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Re: HTTP 2.0 "Upgrade" flow

From: Adrien W. de Croy <adrien@qbik.com>
Date: Wed, 17 Apr 2013 22:36:54 +0000
To: "Martin Thomson" <martin.thomson@gmail.com>
Cc: "Gabriel Montenegro" <Gabriel.Montenegro@microsoft.com>, "Mark Nottingham" <mnot@mnot.net>, "Ilari Liusvaara" <ilari.liusvaara@elisanet.fi>, "Ilya Grigorik" <ilya@igvita.com>, "ietf-http-wg@w3.org Group" <ietf-http-wg@w3.org>
Message-Id: <em221a6930-d6e1-47ea-b735-5f9177f9ddf1@bombed>

------ Original Message ------
From: "Martin Thomson" <martin.thomson@gmail.com>
To: "Adrien W. de Croy" <adrien@qbik.com>
Cc: "Gabriel Montenegro" <Gabriel.Montenegro@microsoft.com>; "Mark 
Nottingham" <mnot@mnot.net>; "Ilari Liusvaara" 
<ilari.liusvaara@elisanet.fi>; "Ilya Grigorik" <ilya@igvita.com>; 
"ietf-http-wg@w3.org Group" <ietf-http-wg@w3.org>
Sent: 18/04/2013 10:11:06 a.m.
Subject: Re: HTTP 2.0 "Upgrade" flow
>I think that you either send the session header immediately after the
>first request (the Upgrade) and risk having it swalled,
that could do nasty things if the server is only 1.1

>or you send it
>immediately before the next (HTTP/2.0) request. In either case, you
>don't incur an RTT delay.
next request may not exist.

