The Internet is running out of space.
The number of Internet Protocol addresses - numerical codes that act a little like phone numbers or house addresses, letting Internet-connected devices communicate with each other - is reaching its limit.
Now, in one of the most significant technical changes in the history of the Internet, the world's biggest technology companies and Internet governing bodies must move the Web to a new address system.
Since the early 1980s, the dominant Internet address protocol has been the fourth version, commonly known as IPv4. This week, the Internet Assigned Numbers Authority, which is responsible for co-ordinating Internet addresses, handed out the last five remaining blocks of IPv4 addresses to its regional partners around the globe. Depending on the region, the last blocks should last another three to six months.
A number of service providers and large enterprises have been trying to figure out temporary solutions to the problem, such as sharing addresses between devices or taking addresses away from networks and devices that aren't connecting to the Web. But in the long run, a more permanent solution is necessary.
"The way business is done on the Internet is going to be different," said Alain Durand, director of software engineering at the infrastructure products group at Juniper Networks. "That doesn't mean the end of IPv4."
IPv4, because of its numerical makeup, can only maintain about four billion unique addresses. In the 1980s, when a select few people in Europe and North America had access to the Internet, four billion addresses were considered more than enough. But today, as the developing world drives rapid Internet growth, the number of free addresses is dwindling.
For the past few years, Internet Service Providers and other companies have been working on a new version of the Internet addressing system, called IPv6. The new generation likely won't run out of addresses for a while, as IPv6 can theoretically hold trillions of trillions of addresses.
In June, a number of major tech companies, including Google Inc., Facebook Inc. and Yahoo Inc., will switch their services to the new protocol for 24 hours, to test how the new system works. Even though IPv6 is expected to become the dominant protocol eventually, the overlap period with the old system, on which the vast majority of today's Internet functions, could last for another decade or two.
Mr. Durand says there are two major challenges related to the transition from IPv4 to IPv6. The first is getting major providers to offer content on the new protocol. That's in part why many companies are participating in the test run this June, to raise awareness about IPv6.
The second challenge is device-based. Many consumers have just gotten around to purchasing expensive new gadgets, such as Internet-ready TVs. However many of those electronics aren't equipped to handle the new protocol - one reason the overlap period between the protocols is expected to be so long.
Still, as long as the two protocols can co-exist, everyday users shouldn't see a disruption of their services as the Internet changes its address system.
"The important thing is the sky's not falling," Mr. Durand said.