User`s guide

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Configuration - Network > Interfaces > ISDN > LAPD > LAPD n
This page allows you to configure the ISDN LAPD interfaces. Link Access Protocol D (LAPD)
is the protocol used for ISDN D-channel signalling and call setup.
LAPD 0 and LAPD 1 can be used as required for SAPI 16 traffic (i.e. X.25 over D-channel).
LAPD 2 is normally reserved for ISDN call control.
Enable LAPD n
Un-checking this parameter will disable the LAPD instance. This may be necessary if you
have an installation where two or more units are connected to the same ISDN “S” bus. In
this case, only one of the units may be configured for D-channel X.25 on TEI1, SAPI16. On
each of the other units you must disable any LAPD instance for which the TEI is set to 1 in
order to prevent it from responding to X.25 traffic on that TEI that is actually destined for
another unit.
When checked, this check box will also reveal the following configuration parameters
Mode
When the DTE/DCE mode parameter is set to DTE, the unit will behave as a DTE. This is the
default value and should not be changed for normal operation across the ISDN network. If
your application involves using two units back-to-back, one of the units should have the
DTE mode value set to DCE.
N400 Counter
This is the standard LAPB/LAPD retry counter. The default value is 3 and it should not
normally be necessary to change this.
RR Timer n msecs
This is a standard LAPB/LAPD “Receiver Ready” timer. The default value is 10,000ms (10
seconds) and it should not normally be necessary to change this.
T1 Timer n msecs
This is the standard LAPB/LAPD timer. The default value is 1000 milliseconds (1 second) and
it should not normally be necessary to change this.
T200 Timer n msecs
This is the standard LAPB/LAPD re-transmit timer in milliseconds. The default value is 1000
milliseconds (1 second) and it should not normally be necessary to change this.
TEI
Each ISDN terminal device connected to your ISDN basic rate outlet must be assigned a
unique Terminal Endpoint Identifier (TEI). In most cases, this is negotiated automatically. In
some cases however, it may be necessary to assign a fixed TEI.
When TEI is set to 255, the TEI is negotiated with the ISDN network. To use a fixed TEI set
the TEI parameter to the appropriate value as specified by your service provider.
D-channel X.25 Tx Window Size
This specifies the transmit window size when using D-channel X.25. The default is 7.
Tx Throughput
The Tx Throughput parameter is used in conjunction with the Rx Throughput parameter to
limit the maximum data throughput on a LAPD link in bits per second.
If this parameter is set to 0, the unit will transmit data across the LADP link as fast as
possible whilst observing hardware or software flow control if enabled.
When set to a value greater than 0, the unit will limit the rate at which data is transmitted
over the LAPD link.