If overlap sending is used, then following the occurrence of one of these conditions:
a) the receipt by the network of a sending complete indication which the network understands; or
b) analysis by the network that all call information necessary to effect call establishment has been received,
and if the network can determine that access to the requested service and supplementary service is authorized and available, the network shall: send a CALL PROCEEDING message to the user; stop timer T302; and enter the Outgoing Call Proceeding state. Similarly if the network determines that a requested service or supplementary service is not authorized or is not available, the network shall initiate call clearing in accordance with 5.3, with one of the following causes:
No. 57 - Bearer capability not authorized;
No. 58 - Bearer capability not presently available;
No. 63 - Service or option not available,unspecified; or
No. 65 - Bearer service not implemented.
NOTES
1. The CALL PROCEEDING message is sent to indicate that the requested call establishment has been initiated, and no more call establishment information will be accepted.
2. If a supplementary service is not authorized or is not available, the procedure to be used is defined in the supplementary service control procedures.
3. When the network cannot assign a channel due to congestion, the procedures of 5.1.2 shall be followed.
When the user receives the CALL PROCEEDING message, the user shall enter the outgoing call proceeding state. If, for symmetry purposes, the calling user employs timer T304, the user shall stop timer T304 when the CALL PROCEEDING message is received. If, for symmetry purposes, the calling user employs timer T304 then, on expiry of T304, the user shall initiate call clearing in accordance with 5.3 with cause No. 102, recovery on time expiry.
An alerting or connect indication received from the called party will stop timer T302 and cause an ALERTING or CONNECT message respectively to be sent to the calling user. No CALL PROCEEDING message shall be sent by the network. If, for symmetry purposes, the calling user employs timer T304, the user shall stop timer T304 on receiving the ALERTING or CONNECT message.
At the expiration of timer T302, the network shall:
i) initiate call clearing in accordance with5.3, with cause No. 28, invalid number format (incomplete number)sent to the calling user and with cause No. 102, recovery on timer expiry is sent towards the called user, if the network determines that the call information is definitely incomplete; otherwise
ii) send a CALL PROCEEDING message and enter the outgoing call proceeding state.