Buyer's Guide to CDN Services 2016
“A rose by any other name would smell as sweet,” a guy named Bill wrote a few centuries ago. He certainly wasn’t talking about online streaming “video delivery, but the notion applies to this buyer’s guide to CDN services.
What’s a CDN?
By definition, it’s a content delivery network, and, as the name implies, it’s a service purpose-built to deliver content. As a service, it comes at a cost, but perhaps a much lower cost—and with a greater probability of success—than building a CDN for the average media content publisher.
While traditional CDNs were designed to handle static files, a number of the early CDNs took on the challenge of delivering live streaming. This meant buying hundreds or thousands of media servers and placing them at strategic points around the U.S. and Europe, and at a limited number of points of presence (POPs) in other parts of the world.
These POPs could be colocated in a data center with other service providers, from ISPs and offsite disaster recovery caches to critical, redundant website servers for larger companies. The cost of installing and maintaining the media servers, which could act as live-streaming origin servers or reflectors, or even as simple on-demand video servers, falls to the CDN provider.
In this era of cloud computing, however, the lines around a CDN service are understandably getting blurred. From stream delivery to storage to dynamic media processing and even virtual media servers, certain core CDN service offerings are now pitched by several discrete companies that offer potential CDN customers a piecemeal alternative to a pureplay CDN.
Even more confusing, not every CDN is created equal when it comes to infrastructure or even delivery philosophy. So what are the major issues to look for when considering CDN services?
The Pure-Play Approach
The buy-versus-build debate of the past decade was a fairly simplistic approach to deciding if CDN services were required. It was primarily a capital expenditure (capex) discussion, and it seldom took into account the total cost of ownership (TCO) that combines an initial, up front capex with ongoing operational expenditures (opex) such as maintenance and server repair.
This binary argument, in the era of cloud computing, has given way to a more-than-binary discussion. As mentioned at the outset, a number of service providers are willing to offer segments of a CDN’s services in a virtualized environment; these include storage, stream delivery, dynamic media processing, and by-the-hour virtual media server instances.
Even if there’s a more compelling capex argument for using multiple providers—one offers storage, another transcoding, and a third data replication closer to the edge, meaning nearer to consumers— there’s something to be said for using a single vendor to offer all these services in a somewhat integrated environment.
The idea of using a single vendor for all your content delivery needs is itself a bit simplistic; you might have a large cache of premium content that needs to be delivered to customers across multiple ISPs or geographies.
To handle demand adequately, the CDN provider might need to place content not just in a large number of data centers, but also on major telecom or cable service provider (CSP) networks. To accomplish this, especially if the CDN provider also happens to own an ISP or a significant network backbone, peering arrangements are established to allow media servers to be placed in strategic locations.
For live events, in addition to transport peering arrangements, also consider whether your CDN provider plays nicely with others. For a Unisphere-Streaming Media-Level 3 research report I authored last year (go2sm.com/level3research), on the topic of over-the-top (OTT) delivery, almost half of the survey respondents said they use a multiple-CDN strategy, with about a quarter saying they use a single-CDN strategy. In order for a multiple-CDN strategy to work properly for large-scale events, though, the customer and all the CDNs involved need to be on the same page when it comes to division of labor, target delivery geographies, and an overall failover approach.
For most CDNs, pricing comes down to three parts: media serving, storage, and transport. Let’s look briefly at all three.
MEDIA SERVING STRATEGY
As mentioned earlier in this article, serving media is at the heart of most CDN providers. This wasn’t always the case, as early CDNs were often as likely to serve small files (webpages, documents, and the like) as they were to serve media. This was especially true when it came to large-scale live streaming delivery: Many CDNs either didn’t have the specialized media server capacity or the global reach to provide large-scale live event delivery, and had to rely heavily on ISPs and other CDNs to bear some of the load.
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