Refiles to correct spelling of executive's name to Curran throughout

SAN FRANCISCO - Thirty years after the first Internet addresses were created, the supply of addresses officially ran dry on Thursday.

But don't panic. The transition to a new version of addresses is already well under way and, for most people, should occur without even being noticed.

At a special ceremony in Miami on Thursday, the organization that oversees the global allocation of Internet addresses distributed the last batch of so-called IPv4 addresses, underscoring the extent to which the Web has become an integral and pervasive part of modern life.

Every computer, smartphone and back-end Web server requires an IP address -- a unique string of numbers identifying a particular device -- in order to be connected to the Internet. The explosion of Web-connected gadgets, and the popularity of websites from Google Inc to Facebook, means that the world has now bumped up against the limit of roughly 4 billion IP addresses that are possible with the IPv4 standard introduced in 1981.

The solution is IPv6, a new standard for Internet addresses that should provide a lot more room for growth: There are 340 undecillion IPv6 addresses available. That's 340 trillion, trillion, trillion addresses.

If all the space of IPv4 were to be sized and compared to a golf ball, a similar-sized comparison for IPv6 would be the size of the sun, said John Curran, the chief executive officer of the American Registry for Internet Numbers, one of five nonprofit organizations that manage Internet addresses for particular regions of the world.

Just in case you're worried, Curran added that we don't ever intend to see another transition.

For companies with websites, the transition to IPv6 means configuring their computer equipment to support the new standard rather than upgrading hardware, Curran said. Those that don't could see the performance of their sites slowed down, and potentially cut off to some users in the future.

Laptops, smartphones and other Web-connected gadgets, as well as Web browsers, already support IPv6, though Curran notes that according to some estimates less than 1 percent of Internet users may not have their equipment configured properly and will need to adjust their settings in the months ahead, as websites increasingly adopt the new standard.

(Reporting by Alexei Oreskovic, editing by Gerald E. McCormick and Carol Bishopric)