CDN Uptime. All the Time. No Matter What.
June 9, 2015 | Robert Gibb
You can listen to an audio version of this blog post as well.
More companies are relying on CDNs to push content to users. This much is evident from research recently conducted that indicates the need for an always-on CDN.
One report by Cisco estimates that 57% of all global Internet traffic will cross CDNs by 2018 (up from 36% in 2013). Another report estimates that the CDN market will grow to $12.16 billion by 2019 (up from $3.71 billion in 2014).
During a time when digital media is becoming more plentiful and people less patient, CDNs close the gap between users and servers and help companies turn new demands into new opportunities. There is a caveat though, and that is that no CDN is foolproof. So for businesses that require a 100% always-on CDN – with absolutely no exceptions – creating a CDN failover strategy is key.
In Designing Your CDN Failover Strategy, we present ways of distributing content across multiple CDNs. This approach uses two or more independent CDNs to increase redundancy, provide load balancing, reduce the impact of outages, and improve the speed of your web services.
Having a CDN failover solution ensures that an issue with one CDN doesn’t cripple your web service. In the event of a performance or networking issue, users are automatically redirected to an alternate CDN.
Types of CDN Failover Strategies
As we cover in the CDN failover strategy PDF, a CDN failover strategy can also become part of your everyday content delivery strategy. This type of failover strategy can be referred to as active.
In other words, one CDN doesn’t have to fail in order for a second CDN to deliver content. Each CDN in the content delivery mix is always active, never just stationed as backup. Usually the CDN with the closest, most available PoP will be used to deliver the requested content. This failover strategy differs greatly from the passive type.
A failover strategy that integrates another CDN into the content delivery mix strictly as a failover solution can be called passive. The second CDN waits in the background, always assuming the worst. Although passive, it’s always ready to deliver content to users should the original CDN fail.
A CDN failover strategy can provide everyday speed benefits (active) or simply act as backup (passive)
One of the key benefits of the passive approach is that you don’t have to actively make changes to multiple CDNs. Instead, you are able to work primarily with one CDN. Because the failover CDN is there just in case, it often doesn’t require the same attention as your original CDN.
To put it another way, in an active approach, the CDN failover strategy also becomes a multi-CDN strategy as described here. In a passive approach, the CDN failover strategy is technically multi-CDN, but not by popular definition.
If you choose the active route, your multi-CDN also provides a load balancing approach for delivering large amounts of data. For websites that deliver high-bandwidth data – streaming services, for instance – distributing content across multiple CDNs prevents bottlenecks from affecting your users.
Important: The active/passive terminology to describe failover strategies is imperfect. It’s being used just to illustrate a point in this post.
Companies that Leverage Multiple CDNs
More companies are deploying their websites using a multi-CDN strategy. A study by Dyn shows that, as of Q3 2014, over 1,400 sites ranked in the Alexa 100K used more than one CDN. This is an increase of 6% from Q1 2014. According to that same study, the top three industries using multiple CDNs were Internet / computer software, media and retail.
Their system called Tealium iQ constantly scans PoPs in over 30 regions and redirects users to the best performing nodes. This approach lets Tealium avoid downtime, reach a larger audience, and deliver tags up to 100 ms faster than with a single CDN.
Companies that deliver large, high demand downloads – such as software updates – can also take advantage of multiple CDNs.
Apple previously partnered with three CDNs to deliver software updates for OS X and iOS. The release of iOS 8 saw traffic spikes of up to 3 Tbps, a jump of 50% above normal volume for some ISPs, that Apple’s private CDN and other third-party CDNs helped handle gracefully.
In each of these scenarios, the companies are using the active approach as previously described. There are many companies, however, that choose one CDN as primary and only use a second CDN when the primary isn’t available.
Implementing a CDN failover strategy boosts the reliability of your web services and gives you 100% confidence that you’ll have an always-on CDN day in and day out.
In Designing Your CDN Failover Strategy, we provide step-by-step instructions on setting up a CDN failover and multi-CDN strategy using traditional and peer-to-peer CDNs.
If you’re still not sure whether a CDN failover or multi-CDN strategy can benefit your company, see our quick guide to multi-CDNs.