d from the UE (step 5). 7. The UE performs synchronization toward the PSCell if instructed by the network. Alter- natively, the UE may immediately start uplink transmission after having applied the new configuration. 8. The SN may also send the X2-AP SN Status Transfer message with the PDCP SN and HFN status, if the PDCP termination point is changed for bearers using RLC AM. 9. Data forwarding between MN and the SN may be performed, if configured. 10. The update of the user -plane path toward the EPC is performed using the S1-AP Path Switch procedure. In some cases the SN Modification procedure can be performed without involving the MN, if SRB3 is established. This may happen if no coordination with the MN is required, for example, in the case of addition, modification, or release of SCG SCells. The most typical case is a PSCell change where the security key does not need to be changed. For instance, a PSCell change may be triggered when a UE configured with EN-DC eventually reports an A3 event (triggered when a neighboring cell becomes better than the serving cell by an offset). An example of the message flow for an SN-initiated SN Modification procedure without MN involvement, in the EN-DC case, is shown in Figure 4.3.14. 1. If If the SN node decides to perform SN medication, for example, after receiving a mea- surement report from the UE), it sends the RRCConnectionReconfiguration message to the UE through SRB3. 4.3 Multi-Radio Dual Connectivity 1. NR RRCConnectionReconfiguration 2. Random access procedure 3. NR RRCConnectionReconfigurationComplete Figure 4.3.14 SN Modification - SN-initiated without MN involvement. (Source: Reproduced by permission of © 3GPP). 2. If instructed by the network, the UE may (optionally) perform synchronization toward the (new) PSCell. 3. When the procedure is finished, the UE replies with the RRCConnectionReconfigura- tionComplete message. 4.3.4.3.3 SN Change The SN Change procedure may be initiated either by the MN or the SN and used to transfer a UE context from a source SN to 