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Re: [quicwg/base-drafts] Fragility in ECN counters with lost acks (#1481)

Martin Thomson <notifications@github.com> Fri, 06 July 2018 05:23 UTC

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From: Martin Thomson <notifications@github.com>
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Subject: Re: [quicwg/base-drafts] Fragility in ECN counters with lost acks (#1481)
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I realize that my example was flawed.  You have to allow for an increase for any unacknowledged packets less than the minimum acknowledged packet number in the ACK.  In the example above, the last ACK stopped at 10 and the new one starts at 20.  The naive interpretation says that 9 packets might have arrived, been acknowledged, and had the acknowledgment lost and subsequently abandoned.  However, packet 8 might have arrived after 10 was acknowledged.

The other thing is that this assumes that if you acknowledge packet 20, then you would also acknowledge packets with higher numbers.  This is probably a safe assumption, but we would have to require it. 

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