On Wednesday, a number of large websites from around the Internet joined the Internet Society to announce World IPv6 day, a 24-hour test period where all the agreed websites will enable the IPv6 protocol alongside the typical IPv4 for the day to test compatability.
On June 8, 2011, Google, Facebook, Yahoo! Akami, Limelight and other websites will join Internet Society in making the first major "test flight" to IPv6. With over a billion combined hits between the websites, these websites will be testing their infrastructure to ensure that they can handle the switch. During World IPv6 day, experts predict that only 0.05% of the Internet users will have trouble connecting to these websites due to misconfigured or misbehaving home network devices.
IPv4 uses a 32-bit (four-byte) address, limiting the number of available unique addresses to 4,294,967,296. However, some of these addresses have been reserved for private networks, limiting the available public addresses. IPv6 uses a 128-bit address, allowing for approximately 3.4 x 10^38, enough public addresses to last us a lifetime.
Available IPv4 addresses are now in the final 2%, with just 91 million addresses left. These publicly available Internet addresses are expected to completely be gone in the next 32 days.