10 things to consider when choosing a CDN

Choosing a CDN (content delivery network) can be a daunting task. There are a range of available solutions out there, and they can appear at first glance to be quite similar. However, when you delve into the details you will find that there are some striking differences between the CDNs.

If you are going through the process of choosing a CDN, typically an organization will conduct an RFP and create a scoring model based on key criteria that are of importance to the business. These criteria are typically scored using a pre-agreed methodology.

The following is a list of 10 criteria you could use to evaluate a CDN. Note that this list is not exclusive, but for many businesses covers the most important features and considerations.

  1. User geography – where are your customers primarily located? Are they US based? If so a CDN that has good international coverage may not be high priority. Do you have a customer base in China? Then you may want to consider some China – specific options. Are your customers in country (and you live in a small country?) Then local hosting with no CDN may be better.
  2. CDN performance – let’s face it, if the CDN is going to make your site slower then there’s no point in running a CDN. When comparing CDNs, you need  to come up with a performance test methodology that helps you to make a sound decision. There are a variety of parameters to play around with here RUM vs Synthetic, location, stress test, the performance event you’re measuring to, etc.
  3. CDN reliability and availability – Since end users are connecting to your site via a CDN, you need to ensure maximum uptime and availability. Assess CDNs on their ability to be held accountable to an SLA.
  4. Cost – large variation here. The larger more established CDNs are costlier.
  5. Support for SSL/TLS – If your site uses SSL/TLS, then termination of this traffic will happen at the CDN level. Therefore you need to assess their support (and cost) for this service.
  6. Analytics – What information about your traffic are you able to get access to? Since  you’re fronting your site with a CDN, they now become the de facto source for traffic measurement.
  7. Purge mechanism – Sometimes you need to remove content from the CDN. How long does this take? How do you go about doing this?
  8. Service and Support – When you have a big launch and there’s a problem with the CDN configuration, how quickly can you turn to your partner and request support?
  9. Security – What mechanisms are in place to prevent DDoS? XSS? Other site attacks? Does the CDN player offer a WAF (web application firewall) solution?
  10. Management portal – What level of control do you have over your CDN’s configuration? Do you require costly engineering support to maintain the configuration?

Rich Howard

Rich Howard

Rich is the founder and CEO of Optimal. He has worked in web development and optimization for almost 20 years, and enjoys working with a diverse range of clients to help them solve their complex technical problems.

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