Illustration: Jack Gallagher Where are the users? That's what popular websites including Yahoo, Google and Facebook are asking the Internet engineering community when they are questioned about their long-range plans to deploy IPv6.

These popular websites -- and tens of thousands of others -- participated in a successful, 24-hour trial of IPv6 on June 8 dubbed World IPv6 Day. Sponsored by the Internet Society, World IPv6 Day was a large-scale experiment designed to test the readiness of IPv6 to replace IPv4, which has been the Internet's main communications protocol since its inception 40 years ago.

The Internet's largest players are providing detailed analysis about their experiences on World IPv6 Day and they are discussing next steps for IPv6 deployment at a meeting of the Internet Engineering Task Force (IETF) being held here this week.

BACKGROUND: World IPv6 Day: Tech industry's most-watched event since Y2K

What's evident at the IETF meeting is a shift in focus on the IPv6 debate from content to carriers. The Internet engineering community appears to be ratcheting up the pressure on ISPs, particularly residential broadband providers, to enable IPv6 to home users as the next step to IPv6 deployment.

"The focus is absolutely on the access networks," said IETF Chairman Russ Housley. "What World IPv6 Day showed is individuals who wanted to participate from home could not get IPv6 support from their ISPs. They had to set up their own [IPv6-over-IPv4] tunnels, and the average user doesn't have the knowledge to do that."

Yahoo said it deployed dual-stack IPv6 and IPv4 proxy servers at seven locations worldwide and created a special infrastructure to improve the performance of the 6to4 tunneling protocol for World IPv6 Day. Yahoo also modified its geolocation and ad-targeting code to be IPv6 aware, and it over-provisioned its IPv6 servers as an extra precaution.

On World IPv6 Day, Yahoo served IPv6 content to more than 2.2 million users, representing a peak of 0.229% of the overall traffic on 30 different Yahoo-affiliated sites. Yahoo hailed World IPv6 Day as a success but turned off IPv6 support after the event.

"IPv6 is not a wide deployment," said Igor Gashinsky, a principal architect with Yahoo. "That was a lot of work for 0.229%. We need more IPv6 access. Can we break single digits, please, and then we can talk about leaving it on?"

Similarly, Facebook served content to more than 1 million IPv6 users on World IPv6 Day. But this represented only a small fraction -- 0.2% -- of Facebook users that are IPv6 capable. Of those Facebook users, 0.16% had native IPv6 access and the other 0.04% used 6to4 tunneling.

"There are some people who are very, very passionate about IPv6 ... but it's difficult for most people to understand," said Donn Lee, a member of Facebook's network engineering team. "It's very much a concept of, 'I have restored my Internet connection.' That's what the user cares about. The user doesn't care about if it's IPv6 or IPv4."

The IETF created IPv6 a decade ago 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 website operators have to upgrade their network equipment and software to support IPv6 traffic.

DETAILS: Getting at the real truth about IPv6

IETF participants agree that World IPv6 Day was a success in terms of setting a deadline for content providers to support IPv6 and encouraging collaboration across the Internet industry.

World IPv6 Day "certainly spurred a number of organizations to roll out IPv6 even on a test-flight basis," said Leslie Daigle, chief Internet technology officer for the Internet Society. "We saw no large-scale breakage ... and the DDoS fears did not pan out. Overall, it was a success. We moved the needle on IPv6 deployment.''

More than half of the participating websites, including content providers such as YouTube and vendors such as Check Point, had such a good experience with IPv6 that they left it turned on after the trial ended.

"We started getting questions from our customers about World IPv6 Day. That was the motivation for us," said Bob Hinden, Check Point fellow. "Our IT team was pretty apprehensive ... but it turned out not to be that hard. ... For enterprises like us, I think you can turn [IPv6] on and leave it on."

Despite Check Point's experience, few of the largest websites -- including Google, Yahoo or Facebook -- left IPv6 on after World IPv6 Day ended.

Ari Keranan, an Ericsson network engineer, said he measured 30% of the Alexa Top 100 most popular websites supporting IPv6 on World IPv6 Day, but none of them retained IPv6 support on their main website addresses when the event was over.

Most of the largest websites turned off IPv6 support after the event because they still have back-office software to tweak and network testing to do before they feel comfortable running the new protocol in production mode.

