Merge pull request #274 from quicwg/mirjak-patch-38

Explain example further

Author: mirjak

draft-ietf-quic-ack-frequency.md

@@ -405,6 +405,13 @@ If the reordering theshold is 3 and acknowledgements are only sent due to reorde
   Receive 10 -> Send ACK because of 7
 ~~~
 
+Note that in this example, the receipt of packet 9 triggers an ACK
+that reports both packets 6 and 7 as missing. However,
+the receipt of packet 10 needs to trigger another immediate ACK
+because only with the reporting of the successful receiption of
+packet 10, the sender will be able to declare packet 7 as lost
+(with a reordering threshold of 3).
+
 If the reordering threshold is 5 and acknowledgements are only sent due to reordering:
 
 ~~~