It's widely known, at least within geekdom, that the number of available IP addresses is on a collision course with the number zero. The depletion of the IPv4 address space, and the necessity of migrating to the next-generation IPv6, has been discussed ad infinitum in geek circles since RFC 2460 was published in December 1998.

That discussion has not always been about the best way to resolve the issue, however. The imminence of IPv4 exhaustion has consistently been denied, and its emergent nature downplayed. Indeed, APNIC Director General Paul Wilson's 2003 statement on the subject — describing depletion predictions as "misinformation" and "rumor", while stating that existing IPv4 would suffice for another twenty years — brings to mind the infamously mis-attributed quote "I think there is a world market for maybe five computers."

That the latter missed the mark by several billion is inconsequential for most of us, but that the former was a dozen over certainly isn't. The timeline that once had decades to go has now dropped into counting by months, and the outlook for meeting the deadline isn't good.

Hence the possibility for some surprise — not that it is happening, but how soon. Though estimates vary considerably, many credible sources place the Internet Assigned Numbers Authority's pool at zero by June 2011 — just over a year from now — with the various regional authorities drying up by early 2012. Some predictions, however, place zero hour before the end of this year.

Meanwhile, nobody is finding encouraging numbers on IPv6 implementation. Decimal points feature prominently in most — figures include 0.15%, 0.2%, 0.238%, 0.403%, and a heartening, but probably skewed, 10% - 13%. Perhaps the Mayans did know a thing or two about 2012...

Even though the numbers are low, work is being done to prepare for the inevitable.

Comcast, one of the largest ISPs in the U.S., will be conducting several IPv6 tests in the near future: 6RD (rapid IPv6 deployment) and CMTS tests are scheduled to begin in June, testers have been selected for a check of fiber-based Ethernet for business beginning "soon", and a trial run of DS-Lite (dual-stack lite) planned for an as-yet unannounced date.

Verizon is conducting tests of its own as well. The company announced earlier this month that a test of its FiOS network is already underway, using Cisco's IPv6 over MPLS solution, 6PE.

Verizon's packet technology director, Jean McManus, highlighted the importance of the experiment: "As a result of this trial, we can begin to validate our strategy for IPv6 migration for the residential market while maintaining service continuity during the transition."