If you're the kind of person who walks down the street worrying about the depletion of IPv4 addresses, the iPhone can now tell you how long you have until that happens.
There are a limited number of addresses left for Internet Protocol, version 4, the system that has powered the Internet since before the Web. After they have all been handed out, service providers and enterprises will have to make their systems work with the next version, IPv6, or use workarounds.
IPv6 network backbone and collocation provider Hurricane Electric introduced on Tuesday an iPhone application that counts down the number of days until that moment of reckoning.
On a simple page, the application lists statistics such as the number of IPv4 addresses remaining and the number of domains already using IPv6. The counter for remaining IPv4 addresses goes down in real time, though it's based on the calculated rate of depletion, not assignments of addresses in real time. (A second page shows Hurricane Electric facilities on a map.) At the bottom of the countdown page, in large type, is the number of days left until IPv4 addresses are exhausted. On Wednesday, it was 699.
Figuring out how long that depletion will take is no easy task, because the IANA (Internet Assigned Numbers Authority) hands out IPv4 addresses on the basis of requests from RIRs (Regional Internet Registries), which in turn allocate them to the entities that use them. Those requests can't be predicted. Several researchers have studied the problem, including Geoff Huston of Asia-Pacific Network Information Centre (APNIC) and Tony Hain of Cisco Systems. Their reports involve detailed mathematical analysis -- and acknowledgments that the predictions are conditional and subject to change.
"That's great, but for some people, to get the message across, you just need the bottom line," said Martin Levy, director of IPv6 strategy at Hurricane. The company compiles information from those and other sources to come up with its own date prediction. Levy acknowledged it's an inexact science.
"There's no Y2K day. There's no flag day," Levy said. "It isn't like on the first day of January 2010, we all have to swap." The actual date could even come much earlier if the impending depletion causes demand to accelerate in a "land rush" for the last addresses, he added. But even though the 699-day prediction is nothing more than an educated guess of educated guesses, it matters, Levy said.
"This counter is nontrivial. It exists, and it exists in a way that will affect nearly everybody in the Internet industry," he said.
There are tools to keep IPv4 clients communicating with IPv6 hosts and vice versa, but they add another layer of complexity and cost to service-provider networks. At least one method, called carrier-class network address translation, could affect an Internet user's experience if a service provider's network gets bogged down by that task, according to Levy.
"We expect to see a lot of translation devices ... but the performance will be best if you've changed your server to have IPv6 as well as IPv4," said John Curran, president and CEO of the American Registry for Internet Numbers, the RIR that assigns addresses in the U.S.
If Hurricane's prediction is correct -- APNIC's Huston is close behind, foreseeing 701 days until depletion -- then the IPv4 address space will be exhausted sometime in mid-2011. But that shouldn't put any large organization at ease if it hasn't moved toward IPv6, according to the Internet Society, the nonprofit group that oversees the Internet Engineering Task Force. IT managers need to train staff, figure out which servers and routers need development work, and test the solutions they create, said Matt Ford, the Internet Society's technology program director.
"If you're going to successfully make the transition to IPv6 ... you really have to start now," Ford said.