Re: HTTP/2.0 section 2.4 "Starting HTTP/2.0 with Prior Knowledge"

Martin Thomson <martin.thomson@gmail.com> Wed, 17 April 2013 21:09 UTC

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Date: Wed, 17 Apr 2013 14:08:14 -0700
Message-ID: <CABkgnnVMgKzbbespzuvsgV0OHn3GEd2VNXx3=fG7aSuHhr4Xbg@mail.gmail.com>
From: Martin Thomson <martin.thomson@gmail.com>
To: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
Cc: Gabriel Montenegro <Gabriel.Montenegro@microsoft.com>, "ietf-http-wg@w3.org" <ietf-http-wg@w3.org>
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Subject: Re: HTTP/2.0 section 2.4 "Starting HTTP/2.0 with Prior Knowledge"
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On 17 April 2013 04:39, Ilari Liusvaara <ilari.liusvaara@elisanet.fi> wrote:
> On Wed, Apr 17, 2013 at 01:15:34AM +0000, Gabriel Montenegro wrote:
>> http://http2.github.io/http2-spec/#known-http says:
>>
>> A client can learn that a particular server supports HTTP/2.0 by other
>> means. A client MAY immediately send HTTP/2.0 frames to a server that
>> is known to support HTTP/2.0. This only affects the resolution of "http:"
>> URIs, servers supporting HTTP/2.0 are required to support protocol
>> negotiation in TLS<http://http2.github.io/http2-spec/#TLSNPN> [TLSNPN].
>>
>> The above fails to include "https:" URIs. It only mentions "http:" URIs.
>
> HTTPS is over TLS, so NPN (ALPN) is a requirement and will reveal if
> server supports HTTP2 without additional RTTs.

That was certainly the intent of the text.  However, I know that
Gabriel is a pretty smart guy and he has been paying attention.  If
this isn't obvious, we should definitely make it more so.

   This only affects the resolution of "http:" URIs, servers
supporting HTTP/2.0 are required to
   support <xref target="TLSNPN">protocol negotiation in TLS</xref>
for "https:" URIs.

https://github.com/http2/http2-spec/commit/329d29e58a88628435ebd4678d3a3bd250155d47

(Note, the ALPN edit isn't in yet, the reference will need to change.)