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NAMEppp.Systems — PPP neighboring systems description file format DESCRIPTIONThe file
/etc/ppp/Systems
describes how to connect with neighboring systems via PPP. FormatEntries 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 ignored in hostname specifications,
but are significant elsewhere.
Fields on a line are separated by horizontal white space (blanks or
tabs).
If a chat script ends with a backslash
(\),
the next line is
considered a continuation of the chat script.
Continuations may only
occur in the midst of a chat script. Each entry must contain six fields, in the following order:
- name
The hostname or IP address of the destination machine, which should be resolvable locally. - when
A string that indicates the days of the week and the times of day when
the system can be called (for example, MoTuTh0800-1740).
The day
portion may be a list containing any of Su, Mo, Tu, We, Th, Fr or Sa.
The day may also be Wk for any weekday (same as MoTuWeThFr) or Any for
any day (same as SuMoTuWeThFrSa). You can indicate hours in a range (for example, 0800-1230).
If you do
not specify a time, calls will be allowed at any time. Note that a time range that spans 0000 is permitted.
For example,
0800-0600 means that all times are allowed except times between 6 AM
and 8 AM. Multiple date specifications that are separated by a vertical bar (|)
are allowed.
For example, Any0100-0600|Sa|Su means that the system
can be called any day between 1 AM and 6 AM or any time on Saturday
and Sunday. The entire (sequence of) days and times may be followed by a semicolon
and up to three decimal numbers separated by hyphens:
- one
If only one number follows the semicolon, it is used as the redial
delay, which is
the initial time (in seconds) before a failed call will be
retried.
For example, Any;60 means call any time, but wait at least
60 seconds after a failure has occurred before trying to call again.
If a call retry fails,
pppd
will double the delay before trying
again.
If no initial retry delay
is specified, 10 seconds is assumed. - two
If two numbers follow the semicolon, the second number is used as the
maximum redial delay, which is the maximum time
(in seconds) to delay before retrying a call.
The retry time will
double with each unsuccessful call until it reaches this value, after
which the call will be retried every time the maximum number of
seconds passes.
If no maximum retry delay is specified, 3600 seconds
is assumed. - three
If three numbers follow the semicolon, the first is used as
the callback delay, the second as the redial delay, and the third as
the maximum redial delay.
The callback delay is the time (in seconds)
to wait before attempting to re-establish a previously active
connection that ended because of an abrupt line disconnection (a
Hangup or SIGHUP event in the log file).
The default is not to delay
before calling back.
During the delay following an unsuccessful call, any level 7 debugging
messages written to
pppd.log
will have the message
dial failed
appended. - device
If set to
ACU,
any device in
Devices
with a matching speed may be used.
The device's dialer chat script
will be executed first, followed by the
Systems
chat script. If set to the name of a device in the
/dev
directory
(tty00,
cua,
etc.), then there may be an optional
corresponding
Direct
entry in
Devices,
Dialers
will not
be consulted, and only the
Systems
chat script will be executed. If set to
tcp,
then it must be followed by a slash, then the
hostname or IP address of the system that will serve as the
destination of the PPP link, then another slash, then the socket
number on which to contact the remote PPP daemon. - speed
The speed of the connection.
If the device field is ACU, the speed field will be
string matched against entries in
Devices.
Speeds must either be valid speed numbers
or must begin with them (2400, 38400, 19200-PEP, etc.).
If the device field is
tcp ...
or
telnet ...,
the speed field is
ignored, but must be present as a place-holder. - phone number
The value to replace the
\T
escape sequence in the dialer
script.
If the device field names an entry in
/dev,
the phone number
field is optional.
If the device field is
tcp ...
or
telnet ...,
the phone number
field is ignored if present, but must be present as a placeholder. - chat script
A description of the conversation that
pppd
holds with the remote machine.
Chat Script ParticularsA chat script takes the form of a word to expect
the remote end to send, followed by a word to send in response.
Unless
a
send
string ends with
\c,
pppd
will follow it by sending a carriage return character (ASCII 0x0d). Chat scripts are
expect send expect send ...
or
expect-send-expect send ...,
where the send following the hyphen is executed if the
preceding expect fails to match received text. Certain special words may be used in chat script
send
strings to
control the behavior of
pppd
as it attempts to dial.
Both ABORT
and TIMEOUT
must be in the
expect
phase of the chat script.
- ABORT abort-string
If
pppd
sees abort-string while executing the remainder of the chat
script, abort the dialing attempt and note the failure in the log
file. - TIMEOUT timeout-time
While executing the current chat script, wait timeout-time
seconds for an expected response before regarding the dialing attempt as
having failed.
Writes have a fixed 60-second timeout.
The expect-send couplet of '"
'
P_WORD
sets the line parity accordingly:
- P_AUTO
Set transmission parity based on the parity observed in characters
received in
expect
strings.
