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By G.F. | SEATTLE

THE scheme to renumber the internet's billions of connected devices will be subject to a significant test of preparedness on June 8th, dubbed World IPv6 Day. IPv6 (internet protocol version 6) will ultimately replace the current IPv4 addressing system, which has nearly run out of addresses for networks to assign to computers and other devices. A complete conversion to the new standard is still a long way off, but the test is the first step on the way. It aims to determine how well big internet firms fare when it comes to providing access to common resources using both old and new addressing conventions at once.

IPv4 has about four billion addresses assigned in blocks of varying size. At one time, a single institution, like Stanford or Apple, might be given an allocation of 16m addresses, and use just a fraction. Others might be allowed just 254 and use one or two. To eke out more time on the IPv4 death watch, owners of idle addresses in the larger blocks had to give up unused portions. IPv6 allows for 3.4x10³⁸ addresses which, boffins reckon, should last until the heat death of the universe. That may seem like overkill, but so did four billion-odd a few decades ago.

The idea is for IPv4 and IPv6 to work side by side indefinitely, as hundreds of millions of pieces of older hardware, including plenty of commercial network equipment and home routers, are incompatible with IPv6. (The idea is that the internet will move from islands of IPv6 in a sea of IPv4, to islands of IPv4 in a sea of IPv6.) The test will reveal whether end users can access websites, the most common public resource on the internet, without too much hassle. But some hassle there certainly will be as operating systems, browsers, home and office broadband gateways, and the internet's backbone of high-capacity routers, all begin talking to each other in a slightly different language. The Internet Society, a think-tank and instigator of the day-long experiment, reckons about one in 1,000 users trying to reach the participating websites could experience a problem.

The Internet Society has championed internet standards for decades, and commands attention. It has beaten the IPv6 drum ever since it became clear that four billion is not such a big number, after all, imploring companies and institutions to take the issue seriously. Some have—Mac OS X, Windows and modern mobile operating systems generally handle IPv6 with gusto—but concern about maintaining pipe pressure along the way from a user to his online destination have kept service providers from hooking up the IPv6 taps in earnest.

To allay providers' fears, as well as their own, big content sites including Facebook, Google and Yahoo! signed on to the World IPv6 Day early. So did content-distribution networks like Akamai and Limelight. Hundreds of other sites large and small are participating, too. Hopefully, any flaws the test reveals—and there are bound to be some—will be easy enough to mend. If so, a world of IPv4 and IPv6 may be schizophrenic; but it ought to prove livable.