IPv4 addresses almost gone

No more IPv4 addresses available after 2011, ARIN predicts

The Internet will run out of unused Internet Protocol version 4 Internet addresses soon, possibly by 2011, predicts the American Registry for Internet Numbers (ARIN). And if new smart grid and wireless WiMax-based services start taking off, total depletion of IPv4 may come even sooner, said Richard Jimmerson, chief information officer of ARIN.

"We're about two years from depleting the resource," Jimmerson said. He met with GCN at the Large Installation System Administration Conference held this week in Baltimore, Md.

IPv4, long used as the numeric addressing scheme for Internet end-nodes, can only offer a total of 4.3 billion addresses because the addresses are encoded in 32-bit blocks. By using 128 bits, IPv6, the next-generation protocol being phased in now, will offer a virtually unlimited reservoir of addresses (about  3.4×1038 to be exact).

About 90 percent of all the IP numbers available under IPv4 are already in use. After IPv4 addresses run out, only IPv6 will be available, along with a scattering of unused IPv4 addresses that organizations with an excess of numbers could sell to other parties.

ARIN is one of five firms that manage the global distributions of IP numbers for the Internet on behalf of the Internet Assigned Numbers Authority, (IANA), which controls the numbering scheme ARIN manages the IP numbering for North America and portions of the Caribbean.

ARIN calculated the remaining time for the remaining time of IPv4 availability by extrapolating how many addresses were procured over the past two years. The company estimates that at the current rate, the world will go through the remaining addresses in about 24 months, Jimmerson said.

However, this calculation did not take into account large new initiatives that would require many blocks of addresses. "There are factors that could change demand for IPv4," Jimmerson conceded. Cellular carriers are working on widescale WiMax deployments, which would require large blocks of addresses to cover the country. And if Smart Grid initiatives go with IPv4 for their addressing, the requests would "significantly change the depletion date," he said. These factors "were not expected five years ago."

The end days for IPv4 distribution seem to be very-well planned: Each registry holds about a year's supply of addresses at any given time, which are doled out by IANA. Whenever a registry runs out of addresses, IANA will issue one or a couple of /8 address blocks to the registry.

At present, IANA has 26 remaining /8 blocks of addresses (a /8 block is 24 bits worth of address space, or 16,777,216 addresses). When IANA has only five remaining /8 blocks, they will distribute one block to each registry. "We're only a few years from that," Jimmerson said.

With this allotment, strings will be attached, which will push the time to depletion even closer. For instance, each registry has to devote a quarter of this last allotment for IPv4 to IPv6 protocol translation. And more requirements for this last allotment may also come up.

ARIN's estimate of IPv4 exhaustion seems to be in line with other estimates. A survey from the European Commission puts address exhaustion in two years, as does GCN's own calculator.

To stem the crunch of IPv4 ARIN, and other registries, have also started allowing organizations with large blocks of IP space to sell their excess inventory to other parties. "All this excess address space that may not be used will come out of the woodwork once the registries run out of new IPv4 numbers," Jimmerson said.

"Basically, it would be a transaction between two organizations. ARIN would not know the details of that transaction. We would only recognize in the database that one organization is retuning address space in ARIN to allocate to another organization," Jimmerson said. The only other requirement for the transactions is that the recipient of the address space would have to demonstrate the need for the address.

Jimmerson said government agencies should equip all their Web, e-mail and domain-name services servers with dual IPv4 and IPv6 network stacks, as equipment using IPv4 will continue to operate on the Internet for decades to come.

About the Author

Joab Jackson is the senior technology editor for Government Computer News.

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