What is a multi-CDN strategy – and why do you need one?

CS Yap

CS Yap

To understand what a multi-CDN strategy is, we have to look back at the era of using single CDN service provider to speed up the performance of your website.

In the past, a website owner would shortlist a few CDN providers and choose a single CDN to improve the performance of their website, when comes to page loading time or content downloads.

Their choice might be based on the CDN’s coverage or the cost of the traffic. It could be because of their support service, or how user-friendly the CDN system is – there are many factors, but typically they would only choose one provider.

In the past 3-4 years, however, it has become more common to use multiple CDN service providers to improve website performance. Why is that?

Why website owners use multiple CDNs – the benefits

It is actually really simple – in fact, I see it as inevitable, because while CDN is really no longer optional for successful websites, there is no single CDN service provider in the market can best fit the needs of ALL websites. Let’s talk about each of the metrics here – the benefits of going for a multiple CDN strategy:

1. Geolocation Coverage

This is one of the major concern for website owners, especially when website visitors are widely spread around the world, or concentrated at a few locations.

In the widespread scenario, perhaps CDN provider A has good coverage in North America and Europe, but not Asia, and CDN provider B is the opposite where their CDN PoPs are mainly located in the Asia region. In that case, it make sense for the website owner to use both provider A and B to have a good coverage worldwide, because that’s where the eyeballs are.

In the second scenario, maybe the website visitors are mainly coming from exotic countries like Mexico, Brazil, and Cambodia (exotic in CDN terms) – thus the website owner may need to select multiple CDN providers to fulfil the website traffic requirement.

2. Difference in Feature Specialization

While most CDN service providers share common features like purge, bring your own SSL, and routing rules, there are CDNs which specialize – for example, in delivering live streaming or VoD. There are also CDN service providers which specialize in static optimization and security, but do not offer streaming services. In this case, for a website which has both static content and live streaming feeds, it makes complete sense to use different CDNs for different purposes on the same website.

3. Cost of Service

CDN is no longer an optional add on. The question has switched from whether to use a CDN or not, to which CDN providers should I go for, since CDN is becoming a commodity service for all websites.

There are website owners who are very price sensitive, and although the price of CDN is getting cheaper and cheaper as the market is becoming more competitive, there is still a big price difference when we compare the big names and the boutique CDN providers. This always reflects in the different pricing scheme of regions.

For example, Provider A may have super-good pricing in North America and Europe but charge a lot higher in Asia, compared to provider B. Meanwhile provider C can offer cheapest pricing of all in South America. In this case, a website owner which needs footprint from all these regions will most likely choose all 3 CDN service providers for their websites use.

There are also CDN service providers who have flexible pricing schemes which, along with regional differences, come with peak hours and off peak traffic costs too. The commercials of CDN are getting a lot more creative than before.


A multi-CDN structure

4. CDN PoP Performance

While most CDN service providers effectively have the same CDN PoPs, because they’re located at Regional Internet Exchange locations like Dallas, Amsterdam or London, they don’t necessarily perform the same. The network pipe of each PoP could be different upstream of the data center, hence the web content being served from CDN PoP at the same geographical location, from providers A, B and C, could have a different resulting latency.

Provider A may have a faster speed for CDN PoP in Amsterdam, but provider B may beat over provider A for CDN PoP in Frankfurt. Website owners who value performance more than other factors would choose multiple CDNs for their website in this case.

5. Capacity and Redundancy

CDN network capacity and the need for redundancy also have a role to play in the trend towards using multiple CDNs.

A website might have a huge project, for example live streaming events for a certain period, and they expect a few hundred or thousand percent traffic spike within a short time frame. In this case, having multiple CDNs to power your website content delivery is the right strategy to go with, because you have larger traffic capacity compared to a single service provider – and the website owner will have redundancy if one of the CDN providers has hiccups during the important live events.


How does OnApp CDN help?

As most of the industry knows, OnApp CDN is powered by a group of regional CDN players who resell their CDN PoP traffic through our CDN Marketplace. This is our federated CDN concept, or as we also call it, hybrid CDN. The federation and hybrid concept tackles almost ALL of the points we’ve discussed above, because our federated CDN is based on a multi-provider network. Just take a look at the following screenshot of OnApp CDN Marketplace:

In Dallas, for example, we currently have four different providers to choose from. There is differentiation of service (HTTP delivery or Streaming), there is differentiation when comes to price, there is difference in performance (the star rating, based on OnApp benchmarks) – all of which helps you choose the right provider for your project – highest performance, or multiple providers to ensure capacity and redundancy.

When you click on the tooltip next to the provider name (refer to the picture below), OnApp shows you performance benchmarks for throughput, uptime, the number of CDN caching servers in that location, as well as the IP address for you to check out the internet upstream providers that the datacenter is using.

At this point, you may still argue that OnApp CDN could still be a single point of failure, because all these federated OnApp providers share the same OnApp CDN software, including our Anycast DNS service. That’s great – now you’re thinking with multiple CDNs!  Of course we agree with you – so for even more choice and redundancy, you would use OnApp as one of the CDN options, alongside another provider. We are more than happy to help you with that 🙂

So that’s the WHY of multiple CDNs. In the next blog post we’ll talk about multiple CDN implementation, the question of HOW.

In the meantime, you can learn about OnApp CDN here, join our upcoming CDN webinar to see what’s new – and please get in touch if you’d like to know more. Thanks!