mirror of https://github.com/tLDP/LDP
102 lines
4.2 KiB
XML
102 lines
4.2 KiB
XML
<sect1 id="ISDN">
|
||
|
||
<title>ISDN</title>
|
||
|
||
<para>
|
||
The Integrated Services Digital Network (ISDN) is a series of
|
||
standards that specify a general purpose switched digital data
|
||
network. An ISDN `call' creates a synchronous point to point data
|
||
service to the destination. ISDN is generally delivered on a high
|
||
speed link that is broken down into a number of discrete channels.
|
||
There are two different types of channels, the `B Channels' which will
|
||
actually carry the user data and a single channel called the `D
|
||
channel' which is used to send control information to the ISDN
|
||
exchange to establish calls and other functions. In Australia for
|
||
example, ISDN may be delivered on a 2Mbps link that is broken into 30
|
||
discrete 64kbps B channels with one 64kbps D channel. Any number of
|
||
channels may be used at a time and in any combination. You could for
|
||
example establish 30 separate calls to 30 different destinations at
|
||
64kbps each, or you could establish 15 calls to 15 different
|
||
destinations at 128kbps each (two channels used per call), or just a
|
||
small number of calls and leave the rest idle. A channel may be used
|
||
for either incoming or outgoing calls. The original intention of ISDN
|
||
was to allow Telecommunications companies to provide a single data
|
||
service which could deliver either telephone (via digitised voice) or
|
||
data services to your home or business without requiring you to make
|
||
any special configuration changes.
|
||
</para>
|
||
|
||
<para>
|
||
There are a few different ways to connect your computer to an ISDN
|
||
service. One way is to use a device called a `Terminal Adaptor' which
|
||
plugs into the Network Terminating Unit that you telecommunications
|
||
carrier will have installed when you got your ISDN service and
|
||
presents a number of serial interfaces. One of those interfaces is
|
||
used to enter commands to establish calls and configuration and the
|
||
others are actually connected to the network devices that will use the
|
||
data circuits when they are established. Linux will work in this sort
|
||
of configuration without modification, you just treat the port on the
|
||
Terminal Adaptor like you would treat any other serial device.
|
||
Another way, which is the way the kernel ISDN support is designed for
|
||
allows you to install an ISDN card into your Linux machine and then
|
||
has your Linux software handle the protocols and make the calls
|
||
itself.
|
||
</para>
|
||
|
||
<para>
|
||
The Linux kernel has built-in ISDN capabilies. Isdn4linux controls
|
||
ISDN PC cards and can emulate a modem with the Hayes command set ("AT"
|
||
commands). The possibilities range from simply using a terminal
|
||
program to connections via HDLC (using included devices) to full
|
||
connection to the Internet with PPP to audio applications.
|
||
|
||
<20> FAQ for isdn4linux: http://ww.isdn4linux.de/faq/
|
||
</para>
|
||
|
||
<para>
|
||
<screen>
|
||
Kernel Compile Options:
|
||
|
||
ISDN subsystem --->
|
||
<*> ISDN support
|
||
[ ] Support synchronous PPP
|
||
[ ] Support audio via ISDN
|
||
< > ICN 2B and 4B support
|
||
< > PCBIT-D support
|
||
< > Teles/NICCY1016PC/Creatix support
|
||
</screen>
|
||
</para>
|
||
|
||
<para>
|
||
The Linux implementation of ISDN supports a number of different types
|
||
of internal ISDN cards. These are those listed in the kernel
|
||
configuration options:
|
||
</para>
|
||
|
||
<20> ICN 2B and 4B
|
||
<20> Octal PCBIT-D
|
||
<20> Teles ISDN-cards and compatibles
|
||
|
||
<para>
|
||
Some of these cards require software to be downloaded to them to make
|
||
them operational. There is a separate utility to do this with.
|
||
</para>
|
||
|
||
<para>
|
||
Full details on how to configure the Linux ISDN support is available
|
||
from the /usr/src/linux/Documentation/isdn/ directory and an FAQ
|
||
dedicated to isdn4linux is available at www.lrz-muenchen.de. (You can
|
||
click on the english flag to get an english version).
|
||
</para>
|
||
|
||
<para>
|
||
A note about PPP. The PPP suite of protocols will operate over either
|
||
asynchronous or synchronous serial lines. The commonly distributed PPP
|
||
daemon for Linux `pppd' supports only asynchronous mode. If you wish
|
||
to run the PPP protocols over your ISDN service you need a specially
|
||
modified version. Details of where to find it are available in the
|
||
documentation referred to above.
|
||
</para>
|
||
|
||
</sect1>
|