Non-Call Associated Signaling (NCAS)

• User-initiated call
• Network-initiated call

NCAS allows users to communicate by means of user-to-user signaling without setting up a circuit-switched connection (it does not occupy B channel bandwidth). A temporary signaling connection is established and cleared in a manner similar to the control of a circuit-switch connection.

NOTES:

1. This feature is supported for the 5ESS protocol only

2. For more on NCAS, refer to Technical Reference 41459, AT&T Network ISDN Primary Rate and Special Application Specification.

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 successfully, 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.

The following figures provide line diagrams that illustrate the operation of the NCAS feature.

Figure 9.  User-Accepted Network-Initiated NCAS Request

Figure 10.  User-Rejected Network-Initiated NCAS Request

Figure 11.  User-Disconnected NCAS Call

The following scenarios demonstrate the procedures for a user-initiated and a network-initiated NCAS call.

User-initiated call

In the following scenario, the user initiates and disconnects the NCAS call for dtiB1.

Synchronous Programming

Application	Device Driver	State	Firmware	Network
cc_Open( ) -->		NULL
	Return with line device <--
Set up NCAS call parameter in MAKECALL_BLK
	Return <--
cc_MakeCall( ) D-channel line devices (dtiB1T24) -->
	CALL_OUTGOING -->		Setup -->
	CCEV_CONNECTED <--	CONNECTED		Connect <--
NCAS call connected
cc_SetInfoElem( ) setup user-to-user information, D-channel line devices (dtiB1T24) -->
cc_SndMsg( ) send User-to-user signaling -->	CALL_UUI -->		UUI -->
	CCEV_USRINFO <--		CALL_UUI <--	UUI <--
cc_GetCallInfo( ) retrieve user-to-user information -->
cc_DropCall( ) -->	CALL_DISCONNECTED -->	IDLE	Release -->
	CCEV_DROPCALL <--		CALL_CLEARED <--
cc_ReleaseCall( ) -->	CALL_DEALLOC -->			Rel_Comp <--
	Driver releases CRN return	NULL	CALL_DEALLOC_ACK <--

The following code samples demonstrate the use of the Dialogic API at various stages of the NCAS call scenario.

1. Opening a D channel line level device:

LINEDEV     D_chan_dev1_hdl;  
      .  
      .  
 rc = cc_Open( &D_chan_dev1_hdl, "dtiB24", 0);  
      .

2. Setting up the MAKECALL_BLK for an 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.

Synchronous Programming

Application	Device Driver	State	Firmware	Network
cc_Open( ) D channel line devices (dtiB1T24) -->		NULL
	Return with line device <--
cc_WaitCall( ) D-channel line devices (dtiB1T24) -->
	CCEV_OFFERED D-channel line devices (dtiB1T24) <--	OFFERED	CALL_INCOMING <--	Setup <--
cc_AnswerCall( ) -->	Call_Connect -->	CONNECTED	Connect -->
NCAS call connected
cc_SetInfoElem( ) setup user-to-user information, D channel line devices (dtiB1T24) -->
cc_SndMsg( ) send user-to-user signaling -->	CALL_UUI -->		UUI -->
	CCEV_USRINFO <--		CALL_UUI <--	UUI <--
cc_GetCallInfo( ) retrieve user-to-user information
		IDLE		Release <--
			Release Comp -->
	CCEV_DISCONNECT <--		CALL_DISC <--
cc_DropCall( ) -->	CALL_DISCONNECTED -->
	CCEV_DROPCALL <--		CALL_CLEARED <--
cc_ReleaseCall( ) -->	CALL_DEALLOC -->
	Driver releases CRN return	NULL	CALL_DEALLOC_ ACK <--

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