NaturalAccess™ ISUP provides service functions and management functions.
The ISUP service functions provide the application access to the ISUP layer services. Applications invoke ISUP services by calling ISUP request functions that send an ISUP message to a remote exchange or endpoint. Request function parameters are converted to messages. The host operating system TX driver sends these parameters to the ISUP task.
The ISUP requests from the remote endpoints are presented to the application as indications, using the same driver and mechanisms through which confirmations are received. The application issues a reply to the endpoint by invoking the appropriate ISUP response function.
All ISUP service functions are asynchronous. Completion of the function implies only that the function was successfully initiated (a request message was queued to the ISUP task). Errors detected by the ISUP 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 ISUP layer, are passed to application processes as asynchronous events. All events for a particular user service access point (subsystem) 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 ISUP raw format to API format.
For more information, refer to the Using the ISUP service section and the ISUP service function summary.
Unlike the ISUP service functions that send and receive messages asynchronously, each ISUP management function generates a request followed immediately by a response from the TX board. ISUP management functions block the calling application waiting for this response for a maximum of five seconds, but typically a few hundred milliseconds. The management functions return an indication as to whether or not an action completed successfully.
For this reason, ISUP management functions are typically used by one or more management applications. Separate applications use the ISUP service functions. ISUP management is packaged as a separate library with its own interface header files.
For more information, refer to the ISUP management function summary.