Translation Please: The Transport Part of IP Video

One of the chewier topics inside the cable-engineering community these days is the giant plate of questions called “IP video,” which also goes by “cable IPTV” and “managed video.”

We’ll define those terms here as the sending of digital video streams over the signal path currently used for broadband data and voice-over-Internet protocol. In the house, those streams spill into gadgets and computers over a (wired or wireless) broadband connection. That could include the TV, but not necessarily through a traditional set-top box.

For cable engineers noodling IP video, this is a conversation about alternatives. There are three.

One option involves sending those video streams through traditional broadband gear — the “CMTS,” in the lingo. (This necessarily requires the channel bonding feature in DOCSIS 3.0.) At home, video streams spill out of the cable modem, to the display screen. Maybe it’s a PC. Maybe it’s a TV with a broadband jack on the side.

The second alternative involves bypassing the CMTS, and instead “wrapping” those video streams in cloaks that make them look, to existing gear, like the streams they’re accustomed to seeing. That means they look like MPEG packets. (Remember MPEG is both a transport and a compression mechanism.)

The third option deals with everything once the streams get to the house. It’s the “residential gateway” or “digital furnace.” Most early designs support bits coming in either way: MPEG or IP. The job of the residential gateway is to make incoming video streams work correctly on any screen.

That’s the short version of how cable operators think through their “it depends” lists, as they consider how to prep their plant for the onslaught of video-thirsty IP gadgets. For (lots!) more, check out our webcast on this topic, Wednesday, May 20, at 2 p.m. ET.

Stumped by gibberish? Visit Leslie Ellis at