The Story With ISDN

and ISDN network is a completely digital network, so ISDN cards are not modems - they do not sound like "tzrrrrr....brrrr....grrr....".
Because of its digital nature, placing an ISDN call takes 2-3 seconds, including the login process.
ISDN lines actually contain two channels, each of them is 64,000 bps (bits per second) wide.
When you dial to your ISP, you may either use a single channel (for a 64K connection) or both channels (for a 128K connection). The ability to use a 128K link relies, of-course, on your agreement with your ISP.
Most ISPs in Israel today have various deals for helping you upgrade your phone line to an ISDN line, and sell you an ISDN card cheaply.
Note: there do exist external ISDN "modems". They connect to the serial port, and appear like modems, in the fact that they allow you to use normal "AT" commands to control them.

ISDN In the Fast Lane - kisdn

The fastest way to set up an ISDN connection, is by using a GUI utility. kisdn is a utility, very similar to kppp, that may be used for that purpose.
Ofcourse, even using kisdn, we have to first make sure our kernel has a driver for our ISDN card loaded. See the discussion of 'isdnctrl' below for a link to a good explanation about that part.
For a short explanatin of configuring KISDN on a mandrake 7 system, please see http://plasma-gate.weizmann.ac.il/Linux/maillists/00/05/msg00445.html.

the isdnctrl utility is used to configure the ISDN system for dialing, and to perform the actual dialing itself.
The major difference between dialing with ISDN and with an analog modem, is that an ISDN line has two phone number, and thus we need to tell our system which phone number it should dial FROM. This - in addition to telling our system which phone number it should dial TO.
The second difference is that instead of using pppd, an ISDN connection uses ipppd - a special version of the PPP daemon for ISDN lines.
Activating ipppd is done directly by isdnctrl - when we tell it to dial out.
For a detailed description of dialing out with isdnctrl - go to http://plasma-gate.weizmann.ac.il/Linux/maillists/99/10/msg00386.html.

Note: you probably already have isdn4linux installed on your system, so skip that part (or install it from your CDROM, if you haven't installed it previously).