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Why use a CDN?

Dror Arie
28.02.2019
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Content Delivery Network (CDN)

A Content Delivery Network (CDN) is a globally distributed network of web servers whose purpose is to provide faster delivery, and highly available content. The content is replicated throughout the CDN so it exists in many places all at once. A client accesses a copy of the data near to the client, as opposed to all clients accessing the same central server, in order to avoid bottlenecks near that server.

To put it more simply, the purpose of a CDN is to improve user experience and provide it with a more efficient network resource utilization. Content providers such as media companies and e-commerce vendors pay CDN operators to deliver their content to their audience, that is, end-users. In turn, a CDN pays ISPs, carriers and network operators for hosting servers in their data centers. There are two key mechanisms that explain how CDN functions:

  • Keep important content distributed to multiple, globally distributed data centers so it is closer to end users, and thus faster to download.
  • Use server optimizations based on content type to get that content to the user most efficiently.

Other than better performance, CDNs also offload the traffic served directly from the content provider’s origin infrastructure, resulting in possible cost savings for the content provider. They are also effective against DDoS attacks, since they provide their own large distributed server infrastructure to absorb the volume of the attack.

We’ve received a lot of questions from our clients about CDN’s, so we decided to create this brief overview of the most asked questions and our answers.

Q1: Why use a CDN ?

Modern CDNs bring 2 major benefits to websites :

  1. Lowering loadtime – As CDNs have global spread Point-Of-Presences (POPs) the global audience of the delivered website experiences a better performance. The POPs are in general topological closer to the customers, so the time-to-first-byte, the time until the first package gets delivered, is way smaller then delivering via the origin server. Secondly, the CDN caches all relevant assets while offering a higher bandwidth. Therefore the website gets delivered significantly faster.
  2. Offloading the origin – As the CDN can cache all static and even some dynamic assets (why not cache a search result for some seconds ?) the origin server gets offloaded tremendously, normally between 70-90%. The CDN also terminates the initial SSL request by the client’s browser. This results in a massive offload of the loadbalancers in front of the web/app-servers. The peaks on the infrastructure, caused by daily (e.g. newspapers) or seasonal peaks (e.g. e-commerce on Black Friday) get balanced out, scalability increases and outages decrease.

Q2: I heard that utilizing a CDN has a negative impact on my SEO. Is that true ?

During the early days of CDNs assets go delivered via the CDN domain. As an example: Your website is www.myshop.com, and you have an asset called fancy-product.jpg. Your CDN was goodoldcdn.net. So the asset was reachable via something like
goodoldcdn.net/myshop/fancy-product.jpg – in case you did not set the Cross Domain Rel then Google did not really like that, for the crawler you used ‘3rd party’ assets.

Since a few years CDNs can be set up inline using the CNAME record of your FQDN. This means that your DNS hold a record like this :
www.myshop.com CNAME myshop.shinynewcdn.net

The asset, even though its delivered via the CDN, show up as www.myshop.com/fancy-product.jpg. Google will love that.

But there is more: Remember in Q1, the CDN decreases the loadtime and boosts the performance ? This means that the Google crawler will be able to scan more pages in one session. This is one of the key indicators for Google that your site is relevant and professional => better SEO.

So the answer is that modern CDNs will help to improve your SEO.

Q3: What are the technological benefits of a CDN ? Do I have to adopt my technology to match the CDN ?

During the last years quite a lot happened in the internet protocol in order to improve the performance and the security : HTTP/2 boosts the download of the assets, IPv6 becomes more and more a standard, Brotli compresses data on a new level. And there is way more in the pipeline.It’s hard to keep up with the newest technology.

But here comes the good news: using a CDN you can lean back and benefit from the newest tech by clicking one button.

There is one thing you need to adopt in case you have a fraud protection system running, this is a common tool if you run a shop. As your clients connect to the CDN and the CDN to your origin, all transactions will show up with the CDN’s IP range. So your fraud detection would go wild as all payments come basically from one IP address. In those cases simply tell the fraud detection to use the XFF header sent by the CDN, most vendors nowadays send the true client IP in a dedicated header.

Conclusion

A Content Delivery Network (CDN) is a globally distributed network of web servers whose purpose is to provide faster delivery, and highly available content to end users.

If you have any questions about how we can help you choose and implement a CDN, contact us today to help you out with your performance and security needs.

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