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.

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