QUIC Version Negotiation Interim

Matt Joras <matt.joras@gmail.com> Thu, 22 April 2021 18:34 UTC

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From: Matt Joras <matt.joras@gmail.com>
Date: Thu, 22 Apr 2021 11:34:03 -0700
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Subject: QUIC Version Negotiation Interim
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Hello all,

As noted in previous mail, the draft minutes are available here[1]. A
high level summary of the meeting, as well as next steps, follows.

About 25 people attended and David kicked us off with a short update
as editor. Some of the attendees spoke briefly to the ideas that they
had shared to the list since the last meeting. Watson presented the
sketch of an alternative mechanism to achieve version negotiation to
the existing draft[2]. This design was very interesting and provoked
much discussion. There was, after a time, agreement that such a scheme
would likely require a change to the QUIC invariants. While not
strictly impossible there doesn't seem to be much motivation in this
direction or for making a change of that magnitude at this stage.

Much of the discussion focused on the notion of "compatible" versus
"incompatible" version negotiation and whether or not we require just
one, both, or neither. For definitions of these, please read sections
2 and 3 of the draft[2].

Regarding incompatible version negotiation, several people made
arguments that incompatible version negotiation is not needed in
practice today and we are unlikely to need it in the future. As the
main complexity of the current draft is mostly from incompatible
version negotiation, there is potentially a benefit from removing it
as a requirement.

On the other hand, many people felt strongly that incompatible version
negotiation is definitely a requirement and they can foresee use cases
for it. No one present strongly opposed a design which includes
incompatible version negotiation.

Similarly, some made the argument that compatible version negotiation
is also not a requirement. Nominally the same functionality is
achievable with a single QUIC version, transport parameters, and
extensions. There were many people who believe there is still value in
compatible version negotiation. No one present strongly opposed a
design which includes compatible version negotiation. There was a
general desire for clarity around when compatible versions should be
utilized versus simply specifying extensions.

To help get a sense of the room as the session was coming to an end,
the chairs took a show of hands for version negotiation requirement

The chairs observed emerging consensus for supporting both compatible
and incompatible version negotiation. We also observed little interest
in alternatives to the design in the current draft[2]. Therefore the
proposal is to move ahead with the current draft and incorporate some
design improvements. Please comment if you disagree with this
proposal, the consensus call will last for one week until Thursday,
April 29th.

QUIC Chairs
Lars, Lucas, Matt

[1] https://github.com/quicwg/wg-materials/blob/main/interim-21-04/minutes.md
[2] https://tools.ietf.org/html/draft-ietf-quic-version-negotiation-03