John C Klensin wrote:
"Four" is in the spec because it is a plausible compromise
without getting bogged down in the details of multiple countries
and cultures and because, if one does get that involved, one
will often come up with four anyway.
As I recall, there was also an empirical basis for this, based on thinking
about the notification "spikes" that were observed over some years.
For obvious and reasonable reasons, one can strongly argue for the time-out to
be 1, 2, 3, 4, 5, 7 and even 10 days. The latter are too long for
effectiveness and the first few cause too many false notices.
That leaves, perhaps, 3, 4 and 5 to debate about and 4 does jump out as a
reasonable compromise, doesn't it?
d/
--
Dave Crocker
Brandenburg InternetWorking
bbiw.net