Comcast expands IPv6 trial

Jun 06, 2011 10:55 am | Network World
by Carolyn Duffy Marsan

Comcast has expanded its IPv6 trial, adding hundreds of cable modem subscribers in the San Francisco, Philadelphia, Chicago and Miami areas to participants in Littleton, Colo., that have been operational all year with this next-generation Internet service.

Comcast’s IPv6 trial expansion, to be announced in a blog post on Monday, is timed so that these subscribers can participate in World IPv6 Day, a 24-hour trial of IPv6 being conducted by popular websites such as Google, Facebook and Yahoo starting at 8 p.m. EST on Tuesday.

BACKGROUND: Large-scale IPv6 trial set for June 8

Comcast was the first cable operator in the United States to begin trials of IPv6, an upgrade to the Internet’s main communications protocol, which is known as IPv4. IPv6 features an expanded addressing scheme that can support billions of devices connected directly to the Internet at faster speeds and lower cost than IPv4, which is running out of address space.

“We’ve put a lot of effort into expanding our IPv6 trial into other parts of the country,” said John Brzozowski, distinguished engineer and chief architect for IPv6 at Comcast. “We’ve added more trial subscribers in dual-stack [running both IPv4 and IPv6] configurations. …We have several hundred subscribers in the trial.”

Comcast is offering a high-speed data service that allows its customers to access Internet content via either IPv4 or IPv6 because they have both types of addresses on their home gateways. Comcast hooked up its first cable modem customers to this service in January.

DETAILS: Comcast claims another IPv6 first

Comcast is participating in World IPv6 Day, having enabled IPv6 on several of its websites that are aimed at network managers, including and

“Now we’ve just got a handful of people doing IPv6, but I fully expect to see a significant increase in IPv6 traffic” on World IPv6 Day, Brzozowski said. “It’ll be a significant increase, but the traffic numbers are still going to be pretty small. We’re not going to reach anywhere near the level of traffic we get for IPv4.”

Comcast and other carriers are migrating to IPv6 because the Internet is running out of addresses using IPv4. The free pool of unassigned IPv4 addresses expired in February, and in April the Asia Pacific region ran out of all but a few IPv4 addresses being held in reserve for startups. The American Registry for Internet Numbers (ARIN), which doles out IP addresses to network operators in North America, says it will deplete its supply of IPv4 addresses this fall.

IPv4 uses 32-bit addresses and can support 4.3 billion devices connected directly to the Internet, but IPv6 uses 128-bit addresses and can connect up a virtually unlimited number of devices: 2 to the 128th power. IPv6 offers the promise of faster, less-costly Internet services than the alternative, which is to extend the life of IPv4 using network address translation (NAT) devices.

One major stumbling block for IPv6 deployment is that it’s not backward compatible with IPv4. That means carriers such as Comcast and website operators such as Google have to upgrade their network equipment and software to support IPv6 traffic.