Cable Faces Uncertain Path to IP Multicast

For cable operators, Internet-protocol video is a mixed blessing. Delivering content via IP to the home is definitely the trend, and a direction that all content distributors are working towards as video is consumed on a variety of screen types.

But the cost of doing so on a one-to-one unicast basis is simply prohibitive, especially for an industry that built its initial prosperity on a broadcast-oriented, one-to-many distribution model.

As a result, IP multicast — a more bandwidth-friendly way to deliver IP video streams to a group of customers — has become a high priority for the cable industry. That interest has helped to spark research from CableLabs on the topic, with a “Best Practices Guide” expected to be out at the end of the month.

“The CableLabs approach sends multicast streams to IP gateways, which then translate these streams to ABR [adaptive bit rate] unicast streams over the last mile to end users,” Matt White, CableLabs’ principal architect of video technologies, said. “In this way, you can effectively serve groups of viewers with a single 6 Megabit per second stream, substantially reducing bandwidth consumption.”

The multicast-assisted ABR gateway model will be able to serve the growing number of COAM [customer owned and maintained] devices in the home, in addition to MSO-supplied set-tops, creating better multicast efficiencies, White said. “Cost-wise, this is a vast improvement from providing unicast streams,” he said.

As the cable industry surveys the IP multicast challenge, there are a number of points that need to be considered. One is the consumer’s desire to keep life simple. “Nobody is interested in having to have special apps running on connected devices to make the usage of IP multicast more complicated than accessing data directly from the Web on your laptop, smartphone or tablet,” Thierry Fautier, vice president of solutions marketing at Harmonic, said. “As far as the users are concerned, there should be no noticeable difference between obtaining content via a direct unicast route, or a combined multicast/unicast route.”

A second consideration is the need to configure key areas of the pathway between cable companies and their end users with multicast-enabled equipment.

“For instance, every router has to be multicast-enabled,” Andy Salo, the vice president of product management at RGB Networks, said. “So IP multicast is not some sort of panacea that can make the problems of one-to-one bandwidth consumption disappear. It can make a real difference, but there are equipment and programming aspects that have to be implemented first.”

Nevertheless, IP multicast is a realistic solution to serving cable TV subs’ multiple screens within the home, while also keeping bandwidth in check during high-demand events such as the Super Bowl.

“The very last thing cable companies want happening is a crash during Super Bowl Sunday,” White said. “This is why making IP multicast work is so important to the cable TV industry.”