Yesterday, the Internet Assigned Numbers Authority (IANA, part of ICANN), allocated two blocks of 16.8 million IPv4 addresses to the RIPE NCC and another two blocks to ARIN. The RIPE NCC and ARIN are the Regional Internet Registries that give out IP addresses in greater Europe and North America, respectively. This brings the global pool of still available "/8" address blocks that IANA maintains from 11 down to 7.

In 2009, IANA gave out eight /8 blocks—four to APNIC (Asia-Pacific) and four to the RIPE NCC. This is lower than the previous four years, when between nine and 13 /8s were given out. After the first 11 months of 2010, we're already at 19. ARIN and the RIPE NCC got four each, LACNIC (Latin America and the Caribbean) two, and AfriNIC (Africa) one. APNIC has received eight blocks so far this year—two every three months like clockwork. And the year isn't quite over.

If APNIC sticks to its earlier schedule, it will come back for two more /8s in mid-January, seven weeks from now. However, RIPE and ARIN requested additional space sooner than expected, and APNIC may very well do the same to make sure that it gets blocks seven and six, because once those are gone, IANA will give one last /8 to each of the five RIRs and then that will be that. So if APNIC wants to make sure that it gets three of the remaining seven blocks, it may request two more blocks from IANA posthaste, so the endgame may play out before the end of the year.

Then what?

At this point, all /8s will have a status of either "allocated" (given out to an RIR) or "legacy," meaning that addresses were given out directly to an end-user organization. This includes the infamous class A blocks that went to IBM, DEC, Apple, HP, MIT, and so on. But there is also class B and class C space, which doesn't consist of monolithic /8 blocks. In that class B and C legacy space, there are actually 128 million unused addresses hiding. It's unclear what the status of this grab-bag of unused space is: each of the /8s in question is "administered" by one of the RIRs. But does that mean that RIR gets to keep that unused space? That would be less than egalitarian, as half of that unused space is administered by ARIN. And ARIN is also sitting on 45/8, which was returned by Interop, but for now is still marked as in-use legacy.

Once the class B and C legacy space is divvied up, the RIRs will be on their own, and run out of IPv4 space at their own rates. The first RIR to deplete its working inventory will be APNIC. This will probably happen at some point next year. The other RIRs will be able to get through 2012 without trouble, and may get by a little longer than that. But soon, the largest ISPs in the world won't be able to get the multi-million blocks they need to connect new broadband customers. Small ISPs and content people will be able to get some space for a little longer.

The good news is that existing IPv4 users can continue to use the addresses they already have—unless their ISP takes those away and puts them behind NAT. And the really good news is that there's centuries worth of IPv6 space available to anyone who needs it.

Listing image by Nicolas Nova