Re: [quicwg/base-drafts] PTO MUST send new data or retransmit data if possible (#3057)

Benjamin Saunders <> Tue, 24 September 2019 03:02 UTC

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From: Benjamin Saunders <>
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Subject: Re: [quicwg/base-drafts] PTO MUST send new data or retransmit data if possible (#3057)
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Ralith commented on this pull request.

> @@ -526,15 +524,16 @@ as a probe, unless there is no data available to send.  An endpoint MAY send up
 to two full-sized datagrams containing ack-eliciting packets, to avoid an
 expensive consecutive PTO expiration due to a single lost datagram.
-It is possible that the sender has no new or previously-sent data to send.  As
-an example, consider the following sequence of events: new application data is
-sent in a STREAM frame, deemed lost, then retransmitted in a new packet, and
-then the original transmission is acknowledged.  In the absence of any new
-application data, a PTO timer expiration now would find the sender with no new
-or previously-sent data to send.
+When the PTO timer expires, and there is new or previously sent data, it MUST

On review, maybe the existing requirement that probes be ACK-eliciting is enough. Nothing wrong with retransmitting some unacknowledged ACKs alongside your PING.

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