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 (see note below).
The Interface ID can be defined per 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 trunk, 1 for the second T1 trunk, and so on, up to the maximum number of trunks).
To define an explicit Interface ID for a T1 trunk (that is different from the default), use the following parameters:
| ■ | ISDNIBehavior_x = 512 (x = 0 to the maximum number of trunks identifying the device's physical trunk) |
| ■ | ISDNNFASInterfaceID_x = ID (x = 0 to 255) |
| ● | 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. |
| ● | 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. |