ACK now includes ECN

Co-Authored-By: martinthomson <martin.thomson@gmail.com>

draft-ietf-quic-transport.md

@@ -2946,7 +2946,9 @@ Congestion Experienced (CE) codepoint set by a network device that is
 experiencing congestion.
 
 If a packet sent with an ECT codepoint is newly acknowledged by the peer in an
-ACK frame, the endpoint stops setting ECT codepoints in subsequent packets, with
+ACK frame without ECN feedback, the endpoint stops setting ECT codepoints in
+subsequent packets, with the expectation that either the network or the peer no
+longer supports ECN.
 the expectation that either the network or the peer no longer supports ECN.
 
 To protect the connection from arbitrary corruption of ECN codepoints by the