Configure ISDN interfaces
Digi TransPort User Guide
242
ISDN LAPD parameters
This page allows you to configure the ISDN LAPD interfaces. Link Access Protocol D (LAPD) is the
protocol used for ISDN D-channel signaling and call setup.
LAPD 0 and LAPD 1 can be used as required for SAPI 16 traffic (such as X.25 over D-channel).
LAPD 2 is normally reserved for ISDN call control.
Enable LAPD n
Disabling this parameter disables the LAPD instance. This may be necessary if you have an
installation where two or more routers are connected to the same ISDN
S
bus. In this case,
only one of the routers may be configured for D-channel X.25 on TEI1, SAPI16. On each of the
other routers 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
router.
When checked, this check box will also reveal the following configuration parameters.
Mode
When the DTE/DCE mode parameter is set to DTE, the router behaves 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 routers back-to-back, one of the routers should have the
DTE mode value set to DCE.
N400 Counter
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
The 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
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
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
The transmit window size when using D-channel X.25. The default is 7.
