It took two months and nearly 3 billion electronic probes for researchers to create a map of the Internet. The Internet census comes from the University of Southern California's Information Sciences Institute in Marina del Rey, Calif. Over two months, ISI computers sent queries to about 2.8 billion numeric "Internet Protocol," or IP, addresses that identify individual computers on the Internet. Replies came from about 187 million of the IP addresses, and researchers used that data to map out where computers exist on the Internet. At one dot per address using a typical printer, the resulting map was about 9 feet by 9 feet. The top finally was taped onto the 8-foot-high ceiling. A condensed version squeezes about 65,000 addresses into a dot, with brighter colors used to show ranges of numbers where a greater number of computers exist.
The figure above shows our map of the allocated address space. They layout follows Randall Munroe's hand-drawn map of allocated Internet address blocks from xkcd #195. The one-dimensional, 32-bit addresses were converted into two dimensions using a Hilbert Curve. This curve keeps adjacent addresses physically near each other, and it is fractal, so we can zoom in or out to control detail. Understanding how addresses are used influences many aspects of the Internet. Routers are more efficient when they serve subnets with addresses with common prefixes. Worms explore the address space at random. Individuals use more addresses as they use the net in new ways, from more computers to mobile telephones or embedded devices.
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