[By Alistair Fairweather]

For most of its 2bn users, the Internet is effectively infinite. It has more sites than we could ever visit, more products and services than we could ever want, and more people than we could ever meet in a lifetime. It seems odd then that this boundless cyberspace could run out of something as mundane as addresses, but that’s just what’s about to happen.

Regardless of how big a leap the Internet is from traditional postal services, it still needs fixed and discrete addresses in order for information to flow from the website you’re visiting from the computer you’re using. In other words it needs to know precisely where to send its digital “letters” (or data), or they will end up lost in the system and never arrive.

The problem is that the old addressing system, named Internet Protocol version 4 (IPv4), simply doesn’t have enough addresses to cope with the demand from the rapidly expanding Internet. Since 1995, the Internet has grown from just 16m users to reach nearly a third of the planet’s entire population today.

But why didn’t the clever scientists who invented the system anticipate this? Well, firstly, they had no real need to. There were only a few thousand computers on the Internet back in the 1970s when they developed the IPv4 standard. Secondly, I suspect they felt pretty comfortable with a limit of more than 4bn addresses, since it exceeded the number of human beings on earth at the time.

Its equivalent to the 14th century, when addressing a letter to Bill the tinker, Old Pye Street, London, would have worked fine because the city had only a few thousand inhabitants, and a few dozen streets. If you’d told those medieval Londoners they needed a proper postal code system in order to prepare for the coming population explosion of the 19th and 20th centuries, they would probably have burned you for being a wizard.

“But hang on,” you cry, “you just said there were 2bn Internet users and over 4bn addresses — so we’re still good to go, right?” Alas, not. The problem is the number of other devices that also use IP addresses, from Internet-enabled mobile phones and gaming consoles, to televisions, printers, household appliances and even traffic lights. Everything we connect to the internet needs an IP address, so they are rapidly being gobbled up.

And “gobbled” is the word. We have just over 100m addresses left, whereas we had more than 1bn in 2006. So is it time to panic? Luckily not. Scientists anticipated this issue way back in 1990s and created a new standard, imaginatively named IPv6.

This new system supports so many addresses that we don’t have an intelligible name for the number. Imagine a 1 with 38 zeroes after it, and then times that by three. That’s trillions upon trillions more addresses than there are cells in a human body, so we should be good for a few decades (or at least until all our cells need IP addresses to send them medicine).

The even better news is that the computing industry has been busy rolling out the new standard for several years already. If you bought your computer within the last three years, chances are that it is ready to switch to IPv6.

But that doesn’t mean there aren’t challenges ahead. Upgrading PCs is a snap by comparison with retooling the plumbing of the Internet, which also needs to be IPv6 compatible. Some service providers and sites already offer support for the new standard. But there are many more hold-outs unwilling to spend money and time on the move until it is absolutely necessary.

Ideally the transition will be smooth and largely invisible to consumers. But, given human beings’ proclivity for last-minute rushes, we should expect a few bumps along the road to IPv6 nirvana. It will, in the end, be well worth it.