>"However, when the loss is at the end of a transmission, near the end of the connection or after a chunk of video has been sent, then the receiver won’t receive more segments that would generate ACKs. When this sort of Tail loss occurs, a lengthy retransmission time out (RTO) must fire before the final segments of data can be sent."
I believe this whole passage is just describing TCP fast retransmit vs a retransmit timeout expiring. However if the final TCP segment from the sender is lost wouldn't the receiver also start sending duplicate ACKs as well? This sentence seems to indicate duplicate ACKs would not be sent if the last segment was the TCP segment that was lost. In other words a duplicate ACK from the receiver is lost and so the RTO expires.