- Add rx_dup_count (local) and tx_dup_count (remote via ACK) to ETCP_CONN - Extend ACK section format: add 16-bit rx_dup_count after last_delivered_id - Reconstruct 32-bit tx_dup_count from received 16-bit diff - Update etcpmon protocol and control_server to expose counters - Update packet dumper for new ACK format