well, the reason I named a specific time interval was to provoke discussion, so I suppose I shouldn't be disappointed... I am not sure that one week is the best figure. I imagine that figure could reasonably be picked to be anywhere between several hours on the low end to a few weeks on the high end. However as I've written in other messages today I believe that trying to use a single mechanism to handle all cases where addresses change is probably too expensive (either in money or reduced performance or both), and to me it makes sense to handle two cases separately - those for which the change is known about well in advance, and those for which it is not. The idea is for l3 or l4 to handle the unanticipated changes and for l7 (or a layer between l4 and l7) to handle those that are anticipated and announced. For the anticipated changes, one week notice/stability does not seem like an onerous requirement. For unanticipated changes of wired networks, I don't think providing redirection for one week is too expensive either. And for mobile networks I think it's reasonable to expect them to pay for redirection services. In this way the costs of providing the infrastructure necessary to compensate for the lack of natural address stability (i.e. the ability to move without one week's notice) can be borne by those who need that service; others need not pay for it. Finally, one week is long enough that most apps (i.e. those whose connections never have to last that long) won't have to worry about it or pay for the extra overhead. You could pick a shorter time interval but it would eventually start to impact a significant number of apps. Of course, there will still be apps that need to worry about user mobility rather than host mobility. Since the network doesn't know anything about users, those apps will still need to provide their own facilities to keep track of users' network locations. Keith p.s. and yes, AOL's IM tracking is quite dynamic, but it's also highly centralized. based on the experience with ICANN I think it would be very difficult to manage the political issues associated with a central Internet prefix mapping service - though the experience with the ongoing ENUM work seems, at least from my distant vantage point, to be somewhat more promising. > as one thinks about VPNs, tunneling, mobility and the like, assuming a > week is probably a bad idea. Think a bit about the way AOL's IM tracks > the binding of an IM handle to an IP address - it is quite dynamic.