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Re: [quicwg/base-drafts] Persistent congestion threshold is unreliable during the early stages of a connection (#3875)

Jana Iyengar <notifications@github.com> Wed, 15 July 2020 02:58 UTC

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Date: Tue, 14 Jul 2020 19:58:04 -0700
From: Jana Iyengar <notifications@github.com>
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Subject: Re: [quicwg/base-drafts] Persistent congestion threshold is unreliable during the early stages of a connection (#3875)
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So, I understand the disconnect now after discussing with @kazuho. This issue is not just about before an initial RTT sample, it's about the case where the network RTT were to similarly reduce later in the connection. In such a case, when loss also happens, the sender could retroactively declare persistent congestion based on the new RTT estimate, while the previous RTT estimate might have caused fewer than 3 PTOs to fire. Specifically, the sender might have sent fewer than 3 packets as PTO responses into the network before marking the network as having persistent congestion.

This seems like a corner case to me that may not be necessary to fix (beyond what is being fixed in #3889). But I want to hear others' opinions.

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