We're running out of IP addresses.

An IP address is a unique numerical identifier for a device connected to a network. Your phone has one, your computer has one, and your Apple Watch has one.

It's not just personal electronics, either. Everything connected to the internet needs to be assigned an IP address: smartphones, smartwatches, smart space heaters. The Internet of Things is more than a just a buzzword, and all those Things are using blocks of IP addresses

Everything that connects to the internet needs a unique IP address, and we just ran out of unique addresses for North America last week. There's a waiting list for new ones. New unique addresses are crucial because lots of software applications that attempt to send out to specific addresses have to be updated to handle duplicates. It works, but it's costly and inefficient, and brings back a problem mobile devices were partly meant to solve: It'd be like everyone in a household sharing one phone number again and passing along the texts and calls that aren't for them until the caller reaches the person they were looking for, but on a much bigger scale. That may not sound too bad, but think about software like Voice over IP services like Skype. The speed and reliability of end-to-end connections is crucial.

This problem is no surprise to anyone who's been paying attention. In fact, we'd have run out of IPs completely back in 2011 if not for some clever stop-gap measures. There are just more devices getting connected to the internet than were anticipated when the framers of the original internet protocol were setting things up.

Enter IPv6, or Internet Protocol version 6, the latest version of the protocol that describes how devices are identified on the internet. The current protocol that we've exhausted is IPv4. (What happened to IPv5? It's complicated, but the gist is that the version 5 name was used for an internet streaming protocol that never really went past the experimental stage.)