Outgoing messages are initiated by a PNS and instruct a PAC to place a call on a telco interface. There are only two messages for outgoing calls: Outgoing-Call-Request and Outgoing-Call-Reply. The PNS sends an Outgoing-Call-Request specifying the dialed party phone number and subaddress as well as speed and window parameters. The PAC MUST respond to the Outgoing-Call-Request message with an Outgoing-Call- Reply message once the PAC determines that:
The call has been successfully connected
A call failure has occurred for reasons such as: no interfaces are available for dial-out, the called party is busy or does not answer, or no dial tone is detected on the interface chosen for dialing
Receive Outgoing Call Request in Error
/Send Outgoing Call Reply with Error
|--------+
| | Receive Outgoing Call Request No Error
| | /Off Hook; Dial
| | +-----------------------------------------
^ V ^ V
+-----------------+ Incomplete Call +-----------------+
| idle | /Send Outgoing Call | wait_cs_ans |
+-----------------+ Reply with Error +-----------------+
^ ^ or Recv. Call Clear Req. V V Telco Answer
| | /Send Disconnect Notify| | /Send Outgoing
| +-------------------------------------+ | Call Reply.
| V
| +-----------------+
+-------------------------------------| established |
Receive Call Clear Request +-----------------+
or local terminate
or telco disconnect
/Hangup call and send
Call Disconnect Notify
The states associated with the PAC for outgoing calls are:
idle
Received Outgoing-Call-Request. If this is received in error, respond with an Outgoing-Call-Reply with error condition set. Otherwise, allocate physical channel to dial on. Place the outbound call, wait for a connection, and move to the wait_cs_ans state.
wait_cs_ans
If the call is incomplete, send an Outgoing-Call-Reply with a non-zero Error Code. If a timer expires on an outbound call, send back an Outgoing-Call-Reply with a non-zero Error Code. If a circuit switched connection is established, send an Outgoing-Call-Reply indicating success.
established
If a Call-Clear-Request is received, the telco call SHOULD be released via appropriate mechanisms and a Call-Disconnect-Notify message SHOULD BE sent to the PNS. If the call is disconnected by the client or by the telco interface, a Call-Disconnect-Notify message SHOULD be sent to the PNS.
Open Indication Abort/Send
/Send Outgoing Call Call Clear
Request +-----------------+ Request
+-------------------------------->| Wait-Reply |------------+
| +-----------------+ |
| Receive Outgoing Call Reply V V Receive Outgoing |
| with Error | | Call Reply |
| +-------------------------------+ | No Error |
^ V V |
+-----------------+ +-----------------+ |
| Idle |<-----------------------------| Established | |
+-----------------+ Receive Call Disconnect +-----------------+ |
^ Notify V Local Terminate |
| | /Send Call Clear |
| | Request |
| Receive Call Disconnect V |
| Notify +-----------------+ |
+---------------------------------| Wait-Disconnect |<-----------+
+-----------------+
The states associated with the PNS for outgoing calls are:
idle
An Outgoing-Call-Request message is sent to the PAC and the session moves into the wait_reply state.
wait_reply
An Outgoing-Call-Reply is received which indicates an error. The session returns to idle state. No telco call is active. If the Outgoing-Call-Reply does not indicate an error, the telco call is connected and the session moves to the established state.
established
If a Call-Disconnect-Notify is received, the telco call has been terminated for the reason indicated in the Result and Cause Codes. The session moves back to the idle state. If the PNS chooses to terminate the session, it sends a Call-Clear-Request to the PAC and then enters the wait_disconnect state.
wait_disconnect
A session disconnection is waiting to be confirmed by the PAC. Once the PNS receives the Call-Disconnect-Notify message, the session enters idle state.