Circuit Reservation

Circuit Reservation from Network

A circuit may be reserved prior to its setup. For the current version of HP OpenCall SS7 ISUP, the application cannot request the reservation. However, it is informed of a circuit reservation request by receiving a CIRCUIT_RESERVATION_IND. Here, the circuit involved is marked incoming busy by HP OpenCall SS7 ISUP. The application must respond to that indication. On receipt of the CIRCUIT_RESERVATION_RESP, HP OpenCall SS7 ISUP sends back a CRA message and starts the timer T_CRA associated with the waiting-for-IAM state. The next steps are those described in the call setup procedure, see “Call Setup Procedures”.

Figure 18-6 Circuit Reservation from Network

Circuit Reservation from Network - T_CRA Expiry

In this example, the timer T_CRA has expired before the IAM message is received. The application is informed of that event by the receipt of a START_RELEASE_IND (indicating TCRA_TIMEOUT) which it acknowledges by sending back a START_RELEASE_IND_ACK primitive. Upon receipt of the latter, HP OpenCall SS7 ISUP sends a Release message and goes into the release procedure previously described.

Figure 18-7 Circuit Reservation from Network - Failure