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.
- 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.
- 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.
- 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.
- Cost – large variation here. The larger more established CDNs are costlier.
- 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.
- 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.
- Purge mechanism – Sometimes you need to remove content from the CDN. How long does this take? How do you go about doing this?
- 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?
- Security – What mechanisms are in place to prevent DDoS? XSS? Other site attacks? Does the CDN player offer a WAF (web application firewall) solution?
- Management portal – What level of control do you have over your CDN’s configuration? Do you require costly engineering support to maintain the configuration?
