Re: [quicwg/base-drafts] Invariant independent (#3684)

Gorry Fairhurst <> Tue, 26 May 2020 10:45 UTC

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Date: Tue, 26 May 2020 03:45:04 -0700
From: Gorry Fairhurst <>
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Subject: Re: [quicwg/base-drafts] Invariant independent (#3684)
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@gorryfair commented on this pull request.

>  # QUIC Packet Headers
-A QUIC packet is the content of the UDP datagrams exchanged by QUIC endpoints.
-This document describes the contents of those datagrams.
+QUIC endpoints exchange UDP datagrams that contain one or more QUIC packets.
+This section describes the invariant characteristics of a QUIC packet.  A
+version of QUIC could permit multiple QUIC packets in a single UDP datagram, but
+the invariant properties only describe the first packet in a datagram.

So if we go down this path I think we need carefully to consider each transport mechanism. And the fate of multiplexed flows start to become entangled, such as when a sender chooses a smaller size or DSCP marking because that endpoint expects a characteristic treatment; the unit of loss can be different to the unit of retransmission; PMTUD will need tighter language; pacing may be impacted;  - basically it makes the transport more complex, if that's needed let's try and explain why and understand the constraints - e.g. do we need rules to say when not to multiplex multiple QUIC packets into one IP packet? 

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