Re: [quicwg/base-drafts] No RTT samples, no persistent congestion (#3889)

[Kazuho Oku <[e-mail]>]

@kazuho commented on this pull request.



> @@ -1580,14 +1586,18 @@ Invoked when an ACK frame with an ECN section is received from the peer.
 Invoked when DetectAndRemoveLostPackets deems packets lost.
 
 ~~~
-   InPersistentCongestion(lost_packets):
+   InPersistentCongestion(largest_lost):
+     // Persistent congestion cannot be declared on the
+     // first RTT sample.
+     if (is first RTT sample):
+       return false

> Specifically, to implement this, you'll need a new global variable `time_of_first_rtt_measurement`, or alternative `first_packet_sent_with_measured_rtt`, and then you'll have to implement a comparison with the time of the packets in `lost_packets`.

Can you implement that way? Persistent congestion is declared across all packet number spaces. That means that you'd have to consult if there any acks were received in the loss period observed in `lost_packets`. But you cannot remember all the moments when acks were received, because the state would be unbounded.

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