Re: [quicwg/base-drafts] Move Generating Acknowledgements to Transport (#2916)

Jana Iyengar <notifications@github.com> Tue, 06 August 2019 21:53 UTC

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Subject: Re: [quicwg/base-drafts] Move Generating Acknowledgements to Transport (#2916)
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janaiyengar commented on this pull request.

Looks good -- a few nits to address

> @@ -376,26 +298,25 @@ min_rtt is set to the latest_rtt on the first sample in a connection, and to the
 lesser of min_rtt and latest_rtt on subsequent samples.
 
 An endpoint uses only locally observed times in computing the min_rtt and does
-not adjust for host delays reported by the peer ({{host-delay}}).  Doing so
-allows the endpoint to set a lower bound for the smoothed_rtt based entirely on
-what it observes (see {{smoothed-rtt}}), and limits potential underestimation
-due to erroneously-reported delays by the peer.
+not adjust for host delays reported by the peer.  Doing so allows the endpoint

why remove this ref? Can you add the right ref in the transport doc?

> @@ -2947,6 +2997,25 @@ to unnecessarily retransmit some data.  Standard QUIC algorithms
 acknowledged.  Therefore, the receiver SHOULD repeatedly acknowledge newly
 received packets in preference to packets received in the past.
 
+### Measuring and Reporting Host Delay {#host-delay}
+
+An endpoint measures the delays intentionally introduced between when an
+ACK-eliciting packet is received and the corresponding acknowledgment is sent.
+The endpoint encodes this delay for the largest acknowledged packet in the
+Ack Delay field of an ACK frame (see Section 19.3). This allows the receiver

change "Section 19.1" to a real reference

> @@ -2947,6 +2997,25 @@ to unnecessarily retransmit some data.  Standard QUIC algorithms
 acknowledged.  Therefore, the receiver SHOULD repeatedly acknowledge newly
 received packets in preference to packets received in the past.
 
+### Measuring and Reporting Host Delay {#host-delay}
+
+An endpoint measures the delays intentionally introduced between when an
+ACK-eliciting packet is received and the corresponding acknowledgment is sent.
+The endpoint encodes this delay for the largest acknowledged packet in the
+Ack Delay field of an ACK frame (see Section 19.3). This allows the receiver
+of the ACK to adjust for any intentional delays, which is important for
+delayed acknowledgements, when estimating the path RTT. A packet might be
+held in the OS kernel or elsewhere on the host before being processed.
+An endpoint SHOULD NOT include these unintentional delays when populating
+the Ack Delay field in an ACK frame.
+
+An endpoint MUST NOT excessively delay acknowledgements of ack-eliciting
+packets.  The maximum ack delay is communicated in the max_ack_delay transport
+parameter; see Section 18.1.  max_ack_delay implies an explicit contract:

change to a real reference

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