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It will be the biggest, the most drastic, and the most comprehensive change to the underlying structure of the Internet in more than 20 years. The deployment of IPv6-the sixth version of the Internet Protocol-will be a massive undertaking that will require the reconfiguration of more than 100 million computers. Not since the adoption of the Internet Protocol itself in January 1983 has there been such a fundamental shift. But when the IPv6 rollout is finally done, not all the effects will be positive: the new Version 6 Internet will be slower, more friendly to peer-to-peer-based copyright violation systems, and the computers on it will almost certainly be less secure.

You might therefore be tempted to dismiss IPv6 as a technological road to nowhere. But if you did that, you would be making a mistake. IPv6 is happening. The code that lets computers talk on an IPv6-enabled network is now built into the current versions of Windows XP, MacOS, Linux, and many forms of Unix. Every router made by Cisco comes ready to run IPv6. So does every Nokia mobile phone. The whole world is getting dressed up for the IPv6 party.

Will we have anywhere to go? Perhaps Japan or China. IPv6 has been very big in Asia. While the networking protocol was being largely ignored by American academia, the Japanese government funded the KAME Project “to create a single solid software set” of IPv6 and related technologies. KAME involves researchers from Fujitsu, Hitachi, Internet Initiative Japan, NEC, Toshiba, and Yokogawa Electric. KAME software has taken hold in Japan and, large parts of the Japanese Internet backbone are running IPv6. In many ways it looks like the United States is falling behind.

So what is IPv6 anyway, and why does it matter?

To answer that will require a bit of a refresher course on the nature of the Net. The Internet is a huge machine that exists for the purpose of transporting little packages of information called packets. You can think about these packets as tiny digital postcards, each about 500 bytes in length and stamped with the address of its sender and the intended destination. To understand these packets, every computer on the Internet needs to communicate with the same fundamental language. Computer designers call these languages “protocols.” Today’s Internet uses IPv4, the 4th version of the Internet Protocol. (Versions 1 through 3 never made it out of the lab. Neither, for that matter, did Version 5.)

IPv4 is pretty good as protocols go, especially for one that was designed back in the 1970s. But it does have problems-all of them tolerable except for one. Every computer on the Internet needs to have its own Internet address, and IPv4 addresses are just 32 bits in length. The result of this decision made nearly 30 years ago is that the Internet simply cannot handle more than 232 or 4,294,967,296 devices. For a variety of technical reasons, the actual number of devices is a lot smaller than that-far closer to 2 billion, in fact.

With hundreds of millions of people using the Internet, with Internet addresses being dropped into cell phones to support tiny Web browsers, and with household appliances like refrigerators and washing machines scheduled to get their own Internet addresses within the next few years, it’s easy to see why we could soon run out of those 32-bit addresses.

The most important thing that IPv6 does is quadruple the size of the Internet address field from 32 bits to 128 bits. Because in principle, any combination of these 128 bits is a valid address, this quadrupling results in a massive increase in space. For example, whereas IPv4 could never supply enough addresses for every human being on the planet, IPv6 can do that and then some: in fact, IPv6 could provide each of us roughly 60 thousand trillion trillion addresses.

Put another way, the switchover will result in roughly 5,000 addresses for every square micrometer of the Earth’s surface. There are so many IPv6 addresses that humanity will never run out of them-never, ever.

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