Tracking udp connection state in nat?

Question

Computer networks

Well, everything is clear with tcp syn ack fin rst. Nat watches, monitors, broadcasts. And in udp, how does nat understand that the connection is still alive?
Well, for example, host 1 (for nat) sends 3 bytes via udp to host 2 (public ip) nat of host 1 sees that there is a connection and host 2 can send a response or several responses to a temporary ip and nat port and it broadcasts them. What if host 1 has already closed the connection endpoint? The packet will be dropped and return ICMP via the same nat from host 1 port unreachable. Will nat close the broadcast?

Answer 1

Depends on the specific implementation. Usually no one bothers, because UDP records have a relatively short (tens of seconds or minutes) lifespan. If there is no data for this period, it is nailed.