[quicwg/base-drafts] Is ACK delay zero for Initial and Handshake ACK frames? (#3459)

Lars Eggert <notifications@github.com> Fri, 14 February 2020 07:31 UTC

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Subject: [quicwg/base-drafts] Is ACK delay zero for Initial and Handshake ACK frames? (#3459)
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Section 5.2.1 of -recovery-25 says:

>   When the PTO is armed for Initial or Handshake packet number spaces,
>   the max_ack_delay is 0, as specified in 13.2.5 of [QUIC-TRANSPORT].

However, Section 13.2.5 of -transport-25 doesn't actually say that (anymore?) Section 13.2.1 says

> For Initial and Handshake packets, a max_ack_delay of 0 is used.

so I guess at least the reference is incorrect.

But since Section 19.3 only has a SHOULD for encoding zero

>   Because the receiver
>      doesn't use the ACK Delay for Initial and Handshake packets, a
>      sender SHOULD send a value of 0.

and the pseudo code simply uses the encoded ACK delay, if the ACK sender doesn't encode zero, the ACK receiver will compute its RTT based on the encoded ACK delay.

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