'Twas the night before World IPv6 Day, when all through the net, sysadmins enabled 128-bit addressing, without breaking a sweat...

O.K. World IPv6 Day may not have the same poetic potential as other days of the year. But on Wednesday, June 8, technologists and network operators around the world will be watching internet traffic especially closely.

For a 24-hour period on Wednesday, several large companies – including Google, Facebook and Yahoo – will enable support for IPv6, the internet's next-generation addressing scheme. It's the first large-scale "test flight" of the new system, and another step in the internet's slow transition away from the decades-old IPv4 standard.

On Feb. 1, 2011, the Internet Assigned Numbers Authority (IANA) handed out two of the very last IP address blocks to APNIC, the internet registrar for the Asia-Pacific region. At the time, I called it "the beginning of the end of IP addresses as we've known them."

There's been a recognition from many large companies and the governing bodies of the internet that the switch to IPv6 is necessary. Part of this has to do with the limitations of the old system, and the number of addresses that are available. Essentially, we've run out of the old style of addresses, so we need a new system with more addresses. But worldwide IPv6 adoption has been slow. For instance, Google currently estimates that only 0.33 percent of all internet users are IPv6-ready.

World IPv6 Day is an attempt to promote awareness of IPv6, but also to iron out some of the potential bugs. On Wednesday, network operators and content providers like Google and Facebook will have a chance to measure the real-world impact of this transition.

So, from the end-user's point of view, what will happen? If everything works as intended, you won't notice a thing. If your connection is properly configured for the older IPv4 system, you'll be fine. If your connection is properly configured for the newer IPv6 system, you'll be fine. But if any part of the chain between you and any of the participating sites is wonky, you may have trouble accessing their online services.

Paul Andersen, who’s with the American Registry for Internet Numbers (ARIN), outlined two possibilities: "The most likely scenario is that you might see a delay. You click on your bookmark, or punch in the website, and it would just seem to be that spinning icon. There is a possibility, too, that the site would be completely unreachable, but I don't think that's very likely on any widespread basis."

According to Google's estimates, "the vast majority of users (99.95%) will be unaffected." But we won't really know until Wednesday, when the test flight goes live.

So, what should you do if you wake up tomorrow and can't reach Google (or Facebook, or Yahoo)? My advice: first, take a deep breath. It's going to be OK. But, your problem could be difficult to diagnose. That's partly because a misconfiguration could be anywhere along the line between you and the server you're trying to reach. It could be with your computer hardware, your router, your ISP's equipment or the destination server. And the problem may very well be out of your control. If the problem is with your ISP, there's not much you can do on your own computer to fix things.

Andersen recommends starting locally. Check your computer to see if there are any obvious misconfigurations. Then, escalate as needed. If you're at home, that might mean calling your ISP. If you're at work, it might mean calling the IT department. Andersen says, "People who configure these devices might not be aware that there are misconfigurations. So from that standpoint, we'll be building awareness where there could be kinks in the system. The good news is that it's only a 24-hour experiment."

Wednesday's World IPv6 day is mostly focused on large content providers and network operators. But there are ways individual end users can prepare, too. Online tests such as Test-ipv6.com or Google's IPv6 test page can help you determine how well equipped your computer is for connecting to IPv6-enabled sites.

World IPv6 Day will likely go unnoticed by most internet users. But for those of us interested in peeking underneath the hood, it'll be a fascinating test.

So, my final suggestion: even though you'll probably (fingers crossed) have no trouble connecting to your favourite sites on World IPv6 Day, if you have mission-critical tasks to do — like watering your crops in Farmville — I'd get them done today. Or Thursday.