Question: When an Unacknowledged Mode (UM) RLC entity receives a UMD PDU with a Sequence Number (SN) that falls outside of the reassembly window, what action(s) will it take regarding the RX_Next_Reassembly and RX_Next_Highest variables?
Option 1: Update RX_Next_Reassembly to the SN of the received PDU and discard any PDUs within the reassembly window.
Option 2: Update RX_Next_Highest to the SN of the received PDU + 1, and if necessary, adjust RX_Next_Reassembly to the first unreassembled SN within the reassembly window.
Option 3: Stop t-Reassembly timer and reset RX_Next_Reassembly to the beginning of the reassembly window.
Option 4: Deliver the out-of-window PDU to the upper layer immediately without updating any variables.
Explanation: When a UMD PDU's SN falls outside the reassembly window, the entity updates RX_Next_Highest to the SN of the received PDU + 1 (to track the highest SN seen so far). Additionally, if RX_Next_Reassembly falls outside the updated window, it is adjusted to point to the first unreassembled SN within the window, ensuring that reassembly efforts focus on missing segments within the defined bounds. This approach maintains the integrity of the reassembly process and efficiently manages the reception buffer.