Re: [quicwg/base-drafts] DPLPMTU merge tweaks (#3702)

Gorry Fairhurst <> Fri, 29 May 2020 13:27 UTC

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Date: Fri, 29 May 2020 06:27:42 -0700
From: Gorry Fairhurst <>
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Subject: Re: [quicwg/base-drafts] DPLPMTU merge tweaks (#3702)
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@gorryfair commented on this pull request.

> +
+From the perspective of DPLPMTUD, QUIC transport is an acknowledged
+packetization layer (PL). A sender can therefore enter the DPLPMTUD BASE state
+when the QUIC connection handshake has been completed.
+### Sending QUIC DPLPMTUD Probe Packets
+DPLPMTU probe packets are ack-eliciting packets.  Probe packets that use the
+PADDING frame implement "Probing using padding data", as defined in
+Section 4.1 of {{!DPLPMTUD}}.  Endpoints could limit the content of probe
+packets to PING and PADDING frames as packets that are larger than the current
+maximum packet size are more likely to be dropped by the network.
+DPLPMTU probe packets consume congestion window, which could delay subsequent
+transmission by an application.

Nearly, could we say:

Probe packets are larger than the current maximum packet size and therefore more likely to be dropped by the network. Endpoints could therefore limit the content of probe packets to ACK-eliciting frames that are not retransmitted (e.g., using PING and PADDING frames).  Loss of a probe packet SHOULD NOT be treated as an indication of congestion and SHOULD NOT trigger a congestion control reaction (see section 3, bullet 7 of {{!DPLPMTUD}}.  However, probe packets do consume congestion window, which could delay subsequent transmission by an application.

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