Avoid conflating credit to move window and CC #193
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draft-ietf-quic-ack-frequency.md
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| variation in the path RTT by setting the Ack-Eliciting Threshold | ||
| to a value no larger than the current congestion window. Alternatively, | ||
| a sender can accomplish this by sending an IMMEDIATE_ACK frame once each | ||
| round trip time or after each application-limited period, although if the packet containing an IMMEDIATE_ACK is lost, |
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What is the "application-limited period"? I assume you mean when transitioning from the application-limited to the cwnd-limited state?
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Actually, good point. Do we need this addition? Even in an application-limited period, you should send on ack per RTT. Why is this needed? Or do you mean idle period @gorryfair ?
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(This could potentially be confusing as an "application period" since "period of time" could infer periodicity - English can be used in multiple ways.)
That aside, the guidance in the application-limited case ought to be to send an ACK at least once per RTT while there is data outstanding... It's a small additional tweak to request an Immediate ACK as soon as the sender transitions from being application-limited to become cwnd-limited, so that the window is released promptly, rather than delayed by upto an RTT.
Obviously (to me) that when idle, you don't request periodic ACKs....
fixes #194