dial-in lines being held for "days"

[Mike.Alexander]

My experience is still that this is mostly a problem with the 9600 bps
lines, not the 19.2 kbps lines.  I don't use the slower speed lines much so
I can't comment on them.  I think the situation has gotten slightly better
since the new modems were installed recently, but not really very much.  I
still have a lot of trouble making a SLIP or ARA call to 747-3400. 
 
An inactivity timer sounds like a good idea, but I'm skeptical tabout
whether it would really work.  While I don't think SLIP or PPP necessarily
send enough background packets to keep the line active, it would be so easy
to make them do so that the timeout would probably not be very effective. 
In fact, it is so easy to do this accidently that it would be difficult to
accuse someone of intentionally lunching the line just because they were
sending a packet every few minutes. 
 
ARA (AppleTalk Remote Access) is even worse.  It would be very difficult,
perhaps impossible to configure it so it doesn't send packets every now and
then.  In fact, I think that if it doesn't receive a packet of some type
from the far end every few minutes it assumes its partner has crashed and
disconnects. 
 
THis seems to imply either an absolute time limit, with or without
activity, or a charging scheme.  Neither of these will be very popular. 
The absolute time limit will be particularly bad because there will
probably be no way to warn that it is about to disconnect.  Perhaps with
PPP there is a way to do this (I don't recall for sure), but not in general
for all the various protocols that will be used on these lines.  Dropping
someone after 4 hours 90% of the way through a big FTP transfer would not
win us any friends.  If you do this a few times to the wrong person, you
will be looking for a new solution (if not a new job).  :-)
 
We have fought with this problem for years and never have come up with a
very satisfactory solution.  It's not an easy problem to solve. 
Fortunately for the last several years we've had enough phone lines that it
hasn't been a big deal.  That's the only real solution it seems to me.  If
people feel confident that they will be able to get a line when they want
one, they won't feel compelled to hang on to one when they get it.  There
is a certain critical point where people start lunching lines.  When this
happens it becomes essentially impossible to get a line.  Below that point
there isn't a problem.  A certain amount of education can help influence
when this happens, but only slightly. 
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