Comcast has laid claim to being the first service provider in North America to activate native dual stack users in a production DOCSIS network.

Comcast's John Brzozowski delivered the news today on Comcast's corporate blog that the nation's largest ISP had successfully activated a group of cable modem customers using IPv6 in a "Native Dual Stack" configuration.

With the native dual stack configuration, Comcast customers can access content and services natively in both IPv6 and IPv4 since they have both protocols' addresses.

The end result is that the customers don't need to use any tunneling or translation technologies, including Network Address Translation. Instead, they can access IPv6 and IPv4 directly at high speed in an unencumbered manner, according to Brzozowski's blog post.

"We are also delighted that these are the first Native Dual Stack users activated in a production DOCSIS network in North America," wrote Brzozowski, who is Comcast's chief architect for IPv6. "This is a tremendous milestone for Comcast, cable operators, DOCSIS technology, and the Internet community at large. This achievement is a key demonstration and ongoing test of our ability to offer Native Dual Stack Internet services leveraging our production DOCSIS 3.0 network."

On Jan. 11, Comcast's first 25 IPv6-enabled users came online in the Littleton, Colo., area near Denver. Since then, Comcast has increased the number of users in Colorado and expects to expand to additional market areas in other parts of the country.

Each user has been delegated an IPv6 /64 block as part of the trial that comprises approximately 18,446,744,073,709,551,616 (18 quintillion) unique IPv6 addresses; it's a first step as Comcast evaluates what will be the optimal IP address allocation size for its customers.

The trial customers were connected using cable modem termination systems and cable modems from Arris and home networking equipment from Apple, both running publicly available software. Comcast said it expects to add additional vendors to the trial soon.

As one of the largest users of IP addresses, Comcast has been one of the most active cable operators when it comes to pursing the transition to IPv6 addresses.

According to a Hurricane Electric press release last week, the last block of IPv4 addresses was due to be used by a regional Internet registry sometime this week, which only added to the urgency of being prepared for the migration to IPv6.