Re: [quicwg/base-drafts] Rework section on persistent congestion (#3961)

ianswett <notifications@github.com> Mon, 03 August 2020 16:19 UTC

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Date: Mon, 03 Aug 2020 09:19:25 -0700
From: ianswett <notifications@github.com>
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Subject: Re: [quicwg/base-drafts] Rework section on persistent congestion (#3961)
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@ianswett commented on this pull request.



> +This design does not use consecutive PTO events to establish persistent
+congestion, since application patterns impact PTO expirations. For example, a
+sender that sends small amounts of data with silence periods between them
+restarts the PTO timer every time it sends, potentially preventing the PTO timer
+from expiring for a long period of time, even when no acknowledgments are being
+received. The use of a duration enables a sender to establish persistent
+congestion without depending on the occurrence of PTOs.
+
+### Establishing Persistent Congestion
+
+A sender establishes persistent congestion on receiving an acknowledgement if at
+least two ack-eliciting packets are declared lost, and:
+
+* a prior RTT sample existed when both packets were sent;
+
+* the duration between the send times of these two packets exceeds the

There's a requirement that all packets between the largest and smallest are marked lost as well, so my suggested change would still not declare this as persistent congestion(assuming 2, 4, 6 or 8 were acknowledged).

I still think this is unclear if more than 2 packets are lost, so maybe you have a suggestion?

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