Re: [quicwg/base-drafts] Fix to ECN section regarding validation (#2113)

Magnus Westerlund <> Wed, 12 December 2018 10:47 UTC

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From: Magnus Westerlund <>
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Subject: Re: [quicwg/base-drafts] Fix to ECN section regarding validation (#2113)
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gloinul commented on this pull request.

 * The total increase in ECT(0), ECT(1), and CE counters reported in the ACK
   frame MUST be at least the total number of QUIC packets newly acknowledged in
-  this ACK frame.
+  this ACK frame. Detects if the network remark ECT(0), ECT(1) or CE to
+  Not-ECT.
+If a sender receives an ACK that contains no new acknowledgments, for example
+due to reordering of the ACKs, then ECN counter comparison SHOULD NOT be
+performed. Also if sender do not have state to determine if a particular PSN
+is newly acknowledge or not, then the comparison SHOULD NOT be performed.

Partly, sender need to track if a packet has been acknowledged or not. But, my assumption is that the sender will have a window where such information will be discarded when likely not relevant anymore. So if everything has been ACKed up to PSN=48. Then cleaning up your state and discarding all below 48 is fine. When the reorderd ACK that indicate reception of PSN 44 and 45 can then be determined to be behind this window and ignored. The second sentence is trying to state that for this example case this is fine to do. 

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