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Selecting a CDN

One of the big questions for a corporate video producer is how to get the videos produced out to the viewers.  For most people in this era, the assumption is the video will be streamed over the internet.  There are still those who want discs, but that’s really dying these days, so we can ignore it for the moment. Web media is delivered using standard servers, but running specialized software to deliver video or audio in a steady stream to users.  The more sophisticated delivery systems are networks of servers designed to distribute the load across tens, hundreds, or thousands of servers worldwide, and are referred to as Content Delivery Networks, or CDNs.

Let me say up front that if you want to know anything at all about the CDN universe, your single best resource is Dan Rayburn’s Business of Online Video blog.  He knows everything there is to know about the technology behind online streaming and the industry that keeps online video going, and you’d really do well to keep an eye on it for the latest news.

Like most other decisions, there’s a build or buy choice here – create your own streaming CDN, or pay someone else to leverage their network.  The build option almost never comes into play for producers looking to deliver their content to an external audience – it’s usually prohibitively expensive, especially if video is a major portion of your external content. Internally may be a different story – companies own their own networks, have the tools and staffing to maintain it, and for the most part there’s likely to be considerably less traffic than on the external side.  There are standard server types designed to redistribute content throughout a network, no matter how spread out it may be, and a company might reasonably decide to manage a small or medium sized internal CDN.

The focus for this post, however, is on the external side – assuming you want to grow beyond the YouTube delivery stage and exercise a bit more control over our media distribution, what are the factors that should be considered when looking for a CDN vendor?

1. Cost

I don’t actually think this is the first thing to worry about, but it is a pretty simple one to work through.  There are two basics that CDNs charge for – storage costs and bandwidth, usually charged on a per-month basis.  Storage is exactly what you think – you use their servers to hold your media files.  All the basic packages at all the CDNs will include a minimum amount of included storage space usually in gigabytes (GB), with a per GB cost for additional storage.

Bandwidth is transmission – how many GB of data will you be sending across their network.  Remember it’s not just sending a 50 MB file across the pipe, but 50MB multiplied by the number of times the video is sent to a viewer.  Don’t forget it will also include partial views, so your usage is increased by people watching half the video as well as complete views.

In the end it’s a math problem:

(# of files you expect to host immediately + # you expect to add over the course of the year/contract) X average filesize = Storage Costs;

(# of files you expect to host immediately + # you expect to add over the course of the year/contract) X average filesize X expected number of views = Bandwidth Costs

You’re much more likely to go over your planned bandwidth costs than you are storage; the latter is cheap, they usually give you a decent amount, and unless you’re a media company delivering hundreds of new videos a week, you can likely work out a storage plan that leaves you plenty of room for growth.  Bandwidth can get trickier, and while I don’t know this categorically, I suspect it’s largely where the CDNs make their money.  With any luck, you’ll develop a following of viewers consuming your content, and it means increased bandwidth use.  If you expect a lot of traffic for any reason, negotiate a higher bandwidth allotment.  If you’re a middle-of-the road user, and again multimedia is not your bread & butter, it’s not unusual to request an upgrade after you’ve watched your traffic for a few months.  As I said earlier, they usually build in an overage cost into the contract, so you generally won’t be cut off if you hit your limit, they’ll just increase your costs on a set basis per GB.

2. CDN Size

There are a number of different levels of CDN out there – the large global networks like Akamai and Limelight, and some more regional players.  [Full disclosure – during my time in this arena my company was a Limelight customer].  The big boys handle enormous amounts of data – they often provide the backend delivery for the largest streaming media distributors around the world, including media companies, online video sites, etc.  The regional players are by design much smaller.

The question as a customer of these vendors is what do you need most, and what are you prepared to pay?  Some of the large companies won’t even talk to you if you’re below their minimum threshold, which may be too high a cost for what you’re trying to accomplish.  On the other hand, they have the largest, best backed up and maintained networks around, so the chances of a complete failure are much smaller.  They’re also more likely to have high-end support systems in place in case you do have a problem. They will also handle virtually every type of media offered, and deliver it to all platforms, which will give you a lot of flexibility as formats change and new platforms are introduced.

The regional CDNs will provide more flexibility in pricing and package levels, especially if you intend to start out small and scale up later.  Just be very certain they actually understand streaming media – there are companies calling themselves CDNs who don’t know anything about multimedia streaming, and this is not what you’re looking for.  The tech support may be less than the larger CDNs can provide, so do make sure you understand the support model of the vendor.

3. Network Reliability

Online multimedia is resource heavy – you can load a lot more text and small graphics in the same amount of time it takes to get a single video running.  Anyone who’s watched online multimedia is familiar with buffering – it’s that pause before a video starts, or in the middle of watching that’s caused by your local computer waiting for data to arrive.  Some of those delays are caused by local machine issues, some by other network traffic, some because of your own Internet Service Provider (ISP) and issues they may be having.

The one thing you don’t want to worry about is the reliability of your CDN’s network. Size is again a factor here – the larger the provider, the more likely they can re-route traffic to alternative paths quickly.  A little research may be in order here – checking with existing customers, or again looking around Dan Rayburn’s blog to see if there are reliability reports.  Consumers expect immediate gratification, and you want to be sure your vendor can provide regular, dependable service.

4. Metrics

The black hole of the internet.  To this day I find that metrics are the most abused, least understood aspects of delivering content over the web. They’re absolutely vital if you want to understand the impact your content is having on viewers, but they’re horrendously difficult to interpret in a way that leads you to make intelligent business and content decisions.  I’ve had this discussion with people before – it’s not what you track, it’s what you do with the information you get.

Multimedia stats are among the most difficult to make sense of, in part because most stats packages can’t actually track users accurately.  Yes, you may be able to tell how many clicks you’ve gotten, but in my experience I rarely got more specific data on how much of a video people watched, or whether individuals watched multiple pieces. Remember that your viewers generally will not be logging into your system to see video, so you haven’t got a lot to use to track them throughout their visit. Some of this may change with HTML 5 media delivery, and maybe things have improved since I last did this regularly, but it’s really an ongoing struggle for content owners.

I’ll probably have to write another post on multimedia stats, but when looking into a CDN you should ask for sample stats in addition to whatever generic information they tell you.  How much can you manipulate or filter when using their stats?  Are the stats real time? Can you export the data into a spreadsheet or database program? Can you set up daily/weekly/monthly emails to yourself and/or others?

You will be asked to provide information to people within the organization, so make sure:

  • you understand what you’re getting from the vendor;
  • you understand what you’re looking at when you get your numbers
  • you can tease out what your organization needs to know
  • you can translate what you see into reporting and actions that matter to the organization

5. Customization

In addition to delivery of your content, many providers offer additional services to customize what viewers see when they visit web pages hosting your multimedia.  Some providers, like Brightcove for example, are built on the premise of providing not just a delivery mechanism but a full suite of production and distribution tools. Others may only provide rudimentary tools for deploying your content out.

If you happen to have a full service web department that will be branding and skinning the media files you’re delivering, customization may not matter much.  If you’re looking for help to display your content, ask the vendor about options to customize the experience for you and the viewers.

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