> I have a fairly crowded network, and in it there is a Sun 3/60 running
> NetBSD.  It is my router; it is connected to a modem, and the modem connects
> to the outside world.

> I have noticed the following symptoms:

>  [ ping some host (the other end of the PPP link?) every 10 minutes 10 times,
>    kill pppd if it doesn't work even once. ]

> 1.  The above script fairly frequently chooses to kill pppd when the link
> is working perfectly well.

I have a 486, so there may be port-specific issues I don't have, but:

On a busy modem, I have seen ping packets lose big time, and wouldn't
be TOO surprised that not one in ten packets could get returned
promptly enough for ping (maybe a little surprised).  My own similar
script runs every two minutes, and insists that the link fail 4
consecutive checks (with fewer packets).  That keeps short-term
saturation from causing the link to be taken down.

> 2.  If I'm doing a fairly large download to either a mac or a windoze PC,
> which is connected to the 3/60 over ethernet, the network feed (which I'm
> watching as modem LED's) will abruptly stop transferring data, and hang for
> several minutes.  However, if I hit return in an rlogin to a machine on the
> other end of the link, everything recovers for a while, running anywhere from
> three seconds to a minute, and then hangs again.

I don't see that.  Sounds like a bug in the serial driver; maybe the receive
interrupt clears out some broken state in the transmit path allowing it to
recover?