Yahoo IPv6 upgrade could shut out 1 million Internet users

ahoo 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.

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."