet architecture aside, the important point to keep in mind is that the closer to you that content is physically hosted, the better your experience will be.

How CDNs Work

CDNs involve a set of servers spread across an area. They can be global or local, as long as they physically cover the areas users are most likely to request content from. The content provider will upload content to their server and then it will automatically disseminate that data to the other nodes on the CDN network. CDN servers are usually connected to each other by fast internet backbone connections, so it takes just a few seconds to shift huge amounts of data between them.

CDNs are also smart and efficient. Let’s say you’re the first person in your region to request a specific file from a website. If the file hasn’t yet been replicated to your closest CDN node, it will be copied there from the next node that does have the data.

The local node will then keep the copy in case other local users also want that file. If no one wants the file after a set time, it might be deleted until someone wants it again. This way long-distance bandwidth is only used once, and then only local bandwidth is used. This is both faster and cheaper, so both the host and the user get a good deal.

The Benefits of CDNs to Companies

CDNs do more than give users a good experience. They can save content providers money by preventing excessive use of expensive international bandwidth. CDNs can also accommodate large numbers of users, spreading the load across the network to make sure there’s no denial of service.  That also means CDNs provide protections against deliberate Distributed Denial-of-Service (DDoS) attacks.

In addition, CDNs provide a way to limit content to areas where the content is licensed. It’s as easy as limiting locally-hosted content to what’s licensed for that region.

Using a VPN Defeats CDNs, For Better or Worse

CDNs can go down from time to time, just like any web server. Usually, users will automatically be rerouted to the next closest CDN. If that doesn’t happen, you may be hit with an error that shows the service is offline when it’s really just that specific CDN node that’s the problem.

In that situation, you can use a VPN (Virtual Private Network) to make it appear like you’re in a different region. This can be a quick fix for local CDN issues, albeit with a performance hit.

Unfortunately, when you use a VPN to get around geographical content blocks, you’ll lose the benefits of a fast local CDN node. Now you’re getting your content from a distant node, which is then fed through an encrypted VPN tunnel. While many premium VPN services can still offer good bandwidth and usage latency, it’s often the case that the quality of service degrades significantly.

Can Anyone Use a CDN?

It’s not just big companies who build their own server networks that can make use of CDN technology. Most CDNs belong to specialized companies that provide hosting and include CDN services as part of the hosting fee. Websites like Wix.com have their own CDN solution, so if you make a website using that service, a CDN ensures that people all over the world get snappy load times and general responsiveness.

Individual users can benefit from CDN technology by using products from companies that rely on them, but if you’re a business user you can approach CDN providers directly too. If you want to build your own CDN, it’s complicated but not impossible. However, it’s about more than simply buying server hardware. You need a CDN software solution and the servers have to be installed in key locations (such as backbone-connected data centers) to make it all work. Custom CDNs are definitely best left to the specialists.

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