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 www.yahoo.com users due to what the company and others call "IPv6 brokenness.''
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COMPARISON: IPv4 vs. IPv6
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 percentage 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 - www.yahoo.com - in the fourth quarter.
"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.