While the Internet is composed not of edge hosts and routers, reaching those devices requires Internet Protocol (IP) addresses. Two reasons make it increasingly important to understand how IP addresses are allocated. First, we hope to understand important basic questions about the Internet, such as how many addresses are used or idle, or how many are dynamically assigned and potentially shared by many computers. Second, most addresses today use IP version 4, and IPv4 addresses are projected to be fully allocated by 2010 or 2011. Observing the efficiencies and costs of address management is an important step in improving use of IPv4 addresses and encouraging use of IP version 6. To explore these questions we have taken censuses, attempting to contact (ping) all allocated IPv4 addresses every few months; and surveys, probing about 1% of the Internet frequently for a week at a time. While many of these questions are still being studied, and firewalls obscure our view of parts of the Internet, this talk will describe our preliminary results. One promising direction is multi-resolution analysis -- evaluating blocks of adjacent addresses, or sequences of probes to each address.
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