Why Cable Should Care About CDNs

This month’s SCTE Cable-Tec Expo features two workshops dealing with content delivery networks (CDNs), and there’s a good chance the topic will come up during the opening session of the show as well.

Just a few years ago, CDNs were considered the purview of such companies as Akamai and Limelight Networks that grew up with the Internet and that provide servers globally to connect the Internet. Until lately, cable operators have been prone to dismissing traditional CDNs with the flip of the wrist or, claiming their own networks were "already CDNs."

Established CDNs cut their teeth delivering HTML pages but, with the explosion of multi-screen video, service providers seem keenly interested in learning more about CDNs. Some of the questions to be examined at the Cable-Tec workshops include: What’s the difference between building and operating a CDN, and being a CDN? Does everyone need a CDN or should they be interconnected or federated?

Comcast has been ahead of the curve on this one, creating its own Comcast CDN (CCDN) during the past couple of years. Its CCDN is specially designed to deliver on-demand video. According to John Schanz, the operator’s executive vice president/National Engineering and Technical Operations, "Think of it as a tiered model; at its core are library servers. Currently 30,000 assets are stored in four locations around the United States: Philadelphia, Atlanta, Chicago and San Francisco. Then further out in the network, we’ve created caching gateways where customers might be watching the same asset." Comcast currently has 90 caching gateways with VOD servers.

When Comcast CEO Brian Roberts first announced at the Consumer Electronics Show in 2008 that the company was building a CDN, he set a goal of 100,000 VOD titles nationwide. Schanz says the MSO is prepared to jump from 30,000 titles to 100,000 even today: "It’s a matter of being customer-driven. It’s not a technology limitation."

Regarding the physical facilities for its servers, Comcast has a couple of data centers it owns and operates, and others where it rents space. Schanz says the caching gateways are mostly in its own headends. "Part of the reason we took on this task is we wanted to optimize the CDN for long-form video," he says. "Lots of early CDNs were millions of assets that were small. This is about tens of thousands of assets that are huge. That’s a big time driver. The core technology looks like the typical Internet technologies, but it is applied in this private cloud for optimization."

In addition to consolidating its VOD servers into two tiers, Comcast also is relying on its fiber network. Another CDN element is service routers that receive requests for video and then decide the optimal caching server to deliver the request.

Why Build Your Own?

Kip Compton, vice president/Strategy and Product Management in Cisco’s Service Provider Video Group, outlined a few reasons why operators — at least the bigger providers — may want to build their own CDNs.

"As video traffic explodes on the net where in a few years 90 percent of traffic is video, CDNs are fundamental to run their networks efficiently," he explains. "When Akamai is running a CDN, they don’t necessarily have the ability to optimize content because it’s not their network that content is delivered over."

By building their own CDNs, service providers have the power to optimize the video across the network, taking into account network topology and network congestion. They also can deal with their own servers, managing any problems with that equipment. Compton says the end-user experience is generally better when the service provider uses its own CDN because the assets are cached into the service provider’s network directly, usually closer to the edge.

"Service providers own the last mile," he points out. "If the flow is coming from an external CDN, they can’t mess with that traffic. They just have to deliver it. If they’re running the CDN, they can actually optimize that traffic. The difference here is service providers are able to manage, control and monetize.”

Finally, Compton says CDNs help operators’ bottom lines. "Their need for bandwidth is growing more quickly than their revenues,” he comments. “There’s concern at a high level that the insatiable desire for video is driving bandwidth needs through the roof. They’re looking for ways to manage that and deliver video content more efficiently. CDNs, architecturally, have won."

More Opportunities

After an operator sets up a CDN, it may consider other business opportunities. Providers potentially could compete with traditional CDN companies. For example, BT Wholesale chose Cisco’s Content Delivery System (CDS) as the backbone for its online video-delivery network. Cisco’s CDS enables the U.K. operator to establish broadband as a TV platform to deliver digital content to any computer, TV or mobile device on behalf of U.K. Internet service providers.

Compton points out that it’s not that expensive for cable operators to set up a CDN. "They have a lot of assets: large networks; operations teams,” he says. “It truly is an incremental investment for them. Getting paid to host content on their CDNs by others, that’s a bigger step. A lot of service providers are getting interested in that. There may be money to be made there."

On the flip side, Comcast’s Schanz says, "That is not a priority for us at all. With Xfinity.com, we actually use third-party CDN services. ‘Off-the-network’ is not a priority for us."

Contact Linda Hardesty at [email protected].