Re: [quicwg/base-drafts] Document TCP RTO vs QUIC PTO (#3441)

MikkelFJ <notifications@github.com> Wed, 11 March 2020 13:29 UTC

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Date: Wed, 11 Mar 2020 06:29:17 -0700
From: MikkelFJ <notifications@github.com>
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Subject: Re: [quicwg/base-drafts] Document TCP RTO vs QUIC PTO (#3441)
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mikkelfj commented on this pull request.



> +### Probe Timeout Replaces RTO and TLP
+
+QUIC uses a probe timeout (see {{pto}}), with a timer based on TCP's RTO
+computation.  QUIC's PTO includes the peer's maximum expected acknowledgement
+delay instead of using a fixed minimum timeout. QUIC does not collapse the
+congestion window until persistent congestion ({{persistent-congestion}}) is
+declared, unlike TCP, which collapses the congestion window upon expiry of an
+RTO.  Instead of collapsing the congestion window and declaring everything
+in-flight lost, QUIC allows probe packets to temporarily exceed the congestion
+window whenever the timer expires.
+
+In doing this, QUIC avoids unnecessary congestion window reductions, obviating
+the need for correcting mechanisms such as F-RTO {{!RFC5682}}. Since QUIC does
+not collapse the congestion window on a PTO expiration, a QUIC sender is not
+limited from sending more in-flight packets after a PTO expiration if it still
+has available congestion window. This occurs when a sender is

sounds like a word is missing before "congestion window".

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