Question: What is the purpose of the INITIAL UL RRC MESSAGE TRANSFER message in the RRC connection reestablishment procedure?
Option 1: To transfer the UE context from the gNB-DU to the gNB-CU, including the new C-RNTI and low layer configuration for the UE.
Option 2: To send an RRCReestablishmentRequest message from the UE to the gNB-DU.
Option 3: To trigger a UE Context Modification procedure by sending a UE CONTEXT MODIFICATION REQUEST message.
Option 4: To forward an RRCReconfigurationComplete message from the UE to the gNB-CU.
Explanation: The INITIAL UL RRC MESSAGE TRANSFER message is used to transfer the UE context from the gNB-DU to the gNB-CU, including the new C-RNTI and low layer configuration for the UE. This allows the gNB-CU to retrieve the UE's old context and replace it with the new one, enabling the RRC connection reestablishment procedure to proceed.