IPv4 addressing protocol (32 bits) allows for four billion IP addresses. You’d think that four billion of anything would be enough, but it isn’t. It’s predicted that in the next year or two we’re going to run out of them.

IPv6 (128 bits) allows for 3.4 times 10, 38 times. That’s actually 340.3 undecillion. It’s a lot. Every Internet user on earth could get an IP address for each of his teeth, his cat’s teeth and his toaster and it wouldn’t even put a dent in the possible range.

Sean Michael Kerner, writing on the Enterprise Working Planet web site has done a feature “IPv4’s Last Day: What Will Happen When There Is Only IPv6?” that foresees the American Registry for Internet Numbers (IRIN) and the other four regional Internet registry organisations doling out smaller blocks of addresses as fewer and fewer become available.

A colleague of mine, Phil Owens, doesn’t foresee the end of anything, he foresees the beginning of a market for IPv4 addresses as enterprises sell off the address space they don’t need.

So, the long-anticipated switch over to IPv6 will really happen NOT when ARIN runs out of IPv4 addresses, but when the IP addresses for sale get more expensive than switching networks over to IPv6.

Since those IP addresses could be “dirty”–used in the past–the new users could get unwanted traffic on them too. And that’s another reason to switch to IPv6.

So, the IPv4 world will end with neither a bang nor a whimper. It will just limp along, like the owner of a Dodge Dart, making the fixes with aftermarket and junk-yard parts, doing anything possible to hold off that inevitable day when he will be forced to buy another junker and have a car payment.

Unless the Mayan calendar gets us first.