Less than 5% of the world's 4.3 billion Internet addresses are left, according to the Number Resource Organization (NRO), which represents the five Regional Internet Registries (RIRs) globally.
The Internet Protocol has undergone four revisions and the fourth is the most widely deployed. Designed for use on packet-switched, or groups of transmitted data Link Layer networks, it is a connectionless protocol.
The number has dipped since the assignment of two blocks of IPv4 addresses to the Asia Pacific region's RIR by the Internet Assigned Numbers Authority. Over 200 million IPv4 addresses have been allocated to the RIRs from the IANA since January 2010, meaning that over 95% are gone.
"This is a major milestone in the life of the Internet, and means that allocation of the last blocks of IPv4 to the RIRs is imminent," said Axel Pawlik, chairman of the non-profit NRO, in a statement. "It is critical that all Internet stakeholders take definitive action now to ensure the timely adoption of IPv6."
The next generation of the Internet Protocol, IPv6 will greatly expand the address space, allowing the Internet to continue to grow, the NRO said. The number of IPv6 address blocks this year is expected to increase by over 70% to more than 2,000 compared with five RIR IPv6 allocations in 2009. The number of IPv4 assignments, by contrast, is only expected to grow by 8% this year. The NRO said the figures indicate increasing momentum for IPv6 adoption and not much concern that IPv4 addresses will be grabbed at the last minute.
The five RIRs are allocating Internet number resources in a fair and equitable way to every region in the world to ensure that IPv4 and IPv6 addresses are distributed fairly, Pawlik noted.
"We are also actively collaborating with stakeholders at the local, regional, and global level to offer training and advice to public and private sector organizations on IPv6 adoption to ensure that everyone is prepared for IPv4 depletion and IPv6 deployment," he said.
There are 256 blocks of IPv4 address space and each is referred to as a "/8" or "slash-8." Since the latest assignment to the Asia Pacific region, only 12 blocks are still available, meaning less than 5% of the whole IPv4 address pool is left. The remaining five IPv4 address blocks will be allocated in early 2011 to the five RIRs, indicating a growing pressure to adopt IPv6.