I've been thinking a lot about the various proposals for new IPv4 transfer policies, many of which seem to want to create a market for IPv4 address blocks. In a recent discussion, someone suggested that there are two things that RIRs can and should do, in order to mitigate the effects of IPv4 exhaustion. 1. Reclaim unused allocations 2. Allow IPv4 address block transfers In most of the discussions about IPv4 exhaustion, these two actions are treated as separate activities. The first is an extension of what the RIRs and IANA have already been doing for many years. And the second is a wonderful new idea that will let organizations buy IPv4 addresses when RIPE runs out. But if you look closely and what "transfer" means, it becomes complex, confusing, and very unclear. In my opinion, is transfer is not separate from reclamation. In fact it *IS* reclamation. Instead of RIPE looking for unused allocations, it is LIRs looking for unused assignments. What happens after the unused addresses are identified is really not as important as the fact that no reclamation/transfer can happen until unused addresses are found. How likely is it that we will find unused address blocks at a time when the fresh supply of IPv4 addresses has run out? The RIRs have always tried to have transparent processes surrounding IP addressing. That's why we have the RIPE database which publishes a directory of who uses any particular IP address range. But how accurate is it. How many of these IP addresses are really in use? As long as we assume that the RIPE database is basically accurate, and that a higher percentage of all IPv4 addresses will be in a "used" state when we reach IPv4 exhaustion, this implies that there will be very few IP address blocks available to be transferred. And if that is true, this implies that the price per address block (if selling is allowed) will be very high, and rise over time as the unused addresses in the RIPE database become more scarce. Those prices could very well rise to such a high level that it is cheaper to simply buy out smaller companies and disconnect less profitable customers in order to get access to their address blocks. I feel that we need to pay more attention to analysing what addresses are really in use (used in source/destination headers of IP packets on the Internet) and to providing support and education to LIRs so that they can better audit their own allocations. --Michael Dillon