Merge pull request #273 from quicwg/mirjak-patch-37

Clarify when RFC9000 sends immediate ACK

Author: mirjak

draft-ietf-quic-ack-frequency.md

@@ -348,8 +348,11 @@ create excessive delays.
 ## Response to Out-of-Order Packets {#out-of-order}
 
 As specified in {{Section 13.2.1 of QUIC-TRANSPORT}}, endpoints are expected to
-send an acknowledgment immediately on receiving a reordered ack-eliciting
-packet. This extension modifies that behavior when an ACK_FREQUENCY frame with
+send an acknowledgment immediately on receipt of a reordered ack-eliciting
+packet with a smaller packet number than the highest-numbered ack-eliciting packet
+or with a higher packet number when there are missing packets between that packet
+and the highest-numbered ack-eliciting packet.
+This extension modifies that behavior when an ACK_FREQUENCY frame with
 a Reordering Threshold value other than 1 has been received.
 
 If the most recent ACK_FREQUENCY frame received from the peer has a Reordering