2. Conventions and Definitions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

Definitions of terms that are used in this document:

Ack-eliciting frames: All frames other than ACK, PADDING, and CONNECTION_CLOSE are considered ack-eliciting.

Ack-eliciting packets: Packets that contain ack-eliciting frames elicit an ACK from the receiver within the maximum acknowledgment delay and are called ack-eliciting packets.

In-flight packets: Packets are considered in flight when they are ack-eliciting or contain a PADDING frame, and they have been sent but are not acknowledged, declared lost, or discarded along with old keys.

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