Dedicated Bearer Creation Call Flow
The following figure describes the Dedicated Bearer Creation procedure.

The dedicated bearer creation or activation procedure for the EPS session is defined in 3GPP 23.401, Section 5.4.1. When the UE is attached to E-UTRAN, the dedicated bearer procedure remains the same as mentioned in the specified 3GPP section except for the following changes:
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Any interaction towards the PCRF (RAR from the PCRF or CCR-U to the PCRF) are replaced by Npcf_SMPolicyControl_UpdateNotify request from the PCF to the SMF and Npcf_SMPolicyControl_Update Request from the SMF to the PCF respectively.
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The PCC rules provided by PCF are mapped to TFTs for the new dedicated bearer and the associated QoS is mapped to 4G QoS as defined in the Generating EPS PDN Connection Parameters from 5G PDU Session Parameters.
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All Gy and Gz interface messages are replaced by Nchf_ConvergedCharging_Update service operations.
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The user plane resources for dedicated bearers are added using the N4 Session Modification procedure towards UPF where PDRs, QERs and FARs are added for the SDF filters for the new dedicated bearer.
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The SMF+PGW-C saves the EBI for the dedicated bearer as received in Create Bearer response.
The following figure describes the PCF-initiated Dedicated Bearer Activation procedure.
