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.