Re: QUIC Version Negotiation Interim

Lucas Pardue <> Fri, 23 April 2021 02:21 UTC

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From: Lucas Pardue <>
Date: Fri, 23 Apr 2021 03:21:41 +0100
Message-ID: <>
Subject: Re: QUIC Version Negotiation Interim
To: Marten Seemann <>
Cc: Matt Joras <>, IETF QUIC WG <>
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Hi Marten,

On Fri, 23 Apr 2021, 03:06 Marten Seemann, <> wrote:

> Thank you for the summary. Is there a recording of the meeting? Would have
> love to attend if it had been at a more suitable time.

The meeting was held on WebEx and it was recorded. The secretariat kindly
publish these for us to YouTube and that can take up to 10 working days [1].

I'll make a note to reply here once I see the video go live on YouTube.


[1] -

> On Fri, Apr 23, 2021 at 01:34 Matt Joras <> wrote:
>> 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
>> options.
>> 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.
>> Thanks,
>> QUIC Chairs
>> Lars, Lucas, Matt
>> [1]
>> [2]