Re: [quicwg/base-drafts] Discuss Application-Limited Sending (#1637)

[Martin Thomson <[e-mail]>]

martinthomson commented on this pull request.



> @@ -989,6 +988,11 @@ The recovery period limits congestion window reduction to once per round trip.
 During recovery, the congestion window remains unchanged irrespective of new
 losses or increases in the ECN-CE counter.
 
+## Application Limited Sending
+
+If the sender is sufficiently application limited that the congestion window is

We don't really get a definition of "application limited" from this.  The point is that you won't increase the congestion window if the entire congestion window isn't being actively used.

Is there precedent for this sort of capping of the window?

I assume that this includes flow control as the source of the limitation.  Which might be worth mentioning.

> @@ -1115,13 +1119,19 @@ acked_packet from sent_packets.
 ~~~
    InRecovery(packet_number):
      return packet_number <= end_of_recovery
+   
+   IsAppLimited():
+     bytes_in_flight >= congestion_window - kMaximumDatagramSize

It reads backwards to me as well.  And is it the right test?  @nibanks' comments suggest that there might be other ways to detect the condition of not being limited.  For instance, as long as data is enqueued for sending, it might be reasonable to say that the application is waiting on the congestion controller (or pacer) to allow sending.

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