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?

The Big Boys
• Akamai claims between 15 percent and 30 percent of all Web traffic passes through its servers.
• Limelight Networks has a global optical network, and it peers directly to MSOs and telcos.
• EdgeCast Networks has partnered with transparent-caching provider PeerApp to offer a comprehensive content delivery solution for network operators.
• AT&T is a new player in the CDN space, but the company has capitalized on its mobile market for streaming. It also has the benefit of last-mile access.
• Level 3 owns an array of data centers in conjunction with its global network. It’s carved a niche for itself with online gaming companies, and its Vyvx broadcast services are used widely to stream major live events.
• Internap has service-level agreements with all the major backbone carriers. Although it has a global footprint, it is U.S.-focused.Know MoreFor more information on CDNs, see" CDNs Bridge First and Last Miles: Online Video Stresses the ‘Middle Mile," at

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."

Other CDN Players
In addition to Cisco’s Content Delivery System (CDS), other vendors offer solutions for service providers that want to build their own CDNs:
• Alcatel-Lucent’s Velocix Digital Media Delivery platform was designed specifically for service providers to help them establish an on-net CDN. The company says an on-net CDN is more than just caching and delivering traffic; it‘s also about acquiring, managing, publishing and monetizing content.
• Verivue has developed its OneVantage Content Delivery Solution that includes all the components needed to operate a competitive multi-tenant CDN network, including a high-performance cache, a request router for dynamic cache selection, and an analytics suite that gives the operator and its customer detailed visibility to optimize the end-user experience.
• Juniper Networks’ Media Flow is a Converged Content Delivery (CCD) solution that also can be used as a foundation for such new content-based services as video delivery to multiple display formats. According to Juniper’s Website, service providers need to optimize their video content while creating new revenue streams, which can be achieved through a CCD architecture.

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, we actually use third-party CDN services. ‘Off-the-network’ is not a priority for us."

Contact Linda Hardesty at [email protected]

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