This formulation is also with "undetectable arbitrary message loss". If you can detect at the sender when a sent message is lost or succeeded (for example like

This formulation is also with "undetectable arbitrary message loss". If you can detect at the sender when a sent message is lost or succeeded (for example like collision detection in Ethernet bus, or wireless collision detection), the result doesn't apply. Because then the parties would know which round was successful and they can stop. So smoke signals would work :-) Assuming bidirectional visibility (no clouds etc.)