Comcast Braces for IPv6

Faced with a dwindling pool of IPv4 addresses, Comcast Corp. (Nasdaq: CMCSA, CMCSK) already has its backbone outfitted for next-gen IPv6 and could begin residential tests as early as this year.

Technical trials could start late this year or in 2010, says Richard Woundy, Comcast's senior vice president of software and applications. "Those dates are not 100 percent solid right now," he adds, noting that a full deployment might not occur for "several years."

"It's still relatively early in the IPv6 game," Woundy says.

The topic comes up because Comcast demonstrated its networkwide IPv6 prowess at this week's North American Network Operators' Group (NANOG) meeting in Philadelphia. Comcast showed how a PC with a Docsis modem could feed IPv6 traffic into the cable modem termination system (CMTS), onto the MSO's production network, and then off to demo partner sites that had been upgraded to IPv6. Limelight Networks Inc. (Nasdaq: LLNW) and Netflix Inc. participated in the demo, Woundy says.

The MSO is already in a position to sell IPv6 transit for wholesale customers, and BitGravity Inc. and The Planet Internet Services Inc. are among those that have already signed on. (See IPv6 Is in the House and Comcast Preps for IPv6 .)

Comcast won't say how many IP addresses it's supporting now, but it's in the tens of millions, based on the fact that it has more than 15.3 million high-speed Internet subscribers, each one using at least one cable modem and one computer or home gateway. Comcast is certain to eat more IP addresses as it starts to support set-top boxes with embedded cable modems.

The American Registry of Internet Numbers (ARIN) fired off a letter to Comcast and other ISPs in mid-April warning that "IPv4 will be depleted within the next two years" at the current rate of consumption. "You should begin planning for IPv6 adoption if you are not doing so already," the letter continued.

Because routers have had IPv6 baked in for a number of years, Comcast already supports the scheme on its fiber backbone. To ease the transition, those routers are running in dual stack mode, meaning they can pass IPv4 and IPv6 traffic concurrently.

But, thanks to Docsis 3.0, which Comcast expects to have installed on all its cable systems by the end of next year, it will also be able to employ IPv6 for its residential and small business customers. (See Comcast Sets Wideband Goal and 40%... & Counting.)

"We really didn't have true IPv6 support in Docsis until Docsis 3.0 was fully specified," Woundy says. He adds that CableLabs has created a specification for running IPv6 on Docsis 2.0 in "certain operator cases," such as when Docsis 2.0 modems are embedded in set-tops, gateway, and other equipment -- "but I think the preferred plan is to use [IPv6] in Docsis 3.0 modems."

Comcast's residential deployment of IPv6 will first happen on Docsis 3.0 cable modems, an environment the operator can control. After that, Comcast will extend IPv6 support to home gateways, which combine the cable modem with home networking capabilities.

— Jeff Baumgartner, Site Editor, Cable Digital News