>If you thought that the server would wait for the client session
>header before sending its SETTINGS, then I don't think that was every
>the intention (the recent edits from Gabriel fix that problem, I
>hope). That would add an RTT and we don't want that.
>On 17 April 2013 15:07, Adrien W. de Croy <adrien@qbik.com> wrote:
>>  my main concern is what does a forward proxy do.
>>  the client may choose to maintain a database of known http2 capable 
>>  This may be too much of a burden for the proxy.
>>  Discovery at the proxy could be a bit of a burden as well.
>>  A proxy offering 2.0 support to 2.0 clients but still having to talk 
>>to the
>>  great unwashed internet has quite a dilemma. The safe/lazy/whatever 
>>  for the proxy may be to always use the Upgrade option. Adding a RTT 
>>in this
>>  case will be seen by clients/customers as a performance degradation 
>>in many
>>  cases.
>>  Or maybe I've not thought this through properly.
>>  Adrien
>>  ------ Original Message ------
>>  From: "Martin Thomson" <martin.thomson@gmail.com>
>>  To: "Adrien W. de Croy" <adrien@qbik.com>
>>  Cc: "Gabriel Montenegro" <Gabriel.Montenegro@microsoft.com>; "Mark
>>  Nottingham" <mnot@mnot.net>; "Ilari Liusvaara"
>>  <ilari.liusvaara@elisanet.fi>; "Ilya Grigorik" <ilya@igvita.com>;
>>  "ietf-http-wg@w3.org Group" <ietf-http-wg@w3.org>
>>  Sent: 18/04/2013 10:00:47 a.m.
>>  Subject: Re: HTTP 2.0 "Upgrade" flow
>>>  So you intend to make client SETTINGS available to the server prior 
>>>  the server commencing transmission. This is the essence of what
>>>  Gabriel intends with his known state proposal. He is concerned by 
>>>  asymmetry of the exchange when Upgrade is involved (as opposed to 
>>>  TLS session startup). You should talk to Gabriel.
>>>  On 17 April 2013 14:56, Adrien W. de Croy <adrien@qbik.com> wrote:
>>>>   I think it would need to go in as a header. Maybe even as an 
>>>>  to
>>>>   the Upgrade? Not sure if that supports such things. E.g.
>>>>   GET /bob.txt HTTP/1.1
>>>>   Host: somewhere.co.nz
>>>>   Upgrade: HTTP/2.0 ; session=[......]
>>>>   so that the server can respond with the resource in any case.
>>>>   Adding a RTT to all HTTP 2.0 connections I thought had been 
>>>>decided was
>>>>  a
>>>>   non-starter. Or compared to TLS setup phase + NPN maybe it's no 
>>>>   Adrien
>>>>   ------ Original Message ------
>>>>   From: "Martin Thomson" <martin.thomson@gmail.com>
>>>>   To: "Adrien W. de Croy" <adrien@qbik.com>
>>>>   Cc: "Gabriel Montenegro" <Gabriel.Montenegro@microsoft.com>; "Mark
>>>>   Nottingham" <mnot@mnot.net>; "Ilari Liusvaara"
>>>>   <ilari.liusvaara@elisanet.fi>; "Ilya Grigorik" <ilya@igvita.com>;
>>>>   "ietf-http-wg@w3.org Group" <ietf-http-wg@w3.org>
>>>>   Sent: 18/04/2013 9:51:47 a.m.
>>>>   Subject: Re: HTTP 2.0 "Upgrade" flow
>>>>>   It's possible that the client could pipeline the session header, 
>>>>>   that does stand a chance of being subsumed into the initial 
>>>>>   I expect packet-based hacks.
>>>>>   On 17 April 2013 14:42, Adrien W. de Croy <adrien@qbik.com> 
>>>>>>    My understanding was that we would not be sacrificing the first
>>>>>>  request
>>>>>>   due
>>>>>>    to a requirement to upgrade.
>>>>>>    In order for the server to send an actual response, if it needs 
>>>>>>   client
>>>>>>    session header, this should be sent in the initial request 
>>>>>>   includes
>>>>>>    the upgrade.
>>>>>>    Otherwise we just added a RTT
>>>>>>    Adrien
>>>>>>    ------ Original Message ------
>>>>>>    From: "Gabriel Montenegro" <Gabriel.Montenegro@microsoft.com>
>>>>>>    To: "Mark Nottingham" <mnot@mnot.net>
>>>>>>    Cc: "Ilari Liusvaara" <ilari.liusvaara@elisanet.fi>; "Ilya 
>>>>>>    <ilya@igvita.com>; "ietf-http-wg@w3.org Group" 
>>>>>>    Sent: 18/04/2013 5:02:01 a.m.
>>>>>>    Subject: RE: HTTP 2.0 "Upgrade" flow
>>>>>>>>     Personally, I'm not thrilled with how the server session 
>>>>>>>>header is
>>>>>>>>    conflated
>>>>>>>>     with a SETTINGS frame... if we're going to require that the 
>>>>>>>>   send
>>>>>>>>    a
>>>>>>>>     SETTINGS frame first (which is fine), let's just come out 
>>>>>>>>and say
>>>>>>>>   that,
>>>>>>>>    rather
>>>>>>>>     than making it a side effect of requiring a (largely 
>>>>>>>>   server
>>>>>>>>    session
>>>>>>>>     header.
>>>>>>>    The spec already says that in section 3.8.4 that a SETTINGS 
>>>>>>>  MUST
>>>>>>>   be
>>>>>>>    the first frame sent by either party in a new session.
>>>>>>>    So that part is fine. If we wish to say that a server has no 
>>>>>>>    header, that would be fine.
>>>>>>>    As for " As proposed by Gabriel, SETTINGS (or equivalent)
>>>>>>>  would/could
>>>>>>>   be
>>>>>>>    carried in the headers in the UPGRADE request."
>>>>>>>    For the record, I did not say that in the Upgrade scenario the
>>>>>>>  client
>>>>>>>    session header is sent in HTTP/1.1 along with the Upgrade 
>>>>>>>  My
>>>>>>>    understanding is that the Upgrade request goes without the 
>>>>>>>   session
>>>>>>>    header. As we have discussed in Orlando, we could add some 
>>>>>>>   headers
>>>>>>>    to address the known state by conveying *some* of the settings 
>>>>>>>   those
>>>>>>>    absolutely necessary to achieve known initial state). But 
>>>>>>>that's a
>>>>>>>   separate
>>>>>>>    proposal/discussion from this thread.
>>>>>>>    At any rate, the server sends back the 101, and begins its 
>>>>>>>    traffic by sending its SETTINGS frame and its response frames, 
>>>>>>>  the
>>>>>>>    client upon receiving the 101, and only then, begins sending
>>>>>>>  HTTP/2.0
>>>>>>>    traffic starting with its client session header (which 
>>>>>>>includes the
>>>>>>>   magic
>>>>>>>    sequence and the client SETTINGS frame).
Received on Wednesday, 17 April 2013 22:37:18 UTC

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