Re: [Doh] Dedicated DoH port

Ben Schwartz <bemasc@google.com> Thu, 11 April 2019 18:21 UTC

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From: Ben Schwartz <bemasc@google.com>
Date: Thu, 11 Apr 2019 14:21:40 -0400
Message-ID: <CAHbrMsBw-zkrGm4Byk3Z2yNxgzaO_dKN-czbbGK-No+0JSWh4Q@mail.gmail.com>
To: Jim Reid <jim@rfc1035.com>
Cc: Tomas Krizek <tomas.krizek@nic.cz>, DoH WG <doh@ietf.org>
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Subject: Re: [Doh] Dedicated DoH port
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Tomas, as you know, DNS-over-HTTPS is an HTTP service, identified by a
unique path.  HTTP is designed to multiplex multiple services on different
paths, sharing the same port.

Rather than choose a fixed port from the ephemeral range (which may already
be in use if you are sufficiently unlucky), I recommend using 443 as the
default for users who do not want multiplexing, and implementing FastCGI
support for users who want to operate their own HTTPS frontend.  This would
give you compatibility with essentially all common HTTPS frontend servers:
https://en.wikipedia.org/wiki/FastCGI#Web_servers_that_implement_it.

On Thu, Apr 11, 2019 at 2:11 PM Jim Reid <jim@rfc1035.com>; wrote:

>
>
> > On 11 Apr 2019, at 18:41, Tomas Krizek <tomas.krizek@nic.cz>; wrote:
> >
> > Since there is currently no IANA assigned DoH port, I've filed the
> > following user port request with IANA to establish a common default that
> > could be used among DNS vendors.
> >
> > Service Name:         [domain-doh]
> > Desired Port Number:  [44353]
> > Description:          [DNS query-response protocol over HTTPS]
>
> This seems a bit hasty. Perhaps there should be an I-D or RFC first?
> Allocating a port number from the well-known range might be a wiser choice
> than arbitrarily choosing 44353.
>
> I'm not sure it's a good idea to allocate a port number just so someone
> can run a web server and DoH-capable DNS server on the same box. That's
> unlikely to be a common use case. Besides, the web server could just
> forward inbound DoH queries to port 53 over the loopback interface. Or
> something like that.
>
> Another solution might be to update the current discovery draft to include
> an (optional?) port number as well as the IP address to use for DoH service.
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