The Internet Is Out of Addresses, But Don't Panic

You would have thought 4,294,967,295 internet addresses was plenty. But less than 30 years after the Internet Protocol was adopted and barely 15 years after the internet went mainstream, the pool of numerical addresses that allow PCs, servers, and an ever-growing flood of mobile devices to find each other on the net has been all but exhausted (graph below). The good news is the solution is at hand, and while consumers may barely notice the change, it will require a long-overdue reworking of some crucial internet infrastructure.

The solution is a different, if not really new, addressing scheme, Internet Protocol Version 6, or IPv6. (The original, and still current, version is 4; version 5 was never implemented.) It makes a number of changes in networking procedures to provide for more efficiency and greater security. But the big change is quadrupling the length of addresses to 128 bits, which provides many trillions of addresses for every person on earth.

IP addresses are a bit like phone numbers. When you want to open, say, www.cisco.com, your browser requests its numerical address from the distributed directory called the Domain Name System. Routers then use the address to connect to the appropriate server. All devices on the network—computers, phones, TV set top boxes, printers, routers, servers—need their own address. My two-person household is more gadget-intensive than most, but as I write this, I have 19 devices assigned addresses on my home network.

With the explosive growth of networks, the original 4 billion addresses lasted as long as they did only because of some tricks. Dynamic address assignment lets different devices share one address, provided they don't both use them at the same time.  More important, network address translation lets the devices on a local network use private addresses. If you look at the IP address of any device in your home, it is probably of the form 192.168.xxx.xxx, a block of addresses reserved for private networks. To the internet at large, everything on your network appears to to use the same public address that was assigned by your service provider. Your router sorts out what data goes to which device.

But this year, the inevitable occurred and the Internet Assigned Numbers Authority, which is responsible for address assignments worldwide, announced it had given out the last unallocated blocks of addresses. There are still lots of unused addresses around in scattered bits, but if you need a large block, it will have to be of the IPv6 variety.
The transition to IPv6 has actually been proceeding glacially since the standard was first published in 1998. With no compelling incentive to expend the effort and money needed to convert to IPv6, companies and service providers have been taking their time. The exhaustion of IPv4 addresses is finally forcing the issue. Fortunately, equipment makers and software publishers, under pressure from the U.S. government and others, have been making their products IPv6-ready. The U.S. Office of Management & Budget has required agencies to support IPv6 since 2008 and all fairly recent computers and operating systems, including Windows, Mac OS X, and Linux, can handle IPv6 addressing. Engineers have also devised a number of ways to let IPv6 and IPv4 networks communicate more or less seamlessly.

As time goes on, new sites will emerge on the internet that will only be accessible through IPv6, since there will be no v4 addresses to give them.  Internet service providers will have to either enable IPv6 or one of the workarounds for their customers, especially residential and small business customers for whom these issues are technically daunting. For example, most if not all of the gear on my home network can support IPv6, but not all home  routers.

A first big trial of the transition will come on June 8, when the Internet Society sponsors World IPv6 Day.  Major internet infrastructure operators, including Comcast, Time Warner Cable, Google, Microsoft, Yahoo!, Akamai, and Limelight will enable IPv6 on their systems for a   24-hour test run.

In the end, the transition to IPv6, will be a bit like a mini version of the Y2K transition of the late 1990s, albeit without warnings of airplanes falling from the skies and other doomsday predictions. Network operators and others responsible for internet infrastructure are going to have to do a lot of heavy lifting. But one of the glories of the internet has been its designers ability to keep the plumbing hidden. The odds are that most users will never realize that the change has been made.