PSTN(9) XR32 REFERENCE MANUAL 2/2/2013
NAME
PSTN -- PSTN Modem Support.
DESCRIPTION
The following text describes a facility which was inherited
from DOS XRouter, but which probably has no relevance
nowadays?...
XR32 may be connected to one or more Public Switched Telephone
Network (PTSN) modems, for dial-in and dial-out operations.
Dial-in would, for example, allow users and/or sysops to
connect to XR32 and operate it using a dumb terminal or a
standard terminal package such as Telix or Hyperterm.
Alternatively, after login, the link may be switched into SLIP
or PPP mode for TCP/IP operations, behaving in exactly the
same way as a dial-up Internet Service Provider.
Dial-out allows Xrouters to be linked with each other or with
an Internet service provider, for the purposes of on-demand
wired routing, or Internet Connection Sharing.
A single modem may be used for both dial-in and dial-out
operations on the same port, although not at the same time
of course!
Suitable Modem Types
~~~~~~~~~~~~~~~~~~~~
Almost any modem is suitable, providing it can be initialised
by a single string of characters and can be configured to
disconnect when DTR is dropped.
Hardware Configuration
~~~~~~~~~~~~~~~~~~~~~~
External modems should be connected to a serial port using a
cable with at least 8 connections, namely TXD, RXD, RTS, CTS,
DTR, DSR, DCD and ground. The RI (ring indicator) connection
is not needed.
Internal modems should be configured to use a spare COM
number and IRQ.
Software Configuration
~~~~~~~~~~~~~~~~~~~~~~
Each modem requires an ASYNC interface definition in
XROUTER.CFG, with COM (or IOADDR & IRQ if non-standard)
configured for the appropriate serial port or modem card.
You should use PROTOCOL=MODEM, FLOW=1 and MTU=576.
To each "modem" interface should be attached a PORT with at
least INTERFACENUM and ID specified. If the modem requires an
initialisation string, add INITSTR=<initstring>, e.g. to set
the modem into auto answer mode use "INITSTR=ATS0=1". If you
don't include the INITSTR keyword, the modem configuration is
not altered.
If your modem does not, by default, hang up when the RS232 DTR
signal is dropped, you should configure it to do so by
including "&D2" in the initialisation string, for example:
"INITSTR=ATM0S0=1&D2".
Example MODEM Interface and Port Configuration
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In XROUTER.CFG:
INTERFACE=5
TYPE=ASYNC
COM=3
SPEED=57600
PROTOCOL=MODEM
FLOW=1
MTU=576
ENDINTERFACE
PORT=2
ID=PSTN Modem port
INTERFACENUM=5
INITSTR=ATS0=1
ENDPORT
If you will be allowing incoming calls, you must set up a
callsign and password entry for each user in USERPASS.SYS.
Dial-in Operation
~~~~~~~~~~~~~~~~~
If you have configured the modem for auto-answer, PSTN callers
must successfully complete a callsign and password challenge
before they are allowed to use the XR32 command interface.
The callsign must be a proper amateur radio callsign, i.e. not
a "username". If a valid callsign is not given, or if the
callsign is not found in USERPASS.SYS, or if an incorrect
password is supplied, the user is immediately disconnected.
If this sounds unforgiving, it is meant to be! It will cost
hackers the price and time delay of a separate phone call for
each attack.
If the callsign and password challenge is successfully
completed, the caller will be allowed full access to the
command shell, exactly the same as a radio caller.
XR32 will disconnect the caller after 15 minutes of
inactivity. You may initialise the modem to disconnect after
a shorter interval if necessary.
The XLINK command
~~~~~~~~~~~~~~~~~
If the caller (e.g. using NOS) wishes to establish a TCP/IP
link with XR32, the XLINK command is used to switch the ASCII
link into SLIP ("XLINK SLIP") or PPP ("XLINK PPP") mode.
XR32 will respond with "Entering SLIP mode" or "Entering PPP
mode", and will thereafter no longer respond to ASCII
commands. SLIP or PPP mode may only be terminated by
disconnection.
In order to use SLIP or PPP modes, XR32 must have at least
a global IPADDRESS, and you must set up IP routing to the
caller's IP address on the modem port. You could either allow
each caller to use their own IP address, and have one routing
entry for each caller, or you may choose to require all
callers on a particular port to use the same IP address (since
only one may connect at any time) and set up a single routing
entry.
For example, you could tell each of your SLIP/PPP callers to
set their IP address to 192.168.73.88, which is one of the
"unregistered" addresses anyone can use. If your modem is on
port 2, you would add the following entry to IPROUTE.SYS:
route add 192.168.73.88/32 * 2 d
Which means "route datagrams for 192.168.73.88 directly on
port 2 using datagram mode".
No ARP entry is necessary for the caller, because SLIP and PPP
do not use "hardware addresses".
XLINK PPP mode
~~~~~~~~~~~~~~
XLINK SLIP mode requires no extra configuration, but PPP mode
optionally uses an extra file to configure the PPP system for
receive operations on the modem port. For example, you may
wish to use one IP address when making outgoing connects and a
different one when receiving incoming connects.
The optional file is named "PPPHOST.n" where n is the number
of the modem port, e.g. "PPPHOST.2". You may have a separate
file with a different configuration for each modem port if
required. The file should be located in the same directory as
XR32 itself and may contain any PPP configuration command.
See the description of PPP commands for details of how to
configure PPP.
The PPP link inactivity timeout defaults to 5 mins, but can
be overridden by including the PPP IDLE command in the
PPPHOST.n file.
SEE ALSO
DIAL(1) -- Dial a PSTN Connection
DUN(1) -- Dial Up Networking Commands.
PPP(1) -- PPP Configuration Commands.
PPPHOST.n(8) -- PPP Configuration File(s)
XLINK(1) -- The XLINK Command.
XROUTER.CFG(8) -- Main Configuration File.
PSTN(9) END OF DOCUMENT
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