The Internet often seems like a limitless landscape

The Internet's Space Shortage
The Internet often seems like a limitless landscape, connecting billions of hyperactive endpoints, with more added by the minute. But ask some of the engineers quietly working to keep those billions of nodes seamlessly connected and they'll tell you the Internet is far from infinite. In fact, it may be starting to get a bit crowded.

The problem, says Leslie Daigle, chief Internet technology officer for the non-profit Internet Society, is simple math: the Internet Protocol addresses that are assigned to differentiate networks and individual computers at the edges of the Internet have 32 digits, allowing for only a finite number of addresses--about 4.2 billion.

That may seem like plenty of space for the world's online population. But huge swaths of IP addresses were originally allocated to the groups that helped build the Internet, starting with the Department of Defense and the Massachusetts Institute of Technology, and can't be reassigned.

Add to that the quick proliferation of computers and Internet-connected mobile devices, Daigle warns, and available slots for new Internet connections will start to run out as early as 2010. "There's not an immediate panic here, but the end is in sight," she says. "Something has got to change."

The solution that about 1,400 engineers at this week's Internet Engineering Task Force (IETF) conference are focused on is Internet Protocol version six, or IPv6, an addressing system that would increase the number of usable address by trillions of trillions--easily enough to account for the Internet's growth for the rest of human history.

Switching to IPv6, Daigle says, would also help solve another nagging problem: spam. In today's addressing system, large groups of IP addresses--what Daigle calls "the swamp"--are often assigned and then left unused for a period of time. Spammers can impersonate those virtual identities to circumvent e-mail filters based on blacklisted IP addresses.

By starting a new accounting system from scratch, IPv6 could allow more careful tracking of which IP addresses are assigned where, limiting the IP identities that spammers can spoof, she says.

But changing the Internet's ordering system isn't as simple as it sounds. In fact, replacing the last generation of IP addresses, IPv4, requires reworking the entire infrastructure of the Internet--not just revamping software but replacing much of the outdated networking equipment installed in Internet service providers, large enterprises and governments.

That kind of massive switchover, which would likely happen gradually, is a great sales pitch for networking giants like Cisco (nasdaq: CSCO - news - people ) and Juniper, whose newest hardware is capable of handling both IPv4 and IPv6 addresses.

But aside from the U.S. government and markets in Asia, where mobile-device use is growing quickly and IPv4 addresses are scarcer than in more mature markets in the West, Cisco director of operations David West says customers aren't that interested. "They're watching and waiting," he says.

Russ Housley, the general chair of the IETF, worries that's not enough. "We've been warning about this for 13 years, so that when the time came, we would be ready," he says. "But of course, everyone held out. Only once IPv4 gets scarce will people get interested."

When service providers notice that addresses are running out, Housley says they may trigger a "bank run" mentality, where businesses and governments race to snap up all the remaining addresses.

There have been some virtual band-aids. Until now, businesses have delayed the inevitable by using a workaround known as a network address translator, or NAT. NATs can allow multiple computers to connect to the Internet through a single IP address--but they also complicate some applications by masking their virtual locations. Voice, video, and peer-to-peer file sharing are all applications that could become slower and more prone to bugs as the Internet becomes increasingly "natted," says the Internet Society's Daigle.

That means the real problem with delaying a switch to IPv6 could be that the tangled configuration of NATs will drag down the network's performance, limiting what new applications can be created.

"The Internet is an organic environment, and it will continue to function into the future," she says. "We just have to make sure the future of the Internet is the one we want."

Gartner research analyst Lawrence Orans is more sanguine. He's heard doomsday warnings for more than 10 years, he says, and year after year, businesses have found solutions other than switching to IPv6. He doubts that a shortage of IP addresses--even with the current technology--will severely cripple the Internet.

Even so, the problem won't go away by itself, Orans concedes. He compares the IP address problem to the so-called "Y2K" bug, the millions of programming hours spent recoding software that wasn't prepared for the switch to the "2" digit before Jan. 1, 2000.

In fact, this is a bigger challenge than Y2K," he says, "But at least with Y2K, there was a deadline."