Remember how, a decade ago, we told you that the Internet was running out of IPv4 addresses? Well, it took a while, but that day is here now: Asia, Europe, and Latin America have been parceling out scraps for a year or more, and now the ARIN wait list is here for the US, Canada, and numerous North Atlantic and Caribbean islands. Only organizations in Africa can still get IPv4 addresses as needed. The good news is that IPv6 seems to be picking up the slack.

ARIN, the American Registry for Internet Numbers, has now activated its “IPv4 Unmet Requests Policy.” Until now, organizations in the ARIN region were able to get IPv4 addresses as needed, but yesterday, ARIN was no longer in the position to fulfill qualifying requests. As a result, ISPs that come to ARIN for IPv4 address space have three choices: they can take a smaller block (ARIN currently still has a limited supply of blocks of 512 and 256 addresses), they can go on the wait list in the hopes that a block of the desired size will become available at some point in the future, or they can transfer buy addresses from an organization that has more than it needs.

“If you take a smaller block, you can’t come back for more address space for 90 days,” John Curran, CEO of ARIN, told Ars. “We currently have nearly 500 small blocks remaining, but we handle 300 to 400 requests per month, [so] those remaining small blocks are going to last between two and four weeks.”

Doesn’t this allow for strategic behavior, where each ISP tries to request a block slightly smaller than the requests already on the wait list? “The wait list is a last resort as very little address space is returned to ARIN,” Curran said. “Trying to figure out how to game the wait list is not strategic. Trying to figure out how to use IPv6 for new customers is strategic.”

“ISPs will have to get used to the transfer market. If you need IPv4 addresses, go there,” Curran continued. “But I’m not sure how long a market is going to be around. Seven billion people with smartphones and home connections, a connection at work, then add Google, YouTube, Facebook, Bing… Four billion addresses, even with a perfectly working market, isn’t going work in the future.”

IPv4 address markets

We spoke to Janine Goodman, vice president of Avenue4, a broker of IPv4 addresses, about what to expect in the short term.

“IPv6 is going to happen, that’s the direction it’s going,” she said. “But it’s going to take a while. Organizations are not ready to turn to IPv6 tomorrow; this will take a few years. A transfer market allows for the transition from IPv4 to IPv6 in a responsible way, not a panicked way.”

“The price for blocks of IPv4 addresses of 65,536 addresses (a /16) or smaller is about $7 to $8 per address in the ARIN region. In other regions, which have fewer addresses out there, the price tends to be a little higher,” Goodman said. “We expect the IPv4 market to be around for at least three to five years. During that time, the price per address will likely go up and then finally come back down as IPv6 is being widely deployed.”

Goodman stressed that buyers of addresses should make sure they are “clean” and have a known history. There have been reports of address sales where the addresses turned out to be in ongoing use after completion of the transaction.

ARIN CEO Curran also suggested that buyers do their due diligence. “With a car, the car and the registration are two different things. Not so with IP addresses: the registration in the whois database is the only thing,” he said. However, ARIN will only modify its whois records if the buyer of the addresses has a documented need for the amount of address space in question. As such, prospective buyers can pre-qualify with ARIN and then go out and buy the address space that covers their documented needs for the next two years, or they can find a seller of address space first and then come to ARIN to make sure they qualify.

Read More It’s official: North America out of new IPv4 addresses | Ars Technica.