Yahoo's findings of declining IPv6 brokenness are holding up for other Internet players, including Facebook and Google.
Facebook's measurements of IPv6 brokenness have fallen from 0.03 percent of Internet users down to 0.02 percent since World IPv6 Day, according to Donn Lee from Facebook's network engineering team.
"We estimate that approximately 0.02 percent of our users will have slowness in loading Facebook if we turn on www.facebook.com with IPv6 permanently," Lee said. "That's what dual-stack brokenness means to us."
Lee said Facebook sent a message to users that it thought might suffer from IPv6 brokenness prior to World IPv6 Day. He said it appears that many of these users are fixing the problem themselves.
"Brokenness seems to be declining after World IPv6 Day. It surprises me," Lee said. "I did not expect any brokenness to change. I thought the users would suffer in silence. ... But it turns out that without any changes to our instrumentation, the dual-stack brokenness is slowly going down."
Lorenzo Colitti, a network engineer with Google, said the most important thing Google did for World IPv6 Day was to warn users that it thought would suffer from IPv6 brokenness ahead of time and encourage them to diagnose their systems.
"We put a drop-down box at the top of the Search page telling users that we're testing IPv6 on June 8 and that they should click here to find out if they're ready," Colitti said. "We prepared an IPv6 test site for them to use."
Google also added what it calls "fast fallback" from IPv6 to IPv4 service in its Chrome browser.
"IPv6 brokenness went down 80 percent to 90 percent in the Chrome browser," Colitti said. "If all browsers behaved like that, we would just publish our Quad A [IPv6] record. Browsers with versions of fast fallback were 99.9995 percent as reliable as IPv4. We saw similar behavior in Firefox 7. Apple is adding this [feature] in OS X Lion. All we need is [Microsoft Internet Explorer] to follow suit."
Palmer wouldn't comment on when Microsoft would offer a patch for Internet Explorer to handle "fast fallback," but he indicated Microsoft planned to address IPv6 brokenness in an upcoming version of the Windows operating system.
IPv6 represents the biggest upgrade to the Internet infrastructure in its 40-year history. That's because IPv6 is not backward compatible with IPv4, so website operators have to upgrade their network equipment and software to support IPv6 traffic.
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 devices.
Read more about LAN and WAN in Network World's LAN & WAN section.