Re: [quicwg/base-drafts] Rewrite of RTT estimation section (#2592)

ianswett <notifications@github.com> Thu, 11 April 2019 19:29 UTC

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Subject: Re: [quicwg/base-drafts] Rewrite of RTT estimation section (#2592)
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ianswett commented on this pull request.



>  ~~~
 latest_rtt = ack_time - send_time_of_largest_acked
 ~~~
 
-First RTT sample:
+An endpoint uses only locally observed times in generating RTT samples and does
+not adjust for any host delays reported by the peer ({{host-delay}}).
+
+A peer reports host delays for only the largest acknowledged packet in an ACK
+frame, which is assumed by subsequent computations of smoothed_rtt and rttvar in
+adjusting for host delays.  As a result, an RTT sample is only generated using
+the largest acknowledged packet in the received ACK frame.
+
+To avoid generating multiple RTT samples using the same packet, an ACK frame
+SHOULD NOT be used to update RTT estimates if it does not newly acknowledge the
+largest acknowledged packet.
+
+An RTT sample MUST NOT be generated on receiving an ACK frame that does not
+newly acknowledge at least one ack-eliciting packet.  A peer does not send an

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