Re: [quicwg/base-drafts] RTTVar is not really a variance (#3223)

Jana Iyengar <> Tue, 19 November 2019 10:31 UTC

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Date: Tue, 19 Nov 2019 02:31:19 -0800
From: Jana Iyengar <>
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Subject: Re: [quicwg/base-drafts] RTTVar is not really a variance (#3223)
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janaiyengar commented on this pull request.

Be consistent with "variation", or say that mean deviation is the same as variation. Otherwise, it's just confusing to someone who doesn't know that the two terms mean the same thing.

> @@ -251,8 +251,8 @@ RTT samples and peer-reported host delays (see Section 13.2 of
 {{QUIC-TRANSPORT}}) to generate a statistical description of the connection's
 RTT. An endpoint computes the following three values: the minimum value
 observed over the lifetime of the connection (min_rtt), an
-exponentially-weighted moving average (smoothed_rtt), and the variance in the
-observed RTT samples (rttvar).
+exponentially-weighted moving average (smoothed_rtt), and the mean deviation

exponentially-weighted moving average (smoothed_rtt), and the variation

> @@ -307,7 +307,8 @@ erroneously-reported delays by the peer.
 ## Estimating smoothed_rtt and rttvar {#smoothed-rtt}
 smoothed_rtt is an exponentially-weighted moving average of an endpoint's RTT
-samples, and rttvar is the endpoint's estimated variance in the RTT samples.
+samples, and rttvar is the endpoint's RTT mean deviation in the RTT samples,

samples, and rttvar is the variation in the RTT samples,

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