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Re: [quicwg/base-drafts] Fixing max_ack_delay (#3938)

Kazuho Oku <notifications@github.com> Wed, 22 July 2020 06:07 UTC

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Date: Tue, 21 Jul 2020 23:07:12 -0700
From: Kazuho Oku <notifications@github.com>
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Subject: Re: [quicwg/base-drafts] Fixing max_ack_delay (#3938)
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@kazuho commented on this pull request.



> @@ -1129,6 +1129,10 @@ follows:
    smoothed_rtt = kInitialRtt
    rttvar = kInitialRtt / 2
    min_rtt = 0
+   // max_ack_delay is initialized to 0 and
+   // updated when transport parameters are exchanged.
+   // If a peer does not specify max_ack_delay,
+   // it is set to 25ms.

These comments look fine, but I am not sure if I agree with the rest of the changes.

IIUC, persistent congestion is a path-wide event rather than a event specific to the PN space. I think we need to have max_ack_delay even if that might turn out to be a bit conservative when 0-RTT / 1-RTT packets are not involved.

Then, there is no point in passing `pn_space` to `InPersistentCongestion` or to the functions that invoke `InPersistentCongestion`.

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