NAME
ppp.Devices — PPP physical device description file format
DESCRIPTION
The file
/etc/ppp/Devices
associates dialer types with physical devices and
speeds.
pppd
examines it when placing a call to a neighboring machine.
If no suitable
speed is found, or if all devices associated with that speed are busy,
pppd
will try again later.
Format
Entries are one to a line; blank lines are ignored.
Comments begin with a
#
and extend to the end of the line.
Upper/lower case distinctions are significant.
Fields on a line are separated by horizontal white space (blanks or
tabs).
Each entry must contain three or more fields, in this order:
- dialer
Either the string
Direct,
or the name of the modem dialing chat script
(found in
Dialers)
to use with this device,
or the name of an external dialer program.
- device
The name of the device in the
/dev
directory
(ttya,
cua,
etc.).
Device names for SnapLink connections are followed by a slash and
the port number in use
(rsd2a/0,
rrz4a/2,
etc.).
- speed
The baud rate of the synchronous connection, or a string to be matched
against the speed field of entries in
Systems
when the
Systems
device field is set to ACU.
Speeds must either be valid async
baud-rate numbers (as found in
<sys/ttydev.h>)
or must begin with them
(2400, 38400, 19200-PEP, etc.), or must be speeds of which the
SnapLink hardware is capable (9600, 56000, 64000, 1536000, etc.)
- optional parameters
Any special handling for this device.
Currently supported values
include:
- xonxoff
Specifies that the line be conditioned for in-band (software)
flow control, using the characters DC3 (^S, XOFF, ASCII 0x13) to stop the
flow and DC1 (^Q, XON, ASCII 0x11) to resume.
The default is to use
no flow control.
For an outbound connection, this may be specified
either in
Devices
or on the
pppd
command line.
- internal-clocking
The SnapLink
will provide the synchronous clock signal.
By default,
it expects the modem, CSU/DSU or modem eliminator to provide the
clock signal.
Internal-clocking cannot be used with RS-232
cables on the SnapLink.
- 32-bit-fcs
The SnapLink
will calculate 32-bit FCS values for transmitted frames, and check
received frames with 32-bit FCS
calculations.
This is not negotiable at connection establishment
time.
32-bit FCS is only available when running synchronous PPP on
the SnapLink.
- min-flags=minflags
The number of additional HDLC flag characters the SnapLink should
insert between data frames.
The default and minimum is 2; the maximum
is 16.
- ignore-cd
Ignore the state of the CD (Carrier Detect, also called DCD, Data
Carrier Detect) signal.
This is useful for systems that don't support
CD but want to run PPP over a dedicated line.
External Dailer
The external dialer program is run with the following arguments:
- device name
The contents of the Device field from the Devices entry.
- speed
The contents of the Speed field of the Systems and Devices entries.
- telephone number
The contents of the Phone Number field of the Systems entry.
- optional parameters
Copied from the Optional Parameters section of the Devices entry.
If the external dialer program exits with status 0, then the dial
attempt is considered to have succeeded.
Any other exit status
indicates a failure.
EXAMPLES
#
# Devices - PPP devices file
#
#Dialer device speed Optional parameters
T2500-PEP cua 19200-PEP rtscts
T1600 cub 38400 rtscts
Direct rsd0a/0 1536000 internal-clocking
Oddball rsd0a/1 64000 cua 9600 5551212
In the last line of this example, the 64Kb synchronous modem on the
SnapLink's port 1 has an asynchronous dialer interface attached to the
workstation's port
a.
The Systems line would look like
host Oddball rsd0a/1 64000 0
There must be a program (or an executable shell script) called
/etc/ppp/Oddball
that dials the modem when invoked as
Oddball rsd0a/1 64000 0 cua 9600 5551212
A warning message will be printed for each unrecognized optional
parameter if the
debug
level is 2 or more.
The external dialer is invoked as
root,
so you should take
appropriate security precautions with its content and file protection.
AUTHOR
ppp.Devices
was developed by the Progressive Systems.
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