On 03.08.2012, at 20:25, Mark Andrews wrote: >> >> IPv4 addresses used to be regarded as non-scarce not so long ago. > > I don't know what planet you have been living on but it was clear > IPv4 addresses were a scarce resource 2+ decades ago longer than > some IETF attendees have been alive. IPv6 was started because they > were a scarce resource that would run out in the foreseeable future. I may have been too terse for some readers. What I intended to point out is that the life time of address spaces has been underestimated more often than not, especially early on in their deployment. This is particularly true for network level addressing. Arguments that "addresses are not scarce" in any finite address space should be judged in the light of this historic experience. In other words: I expect that it will be not more than 20 years from now that we will hear cries of "Why were we so wasteful with IPv6 addresses in the beginning?" This is why I disagree with Phillip Hallam-Baker's opinion. Daniel PS: I have been living on Earth, the densest and fifth-largest of the eight planets in the Solar System. Personally I have been aware of the general state of the IPv4 address space since the 1980s and I have contributed towards making it last as long as it did; refer to RFC1597 (now RFC1918) of the year 1994 as an example.