Some IPv4 address sales - or transfers as Internet policymakers prefer to call them - are being recorded through official channels such as the American Registry for Internet Numbers (ARIN), which allocates IPv4 and IPv6 address space to North American ISPs and other network operators.
As of March 31, ARIN had recorded 88 IPv4 address blocks transferred that total more than 4 million IPv4 addresses. Two of these transfers involved what are called /12 blocks of addresses, with more than 1 million IPv4 addresses each. (These IPv4 address sales - which are known as 8.3 transfers in ARIN parlance - are different than transfers of IPv4 addresses that occur as the result of a merger or acquisition, which ARIN calls 8.2 transfers.)
"The largest amount of space being transferred is because companies are going through bankruptcy proceedings," said John Curran, President and CEO of ARIN, which still has more than 77 million unused IPv4 addresses in its coffers to dole out for free. "This [transfer process] provides them with a way to make sure they achieve an appropriate value for their number resources. They have to do work to de-configure the addresses and make them available to the community, so it makes perfect sense for them to be compensated for that work."
Curran said some network operators prefer to buy IPv4 address space through an 8.3 transfer rather than receive it free from ARIN because of differing policies over the two types of allocations. Network operators must justify their need for IPv4 addresses for either process, but they can receive 24 months' worth through an 8.3 transfer and only 90 days' worth through a free allocation.
"You can get two years' worth of the space you need and get it locked up based on forward-looking projections and past history of usage with an 8.3 transfer," Curran explained. "But if you come to us for a regular allocation, we will give you what you need for 90 days. Then you'll have to keep coming back every 90 days."
More 8.3 transfers are likely to occur soon if ARIN and the other regional registries agree to a proposed policy change that will allow IPv4 address transfers between regions. That would allow companies in Asia -- which has run out of all but a handful of IPv4 addresses held in reserve for startups -- to buy unused IPv4 address space from the U.S. entities that hold /8 blocks.
"The inter-regional transfer policy has been recommended for adoption. It could be approved any day," Curran said. "It will definitely create some additional transfers. Again, you need to have some IPv4 address space even if you deploy IPv6 because you have to gateway back to old Internet users. Even companies going to IPv6 need IPv4 addresses."
Meanwhile, experts say just as many -- if not more -- IPv4 address sales are going on outside of ARIN's 8.3 transfer process as there are being recorded by ARIN. That's because many of the original recipients of /8 IPv4 address blocks -- so-called "legacy" holders that received their IPv4 addresses before ARIN was created -- consider themselves outside ARIN's oversight.