Natural Access organizes services and their associated resources around a processing object known as a context. Each instance of an application binding to an ISUP service access point is a unique Natural Access context. Contexts are created with ctaCreateContext.
All events and messages from the ISUP service are delivered to the application through a Natural Access queue object. Queues are created with ctaCreateQueue. Each context is associated with a single queue through which all events and messages belonging to that context are distributed.
ISUP supports a single-context, single-queue application programming model, as shown in the following illustration: