U.S. ISPs are reporting a significant rise in IPv6 traffic during the last three months, even though the overall numbers remain tiny -- less than 1% of Internet traffic.
IPv6 is an upgrade to the Internet's addressing scheme, which was created 40 years ago using a protocol known as IPv4. 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 can support a virtually limitless number of devices: 2 to the 128th power. IPv6 is necessary because the Internet is running out of IPv4 addresses. However, IPv6 is not backwards compatible with IPv4, requiring network operators to support both protocols at an added cost.
U.S. carriers, content providers and network companies are surging ahead of their global rivals in the push to deploy IPv6. But despite their efforts, IPv6 remains a sliver of overall Internet traffic for now.
Comcast has deployed IPv6 across more than half of its broadband footprint in the United States and will be done upgrading the rest of its network by 2013. Currently, 2.5% of Comcast customers are using its native dual stack IPv6 broadband service, according to John Brzozowski, chief architect for IPv6 and distinguished engineer at Comcast.
"We saw our IPv6 traffic increase around 400% this year and 1,000% since last June," Brzozowski says.
Although IPv6 remains below 1% of Comcast's overall traffic, it peaked at around 6% of traffic during the Summer 2012 Olympics. This was a result of YouTube streaming video from the Olympics to Comcast customers over IPv6.
Brzozowski says the biggest challenge to IPv6 usage in the United States is legacy home routers and other electronic gear such as TVs and gaming systems, which need to support IPv6 by default.
"When one of our customers starts using IPv6, up to 40% of the traffic in and out of their home is IPv6," Brzozowski says, adding that the bulk of IPv6 traffic that Comcast sees is driven by YouTube, Netflix and the iTunes App Store. "Once IPv6 is on the home router, a lot of IPv6 starts to get consumed."
Comcast is focused on providing IPv6 to its residential broadband customers right now, but starting next year it will give its business customers IPv6 by default in order to help drive enterprise usage of the new protocol.
"Consumer electronics is the area that needs the greatest amount of work," Brzozowski says. "In residential, you can expect to see more penetration this year. Commercial usage will be a close third. You can expect to see expanded deployment as it relates to commercial services soon."
Limelight, a Tempe, Ariz.-based content delivery network that has been IPv6 enabled for two years, has seen its IPv6 customer base grow from three to 87 during the last three months. About 6% of Limelight's customers, including Microsoft, Netflix and NASA, are using IPv6.
Limelight is driving up IPv6 usage because it enables the protocol by default. All new customers get IPv6 unless they opt out.
"We've seen our IPv6 traffic go from a mere dribble - a couple megabits/sec - to about 2Gbps steady state, with spikes of 8Gbps. We've seen about 150% growth in two months," says Guy Tal, director of new markets for Limelight. "But it's still very small compared to our overall traffic. It's just over 0.1% of our traffic. . . If the trajectory holds, we're hoping to be at a couple percentage points of IPv6 traffic by the end of next year.''
Tal points out that most Limelight customers don't care if their application is running over IPv6 or IPv4; they just want it to work reliably and with high performance.
"The customers who do come and ask us about IPv6 tend to be the ones using our mobile monetization suite of services. These are the people concerned with iPads and Android devices," Tal says. "They want to know what new functionality they can enable because of IPv6. So mobile is driving IPv6 to some degree."
Some U.S. carriers are deploying IPv6 even if they aren't seeing much customer demand for it yet. Fibertech, a Rochester, N.Y., provider of fiber-optic transport services, has rolled out IPv6 across its entire network using a dual-stack service, where IPv4 and IPv6 run side-by-side. Currently, less than 1% of Fibertech's traffic runs over IPv6. Customers that are interested in IPv6 tend to be educational institutions such as the University of Pittsburgh.
"Less than 5% of our new and existing customers are asking us for IPv6," says Tom Perrone, director of engineering and planning at Fibertech. "It's slow. We're doing everything we can to help customers set it up. We're sitting here patiently waiting for the IPv6 traffic to come."
One IPv6 proponent that's betting the IPv6 traffic will come soon is Google. At an Internet Society event in Vancouver in July, Google network engineer Lorenzo Colitti noted that IPv6 adoption grew by 150% in the last year. "At this rate, 50% of Internet users will have IPv6 in about six years," he said.
Among the statistics that Colitti highlighted were the fact that carriers such as AT&T had enabled 1 million of its DSL subscribers with IPv6 and planned to enable another 4 million by year's end. He said that AT&T's IPv6-enabled customers see 20% of their traffic transition from IPv4 to IPv6.