Big step for IPv6: Comcast starts trials

ISP to test transition mechanisms for next-gen Internet services starting in Q2

Comcast will begin in April a series of public trials of three different mechanisms that are aimed at helping the Philadelphia-based ISP transition its network to IPv6, the next-generation Internet Protocol.

Comcast announced that it is starting IPv6 production-level network trials on its blog on Wednesday. The carrier has been working on IPv6 development for five years.

IPv6: The essential guide  

Comcast is looking towards IPv6 as an enabling technology that will allow the carrier to continue adding new subscribers to its network in the long-term. The largest cable operator in the United States, Comcast had 23.8 million customers for its video, high-speed Internet and voice services as of Sept. 30, 2009. 

Comcast is moving toward IPv6 because the Internet is running out of address space using its current protocol, which is known as IPv4. IPv4 uses 32-bit addresses and can support around 4 billion IP addresses. More than 90% of IPv4 addresses have been distributed to ISPs and other network operators.

Designed as an upgrade to IPv4, IPv6 uses a 128-bit addressing scheme and can support so many billions of IP addresses that the number is too big for most non-techies to understand. (IPv6 supports 2 to the 128th power of IP addresses.)

IPv6 has been available since the mid-1990s, but deployment of IPv6 began in earnest last year. Among the U.S. ISPs that are leading the charge to IPv6 are Comcast, Hurricane Electric and NTT America.

Comcast plans to complete its transition to IPv6 in 2012, which is when the last IPv4 addresses are expected to be allocated.

Comcast is recruiting corporate and residential customers to participate in the IPv6 trials, which will run for several months during 2010.

Comcast will use the trials to identify the best way to migrate its access network to IPv6.

"We've done all the upgrades to prepare our backbone, our back office and our peering points to be IPv6 compliant, but what remains is our access network," says Jason Livingood, Executive Director of Internet Systems Engineering at Comcast.

Comcast will test three IPv6 transition mechanisms:

* Phase one will use 6rd, a technique developed by French ISP Free that allows for rapid deployment of IPv6 by tunneling IPv6 traffic over IPv4 addresses.

* Phase two will support native IPv4 and IPv6 traffic running side-by-side in an approach dubbed dual-stack. This is Comcast's preferred method of transition to IPv6 and may require the carrier to reclaim unused blocks of IPv4 addresses.

* Phase three will test a technique developed by Comcast called Dual-Stack Lite, which uses network-address translation to share one IPv4 address among many customers.

"We really want to kick the tires on these various technologies so we can understand what needs to happen for a wide-scale roll out," says John Brzozowski, chief architect for the IPv6 Program at Comcast. "We want to understand what the challenges are and what the various issues are so we can make sure we do what's in the best interests of our subscribers."

Livingood says Comcast wants to use the trials to figure out which IPv6 transition mechanism will work best in a production environment.

"Our attitude on this is that the sooner we can begin to really know how to make the transition, the better," Livingood says. "We don't want to wait until the last minute to figure this out because there might be standards development or industry-wide things needed or operational tools to develop. We want to have plenty of time to focus our energy on this transition."

Comcast is providing details about its IPv6 trials and how to sign up for them at the Web sites www.comcast6.net and www.ipv6.comcast.net.

Comcast hopes to attract hundreds -- perhaps thousands -- of its commercial and residential customers to participate in its IPv6 trails.

"We're looking for a wide variety of customers to participate in our IPv6 trials -- some that might be tech savvy and some that might not," Livingood says. "Some of the trials might be geographically bound…but others will not be geographically bound, [and] we'll cherry pick subscribers from all across the network to participate."

Only Comcast customers can participate in the trials, which will be free of charge.

Each of the trials will last three to six months, depending on the problems encountered with the IPv6 transition mechanisms that are being tested.

"Some of the concerns we have are about the ability of home gateway devices to be able to be upgraded for native dual stack IPv4 and IPv6, and legacy applications on computers or scattered hardware throughout the home," Livingood says. "Home networks are very diverse, and there's a lot of complexity in them. So we're worried about some of those things."

Another concern with the trials is how Comcast's IPv6 traffic will traverse the networks of other carriers as it is sent across the Internet.

"We're also watching closely all the operational and routing aspects of getting IPv6 traffic around the Internet," Livingood says. "There will be some learning there."

Comcast wouldn't announce the names of the hardware and software vendors participating in its IPv6 trials, but it did say that the trials would involve open source software from ISC and Dibbler.

Comcast's IPv6 trial was announced a week after the Internet regional registries said that less than 10% of IPv4 addresses  were available for allocation to carriers.

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