The PCRF is a functional element that encompasses policy control decision and flow based charging control functionalities. The PCRF uses the information received from SCEF and other available information to determine one or more transfer policies for background data to the application service provider. The PCRF provides the selected transfer policies with a reference ID to the SPR for storage.

The SCEF is a functional element which provides a means to securely expose the services and capabilities provided by 3GPP network interfaces. The SCEF is triggered by an SCS/AS which requests for the negotiation with the PCRF for providing necessary policy to transfer background data.

Based on the SCS/AS request, the SCEF shall send the Background-Data-Transfer-Request (BTR) command to the PCRF including the Transfer-Request-Type AVP with the value TRANSFER_POLICY_REQUEST(0), it shall also include the ASP identifier within the Application-Service-Provider-Identity AVP, volume of data per UE within the CC-Output-Octets AVP for downlink volume and/or the CC-Input-Octets AVP for uplink volume, or the CC-Total-Octets AVP for total volume regardless direction, expected number of UEs within the Number-Of-UEs AVP and desired time window within the Time-Window AVP. The Time-Window AVP shall include desired start time within the Transfer-Start-Time AVP and desired end time within the Transfer-End-Time AVP. The SCEF may also provide network area information within Network-Area-Info-List AVP. Once the PCRF receives the BTR command, the PCRF shall retrieve all existing transfer policies stored for any ASP from the SPR. When all existing transfer policies are retrieved, the PCRF shall determine one or more transfer policies based on the information received from the SCEF and other available information (e.g. network policy, congestion level (if available), load status estimation for the required time window and network area, existing transfer policies) and respond with a Background-Data-Transfer-Answer (BTA) command including the possible transfer policies within Transfer-Policy AVP (s) and a reference ID within Reference-Id AVP. The Transfer-Policy AVP(s) shall include the Transfer-Policy-Id AVP, the Time-Window AVP, the Rating-Group AVP, and may also include an Max-Requested-Bandwidth-DL AVP and/or an Max-Requested-Bandwidth-UL AVP. If more than one transfer policies are included in the BTA command, the PCRF shall also include the PCRF Id within the PCRF-Address AVP in the BTA command. If there is more than one Transfer-Policy AVP included in the BTA command, the PCRF waits for the transfer policy selected by the SCS/AS before communicating with the SPR. If there is more than one transfer policy provided from the PCRF to the SCEF in the BTA command, when the SCEF receives the selected transfer policy from the SCS/AS, the SCEF shall send Background-Data-Transfer-Request (BTR) command to the PCRF including the Transfer-Request-Type AVP set to the value TRANSFER_POLICY_NOTIFICATION (1). The SCEF shall also include the reference ID in the Reference-Id AVP, the identity of the selected transfer policy within the Transfer-Policy-Id AVP and the destination PCRF Id within the Destination-Host AVP. If there is more than the one transfer policy included, the SCEF forwards these transfer policies to the SCS/AS and waits for the answer including the identity of the transfer policy selected by the SCS/AS. The PCRF shall acknowledge the BTR command by sending Background-Data-Transfer-Answer (BTA) command.