Re: Alt-SvcB

David Schinazi <> Tue, 25 October 2022 18:30 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 75BCEC14CF10 for <>; Tue, 25 Oct 2022 11:30:03 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -7.759
X-Spam-Status: No, score=-7.759 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, HEADER_FROM_DIFFERENT_DOMAINS=0.249, HTML_MESSAGE=0.001, MAILING_LIST_MULTI=-1, RCVD_IN_DNSWL_HI=-5, RCVD_IN_MSPIKE_H2=-0.001, RCVD_IN_ZEN_BLOCKED_OPENDNS=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01, URIBL_DBL_BLOCKED_OPENDNS=0.001, URIBL_ZEN_BLOCKED_OPENDNS=0.001] autolearn=ham autolearn_force=no
Authentication-Results: (amavisd-new); dkim=pass (2048-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id HEyU4EhmOuuX for <>; Tue, 25 Oct 2022 11:29:59 -0700 (PDT)
Received: from ( []) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by (Postfix) with ESMTPS id B108AC14CF0E for <>; Tue, 25 Oct 2022 11:29:59 -0700 (PDT)
Received: from lists by with local (Exim 4.94.2) (envelope-from <>) id 1onOci-0043iX-CZ for; Tue, 25 Oct 2022 18:26:00 +0000
Resent-Date: Tue, 25 Oct 2022 18:26:00 +0000
Resent-Message-Id: <>
Received: from ([]) by with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from <>) id 1onOch-0043ha-8j for; Tue, 25 Oct 2022 18:25:59 +0000
Received: from ([2a00:1450:4864:20::535]) by with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94.2) (envelope-from <>) id 1onOcf-001gQ5-R2 for; Tue, 25 Oct 2022 18:25:58 +0000
Received: by with SMTP id y12so17361224edc.9 for <>; Tue, 25 Oct 2022 11:25:57 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=zLUGI5wBknISrz1qiCLtoNZAwxLU974s5TYHDKQ8VJM=; b=NyEVA1LeX4ptskpZ+3yKuF2tUhWoA9Ylv8I+Q78fsL9Tu+H4uPaQQZt17hksGUEJEf i8DbzYMole9BMsndmYeBqCGq0hmAq1YOtyvg2KGAlQS8qYNYSsw6pQo/jQNYqaO8DOt5 fYnTcBlZQGGo8MvFObOmTk+qU12FiRHy1d85eBLwVeP4EW1wxuNqXXIj0RAIsINIQvPs FqDbLgQjSBhyxX2LQ71QaqfYGL3/K3Mc5+DalUXMSyc0TNKNG+DWYWsXhT25X/VZORnt FqVLnJH+SBoFj7xBXG0maqMgQyd0RPuqQMND00votf3J6ktyobMJWVcoMe7iXanN7Rmh SMkQ==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=zLUGI5wBknISrz1qiCLtoNZAwxLU974s5TYHDKQ8VJM=; b=lRu2Wm9Dm/hn/a31va0z1Kypo1+dfadFqZOSiYgQqqUcsc9qAWcbEn9Ily6xQCYKGP f2oPhxoGJjpIYyusvHmqDpFPOYG/KjTCzgVDe+IW1z2HIVHeguhOORSaCnsrymQJ3goG Wjt4LoIQfKIxXWFcaJOD9e3tcQFOjNrI2qoxkaW6PzFBM+AtxjUCTIDhhEaMQayAKtww sgCAisEqccOgaUBRb9+wbLtLlOZ0gM+XC8NbQlXPPEh8DyPS8QY41JDEUQ2EBc/HwaC2 9bdhEi6+YsBVT1M6j1QvhQlLuI1CxfpliRNdzlYmLk3cUQXwBMmPDnJUz2NE0p4FknA4 6L1Q==
X-Gm-Message-State: ACrzQf23mkreoTu4OMvf3NmIxr3Jp3aTFFCww7/4Jgvn4oe83dgDPRS9 vhyfMMUs0Gak/l7IjulEmoS/FqI3Xt+X6e25vSKeGKnz
X-Google-Smtp-Source: AMsMyM5UKyioIBhKR4ynku0hkn40PZG0pEDbnYKbMznbq/8vOse5aLXEKscG6FAP7n1xlz2vWeFU9sJDOS+3hZk93oI=
X-Received: by 2002:a05:6402:114a:b0:454:85e4:2295 with SMTP id g10-20020a056402114a00b0045485e42295mr37986293edw.348.1666722346559; Tue, 25 Oct 2022 11:25:46 -0700 (PDT)
MIME-Version: 1.0
References: <>
In-Reply-To: <>
From: David Schinazi <>
Date: Tue, 25 Oct 2022 11:25:34 -0700
Message-ID: <>
To: Martin Thomson <>
Content-Type: multipart/alternative; boundary="00000000000067ece605ebe009ac"
Received-SPF: pass client-ip=2a00:1450:4864:20::535;;
X-W3C-Hub-DKIM-Status: validation passed: (, signature is good
X-W3C-Hub-Spam-Status: No, score=-6.1
X-W3C-Hub-Spam-Report: BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, W3C_AA=-1, W3C_DB=-1, W3C_IRA=-1, W3C_WL=-1
X-W3C-Scan-Sig: 1onOcf-001gQ5-R2 0ef039a30d879fc8f22c5e47c5634ee6
Subject: Re: Alt-SvcB
Archived-At: <>
X-Mailing-List: <> archive/latest/40483
Precedence: list
List-Id: <>
List-Help: <>
List-Post: <>
List-Unsubscribe: <>

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.


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