Re: [Doh] re original_transport indicator

Martin Thomson <> Fri, 06 April 2018 01:12 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 0EE811252BA; Thu, 5 Apr 2018 18:12:11 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -2.7
X-Spam-Status: No, score=-2.7 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_LOW=-0.7, SPF_PASS=-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 eDV-Su_a1ZuM; Thu, 5 Apr 2018 18:12:09 -0700 (PDT)
Received: from ( [IPv6:2607:f8b0:4003:c06::229]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id EECAF1200A0; Thu, 5 Apr 2018 18:12:08 -0700 (PDT)
Received: by with SMTP id 188-v6so24147066oih.8; Thu, 05 Apr 2018 18:12:08 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=AzBiRJWqPDZpMb2hezClDiI8osS5/IpvKF/3+ermPDg=; b=IP+QrvXdyxaTCp7WbChSS7MCTo+J8jRvVxIg5LPPNSTIafavRwhQ/RpDv32YvIakXH LbCHyJpttnzn6kcjI1Hm5santIbIlI3wKSLXDaY3DF5yHrO9oNMNgllPKxVfKiYR0TqN 0tVcVnFB4J8dA4aHVAwQGjFUqJ6RpS/6xyJs1xVXWG3ykzKtXVHR+0fzB87A7TImSDmQ GSg5z80ZO2bFFTpg+2QEzJNeo131s4PB/9P8Ka1KdcRb9BK50VHr3zUUKvUG1krXfDFz 2CFiNoK9MqH6C0LSihFq03eGSEyzYmPUs6S3BqojNzYdNS42mg/sKzj2EyQIFmq48lxx EGlw==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=AzBiRJWqPDZpMb2hezClDiI8osS5/IpvKF/3+ermPDg=; b=R3cOresuCb6tmfqWdaUu4zHY7I4Ash6fvreRuc747aE+Xrlk7TP4kxF5WJw803kkxt PdeSKmiH7MMsMqTcg6Kcnc25UFD10r+a7jjxvXcsR8Gl5RSSDTdPVeFc3aUNLaq6+n3t vccj3RCtA1l9Fz0qjOUVmtBMl8A0IjLlGE4X3MpRwyOKowGo6/kVTz7/552nRq6N22Am W6xSqD8r526tLQZ5WpEuvyhrsRcLW8ghA83zTRB8thkdB4CdT8LayejYWnFkuTOdx1n3 Xf6C6uLDA5tBC6ec4zxKQiipoC1hmRBiT8YVJLucrsAxiC+vvq9S/HlrYro1/VbwAp5W s0Jw==
X-Gm-Message-State: ALQs6tAI8VhzzI0K3yHojpWLOpbhDeOQNIIBYZOG/jgJPk2RZDAXaVNY kdE06eVwdOeMQFfcW1blsZ/zNMTZyBmHGTdnM5I=
X-Google-Smtp-Source: AIpwx496FKjtlmEN7aW6Kv1iRMXt9SwUHaR1FKLJe23UliHgrB4AM4OQp2J8ho8UI2cqXSRoq7H6w/puRfMOEOG9iTs=
X-Received: by 2002:aca:4ac2:: with SMTP id x185-v6mr13163778oia.295.1522977128046; Thu, 05 Apr 2018 18:12:08 -0700 (PDT)
MIME-Version: 1.0
Received: by 2002:a9d:ac7:0:0:0:0:0 with HTTP; Thu, 5 Apr 2018 18:12:07 -0700 (PDT)
In-Reply-To: <>
References: <>
From: Martin Thomson <>
Date: Fri, 6 Apr 2018 11:12:07 +1000
Message-ID: <>
To: Patrick McManus <>
Cc: Paul Vixie <>, dnsop <>, DoH WG <>, Ted Lemon <>, Ray Bellis <>
Content-Type: text/plain; charset="UTF-8"
Archived-At: <>
Subject: Re: [Doh] re original_transport indicator
X-Mailman-Version: 2.1.22
Precedence: list
List-Id: DNS Over HTTPS <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Fri, 06 Apr 2018 01:12:11 -0000

+1 to this.

And maybe there is an outcome that doesn't need this parameter.  I
probably misunderstood some of the expectations people have for the
parameter.  With the benefit of time and sleep, it's possible that I
now understand the disconnect.

My model of content-type - and by extension its parameters - is of a
description of the content.  However, it appears as though at least
some people had different uses for the parameter: for requests, it
would be an instruction/suggestion to the server to make a DNS request
using the identified transport; for responses, it would be a
description of where the DNS request came from.

I never considered that interpretation, but - assuming that this is
what it was - and the intent was to provide a means for the client to
control how the server makes requests (and to see how they were made).
In that case, I have a possible alternative design for the use case in
the dnsop draft.

Right now, DOH doesn't really say how a DNS API Server gets its
responses.  It could be that the API server is part of a resolver, or
it could be that the DNS API Server makes a request to another
resolver.  But specific uses of the DOH protocol could come with
additional constraints that would enable the use cases in the dnsop
draft, at least as I understand them.

If the goal of the dnsop draft is to extend the reach of a DNS client
(note: not a DNS API client) across a network that is in some way less
hostile to HTTP than it is to DNS, then I think that it can still use
DOH.  A DNS API server could be configured to operate in a very simple
mode with no caching, just direct transposition of a request from HTTP
to a request on UDP or TCP.  A DNS client could be configured with two
DNS API clients.  Each client uses a different DNS API Server
endpoint.  Those endpoints would be specifically configured to use
only UDP or TCP.

For instance:
https://use.only/tcp{?dns} would cause the server to make a request using TCP.
https://use.only/udp{?dns} would cause the server to make a request using UDP.

At this point, this is simple DOH, but with extra contextual
information about server operation.

The concerns about the requirement for HTTPS is a relevant concern.
If there are cases where an unprotected HTTP connection carrying DNS
is expected to traverse a network without modification where DNS
encounters difficulty, maybe the dnsop draft can concentrate on that
particular aspect of this.  I don't think that the suggestion in DOH
to use HTTP/2 is a problem; DOH permits the use of any version of

On Fri, Apr 6, 2018 at 6:53 AM, Patrick McManus <>; wrote:
> Hi All,
> We've had quite a thread re the -05 optional parameter to the
> dns-udpwireformat registration.
> The parameter is defined as having no meaning for DoH, but was included to
> accommodate a use case the dnsop wg is considering. Future proofing, if you
> like.
> Upon consideration (and a read of 6838), I think including this in doh is
> premature because Media Type registrations can be updated by mechanisms laid
> out in RFC6838 and in this case such an update could occur without impacting
> existing DoH deployments. (i.e. it does not need to be future proofed).
> Therefore the definition of the parameter should accompany the work that
> makes use of it if a future standards document chooses to go down that path.
> As a bonus we avoid unused clutter if it doesn't happen. I also get the
> feeling that there isn't yet strong consensus on the anticipated use case or
> the exact form it needs to take - we should let that process work itself out
> separately before registration.
> I've chatted with Paul, and our recommendation is to remove the
> original_transport parameter from DoH and encourage dnsop to update the
> registration if/when a different standard needs to make use of it.
> thoughts?
> -Patrick