Scenario 1
A user who has subscribed to a service is configured on the PCRF. When the user goes online, the PCEF is requested to send a CCA-Initial message to the PCRF.
Processing
When the PCRF detects the subscription information about the user and a session is established successfully, the PCRF returns a CCA-Initial message carrying the PCC rule for the user.
Scenario 2
A user is not configured on the PCRF. When the user goes online, the PCEF is requested to send a CCR-Initial message to the PCRF.
Processing
When the PCRF does not detect the subscription information about the user and a session fails to be established, the PCRF returns a CCA-Initial message carrying the Result-Code AVP whose value is DIAMETER_UNKNOWN_SESSION_ID.