Re: [quicwg/base-drafts] compensation of ack_delay is fragile against errors (#2060)

ianswett <> Fri, 30 November 2018 14:06 UTC

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Subject: Re: [quicwg/base-drafts] compensation of ack_delay is fragile against errors (#2060)
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Yes, those are the two issues, and they're somewhat separate.

For 1, I'm concerned we could ignore samples for a long time under some circumstances.  If the RTT is 25ms and a connection is always sending 1 packet and hitting the delayed ack timer, then the min_rtt will be 50ms, not 25ms.  And I believe ignoring SRTT samples that are less than min_rtt would result in ignoring every SRTT sample until an immediate ack was sent.  Admittedly, we say to ACK crypto packets immediately, but if one used a 1ms timer as 'immediate', I think the same problem results?

For 2, I think putting it into SRTT is the natural thing.  Adding another EWMA doesn't seem worthwhile, and in most cases it is very similar to incorporating it into SRTT.

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