This is the default. - P_ZERO
Transmit characters with the parity bit set to zero (8 bits, no parity). - P_ONE
Transmit characters with the parity bit set to one. - P_EVEN
Transmit characters with even parity. - P_ODD
Transmit characters with odd parity.
The backquote character
(`)
surrounds the name of a program that
is to be run before proceeding.
If the program is run in the
send
phase of a chat script couplet, its standard output will be sent to
the peer when the program exits.
Chat script processing continues
when the program exits. In the midst of either an
expect
string or a
send
string,
^x
gets translated into the appropriate control character,
and
\x
gets translated into
x.
Other special sequences are:
- \s
Send or receive a space character (ASCII 0x20). - \t
Send or receive a horizontal tab character (ASCII 0x09). - \n
Send or receive a line feed character (ASCII 0x0a). - \r
Send or receive a carriage return character (ASCII 0x0d). - \\
Send or receive a backslash character (ASCII 0x5c). - \^
Send or receive a carat character (ASCII 0x5e). - ^character
Send or receive the single character Ctrl-character (ASCII 0x00
through 0x1f). - \ddd
Send or receive a character, specified in octal digits. - \p
Pause for .25 second before proceeding (send only). - \d
Delay for two seconds before proceeding (send only). - \K
Send a break (.25 second of zero bits). - \M
Disable hangups (sets CLOCAL or LNOHANG). - \m
enable hangups (unsets CLOCAL or LNOHANG) (the default). - \c
Don't append a carriage return character after sending the preceding string (send only). - \q
Don't print following send strings (e.g., a password) in any debugging
or logging output.
Subsequent
\q
sequences toggle
quiet
mode. - \A
Parse the incoming string as an IP address, written as four decimal
numbers separated by periods, and use it for the local end of the
point-to-point connection (receive only).
EXAMPLESIn the example below, we call host
everyone
using a Telebit PEP
modem with its DTE interface set at 19200 bps.
We call host
nobody
using a V.32/V.42/V.42bis modem that's capable of driving a 38400 DTE,
and we are connected to host
someone
via a direct cable attached to
/dev/ttya,
running asynchronous PPP.
We talk to
anyone
via a T1
CSU/DSU attached to port 0 on a SnapLink.
And we connect with
pseudo-one via a PPP connection tunneled
across a TCP stream to port
77 on realone.somewhere.com. If we are unsuccessful at connecting with
someone
we will try again
in two seconds.
If that attempt fails, we will wait four seconds
before the next attempt; then eight, then sixteen, then thirty two,
then forty seconds.
We will continue attempting to contact
someone
every forty seconds.
Our retry intervals and maximum backoff values
for
everyone
and
nobody
are the default
10-3600. The notation "" "" means to expect nothing, then send nothing
(followed by a carriage return).
The implicit carriage return is
often useful for eliciting a response from a remote system.
#
# Systems - PPP systems file
#
everyone Any ACU 19200-PEP 5551212 in:--in: Pwe word: \qfoObar
nobody Any ACU 38400 5551213 in:--in: Pthey word: \qbaZz1ng
someone Any;2-40 cua 38400 0 in:--in: Pthem word: \qmeumBle
anyone Any rsd0a/0 1536000
pseudo-one Any;2-2 tcp/realone.somewhere.com/57 RECOMMENDATIONSThe default retry time and backoff (i.e., Any;10-3600) are appropriate
for use with dialup connections where the PPP connection must be
reestablished as quickly as possible after an interruption but where
it is not desirable to continuously redial a host that may be down.
A much shorter maximum would be appropriate for a dedicated
line between two systems, or where call attempts cost nothing. Moderate
call retry times, such as 60 seconds, work well on systems that can
establish connections in either direction using dialup modems, to
avoid deadlocks waiting for telephone busy signals from each calling
the other at the same time.
Because of the difference between the
behaviors of originating and answering modems, the 60-second clocks
will usually start ticking at different times, allowing one side to
call the other without interference.
Alternatively, different call
retry times may be specified at either end of a link to help keep
the two systems from calling each other simultaneously. If you specify host names,
be sure that their addresses are available locally, even with the
connection down.
If you find that you must bring up a connection to
resolve a domain name, consider using that host's IP address (decimal
numbers separated by periods) in both
Filter
and
Systems
instead. Automatic failover
recovery can be arranged between systems that each have multiple
modems, or multiple connection methods.
If two systems are connected
via a dedicated
line (sync or async), that entry should be first in
Systems,
followed by another entry describing an on-demand dial-up connection.
See the
HP PPP User Guide
for more details. SECURITY CONCERNSThe file
/etc/ppp/Systems
should be mode 600. AUTHORppp.Systems
was developed by the Progressive Systems. |
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