There is work going on in the isdn4linux camps to support the NI1 protocol
for the Hisax driver. The Hisax driver support ISDN cards based upon the
Siemens chipset (Teles, ELSA, among others). These also happen to be very
inexpensive cards.

Isdn4linux is very robust in terms of features, including MLPPP.

You might want to watch the isdn4linux list (much of it is in German, they
always answer English questions and announce in English and German).

Al Youngwerth
alberty@apexxtech.com