Re: [quicwg/base-drafts] Add more context and text around ACK frequency (#3706)

ianswett <> Mon, 01 June 2020 04:50 UTC

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Date: Sun, 31 May 2020 21:50:08 -0700
From: ianswett <>
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Subject: Re: [quicwg/base-drafts] Add more context and text around ACK frequency (#3706)
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@ianswett commented on this pull request.

> -limits on how frequently they can be sent.  An endpoint MUST NOT send more than
-one ACK-frame-only packet in response to receiving an ack-eliciting packet.  An
-endpoint MUST NOT send a non-ack-eliciting packet in response to a
-non-ack-eliciting packet, even if there are packet gaps which precede the
-received packet. Limiting ACK frames avoids an infinite feedback loop of
-acknowledgements, which could prevent the connection from ever becoming idle.
-However, the endpoint acknowledges non-ACK-eliciting packets when it sends an
-ACK frame.
+### Acknowledgement Frequency
+A receiver determines how frequently to send acknowledgements in response to
+ack-eliciting packets. This determination involves a tradeoff.
+Endpoints rely on timely acknowledgment to detect loss; see Section 5 of
+{{QUIC-RECOVERY}}. Window-based congestion controllers, such as the one in
+Section 6 of {{QUIC-RECOVERY}}, rely on acknowledgments to manage their sending

Thanks, I think that's better, but I also think it doesn't highlight a key point, which is if a receiver delays sending an ACK for Xms, the sender may be blocked from sending for Xms.

Except for slow start, I don't think the congestion window itself is the issue, but rather the available congestion window.

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