User`s manual

H.323 User's Manual 10. Advanced PSTN Configuration
Version 5.0 295 December 2006
10.3.1 NFAS Interface ID
Several ISDN switches require an additional configuration parameter per T1 trunk that is
called ‘Interface Identifier’. In NFAS T1 trunks the Interface Identifier is sent explicitly in
Q.931 Setup / Channel Identification IE for all NFAS trunks, except for the B-channels of
the Primary trunk (refer to note 1 below).
The Interface ID can be defined per each member (T1 trunk) of the NFAS group, and must
be coordinated with the configuration of the Switch.
The default value of the Interface ID is identical to the number of the physical T1 trunk (0
for the first Mediant 1000 trunk, 1 for the second Mediant 1000 T1 trunk, and so on).
To define an explicit Interface ID for a T1 trunk (that is different from the default), use the
following parameters:
 ISDNIBehavior_x = 512 (x identifies the Mediant 1000 physical trunk)
 ISDNNFASInterfaceID_x = ID (x = 0 to 255)
Note 1: Usually the Interface Identifier is included in the Q.931 Setup/Channel
Identification IE only on T1 trunks that doesn’t contain the D-channel. Calls
initiated on B-channels of the Primary T1 trunk, by default, don’t contain the
Interface Identifier. Setting the parameter ‘ISDNIBehavior_x’ to 2048’
forces the inclusion of the Channel Identifier parameter also for the Primary
trunk.
Note 2: The parameter ‘ISDNNFASInterfaceID_x = ID’ can define the ‘Interface ID’
for any Primary T1 trunk, even if the T1 trunk is not a part of an NFAS
group. However, to include the Interface Identifier in Q.931 Setup/Channel
Identification IE configure ‘ISDNIBehavior_x = 2048’ in the ini file.
10.3.2 Working with DMS-100 Switches
The DMS-100 switch requires the following NFAS Interface ID definitions:
 InterfaceID #0 for the Primary trunk
 InterfaceID #1 for the Backup trunk
 InterfaceID #2 for a 24 B-channel T1 trunk
 InterfaceID #3 for a 24 B-channel T1 trunk
 Etc.
For example, if four T1 trunks on a gateway are configured as a single NFAS group, with
Primary and Backup T1 trunks, that is used with a DMS-100 switch, the following
parameters should be used:
NFASGroupNumber_0 = 1
NFASGroupNumber_1 = 1
NFASGroupNumber_2 = 1
NFASGroupNumber_3 = 1
DchConfig_0 = 0 ;Primary T1 trunk
DchConfig_1 = 1 ;Backup T1 trunk
DchConfig_2 = 2 ;B-Channel NFAS trunk
DchConfig_3 = 2 ;B-channel NFAS trunk