In the same way your phone is associated with a unique number, your computer is assigned a unique Internet Protocol (IP) address when you connect to the Internet. The current protocol, IPv4, allows for approximately 4 billion unique addresses?and that number is about to run out. This morning the Internet Corporation for Assigned Names and Numbers (ICANN) announced (PDF) that it has distributed the last batch of its remaining IPv4 addresses to the world?s five Regional Internet Registries, the organizations that manage IP addresses in different regions. These Registries will begin assigning the final IPv4 addresses within their regions until they run out completely, which could come as soon as early 2012. As the last blocks of IPv4 addresses are assigned, adoption of a new protocol?IPv6?is essential to the continued growth of the open Internet. IPv6 will expand Internet address space to 128 bits, making room for approximately 340 trillion addresses (enough to last us for the foreseeable future). Google, along with others, has been working for years to implement the larger IPv6 format. We?re also participating in the planned World IPv6 Day, scheduled for June 8, 2011. On this day, all of the participating organizations will enable access to as many services as possible via IPv6. Today?s ICANN announcement marks a major milestone in the history of the Internet. IPv6, the next chapter, is now under way.