In January, Comcast activated 25 customers in the Littleton, Colo., area with what's called a native dual-stack configuration, where IPv6 runs alongside the current standard called IPv4.
Comcast announced in a blog post Monday that it was the first to enable native dual stack users to be activated in a DOCSIS network in North America. DOCSIS -- which stands for Data Service Over Cable Service Interface Specification -- is the standard for sending high-speed data over cable television networks.
With a native dual-stack configuration, Comcast's customers can access Internet content via either IPv6 or IPv4 because they have both types of addresses on their home gateways. These customers can avoid network address translation and tunneling mechanisms that could cause delays or slow down access.
"This is a tremendous milestone for Comcast, cable operators, DOCSIS technology, and the Internet community at large," wrote John Brzozowski, distinguished engineer and chief architect for IPv6 at Comcast, in his blog post. "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."
Comcast's announcement comes the same week that the Internet's free pool of IPv4 address space has been depleted, which ratchets up the pressure on network operators to migrate to IPv6.
Carriers such as Comcast are upgrading their networks to IPv6 because the Internet is running out of IPv4 address space.
IPv4 uses 32-bit addresses and can support 4.3 billion devices connected directly to the Internet. IPv6, on the other hand, uses 128-bit addresses and supports a virtually limited number of devices -- 2 to the 128th power.
Monday's announcement continues to lengthen Comcast's lead in IPv6 technology in the United States. Comcast has vowed to transition its network infrastructure to support IPv6 by 2012.
Comcast said it was adding more customers in the Littleton area to its dual stack service and will soon expand the service to other parts of the country.
Comcast is experimenting with how many IPv6 addresses to give each of its customers. Comcast gave each individual user what's called a /64 block of IPv6 addresses -- a block of 18 quintillion addresses that is vastly larger than the entire IPv4 address space. Brzozowski called this "a first step as we evaluate what will be the optimal IP address allocation size for our customers."
Comcast said it was connecting the Colorado IPv6 users to its network using cable modem systems from Arris and home networking equipment from Apple. The company plans to broaden its trial to include other network vendors in the future.