BBC ClickOnline's Ian Hardy investigates what is going to happen when the number of net addresses - Internet Protocol numbers - runs out sometime in 2005.
In the early days of the internet, it seemed improbable that all of the four billion available IP addresses would be used, but that is exactly what is happening.
IP addresses are set to run out in 2005
Every mobile phone, PC and server has an address which, like a phone number, needs to be dialled when it is accessed over the web.
But as more people log on around the globe, the available number of IP addresses is dwindling.
A taskforce of experts hope to solve the problem by creating what is called IPv6 and would provide billions of extra IP addresses.
Anyone who logs onto the internet will automatically receive an IP address. It is made up of four sets of numbers, each separated by a dot.
Each of these decimal numbers falls between 1 and 255 and represents a binary code that the machine understands.
This is how computers identify each other.
"Just as you can't call someone without having their telephone number to tell the telephone system how to route your call," explains Perry Metzger, from the IPv6 Task Force, "every computer on the internet gets something called an IP address, which is almost exactly like a phone number."
The current version of IP addresses is called IPv4. It was designed in the 1980s and has about four billion possible combinations.
Once they have been used up, that is it.
"I don't think people anticipated that we would have quite the utilisation that we have today," said Phillip Benchoff, a computer network engineer at Virginia Tech in the US.
The global distribution of available IP addresses is extremely unbalanced. Most of the numbers remain in the USA, where the technology was originally invented.
More than two-thirds of the world's IP addresses were bought by American companies.
"Level Three Communications, which is a really large ISP, has more IP addresses than the whole of Asia," said Matthew Sarrel, Technical Director of PC Magazine Labs.
"As companies and people in Asia get more devices they are going to run out of IP addresses."
One of the biggest pressures on IPv4 is the 'always on' internet connection. At the moment, when you dial your ISP they assign you a temporary IP address, which is taken away the moment you log off and given to someone else.
But in the new era of 3G wireless computing, each of us needs a static, or permanent IP address.
That is why the world needs an upgrade from 32 bit IPv4 addresses to 128 bit IPv6 within a matter of a few years.
This is intended to provide four billion times four billion times four billion as many as currently exist.
"We could assign IP addresses to every grain of sand in the Sahara and still have extra," said Mr Sarrel.
The IPv6 standard will bring sweeping improvements. Soon you will be able to send specific instructions to the device of your choice, anywhere in the world, with added security and reliability.