rds the SN configuration to the mobile in the message RRC ConnectionReconfiguration. 4) The mobile applies the new configuration and acknowledges the MN (eNB entity) of the new allocation of the radio resource in the RRC ConnectionReconfigurationComplete message, including, if necessary, an NR RRC response message. 5) The MN (eNB entity) informs the SN (en-gNB entity) that the mobile has successfully completed the reconfiguration procedure, via the X2-AP SgNB Reconfiguration Complete message, eventually including the NR RRC response message. 6) In case of the EN-DC option 3x dual connectivity, the MN (eNB entity) only transmits the SN Status Transfer message for packets in the Radio Link Control Acknowledged mode (RLC-AM). The mobile synchronizes on the MN (PCell of the en-gNB entity) and performs the random access procedure. To establish the SI-U bearer between the en-gNB and SGW entities, the MN (eNB entity) transmits the S1-AP E-RAB Modification Indication message to the MME entity. The SI-U bearer continues to set up, with GTPv2-C messages exchanged between the MME and SGW entities. The MME entity acknowledges the MN (eNB entity) request by sending the S1-AP E-RAB Change Confirmation message. The S1-U bearer between the SGW and en-gNB entities is complete. NG-RAN Network - Procedures 3.1.3.3. Changing a secondary node The procedure for changing a secondary node is initialized by either the MN (eNB entity - Figure 3.5) or the SN (en-gNB entity). It is used to transfer the mobile context of the source en-gNB entity to the target en-gNB entity. SN source SN target en-gNB en-gNB Measurement report (LTE,NR) X2-AP SgNB Addition Request X2-AP SgNB Addition Request ACK X2-AP SgNB Release Request X2-AP SgNB Release ACK RRC Connection Reconfiguration RRC Connection Reconfiguration, Complete X2-AP SgNB Reconfiguration Complete Synchronization and collision-free random access procedure X2-AP SN Status Transfer X2-AP SN Status Transfer X2-AP UE Context Release Figure 3.5. Procedure initiated by the eNB to change the secon