An electronic census of the internet鈥檚 2.8 billion addresses has been completed by US researchers. It is the first attempt to contact every web address since 1982 鈥� the results could help tackle the problem of the supply of unique internet addresses running out.
and colleague Yuri Pradkin at the University of Southern California, US, sent probes 鈥� known as pings 鈥� to each of the billions of unique IP addresses that make up the internet over a period of 62 days.
IP addresses uniquely identify network devices on the internet. Some map to human-friendly web addresses such as www.newscientist.com.
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Due to security settings on some servers, about 61% of the pings received no response at all, and others received responses equivalent to 鈥渘o comment鈥�. Millions of servers did respond, though, allowing Heidemann and Pradkin to build an 鈥榓tlas of the internet鈥� (see right, top).
鈥淭o our knowledge,鈥� says Heidemann, 鈥渢he only other census of the Internet was in 1982, when the Internet consisted of 315 allocated addresses.鈥�
Tracing viruses
The atlas is numerical. Each square of the atlas鈥檚 grid represents all the IP addresses that start with the same number. Squares are in numerical order, but in a looping fractal pattern called a to keep adjacent addresses physically near each other.
A single pixel inside each square represents colour-coded averaged responses from some 65,536 (216) addresses. All-positive responses are bright green, all-negative bright red, and equal numbers bright yellow, with brightness declining where fewer addresses responded.
The number of addresses provided by the current IP address system is estimated to run out in 2010, and the atlas could help illustrate the need to speed up work on its replacement, Heidemann says, or to map the spread of viruses through the internet.
The team are now working on movies of Internet evolution, which could aid in detecting and monitoring trends.
