Re: [quicwg/base-drafts] Rewrite section on ack range limiting (#3315)

Martin Thomson <> Thu, 02 January 2020 22:50 UTC

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From: Martin Thomson <>
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Subject: Re: [quicwg/base-drafts] Rewrite section on ack range limiting (#3315)
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martinthomson commented on this pull request.

> -number of ACK Ranges it sends.  A receiver can do this even without receiving
-acknowledgment of its ACK frames, with the knowledge this could cause the sender
-to unnecessarily retransmit some data.  Standard QUIC algorithms
-({{QUIC-RECOVERY}}) declare packets lost after sufficiently newer packets are
-acknowledged.  Therefore, the receiver SHOULD repeatedly acknowledge newly
-received packets in preference to packets received in the past.
+A receiver MAY limit the number of ACK Ranges it sends to limit receiver state
+and the size of ACK frames.  A receiver SHOULD track which ACK frames have been
+acknowledged by its peer, so that it can limit ACK Ranges ({{ack-ranges}}) to
+those not yet acknowledged by the sender.
+It is possible that the ACK frame is too large, despite limiting ACK Ranges to
+those not yet acknowledged. A receiver can stop repeating unacknowledged ACK
+Ranges to further limit the size of the ACK frame.  When doing so, a receiver
+SHOULD give preference to acknowledging newly received packets to those received
+earlier.  It is possible that such ACK Ranges are not received by the sender

Larger packet numbers should be a very good approximation of that, for sure.

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