IP-CAN Session Establishment - Gx

1. The PCEF receives an Establish IP-CAN Session Request
    
2. The PCEF starts a new Gx session by sending a CCR to the PCRF using the CC-Request-Type AVP set to the value INITIAL_REQUEST. The PCEF provides UE identity information, PDN identifier, the UE IPv4 address and/or UE IPv6 address prefix and, if available, the PDN connection identifier, IP-CAN type, RAT type and/or the default charging method. The PCEF provides, when available, the Default-EPS-Bearer-QoS and the APN-AMBR to the PCRF.
    
3. The PCRF stores the information received in the CCR.
4. If the PCRF requires subscription-related information and does not have it, the PCRF sends a request to the SPR in order to receive the information.
    
5. The SPR replies with the subscription related information containing the information about the allowed service(s), QoS information and PCC Rules information.
    
6. The PCRF selects or generates PCC Rule(s) to be installed. The PCRF may also make a policy decision by deriving an authorized QoS and by deciding whether service flows described in the PCC Rules are to be enabled or disabled.
    
7. The PCRF provisions the PCC Rules to the PCEF using CCA. The PCRF may also provide event triggers listing events for which the PCRF desires PCC Rule Requests. Furthermore, the PCRF may provide authorized QoS including the APN-AMBR and the Default-EPS-Bearer-QoS, User Location
   Information, user CSG information (if received from the BBERF).
   
   If usage monitoring is enabled, the PCRF may provide the applicable thresholds for usage monitoring control at PCEF within the Usage-Monitoring-Information AVP.
    
8. The PCEF installs the received PCC Rules. The PCEF also enforces the authorized QoS and enables or disables service flows according to the flow status of the corresponding PCC Rules. If QoS information is received per
   QCI, PCEF sets the upper limit accordingly for the MBR that the PCEF assigns to the non-GBR bearer(s) for that QCI.
    
9. The PCEF sends a response to the Establish IP-CAN Session Request
   
   

    PCRF Gx explained here