The final stages of the squeeze are arriving: of the 4.3 billion Internet addresses possible with today's Net mainstream technology, 95 percent are gone.
That's the word Monday from the Number Resource Organization, a group representing the world's five regional Internet registries (RIRs) that dole out the numeric addresses.
"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," Axel Pawlik, chairman of the Number Resource Organization, said in a statement.
, such as http://news.cnet.com, are a convenient label for the numeric addresses that actually do the behind-the-scenes work when it comes to sending data such as a Web page across the Internet. Using today's IPv4 (Internet Protocol version 4), though, the number of numeric addresses are dwindling. This is why Pawlik and many others are urging those with Internet operations to start supporting the more capacious IPv6.
A single IPv4 numeric address can be shared by multiple computers through a technique called network address translation. But NAT has its limits, so it's no surprise that IPv4 addresses are in high demand.
Major companies including Comcast,, and Facebook are working to , but countless smaller companies have yet to begin taking the plunge. Although IPv4-based Internet operations will continue to work, those with IPv4-only technology won't be able to reach the IPv6 realm.
It was only last January that IPv4 exhaustion, as it's called, crossed the 90 percent mark. Despite that rate and the difficulties of migrating to IPv6, the NRO does not believe there is a last-minute rush for IPv4 addresses. Meanwhile, the NRO is urging IPv6 action to head off fears of a "chaotic scramble for IPv6, which could increase Internet costs and threaten the stability and security of the global network."
The entire IPv4 address space is divided into 256 blocks, each called a slash-8 or /8. There are now 12 /8s remaining. After seven more are allocated to the five RIRs, each RIR will get one of the last remaining five.
Those last five /8 blocks likely will be handed out to the registries in early 2011, NRO said.
That won't be the complete end of IPv4 addresses, though, as the RIRs allocate the numbers to direct and indirect customers downstream.
IPv4 addresses are divided into four 8-bit chunks that together mean an IPv4 Internet address is a 32-bit number. IPv6 addresses, in comparison, use four 32-bit chunks for a 128-bit number. If you're not conversant with binary math, that means there are 340,282,366,920,938,463,463,374,607,431,768,211,456 IPv6 addresses. So while the transition to IPv6 has been painful, IPv6 isn't likely to run out of room any time soon.