Re: [quicwg/base-drafts] Ack delays are adjusted by ack_delay_exponent (#3362)

Jana Iyengar <notifications@github.com> Tue, 21 January 2020 00:54 UTC

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Date: Mon, 20 Jan 2020 16:54:16 -0800
From: Jana Iyengar <notifications@github.com>
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Subject: Re: [quicwg/base-drafts] Ack delays are adjusted by ack_delay_exponent (#3362)
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janaiyengar commented on this pull request.



> @@ -315,14 +315,17 @@ samples, and rttvar is the variation in the RTT samples, estimated using a
 mean variation.
 
 The calculation of smoothed_rtt uses path latency after adjusting RTT samples
-for ACK delays.  For packets sent in the ApplicationData packet number space,
-a peer limits any delay in sending an acknowledgement for an ack-eliciting
-packet to no greater than the value it advertised in the max_ack_delay transport
-parameter.  Consequently, when a peer reports an Ack Delay that is greater than
-its max_ack_delay, the delay is attributed to reasons out of the peer's control,
-such as scheduler latency at the peer or loss of previous ACK frames.  Any
-delays beyond the peer's max_ack_delay are therefore considered effectively
-part of path delay and incorporated into the smoothed_rtt estimate.
+for ACK delays. ACK delays are communicated in the ack_delay field of the

We shouldn't be using "ACK delays" as a term, only as a field name. I suggest the following text instead:
``` ... after adjusting RTT samples for acknowledgement delays. These delays are computed using the ACK Delay field of the ACK frame as described in Section 19.3 of {{QUIC-TRANSPORT}}.```

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