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

Jana Iyengar <> Mon, 25 May 2020 22:06 UTC

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From: Jana Iyengar <>
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Subject: Re: [quicwg/base-drafts] Invariant independent (#3684)
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@janaiyengar 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.

I think it's a design change. I think this allows for some freedom in the future on the part of endhost stack developers, so I like it, but I'm not sure I can simply justify it with that rationale.

That said, the way I read it, a new version of QUIC _could_ have a packet_len field, but the following packet within the same dgram is then not guaranteed to follow the invariants. This seems to deviate from the previous simple model about packets. Why can this not apply to all packets, even if it cannot be enforced?

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