Question: For the 'Downlink delay in gNB-DU for a network slice subnet' (DLDelay_gNBDU_Nss) KPI, what determines the end point of the measured packet transmission delay to the UE in AM (Acknowledged Mode)?
Option 1: Receipt of HARQ feedback information
Option 2: Receipt of RLC ACK (Radio Link Control Acknowledgement)
Option 3: Arrival of an RLC SDU at the RLC ingress F1-U termination
Option 4: Transmission of the first part of an RLC SDU packet from gNB-DU
Explanation: According to the context, for AM (Acknowledged Mode), the end point of the measured packet transmission delay is determined by when 'the last part of an RLC SDU packet was received by the UE according to received RLC ACK', highlighting acknowledgement's role in confirmed transmissions.