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World IPv6 Day

What is 'World IPv6 Day' - and why does it matter?

A bluffer’s guide to ‘World IPv6 Day’ – an initiative by big internet companies to prepare for a major online transition.

TODAY MARKS A major step in the development of the internet, as some of the world’s biggest internet companies test out how their sites will cope with the next generation of internet connections.

‘World IPv6 Day’ will see companies like Facebook, Google, Bing and Yahoo! holding day-long trials of new versions of their sites operating the IPv6 (Internet Protocol, version 6) system.

The event has two purposes: to help major websites test out the flexibility of their new systems, which will eventually replace the current IPV4 used by almost all of the world’s current internet users, and to encourage other businesses and customers to upgrade to the newer model.

So what’s the whole thing about – and should we be worried?

The current internet architecture, IPv4, will be recognised by most internet users as being responsible for the unique postcode (the ‘IP address’) assigned to every single device on the internet.

Every single device with an internet connection – whether it be your home laptop, work computer, mobile phone or a web server – has its unique address, a little bit like a postcode. For example, the address of’s web server is (type it into your browser’s address bar and see what happens).

Usually you don’t see web addresses written in numerical format, because a series of international servers can convert them into numbers on your behalf. (Imagine how much more productive you might be if you had to remember the web address ‘‘ every time you had a few minutes to spare.)

The problem with this current system is that it was originally designed in the early 1980s, when few could have imagined the sheer volume of devices which would ultimately be connected to the internet.

The current system can support 4,294,967,296 devices. That might sound like a lot, but most mobile phones now have an internet connection, and even video games consoles and digital TV receivers have online capability these days.


In fact, the limit has already been reached – the international body responsible for assigning chunks of IP addresses exhausted its pool of spare addresses in February, and the regional internet providers to whom those addresses have been assigned will run out in years – if not months.

It’s a little bit like using up every possible phone number: if Dublin became so big that it had ten million telephone connections, eventually every single phone number between (01) 0000000 and (01) 9999999 would be totally used up.

What’s the solution? Simply add a few more digits.

While there are certain measures that can be taken to help extend the longevity of the current system, the only real long-term solution is to move over to IPv6, which assigns much longer individual addresses – and can therefore handle way more devices.

Here’s an example.’s IP address under the current scheme (IPv4) looks like this:

The same address under IPv6 looks like this:


(In a condensed format, reader Keith Byrne has pointed out, this can be written simply as ’2002::2e89:6485′, with two colons marking the spaces which can be read as ‘zero’.)

You might notice that aside from being longer, the new address also includes letters (specifically, the letters A to F) – meaning the new system can handle 340,282,366,920,938,463,463,374,607,431,768,211,456 devices. That’s 340 billion billion billion billion different devices – enough to bring us well into the next century.

The whole point of IPv6

It’s precisely to raise awareness of this problem that IPv6 Day is being held. As the Internet Society explains:

The goal is to motivate organisations across the industry — Internet service providers, hardware makers, operating system vendors and web companies — to prepare their services for IPv6 to ensure a successful transition as IPv4 address space runs out.

The whole point is that once we run out of IPv4 address, new internet devices can only be issued with IPv6 addresses – but moving over every single device to the new system will take a lot of time, and cost a lot of money.

The difficulty with the transition means we’ll have to run both systems parallel to each other for years to come – meaning web companies will have to run servers that can deal with both types of address.

What this means is that if you’re one of the latest internet users with an IPv6-only address, you’ll need every single website you visit to have this kind of dual support (or ‘stacking’) already in place.

That’s what today, World IPv6 Day, is all about. Google, Facebook and others are trialling IPv6 versions of their websites, working in parallel with their older IPv4 models, in order to check how well they cope with the mixed traffic.

To quote the Internet Society again:

The vast majority of users should be able to access services as usual, but in rare cases, mis-configured or misbehaving network equipment, particularly in home networks, may impair access to participating websites during the trial.

Current estimates are that 0.05% of users may experience such problems, but participating organisations will be working together with operating system manufacturers, home router vendors and ISPs to minimize the number of users affected.

Participants will also be working together to provide tools to detect problems and offer suggested fixes in advance of the trial.

What this means to the average user is that if all goes well, you won’t notice any disruption to your internet traffic. The only disruptions that should occur is if you’re on an IPv6-only connection and you’re trying to access IPv4-only websites.

The best way to figure out how well your current connection will cope is to visit That’ll tell you, simply, whether you currently have an IPv6 address and whether you should expect any issues in the future.

If there are issues, you should speak to your internet provider about whether it’s ready to make the move to IPv6 – before it’s too late.

Previously: Watch out: we’re about to fill up the internet >

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