Microsoft's search engine will be one of the major Web sites available in a synchronized effort to iron out problems moving to a vastly more spacious Internet based on the coming IPv6 standard.

"On June 8, we will enable worldwide IPv6 connectivity to Bing.com, for the purposes of a one-day test," Bing program manager Kevin Boske said. "Consumers with IPv6 Internet capabilities will automatically access this new method of connectivity. This necessitates both a device that supports IPv6 (like a Windows 7 PC), and support from your Internet provider."

IPv6, or Internet Protocol version 6, comes with 340 trillion trillion trillion (that's 340 followed by 36 zeroes) Internet addresses. It's a lot more than the 4.3 billion enabled by the current IPv4. Moving to IPv6 is a complicated, global event that ultimately involves any device that attaches to the Internet.

Its urgency is hastened by the fact that yesterday the Internet's central overseers handed out the last batches of IPv4 addresses. It'll be months before that IPv4 exhaustion cascades down to the level of companies that need to lease those addresses permanently, but the clock now is ticking.

Some companies such as Facebook and Google already offer IPv6 access to their services, but generally only with IPv6-specific domains such as ipv6.google.com. On World IPv6 Day, the main domains will be available over IPv6, too.

Mostly, this isn't a big deal--those with IPv4 will see the same IPv4-based versions of the Web sites, and those with IPv6 will get the content over IPv6. But for small fraction of IPv6 users with configuration issues, the Web sites aren't available, Yahoo and Google have said. World IPv6 Day is designed to track down such errors so they can be fixed before a broader transition to IPv6.

The expense of shifting to IPv6--combined with the lack of much of an immediate reward for most IT administrators--has slowed the transition to a crawl over recent years, with cheaper incremental fixes such as address translation that can let multiple devices share a single IP address.

That approach, though, threatens to fragment the Internet and make it hard for devices to be full peers on the network.

"Such an Internet is likely to grow increasingly less capable of serving our needs today. Rather than maintaining the status quo, the IPv4 Internet is likely to degenerate. If you get too many layers of [network translation], you cripple your ability to do end-to-end communications. Accessing a Web site might be possible, but accessing a file-sharing protocol or hosting your own content may become more and more difficult," Olaf Kolkman, chairman of the Internet Architecture Board, said at a press conference yesterday.

Bing is, of course, a supplier of content on the Web, but Microsoft has an even greater presence at the consumer end of the Internet connection with Windows. Versions of its operating system since Windows XP Service Pack 1 have been able to handle IPv6.

"Microsoft and other major technology companies have been working behind the scenes for years to outline a clear path to the next generation Internet Protocol, IPv6," Boske said. "Although a complete migration will take years, we are hopeful that the vast majority of people will never notice the transition."