>Another point that comes to mind here: it has been proposed to treat
>ISDN just as another link level network interface, create a socket address
>variant carying ISDN phone no's and use the full socket interface as the
>API of choice. This would fit nicely here...

Yes. What I don't understand is, why anyone would do anything *else* :).

Seriously, IIRC, that' show netiso and netccitt worked in 4.3-Reno, at
least as far as they worked at all. (they've been fixed a lot since.)
That is *the* right design choice, given a BSD networking stack.

as there a conflict between ISDN, and the ppp code requiring that the
lower-level device implement the tty software interface?  That would
explain a lot.