[YZF]

I agree this is what you'd consider delivery. Also agree everyone else is wrong an I am right ;)

The similar question in TCP is what happens when the sender writes to their socket and then loses the connection. At this point the sender doesn't know whether the receiver has the data or not. Both are possible. For the sender to recover it needs to re-connect and re-send the data. Thus the data is potentially delivered more than once and the receiver can use various strategies to deal with that.

But sure, within the boundary of a single TCP connection data (by definition) is never delivered twice.