You're correct that this sentence is in contrast to the first sentence of the section: "When a PTO timer expires, a sender MUST send at least one ack-eliciting packet in the packet number space as a probe."
The intent was 2, that when there is no unsent or unacknowledged data available, a sender MAY mark all packets in flight as lost. As an individual, I would not recommend this, but in the same way we allow retransmitting packet contents in their entirety, we allow this. I agree this is slightly unclear and whenever we do 9002bis, it'd be ideal to clarify this. Ian On Thu, Apr 20, 2023 at 3:13 AM Timo Völker <[email protected]> wrote: > Hi, > > I wonder what the word “Alternatively” refers to in RFC9002 Section 6.2.4. > Sending Probe Packets. > > I would summarize the Section before the word as follows: > > "When a PTO timer expires, a sender MUST send at least one ack-eliciting > packet [...] > An endpoint SHOULD include new data in packets that are sent on PTO > expiration. > Previously sent data MAY be sent if no new data can be sent. [...] > When there is no data to send, the sender SHOULD send a PING or other > ack-eliciting frame in a single packet, rearming the PTO timer." > > Then, the sentence that confuses me: > > "Alternatively, instead of sending an ack-eliciting packet, the sender MAY > mark any packets still in flight as lost." > > Alternatively to what? > > (1) Alternatively to send a probe packet at all. > Or > (2) Alternatively to send a probe packet in case the sender has no unsent > or previously sent data available? > > Based on the history of the Section, my guess is (2). But, I can’t tell > based on the current text. Since both options are in contrast to the first > sentence of the Section, I might have missed something. > > Timo
