NMS SCCP functions

NMS SCCP provides two sets of functions:

• Service functions

• Management functions

Service functions

The SCCP service functions provide the application access to the SCCP layer services. Applications invoke SCCP services by calling SCCP request functions that send an SCCP message to a remote exchange or signaling point (SP). Request function parameters are converted to messages. The device driver sends these parameters to the SCCP task.

The SCCP 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 SCCP service 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 SCCP 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 returning a connect confirm message in response to a connection request.

Indication and confirmation messages, as well as status messages from the local SCCP layer, are passed to application processes as asynchronous events. All events for a particular user service access point are delivered through the associated Natural Access queue. For more information about queues, refer to the Natural Access Developer's Reference Manual.

Applications detect that an event is pending through an operating system specific mechanism such as poll in UNIX or WaitForMultipleObjects in Windows. The application retrieves the event data (or message) through a function that also translates the confirmation parameters from SS7 SCCP raw format to API format.

The following table lists the SCCP service connectionless data transfer functions and events:

The following table lists the SCCP service connection-oriented data transfer functions and events:

Management functions

Unlike the SCCP service functions that send and receive messages asynchronously, each SCCP management function generates a request followed immediately by a response from the TX board. SCCP management functions block the calling application waiting for this response (for a maximum of five seconds, but typically a few hundred milliseconds) and return an indication as to whether or not an action completed successfully. For this reason, the SCCP management functions are typically used by one or more management applications. Separate applications use the SCCP service functions. SCCP management is packaged as a separate library with its own interface header files.

The following table lists the SCCP management and status functions and events: