No problem, thanks for clarifying! So basically the benefit to the TCP NACK approach is that the TCP layer will also do a sort on the packets received?
Yeah, which is imperfect but there you are. It means sometimes out-of-order packets will be reordered, and sometimes dropped (since TCP acked it, the (existing) TCP code will discard the out-of-order packet as 'duplicate'. Which turns out works pretty well in practice, since out-of-order are almost always in a burst (no delay inter-packet)
But reordering also happens simply by examining received packets in a burst, and putting them right.
So its six of one and a half-dozen of the other I guess. Sorry for coming off so abrupt.