The ISDN4BSD ISDN subsystem, which is also integrated into FreeBSD,
has been brought into shape for NetBSD and imported into NetBSD-current.
Drivers are available for a multitude of ISA, PCI, and PCMCIA cards.
Currently only the EuroISDN (DSS1) variant is supported, which means
there's some needed work for the protocol variants used in the U.S. 

To use ISDN, you need NetBSD-current as of 20010108. You may see the
"Steps to connect via ISDN"[1] in the NetBSD Documentation[2] section
of the web site for further instructions.  Also, a full set of
documentation is available at the ISDN4BSD site[3]. 

The NetBSD integration work was done by Martin Husemann. 

1. http://www.netbsd.org/Documentation/network/isdn/
2. http://www.netbsd.org/Documentation/
3. http://www.freebsd-support.de/i4b/

-- 
Reed <aiko@antigone.net>