Comcast has developed an innovative approach for gradually migrating its customers to the next-generation Internet, and the ISP is promoting this approach to the Internet's leading standards body.

Comcast is the largest cable operator in the United States, with 24.7 million cable customers, 14.1 million broadband customers and 5.2 million voice customers.

Comcast is upgrading its networks from IPv4, the Internet's main communications protocol, to the standard known as IPv6. IPv4 uses 32-bit addresses and can support 4.3 billion devices connected directly to the Internet. IPv6 uses 128-bit addresses and supports an unlimited number of devices.

At issue is how Comcast will support new customers when IPv4 addresses run out, which is expected in 2011. Comcast can give these customers IPv6 addresses, but their home computers, printers, gaming systems and other Internet-connected devices are likely to support only IPv4.

Comcast engineers have come up with a solution to this problem, dubbed Dual-Stack Lite, which it says is backwards compatible with IPv4 and can be deployed incrementally.

Comcast outlined Dual-Stack Lite in a draft document published by the Internet Engineering Task Force on July 7. Dual-Stack Lite will be discussed at an IETF meeting in Dublin scheduled for later this month.

"This is about making IPv6 deployable incrementally," says Alain Durand, director of Internet governance and IPv6 architecture in the Office of the CTO at Comcast. Durand, a longtime IETF participant and IPv6 developer, chairs the IETF's Softwires working group, which is looking at IPv4-to-IPv6 transition issues.

"If you look at all the technologies deployed on the Internet in the last 15 years, all the successful ones have been deployed incrementally," Durand says. "You can deploy [Dual-Stack Lite] in your own network and get some benefits immediately regardless of whether your neighbors are doing it."

Durand points out that Comcast has not yet committed to using Dual-Stack Lite internally.

"This is a technology that we are looking at, but we have not committed to deploy it," Durand says. "It seems promising, but we have to make sure that it actually works and that it actually scales to the size of our network before we put it in our network."