About What Addresses We Probe

A person asked us:

I was reading: https://ant.isi.edu/address/whole_internet/ but what does this mean?: Blue indicates areas that were not probed because they were not public allocated unicast address space. most of the internet consists of this "not public allocated unicast address space"? what is this? can you give an example?

We only probe address space that is: public and unicast.

Of the 2³² IPv4 addresses, about 18 million addreses are not public, but private (for internal use). See http://tools.ietf.org/html/rfc1918 and http://en.wikipedia.org/wiki/Private_network for a description. We do not probe these addresses because they are not globally routable. As an example, 10.0.0.1 is not a public IP address (if you can see it, you're probably behind a NAT), and 127.0.0.1 is also not public (it means localhost, the computer you're on).

Of the 2³² IPv4 addresses, about 2²⁸ (prefix 224.0.0.0/4) are allocated for IP multicast See http://tools.ietf.org/html/rfc3171 and http://en.wikipedia.org/wiki/IP_Multicast for a description. We do not probe these addresses because they are are not unicast addresses. As an example, 224.0.0.1 means multicast to all hostss on the same network you're on.

Of the 2³² IPv4 addresses, some are unallocated. The Internet Assigned Numbers Authority (IANA) assigns addresses to registries. This list is constantly changing, but a current list of allocated and unallocated addresses is at http://www.iana.org/assignments/ipv4-address-space See also http://www.potaroo.net/tools/ipv4/index.html. An example unallocated address is 1.0.0.1, while an example allocated address is 128.150.4.107 (http://www.nsf.gov).

We also omit blocks of addresses whose owners request that they not be probed.

We probe whatever's left when you remove these categories (private, multicast, and unallocated, plus blocks that have requested they be omitted). In other words, we probe only addresses that are public, unicast, and allocated (and haven't objected).

Is of the data in USC/LANDER internet_address_survey_it15w-20061108, this corresponds to about 2.8 billion addresses.