NMS TCAP provides two sets of functions:
The TCAP service functions provide the application access to the TCAP layer services. Applications invoke TCAP services by calling TCAP request functions that generally result in a TCAP message to a remote exchange, or signaling point (SP). Request function parameters are converted to messages and sent through the device driver to the TCAP task.
The TCAP requests from the remote signaling points are presented to the application at the receiving side as indications.
The receiving application then issues a reply to the originating signaling point by invoking the appropriate TCAP response function. The response function is typically translated by the SCCP layer into a protocol message back to the originating signaling point. That response is presented back to the application as a confirmation.
This communication model is shown in the following illustration. Some operations, such as sending unit data, include only the request or indication steps. These operations are called unconfirmed operations.
All TCAP service functions are asynchronous. Completion of the function implies only that the function was successfully initiated (a request message was queued to the SCCP task). Errors detected by the SCCP task result in asynchronous status indications being sent to the application. Successfully delivered requests generally result in no notification to the application until the far end takes some corresponding action such as responding to a transaction invoke component with a return-result component.
Indication and confirmation messages, as well as status messages from the local TCAP layer, are passed to application processes as asynchronous events. All events for a particular user SAP (subsystem) are delivered through the associated Natural Access queue. For information about queues, refer to the Natural Access Developer's Reference Manual.
Applications detect that an event is pending through a call to ctaWaitEvent. The application retrieves the event data through a function that translates the event parameters from SS7 TCAP raw format to API format.
For more information, refer to the TCAP service function summary.
Unlike the TCAP service functions that send and receive messages asynchronously, each TCAP management function generates a request followed immediately by a response from the TX board. TCAP management functions block the calling application waiting for this response (typically a few hundred milliseconds) and return an indication as to whether or not an action completed successfully. For this reason, the TCAP management functions are typically used by one or more management applications, separate from the applications that use the TCAP service functions. TCAP management is packaged as a separate library with its own interface header files.
For more information, refer to the TCAP management function summary.