Re: Alt-SvcB

Ian Swett <> Tue, 25 October 2022 20:25 UTC

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From: Ian Swett <>
Date: Tue, 25 Oct 2022 16:21:29 -0400
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To: David Schinazi <>
Cc: Martin Thomson <>,
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Subject: Re: Alt-SvcB
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I would second David's statement.  In the world we live in today, we still
need to use the Alt-Svc header for a substantial number of users.

On Tue, Oct 25, 2022 at 2:31 PM David Schinazi <>

> Hi Martin,
> Thanks for writing this up. Overall I think the long-term strategy makes
> sense, but I think it's too early to obsolete/deprecate 7838. It's fairly
> common for browsers to use getaddrinfo() on some platforms and that does
> not provide access to HTTPS RRs. In those cases, 7838 is the only path to
> using HTTP/3, so I expect browsers to keep using it for quite some time.
> Marking 7838 as obsolete doesn't reflect that reality.
> David
> On Mon, Oct 24, 2022 at 5:10 PM Martin Thomson <> wrote:
>> Hey everyone,
>> The Alt-Svc design team has been very busy recently and making some
>> progress on working out an alternative alternative services design.
>> I just posted
>> as a -00 draft.  This outlines the alternative design that we've been
>> exploring in the design team.
>> The basic idea is split into two procedures:
>> 1. Use: When an Alt-SvcB field or ALTSVCB frame is encountered, the
>> client looks for HTTPS records for the provided name in the DNS and creates
>> a connection using what it learns.
>> 2. Reuse: When a client that has previously used an alternative service
>> connects again, it remembers the HTTPS record that worked.  It performs a
>> regular HTTPS record lookup for the server - not using the alternative that
>> it learned, but the name from the URI - but it prefers the alternative it
>> previously used if that alternative appears in the results.
>> The draft explains in more detail and goes into some of the implications
>> of the design.
>> This is not done by any imagining.  We have a bunch of open issues at
>> that do require some
>> amount of input.  But we think that this is a promising approach and would
>> appreciate more input.
>> Cheers,
>> Martin