Carriers, enterprises, universities and other entities in the Asia-Pacific region would be able to get unused IPv4 addresses from users in North America as long as they qualify under the rules of Asia-Pacific Network Information Center (APNIC), according to John Curran, president and CEO of American Registry for Internet Numbers (ARIN). Curran said his organization is doing a final evaluation of APNIC's policies, but it expects to begin allowing transfers by the end of the month.

ARIN is one of five RIRs (regional Internet registries) around the world. Each has its own pool of IP addresses, which servers, routers, PCs and other devices need to communicate on the Internet. Addresses based on IPv4, the version of Internet Protocol still used by most systems, are becoming more scarce. Those addresses were assigned to the RIRs by the global Internet Assigned Numbers Authority (IANA), which its last blocks of unused addresses to the regional bodies last year.

Up to now, IPv4 addresses have largely had to stay within their regions. But recently, ARIN and APNIC each decided to allow transfers to other parts of the world that have policies compatible with their own, Curran said. Both ARIN and APNIC require applicants that want more addresses to prove they need them, partly to prevent hoarding and speculation. Last August, APNIC modified its procedures so users requesting transfers have to show why they need them, said APNIC Director General Paul Wilson.

North America has a dwindling supply of never-used IPv4 addresses: approximately three so-called /8 blocks, each of which has about 16 million addresses, according to ARIN's chief technical officer Mark Kosters. That's down from five such blocks in March, he said. ARIN is expected to exhaust those next year. By contrast, APNIC stopped doing conventional allocations and is now strictly rationing addresses, according to Wilson. Its region has about half the world's population and rapidly growing Internet economies, Wilson said.

Until recently, applicants in any region have been able to get fresh, never-used addresses from the regional registry itself.