Comcast showed its support for Internet Protocol version 6 (IPv6)  in a meeting of the North American Network Operators Group last week in Philadelphia.

NANOG is an educational and operational forum for Internet service providers (ISPs). It was formed in 1994, having evolved from the regional tech meetings of NSFNET, the pioneering National Science Foundation-backed network that went live in 1986.

Comcast hosted the NANOG meeting last week and took the opportunity to announce the availability of IPv6 transit for wholesale customers and to demonstrate its end-to-end network readiness for IPv6.

"The pool of available IPv4 addresses is running out, which is why we are pushing for IPv6," said Rich Woundy, SVP of software and applications at Comcast. (For an early backgrounder on IPv6 from another Comcast engineer, click here.)

Wholesale transit and end-to-end

To prepare for the launch of its IPv6 wholesale transit capability, Comcast worked with several of its current wholesale transit customers including The Planet, an IT hosting provider, and BitGravity, a video service provider.

"We host 17.8 million Web sites, so ensuring our customers have the IP space necessary for their critical content and applications is crucial," said William Charnock, vice president of technology for The Planet, in a statement. "We are committed to providing our customers with IPv6-ready services before IPv4 depletion reaches a critical point. The widespread adoption of IPv6 depends on broadband leaders like Comcast enabling it on their networks."

The wholesale services are targeted at more sophisticated customers that have some IPv6 knowledge of their own. Comcast has already upgraded its backbone routers to support IPv6 so the company can pass both IPv4 and IPv6 traffic, said Woundy. "This announcement shows that we have the maturity to do this for customers."

The next step is to bring IPv6 into the home over Comcast’s DOCSIS 3.0 network. In this case, the use of the IPv6 address is hidden from the user. In a demonstration with Netflix, Limelight and The Planet, Comcast showed last week that it was possible to provide end-to-end IPv6 over the DOCSIS and Comcast backbone network to various content providers who have upgraded their facilities to support IPv6. They are now preparing for the technical trials in order to iron out any potential bugs.

"One part is making sure we are ready for IPv6 and ready to promote it," Woundy explained. "At the same time, we know there are devices that don’t support it well and a bunch of Web sites that will not support IPv6 for some time. We want a technology to help bridge that gap."

Transition challenges

There are some interesting challenges in the home. One is making sure that the home gateways support IPv6. There are still a number of devices that only understand IPv4.

For example, Windows XP supports a little bit of IPv6, but not enough to make it work transparently, said Woundy. It would be difficult to get IPv6 operational on the average consumer’s Windows XP computer today. It is important to weave network address translation (NAT) into the backbone network seamlessly between the existing IPv4 world and the virtually limitless IPv6 world.

Many devices in the home, such as portable media players and cameras, only support IPv4, so Comcast will have to retain legacy support for these devices over its network. To help overcome these concerns, consumer electronics vendors have started labeling their equipment with an IPv6-ready logo.  (http://www.ipv6ready.org/). For the older devices, Comcast has proposed using Dual-stack lite (http://tools.ietf.org/html/draft-durand-dual-stack-lite-00) to bridge legacy IPv4 in the home and on certain Web sites with IPv6.

Woundy said Comcast wants to iron out any kinks in the test phase in order to reduce the number of consumer calls as the company begins to make the transition.

"That is one reason we are being very methodical to make sure that as we upgrade systems and enable IPv6 operation on devices, there is no customer impact," he said. "The other thing we are doing is lots and lots of testing to make sure that these IPv6 devices operate the way they are supposed to."

Comcast is also doing a fair amount of internal training to make sure its engineers and operations personnel really understand how IPv6 works. "While we don’t want Grandma to have to understand it, we want our network folks to understand how it works," said Woundy.

Comcast had to put together its own curriculum because very little of the existing IPv6 training material was directed at cable operators. (For a look at two approaches to IPv6 adoption, click here.)

– George Lawton

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