Since Ehud got on his soapbox, I thought I'd get on mine as well. When we use IP addresses, there are two distinct purposes they serve. The first is the unique identification (EID) of a machine. The second is the choice of the next hop for routing. If we could split the two parts into separate address spaces, then the current 32 bit address space would be plenty large for EIDs (if you went to 48 bits, then it would be hard to imagine it ever running out.) If the route side of the address space was structured into levels of hierarchy, then the total number of routes anyone would be required to carry would also be far smaller. Unfortunately, I have never seen an acceptable solution to discovering the route path for a random host. It's a real pain, with lookups, tests and redirects all over the place. If anyone has a solution to this that can scale for the next 20-30 years, many people will throw flowers at your feet. Until this happens, the number of bits only skews the balance. The tension between addressing and routability is inherent in the dual use and will continue to drive the allocation system and router design. Jerry