The SS7 TUP task provides the interface for applications to establish, maintain, and clear circuit switched connections through the SS7 network in accordance with the ITU-T (CCITT) recommendations Q.721-Q.725 and GF 001-9001 (China). TUP is not used in ANSI networks, so there is no applicable ANSI standard for TUP.
The TUP task maintains a database of circuits and circuit groups that are controlled by the application and keeps track of the state of each circuit. The initial characteristics of each circuit (group), such as the circuit identification code (CIC) and destination point code are specified in the TUP configuration file. The TUP task reads the TUP configuration file at startup time.
For outgoing call setup requests, the application specifies the circuit to be connected. For incoming calls, the TUP task verifies that the circuit state and characteristics are compatible with the incoming call request parameters before passing the incoming call indication to the application. For both incoming and outgoing calls, the TUP task provides all necessary connection timers, notifying both the application and the far exchange with necessary indications such as connection clearing when critical timers expire.
The TUP task:
Provides circuit supervision for the duration of the connection.
Adjusts the circuit state as needed based on requests from the application and TUP messages received from the far exchange.
Provides connect and disconnect timing.
Handles circuit (group) blocking and unblocking, updating the state of the affected circuits as needed.
Detects protocol errors on behalf of the application.