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

Benjamin Saunders <> Wed, 12 December 2018 01:58 UTC

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From: Benjamin Saunders <>
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Subject: Re: [quicwg/base-drafts] Fix to ECN section regarding validation (#2113)
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I think the verification procedure defined here still spuriously fails when the receiver sends a pair of ACK such that each ACK newly acknowledges at least one packet not acknowledged by the other (for example, due to an implementation aggressively limiting the number of ACK blocks sent), and the ACKs are reordered such when the sender receives them, it sees the one with higher ECN counters first. By my reading, the apparent reduction in ECN would cause verification to fail.

Ignoring ECN blocks from ACKs whose largest acked PN is not higher than that of every previous ACK would resolve this problem by ensuring that reordered ECN blocks are always ignored, and subsumes the "no new acknowledgements" test.

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