The Internet hasn't had a census done in 25 years. At that time only 315 IP addresses were surveyed. Scientists have re-run the census, pinging 2.8 billion IP addresses.
Due to security settings on some servers, about 61% of the pings
received no response at all, and others received responses equivalent
to "no comment". Millions of servers did respond, though, allowing
Heidemann and Pradkin to build an 'atlas of the internet.'
"To our knowledge," says Heidemann, "the only other census of the
Internet was in 1982, when the Internet consisted of 315 allocated
What's the point, however, of doing such an exercise, if most servers / routers block pings? That should have been obvious from the start. With the security measures even on home routers of not responding to a ping, this sort of survey is useless.