Huston says the uncertainty in his projections result from the unpredictable actions of the largest European carriers.
"Predicting the individual actions of 10 larger folk, or even 50 larger folk, is far harder,'' Huston explains. "They may take a break over August, or they may not. They may get spooked by the current address take-up projections and accelerate their final requests, or they may not. They may be in the middle of a business down cycle due to the prevailing adverse economic conditions in many of the European consumer markets. Or they might panic and rush the registry for the remaining address stocks. It's extremely hard to tell."
RIPE NCC confirms on its website that "in the coming months the RIPE NCC will reach the last /8 of IPv4 address space that it holds." A RIPE NCC spokesman did not reply to questions about a more precise IPv4 address depletion date.
No matter the exact date, it's clear that Europe's supply of IPv4 addresses will be gone by the end of the summer. And that will put more pressure on U.S. companies that do business in Europe to add the capability of handling IPv6-based traffic to their websites, email and other Internet services as more users get IPv6-enabled smartphones, tablets and other devices.
"Since this will be the second of the three largest registries to run out of [IPv4] space, and the two together represent a significant fraction of the world population, it's certainly likely to represent a turning point in IPv4 preservation strategies and a clear indication that sustaining IPv4 is a doomed strategy going forward," says Owen DeLong, IPv6 evangelist with Hurricane Electric, a Fremont, Calif., ISP that boasts the Internet's most interconnected IPv6 backbone.
DeLong says that IPv6 traffic is rising in Europe, where carriers such as France's Free ISP has been fully IPv6-enabled since 2007.
"We're definitely seeing an increase in IPv6 uptake lately" by U.S. multinationals, DeLong says. "[It's] hard to say how much of it is from outreach efforts, IPv6 Launch Day on June 6, increased awareness from content providers now being available on IPv6 or the RIPE NCC impending runout.''
Meanwhile, the American Registry for Internet Numbers (ARIN) is expected to run out of IPv4 address in February 2013.