We could be just a few weeks away from running out of Internet addresses.

Vint Cert, one of the fathers of the Internet, didn’t realize back in the 1970s that we might one day run out of addresses for his creation. Back in 1977, he was one of those who came up with a system which allocated 4.3 billion addresses for users and other entities, an unfathomably large number at the time. No one, Cerf included, foresaw that billions of smartphones, PCs and laptops would need their own unique addresses.

Addresses matter because they are the key to finding things and people on the Internet. They’re part of the identification system of the Internet and have to be assigned for every new device that signs on to the web. (They’re the four numbers ranging from 0 to 255, separated by dots).

If there aren’t enough of them, then communications problems can occur, where some devices won’t be able to access certain web sites. It may not be “internet armageddon” as some newspapers have claimed, but it could be a very frustrating experience — all because the creators of the original technology didn’t have enough vision about how big their creation could become.

“Who the hell knew how much address space was needed?” Cerf recently said. “It doesn’t mean the network stops, it just means you can’t build it very well.”

We’re very close to running out of Internet Protocol version 4 (IPv4) addresses. Owen DeLong, the IPv6 evangelist at Internet service provider Hurricane Electric, says that the first step in running out of numbers will happen on Thursday when the final allocation of numbers is released to the bodies that give them out.

The problem is that IPv4 uses 32-bit addresses, which limits the address space to a total of 2 to the 32nd power, or 4,294,967,296 unique addresses. Some of those are reserved for private networks or multicast addresses, limiting further the number of addresses that can be allocated for routing on the public Internet. While many devices use privately held addresses that are used over and over again on the same network, unique IP addresses are usually needed for servers and other types of endpoints.

The replacement for IPv4 is IPv6, which uses four 32-bit numbers, or 128 bits in total, for a possible address space in the trillions (340 undecillion addresses, or 340 billion billion billion billion). That should last a while, but in the meantime, we have a problem. IPv6 is supported in laptops and PCs but not in smartphones for the most part. Companies such as Google, Facebook and Yahoo have begun to support the change in versions. Mobile operators, however, aren’t supporting IPv6 broadly and still rely on IPv4.

The problem is that IPv4 and IPv6 versions aren’t compatible. A client system that has only an IPv6 address can’t get to content on servers that have only IPv4 addresses. The result is that a lot of devices may have trouble connecting to the internet. The Economist says that two separate Internets will have to live side by side for the foreseeable future, wasting a lot of computer and network resources.

Given the fact that the address exhaustion is so near for IPv4 addresses, it’s surprising we haven’t heard more about this problem. Experts have warned the day would come, but their words were unheeded, much like the approach of the Y2K crisis (when computers failed because they couldn’t tell what year it was) in 2000. The speed with which we’ve run out of addresses is a sign of how many internet devices are being created.

“The existing internet will still function, but the crazy hacks we use to fix this will reduce the functionality of the internet in exchange for putting more people on it,” DeLong said.

The BBC reports that APNIC, which assigns net addresses in the Asia Pacific region, will fall below a certain threshold and request the final five blocks, with 16 million addresses a piece, being held by the Internet Assigned Numbers Authority. It is parceling those addresses out to five regional agencies that govern IP addresses across the globe. Those will run out in a matter of months (DeLong believes it will be six to nine months, as the world is adding 30,000 to 50,000 brand new users — not counting replacements — per day). In fast-growing parts of the world such as China and India, the unique addresses are being consumed at very fast rates.

With no addresses left, the internet will have nowhere to expand. The United Kingdom has begun a campaign urging every web site to make the shift to IPv6. The U.S. government has also begun mandating the use of IPv6-compatible networks, and ISPs such as Hurricane Electric have adopted a dual-protocol structure for their internet backbones, which are the big lines that carry much of the internet’s traffic around the world.

The odd thing about this crisis is that preparations for it began so long ago. IPv6 was introduced in the late 1990s (the standard was approved in 1998). Still, usage of IPv6 is tiny, according to Arbor Networks, which supplies network monitoring gear to most internet service providers. A survey by Arbor showed that less than a tenth of 1 percent of all traffic used IPv6. One reason is that moving to IPv6 costs money and usually offers no economic benefit. DeLong believes around five percent of the industry has upgraded to IPv6.

There are ways to get around the problem, such as network address translation, a process which allows IPv6 addresses to be changed into IPv4 addresses. But the systems doing the translation could become bottlenecks. They make networks more complicated to configure. The translation could also interfere with accelerating applications on the web and could disrupt targeted advertising based on shared IP addresses. IPv6 security products are also more expensive.

The consequences shouldn’t set off a huge panic, DeLong said, but he says the bad effects come from people doing too little too late. We may see disruptions such as the failure of Skype calls to connect because users are on incompatible protocols. That’s because users will have to negotiate communications through a third party rather than directly connect over the Internet. That introduces complexity and potential slowdowns to the network.

[Photo credit: Sydney Morning Herald, front photo via Jim Epler]

VentureBeat's mission is to be a digital town square for technical decision-makers to gain knowledge about transformative enterprise technology and transact. Discover our Briefings.