Yahoo moves to IPv6 despite access woes

Yahoo is forging ahead with a move to IPv6 on its main Web site by year-end despite worries that up to 1 million Internet users may be unable to access it initially.

Yahoo’s massive engineering effort to support IPv6— the long-anticipated upgrade to the Internet’s main communications protocol — could at first shut out potential users due to what the company and others call “IPv6 brokenness.”

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Yahoo has been one of the most vocal Internet companies to express concern about industry estimates that 0.05% of Internet users will be unable to access Web sites that support both IPv6 and the current standard, IPv4.

IPv6 experts say some Internet users will experience slowdowns or have trouble connecting to IPv6-enabled Web sites because they have misconfigured or misbehaving network equipment, primarily in their home networks. Corporate users also could experience IPv6 brokenness because of faulty firewall settings.

The Internet Society’s estimate that 0.05% of users will be unable to reach IPv6-enabled content may seem miniscule, but it actually represents around 1 million Internet users based on estimates that 2 billion people access the Internet.

“The numbers are going to vary from site to site, but it’s definitely very critical that everybody understands that when they do make themselves available through both IPv4 and IPv6 at the same time what impact there will be on a small per centage of users,” says Jason Fesler, an IPv6 architect with Yahoo.

Fesler explained that for end users with IPv6 brokenness, Web sites that support IPv6 and IPv4 simultaneously in what’s called dual-stack mode will appear to be suffering from an outage.

“A certain number of users do have IPv6 on their systems, but they have it configured in such a way that their system believes they have a working IPv6 Internet connection when in reality they don’t. Or their Web site browser will prefer IPv6,” Fesler explains. “This will result in timeouts that can be anywhere from 5 seconds to several minutes. From an end user’s point of view, the first major Web site that goes dual-stack is going to appear broken while other Web sites will appear to be up.”

Concern about IPv6 brokenness is one of the reasons that Yahoo has agreed to participate in the Internet Society’s World IPv6 Day along with Facebook and Google. Scheduled for June 8, World IPv6 Day is a 24-hour trial of IPv6 connectivity that will allow participating Web sites to gauge the true level of IPv6 brokenness.

“One of the aspects of World IPv6 Day is to help people understand that it may not be a particular site that’s down,” Fesler says. “Multiple sites will be in this together” and will all appear to be down to end users suffering from IPv6 brokenness.

Following the World IPv6 Day trial, Yahoo plans to offer IPv6 on its main Web address – – in the fourth quarter.

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IPv4 vs. IPv6

“We could turn on IPv6 today and have users hit it, but we don’t think it would be seamless,” says Adam Bechtel, vice president of infrastructure at Yahoo.

Web sites such as Yahoo are upgrading their Web servers, load balancers and software to support IPv6 because the Internet is running out of address space using 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 supports a virtually unlimited number of devices – 2 to the 128th power.

Less than 5% of the world’s IPv4 address space remains unallocated, and experts predict that the remaining IPv4 addresses will be assigned from the central pool to the regional registries in February. Regional registries, in turn, are expected to hand out the remaining blocks of IPv4 addresses to network operators by October.

Once IPv4 addresses are depleted, Web sites will need to either support IPv6 or use complex mechanisms such as carrier-grade network address translation (NAT) to communicate with IPv6-based users.

Second-largest engineering project

Yahoo has been working on IPv6 development since 2008, but in the last year it has become the company’s second-largest IT infrastructure project. Only ongoing tech refresh efforts are costing Yahoo more engineering time and effort these days, executives say.

“In 2010, we rolled IPv6 into a corporate program called IP Survivability. We’re taking a two-pronged approach. We need to stretch out our IPv4 usage longer, as well as get to the point where we can deploy IPv6. We probably have around 100 to 150 people involved,” Fesler says.

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Yahoo has IPv6-enabled routers deployed, supports IPv6 peering with other carriers, and has connected one of its data centres to the Internet via IPv6. In order to serve up IPv6 content, the company’s engineers developed software for address translation, caching and proxying – dubbed the Yahoo Traffic Server – that it provided to the Apache Foundation last year as open source code.

“We have the Yahoo Traffic Server up and running, but we don’t have it available to end users yet,” Bechtel says. “We’re still in the process of vetting it and getting our processes in line to make sure we get all the kinks worked out.”

Bechtel describes IPv6 as presenting “an immense, immense set of challenges” for a Web site with as much traffic as Yahoo’s.

“The network piece is pretty far along for most, but you’ve got all the operational pieces and the instrumentation,” Bechtel says. “One out of every 2,000 users is going to have some level of brokenness. There are issues that carrier-grade NATs are going to introduce with the aggregation of IP addresses. The issue of geo-targeting is very significant, too… IPv6 is touching a lot of our people.”

Yahoo is hoping that it can deploy IPv6 on its main Web site without having to rely on DNS whitelisting, a technique that Google has deployed to serve up IPv6 content only to users who are known to have end-to-end IPv6 connectivity and no IPv6 brokenness.

“At this time we don’t see a way to avoid [DNS whitelisting],” Fesler says. “But hopefully as part of the outcome of World IPv6 Day and further benchmarking of users, we’ll be able to find out that the level of IPv6 brokenness is such that it’s not necessary.”

Yahoo’s embrace of IPv6 is good news for IPv6 proponents because the site reaches more than 25% of all Internet users, Alexa says. Yahoo is the fourth most popular Web site on the Internet.

The top three traffic-producing Web sites – Google, Facebook and YouTube – already support IPv6 on special-purpose Web addresses, rather than their main Web sites.

Yahoo is embracing IPv6 because it believes that an increasing number of those users will be accessing the Internet on IPv6-based devices, such as smartphones that connect to Verizon’s LTE network.

“What are really driving us to IPv6 are two concerns,” Bechtel says. “We couldn’t scale with the available IPv4 space, and equally important was having IPv6 customers be able to connect to us. We realized that customers would not be able to get to us in the 2012 time frame.”

Having focused on IPv6 for several years, Yahoo executives say they are surprised by the number of Internet companies seemingly in denial that IPv4 depletion is a serious issue.

“There is still some sentiment that people think this isn’t real, that IPv4 may exhaust but we may figure out ways around it,” Bechtel says. “In the end, people are going to spend as much time on those workarounds as they would going to IPv6.”

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