The application requests blocking of a circuit by invoking ISUPStatusReq with the event type of CIRBLKREQ. The application is notified of the completion of the blocking procedure (the receipt of a blocking acknowledgment message) by receipt of a status indication (EVTSITSTAIND) with the event type of CIRBLKRSP.
Note: The BICC variant does not support blocking or unblocking circuits.
The following illustration shows a blocking request initiated by the application:
If the far exchange initiates the blocking of the circuit, the application receives a status indication (EVTSITSTAIND) with the event type of CIRBLKREQ from the ISUP layer. The application then acknowledges the circuit blocking by invoking ISUPStatusReq with the event type of CIRBLKRSP.
The following illustration shows a blocking request initiated by the far exchange:
The application requests unblocking of a circuit by invoking ISUPStatusReq with the event type of CIRUNBLKREQ. The application is notified of the completion of the unblocking procedure (the receipt of an unblocking acknowledgment message) by receipt of a status indication (EVTSITSTAIND) with the event type of CIRUNBLKRSP.
The following illustration shows an unblocking request initiated by the application:
If the far exchange initiates the unblocking of the circuit, the application receives a status indication (EVTSITSTAIND) with the event type of CIRUNBLKREQ from the ISUP layer. The application then acknowledges the circuit unblocking by invoking ISUPStatusReq with the event type of CIRUNBLKRSP.
The following illustration shows an unblocking request initiated by the far exchange: