Every router, smart phone, or other device on the Internet must have its own Internet Protocol (IP) address. Since long before it became a part of everyone's daily life, the Internet has used the 32-bit IPv4 standard. You've seen the numbers; they look something like 192.168.123.190. There are almost 4.3 billion possible 32-bit numbers. At the dawn of the Internet, that probably seemed like more than enough. Not anymore. Last month the Internet Corporation For Assigned Names and Numbers (ICANN) announced that it had handed out its last batch of IPv4 numbers. But don't panic. It will take awhile before those numbers are actually assigned to devices. Besides, there's a replacement in the wings. IPv6 uses 128-bit numbers. There are an awful lot of those--more than I can describe with words like billion. Let me put it this way: If every one of the seven billion people in the world got their own private stash of a trillion addresses, we'd still have much more than 99.99 percent of the numbers free. I don't think we're going to run out any time soon. The transition from IPv4 to IPv6 is a little like Y2K (remember that). Everyone has known for years that something had to be done, but few have bothered to make the necessary changes. Very soon, they will have to. But let's not panic like it's 1999. This is a problem for ISPs and big networks. For regular users, the worst-case scenario is that your ISP may send you a new modem and you'll have to replace your router. And what about software? Windows has supported IPv6 since XP SP1. Microsoft has offered to pay $7.5m (£4.7m) for net addresses from bankrupt telecoms firm Nortel. The 666,624 IP version 4 (IPv4) net addresses were put up for auction as part of the sell-off of Nortel's assets. Does anyone know if IPv6 is supported in OS X?