IPv4 Space Continues to Dwindle

The end is near for IPv4.

The number of unallocated IPv4 address blocks declined this week after IANA (Internet Assigned Numbers Authority) distributed four slash 8 address blocks to a pair of Regional Internet Registries (RIRs). Each /8 address block contains 16 million IPv4 addresses. There are now only seven remaining blocks of unallocated IPv4 address space from IANA, which might not be enough to make it into 2011. At the beginning of 2010, IANA had forecast that there were 625 days worth of unallocated IPv4 addresses remaining.

The IPv4 address space in total only has room for 4.3 billion addresses, the majority of which have already been allocated. The allocation for the final five blocks of /8 addresses is part of a long standing policy at IANA for the last days of IPv4.

"When the IANA free pool has only five /8 blocks remaining, they will be simultaneously distributed to the five RIRs in accordance with global policy," John Curran, president and CEO of ARIN, told InternetNews.com. "With only two /8s remaining before that global policy is triggered, it is possible the IANA free pool will be fully depleted before the end of the year."

Demand for IPv4 address space continues, which is why ARIN (American Registry for Internet Numbers) and RIPE NCC (Réseaux IP Européens Network Coordination Centre) received the additional /8 allocations this week.

"IANA allocates IPv4 address space to the RIRs based on need. ARIN, like RIPE NCC, qualified for two additional /8s this week," Curran said. "ARIN's two additional blocks will be allocated to ISPs, enterprise organizations, and other network operators based on need, just as every other /8 block has been distributed - based on existing, documented ARIN policy. "

With the two new /8s in hand, Curran expects that ARIN has enough address space to fulfill current and short-term anticipated requests in its region.

Organizations returning unused address space

Though the large allocation blocks are nearly gone, there are still millions of unallocated IPv4 addresses left to be had. Each of IANA's remaining slash 8 (/8) address blocks contains 16 million IPv4 addresses each. There are also blocks of unused IPv4 address space that are being returned.

"ARIN continues to encourage organizations with unneeded address space to return it to ARIN or one of the other RIRs," Curran said.

The Interop trade show recently announced that it was returning a portion of its /8 allocation.

"ARIN accepted Interop's returned space in October and will not reissue it for a short period, per existing operational procedure," Curran said. "After the hold period, ARIN will follow global policy at that time and return it to the global free pool or distribute the space to those organizations in the ARIN region with documented need, as appropriate."

The end of the free pool of unallocated IPv4 address space from IANA, doesn't mean that there won't be IPv4 addresses available to for service providers either.

"Once the IANA free pool is depleted, the RIRs will still have some address space to hand out," Curran said. "Each RIR will have the final full /8 it received at IANA depletion, plus any existing inventory. Depending on incoming address space requests, an RIR pool could last anywhere from days to months. "

IPv6 demands increase

With new IPv4 space nearly gone, ARIN has seen a corresponding increase in requests for new IPv6 addresses.

"Over the last six months, IPv6 requests have certainly picked up, and 2010 requests are much higher than requests in 2009," Curran said.

Sean Michael Kerner is a senior editor at InternetNews.com, the news service of Internet.com, the network for technology professionals.