ated SN Modification to change the bearer type by removing the SCG RLC bearer while keep- ing the bearer termination point in the SN. Figure 4.3.13 shows the message flow for an SN-initiated SN Modification procedure, with MN involvement, in the EN-DC case. 1. If the SN decides to initiate the SN Modification procedure, it sends the X2-AP SgNB Modification Required message, which may contain: PDCP change indication, E-RABs to be modified list, E-RABs to be released list, and the NR RRC configuration message with UE context-related information and the new SCG radio resource configuration. 2. The reception of the X2-AP SgNB Modification Required message may also trigger a nested MN-initiated SN Modification procedure, in which case the MN sends the X2-AP SgNB Modification Request message. 3. If the nested MN-initiated SN Modification procedure was triggered in step 2, the SN responds with the X2-AP SgNB Modification Request Acknowledge. The nested procedure is used, for example, to provide information such as data forwarding addresses, new SN security key, measurement gap configuration, etc. 4. The MN sends the ERCConnectionReconfiguration message to the UE with an NR RRC configuration message carrying the new SCG radio resource configuration. 4 NG-RAN Architecture 1. SgNB Modification Required 2. SgNB Modification Request 3. SgNB Modification Request Acknowledge 4. RRCConnectionReconfiguration 5.RRCConnectionReconfigurationComplete 6. SgNB Modification Confirm 7. Random Access Procedure 8. SNStatus Transfer 9. Data Forwarding 10. Path Update procedure Figure 4.3.13 SN Modification procedure - SN-initiated with MN involvement. (Source: Reproduced by permission of © 3GPP). 5. The UE replies with an RRCConnectionReconfigurationComplete message, which may also carry an NR RRC response message. 6. If the procedure is successful, the MN sends the X2-AP SgNB Modification Confirm message to the SN, which may carry the encoded NR RRC response message via the MeNB to SgNB Container IE, if the NR RRC message has been receive