"Making sure all of our back-end tools understand IPv6 is the largest effort for us," Lee said. "We also found with moving to IPv6 that there's nothing to fear. It works. It's ready to deploy. It wasn't that hard to do."

Now that popular websites have demonstrated that IPv6 works, the Internet engineering community is coming to the conclusion that the main problem facing IPv6 deployment isn't a lack of content, but a lack of users to view it.

Despite the success of World IPv6 Day, the vast majority of Internet traffic -- 99.98% -- remains on IPv4. And that reality makes it difficult for content providers to justify spending engineering time and dollars on IPv6 until the new standard represents at least 1% of all Internet traffic.

MORE: Lack of IPv6 traffic stats makes judging progress difficult

Consider the experience of Microsoft, which enabled IPv6 on three websites -- www.bing.com, www.xbox.com and www.microsoft.com -- for World IPv6 Day. Christopher Palmer, an engineer in Microsoft's Windows Networking area, said IPv6 users represented 0.46% of the visitors on these websites.

"IPv6 was easier than we expected. ... Our [content delivery network] really delivered," Palmer said. But he emphasized that Microsoft saw less than 0.5% of its users with IPv6 enabled. "Two million IPv6 users -- that's not scale. ... We really need to get to 1% of traffic.''

Palmer said Microsoft's positive experience on World IPv6 Day had removed the IT department's fear of deploying IPv6. In fact, Microsoft has since enabled IPv6 on two of its websites: www.zune.net and www.marketplace.xbox.com.

"Operationally, we are confident we can deploy it quickly," Palmer said. "The biggest issue for us to take more of our sites to IPv6 is access."

Cisco was the only company to report more than 1% of its Web traffic being IPv6 on World IPv6 Day. Mark Townsley, distinguished engineer with Cisco Systems, said 1.11% of the traffic on www.cisco.com was IPv6 during the 24-hour trial period. He attributed this to the fact that Cisco's customers are "an order more magnitude interested in IPv6 than the broader population of users."

BY THE NUMBERS: Most IT pros say their websites, networks will support IPv6 by 2013

Content providers said getting 1% of all Internet traffic to be IPv6 capable will require ISPs to enable millions of homes with IPv6 access.

Gashinsky estimates that ISPs will need to deploy IPv6 to 10 customers for every one customer that will have current enough home gateways, PCs and gaming equipment to take advantage of it.

If Gashinsky's estimate is correct, ISPs would have to enable IPv6 to 200 million customers in order for 20 million of them -- or 1% of the Internet's 2 billion users -- to be IPv6 capable.

"It's going to be a long, slow transition for access networks," the IETF's Housley agreed. "At least now there is some content to see and some users who can't get IPv4 addresses. So it's a different discussion for us with the access networks since we ran out of IPv4 addresses in [the free pool] and in Asia Pacific."

Housley said that broadband providers such as Comcast, Verizon, Time Warner and Cox are making progress on their plans to deploy IPv6 to residential customers in the United States.

"Each has a significant effort in front of them, but they have deployment plans," Housley said. "A year from now, they should all be past their pilots and executing on their rollouts. Globally, we might be past the 1% mark a year from now, but the U.S. will be lagging behind."

Lorenzo Colitti, a network engineer with Google, explained the role that individual ISPs such as the French ISP Free, which started deploying IPv6 in 2007, and the Japanese ISP KDDI, a recent convert to IPv6, play in driving IPv6 traffic.

"IPv6 adoption is pretty flat. It's 0.3%," Colitti said. "The bulk of IPv6 adoption is in two networks in France and Japan. ... KDDI gave IPv6 to 15% of their users in five weeks, just in time for World IPv6 Day. One ISP, by itself, made a significant difference in the adoption of IPv6 in Japan."

Google has been a leader in IPv6 adoption, serving 60% of the IPv6 Internet with IPv6-enabled services such as YouTube, Voice, Talk, Analytics and Adwords. "There are very few Google services that aren't available over IPv6," Colitti said.

But even Colitti conceded that the overall view of content providers about IPv6 at this juncture is: "Show me the users, and I'll turn it on."

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This story, "Yahoo, Facebook, Google to IETF: Where Are the IPv6 Users?" was originally published by Network World .