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It's official: The Internet just ran out of addresses

The pool of new IP addresses, the phone numbers of the Internet, has finally run dry. What do we do from here?

By Bobbie JohnsonTechnology Review / February 8, 2011

With so many devices online, the world has run out of new IP addresses. What now?

San Jose Mercury News/Newscom

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On February 3, it finally happened: the clock ran out on the Internet as we know it. That was the day that the stash of Internet protocol addresses that are used to identify and locate computers connected to the Internet—the telephone numbers of the online world—was exhausted.

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The problem is that the current system for IP addresses, IPv4, uses numeric addresses that are 32 bits long—giving a total of just over four billion potential numbers, which must have seemed like a lot when IPv4 was introduced in 1981. But there are now seven billion people on Earth, and more and more of them—and their devices—are going online all the time. Fortunately, engineers realized the limitations of IPv4 a long time ago and lined up a successor, called IPv6, in 1998. (IPv5 was an experimental system that never went public.)

IPv6 uses 128 bits rather than 32, producing a pool of numbers that is staggeringly huge—some 3.4 x 10 to the 38, or 48 octillion addresses for every person on Earth. The trouble is that although most servers and all major operating systems have adopted support for IPv6, Internet service providers have been agonizingly slow to follow suit.

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For ISPs, it's a straightforward business dilemma: the two addressing schemes are not directly compatible, which means it would take a significant investment to let IPv4 users connect to IPv6 services. And having relied on the same system for as long as 30 years, they may not feel the need to change.

"It really highlights the failure of the Net at the most basic level to innovate, despite the fact that at the visible levels, it has had unbelievable innovation," says Jon Crowcroft, Marconi professor at the University of Cambridge's computer lab.

He points out that the current concerns about IPv4 space don't really affect those who already have an address—only those who need new numbers. So it is a minor problem for ISPs that have already stockpiled blocks of IPv4 addresses.

"Why does anyone with IPv4 space care? It's all working, and there's been no big, terrible disaster," Crowcroft says. "But it will be interesting to watch how this slow degradation of things [affects] new entrants."

"New entrants," in this case, could mean nations with rapidly expanding online populations. Such countries may face significant trouble if their allocation of IPv4 addresses fails to keep up with their appetite for connectivity. Countries like China are already beginning to concentrate on IPv6 support, with the result that parts of the Internet are being created that are, effectively, inaccessible from the parts of the world that only use IPv4.

While the idea of Internet balkanization might sound disturbing, in practice this is still not a pressing issue for ISPs in the West. There is, however, one area where Western nations might begin to feel the squeeze: the "Internet of things."