Question: Upon receiving a PDCP (Packet Data Convergence Protocol) PDU with reserved or invalid values in a 5G New Radio (NR) network, how should the receiving PDCP entity handle it?
Option 1: Send an error message to the transmitting entity and request retransmission.
Option 2: Discard the received PDU to prevent potential protocol disruptions.
Option 3: Attempt to correct the invalid values based on context if possible.
Option 4: Buffer the PDU for a specified period awaiting further instructions.
Explanation: Discarding the PDU prevents potential disruptions or security vulnerabilities that could arise from processing invalid or reserved protocol data. This approach aligns with the principle of robustness in telecommunications, ensuring the network's stability by rejecting malformed packets. In the context of NR sidelink communication, especially for unicast, this ensures that even specific invalid values (like an invalid KNRP-sess ID) do not compromise the communication integrity.