Making Outgoing Calls

If an application attempts to make an outgoing call, it must first open a line. A line is opened as a result of an application calling the TAPI lineOpen function. To place a telephony call on the previously opened line, the application calls the TAPI lineMakeCall function and passes a pointer to the specific destination address. If anything but default call-setup parameters are requested, the application also passes a pointer to a LINECALLPARAMS structure. If the application uses default call-setup parameters, lineMakeCall provides those parameters in a LINECALLPARAMS structure. Members of this structure specify how the telephony call should be set up.

These TAPI-function calls cause the NDPROXY driver to first create a virtual connection (VC) with the CoNDIS WAN miniport driver and then to encapsulate TAPI parameters in NDIS structures in order to make the outgoing call. The miniport driver will use these TAPI parameters to set up the outgoing call. The following describes how the outgoing call is connected, set up, and made:

• NDPROXY calls NdisCoCreateVc to initiate the creation of the VC with the miniport driver. After NDPROXY calls NdisCoCreateVc, NDIS calls, as a synchronous operation, the ProtocolCoCreateVc function of the call manager integrated into the miniport driver. NDIS passes to ProtocolCoCreateVc a handle that represents the VC. If the call to NdisCoCreateVc is successful, NDIS fills and returns the VC handle. ProtocolCoCreateVc performs any necessary allocations of dynamic resources and structures that the miniport call manager (MCM) driver requires to perform subsequent operations on the VC that will later be activated. Such resources include, but are not limited to, memory buffers, data structures, events, and other such similar resources.

• NDPROXY specifies the TAPI parameters for an outgoing call in a CO_AF_TAPI_MAKE_CALL_PARAMETERS structure. NDPROXY fills this structure's members with the following information that was passed in the TAPI lineMakeCall function:

  • The destination address in the DestAddress member
  • The open-line identifier in the ulLineID member
  • The LINECALLPARAMS structure in the LineCallParams member

• NDPROXY overlays the CO_AF_TAPI_MAKE_CALL_PARAMETERS structure on the Parameters member of a CO_SPECIFIC_PARAMETERS structure and sets the Length member of CO_SPECIFIC_PARAMETERS to the size of CO_AF_TAPI_MAKE_CALL_PARAMETERS.

• NDPROXY sets the CO_SPECIFIC_PARAMETERS structure to the MediaSpecific member of a CO_MEDIA_PARAMETERS structure.

• NDPROXY sets a pointer to the CO_MEDIA_PARAMETERS structure to the MediaParameters member of a CO_CALL_PARAMETERS structure.

• Once NDPROXY encapsulates TAPI parameters, NDPROXY calls the NdisClMakeCall function to initiate the outgoing call. In this function call, NDPROXY passes a pointer to the filled CO_CALL_PARAMETERS structure. NDIS in turn calls the ProtocolCmMakeCall function of the CoNDIS WAN miniport driver's call manager. The miniport driver should examine only the CO_AF_TAPI_MAKE_CALL_PARAMETERS structure embedded in CO_CALL_PARAMETERS. No other call parameters are meaningful in this case. If the miniport driver subsequently activates the VC for the outgoing call, the miniport driver calls the NdisMCmActivateVc function and passes a pointer to the filled CO_CALL_PARAMETERS.

• After the miniport driver has negotiated with the network to establish the telephony-call parameters for the VC and set up a NIC for those call parameters, the miniport driver calls the NdisMCmMakeCallComplete function to indicate that it is ready to make data transfers on the VC. In this call, the miniport driver must pass the handle to the VC and modifications made to telephony-call parameters.

• The miniport driver must modify the CallMgrParameters member of the CO_CALL_PARAMETERS structure to specify the quality of service (QoS) of transferring packets, such as the bandwidth. To set this CallMgrParameters member, the miniport driver fills members of a CO_CALL_MANAGER_PARAMETERS structure and points this structure to CallMgrParameters. For example, to identify the transmit and receive speeds in bytes per second for the VC, the miniport driver must set the PeakBandwidth members of the Transmit and Receive members of CO_CALL_MANAGER_PARAMETERS. The Transmit and Receive members are FLOWSPEC structures. For more information about the FLOWSPEC structure, see the Microsoft Windows SDK.

• If the miniport driver has modified telephony-call parameters, it must set the Flags member in the CO_CALL_PARAMETERS structure with CALL_PARAMETERS_CHANGED. As a result of the NdisMCmMakeCallComplete call made by the miniport driver, NDIS calls NDPROXY's ProtocolClMakeCallComplete function to complete the asynchronous operations that were initiated with NdisClMakeCall.

• After the miniport driver successfully completes the outgoing call, NDPROXY notifies a TAPI application that the call is connected. This TAPI application then calls the TAPI lineGetID function to inform NDPROXY to locate the appropriate CoNDIS client. In this lineGetID call, the TAPI application supplies a string for a particular TAPI device class to which the application requires a handle. NDPROXY uses this string to locate the CoNDIS client that previously registered a SAP for the particular TAPI device class. If the CoNDIS client is NDISWAN, the string is NDIS. If NDPROXY locates a SAP with a string that matches the string passed by the TAPI application, NDPROXY calls NdisMCmCreateVc to set up a connection endpoint with NDISWAN on which it can dispatch notification of the outgoing call that was made. NDIS in turn calls NDISWAN's ProtocolCoCreateVc function and passes a handle that represents the VC.

• After NDPROXY sets up the connection endpoint with NDISWAN, it calls the NdisCmDispatchIncomingCall function to notify NDISWAN about the outgoing call. In this call, NDPROXY passes the encapsulated CO_AF_TAPI_MAKE_CALL_PARAMETERS structure that contains the outgoing call parameters. NDIS in turn calls NDISWAN's ProtocolClIncomingCall function, within which NDISWAN either accepts or rejects the requested connection. If NDISWAN changes the call parameters passed to it, it must set the Flags member in the CO_CALL_PARAMETERS structure with CALL_PARAMETERS_CHANGED.

• After deciding whether to accept the connection and after possibly changing the call parameters, NDISWAN calls the NdisClIncomingCallComplete function. NDIS in turn calls the miniport driver's ProtocolCmIncomingCallComplete function. Depending on whether NDISWAN accepted the outgoing call and whether the miniport driver accepts or rejects NDISWAN's proposed changes to the call parameters, the miniport driver calls either NdisCmDispatchCallConnected or NdisCmDispatchIncomingCloseCall functions. NdisCmDispatchCallConnected notifies NDISWAN that data transfers can begin on the VC that NDPROXY created for the outgoing call. NdisCmDispatchIncomingCloseCall informs NDISWAN and NDPROXY to tear down the proposed outgoing call.

• After NDISWAN accepts the outgoing call, NDPROXY calls the NdisCoGetTapiCallId function to retrieve a string that identifies NDISWAN's context for the VC. NDPROXY passes this string back to the TAPI application. The TAPI application uses this VC-context string to complete its call to lineGetID.