Non-Call Associated Signaling (NCAS) (synchronous Mode)

NCAS allows users to communicate by user-to-user signaling without setting up a circuit-switched connection (this signaling does not occupy B channel bandwidth). A temporary signaling connection is established (and cleared) in a manner similar to the control of a circuit-switched connection. This feature is supported for the 5ESS protocol only.

Since NCAS calls are not associated with any B channel, applications should receive and transmit NCAS calls on the D channel line device. Once the NCAS connection is established, the application can transmit user-to-user messages using the CRN associated with the NCAS call. The Dialogic software and firmware support 16 simultaneous NCAS calls per D channel.

Figure30, Figure31 and Figure32 provide line diagrams that illustrate the operation of the NCAS feature.

The NCAS scenarios are shown in Figure34, Figure35, and Figure36.

Figure 30. User-Accepted Network-Initiated NCAS Request

Figure 31. User-Rejected Network-Initiated NCAS Request

Figure 32. User-Disconnected NCAS Call

User-initiated call - in the following scenario, the user initiates and disconnects the NCAS call for dtiB1.

Figure 33. User-Initiated Call

Figure 34. NCAS Call Connected

The following example code illustrates the use of the GlobalCall API at various stages of the NCAS call scenario.

Opening a D channel line level device:

 LINEDEV     D_chan_dev1_hdl; 
      . 
      . 
 rc = gc_Open( &D_chan_dev1_hdl, ":N_dtiB24:P_isdn", 0); 
      . 

Setting up the MAKECALL_BLK for NCAS call:

 MAKECALL_BLK *makecallp; 
      . 
      . 
// initialize makecall block 
      makecallp->isdn.BC_xfer_cap              =  BEAR_CAP_UNREST_DIG; 
      makecallp->isdn.BC_xfer_mode             =  ISDN_ITM_PACKET;     
      makecallp->isdn.BC_xfer_rate             =  PACKET_TRANSPORT_MODE; 
      makecallp->isdn.usrinfo_layer1_protocol  =  NOT_USED; 
      makecallp->isdn.usr_rate                 =  NOT_USED; 
      makecallp->isdn.destination_number_type  =  NAT_NUMBER; 
      makecallp->isdn.destination_number_plan  =  ISDN_NUMB_PLAN; 
      makecallp->isdn.destination_sub_number_type     =  OSI_SUB_ADDR; 
      makecallp->isdn.destination_sub_phone_number[0] ='1234' 
      makecallp->isdn.origination_number_type  = NAT_NUMBER; 
      makecallp->isdn.origination_number_plan  = ISDN_NUMB_PLAN; 
      makecallp->isdn.origination_phone_number[0]   = '19739903000' 
      makecallp->isdn.origination_sub_number_type   = OSI_SUB_ADDR; 
      makecallp->isdn.origination_sub_phone_number[0] = '5678' 
      makecallp->isdn.facility_feature_service        =  ISDN_SERVICE; 
      makecallp->isdn.facility_coding_value    =  ISDN_SDN;  
// or ISDN_ACCUNET, please check with your service provider 
      makecallp->isdn.usrinfo_bufp             =  NULL; 
      makecallp->isdn.nsfc_bufp                =  NULL; 
            . 
            . 

Network initiated call - in the following scenario, the network initiates and disconnects the NCAS call for dtiB1.

Figure 35. Network Initiated Call

Figure 36. NCAS Call Connected

The following example code illustrates the use of the GlobalCall API to open a D channel line level device in the preceding NCAS call scenario.

 LINEDEV     D_chan_dev1_hdl; 
      . 
      . 
 rc = gc_Open( &D_chan_dev1_hdl, ":N_dtiB24:P_isdn", 0); 
      . 

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