Question: What action may an en-gNB take if the timer TDCoverall expires before receiving a SGNB MODIFICATION CONFIRM or REFUSE message for a requested modification?
Option 1: Retry the SgNB Modification Procedure immediately
Option 2: Trigger the MeNB initiated Handover Procedure to relocate the UE
Option 3: Trigger the SgNB initiated SgNB Release procedure to release all en-gNB resources allocated for the UE
Option 4: Send a SGNB MODIFICATION REQUEST message to the MeNB for clarification
Explanation: According to the specified abnormal conditions in E-UTRAN's X2 Application Protocol, if the timer TDCoverall expires before the en-gNB receives confirmation or refusal for a modification, it regards the modification as failed. A plausible next step, as per telecom network resource management principles, is to release allocated resources to maintain efficiency and prevent resource leaks, which aligns with triggering the SgNB Release procedure. This action ensures the en-gNB's resources are freed up for other UEs or operations, highlighting practical telecom network housekeeping.