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Re: [hybi] New Version Notification for draft-mcmanus-httpbis-h2-websockets-00.txt

From: Patrick McManus <pmcmanus@mozilla.com>
Date: Mon, 16 Oct 2017 17:31:45 -0400
Message-ID: <CAOdDvNpCGnZcAUaVaVq7eOLkvQFMbd5qf5BAX30nR8iU9=696A@mail.gmail.com>
To: Mike Bishop <Michael.Bishop@microsoft.com>
Cc: Patrick McManus <pmcmanus@mozilla.com>, Andy Green <andy@warmcat.com>, Martin Thomson <martin.thomson@gmail.com>, hybi <hybi@ietf.org>, Cory Benfield <cory@lukasa.co.uk>, Patrick McManus <mcmanus@ducksong.com>, HTTP Working Group <ietf-http-wg@w3.org>
On Mon, Oct 16, 2017 at 1:13 PM, Mike Bishop <Michael.Bishop@microsoft.com>
wrote:

> Generalizing CONNECT to allow you to tunnel protocols other than TCP – or
> rather, to explicitly state what protocol the other side should be
> expecting the TCP connection to speak – is a neat approach.  So first off,
> kudos!
>
>
>
> If you say you’re upgrading to WebSockets, then I’d expect it to actually
> upgrade straight to WebSockets, not an HTTP/1.1 request which is expected
> to then upgrade to WebSockets.  I understand that would entail putting all
> the WebSocket negotiation headers on the CONNECT itself, etc. and I’m
> sympathetic to the argument that it is a larger change that may produce a
> roadbump.  But you’re making a commitment at the HTTP/2 layer that actually
> means nothing (“wss” scheme, “websocket” :protocol).
>
>
I hear what you're saying.. but I think you're going a touch too far.
websocket means 6455 which has all that h1 stuff as part of its
configuration.. I think it would be totally fair to say such a server could
have a more constrained parser that failed any non-ws compliant handshake
even if it were valid h1. Mostly I think it becomes an insanely ugly what
to do websocket parameter exchange.

I think of origin info (scheme and authority) more as keys to route the
CONNECT request.. it's :protocol that defines what to do in the tunnel. I
admit I did consider calling it :alpn (which has a similar kind of
property.. its a route of sorts but it doesn't bear the SETTINGS or magic
of h2)

You have kind of let the cat out of the bag at just doing an h1 connect.
That's actually possible with the draft (or at least envisioned) as I
defined :protocol separate from the websocket specific stuff... but I kinda
hope to never speak of it again :)

This is a tough one - its definitely going for simplicity as its main
goal.. that means ignoring many places that can be improved. That's a
choice based on
 a] the history of other efforts seem to suggest there is no stomach for
complexity/risk here
 b] we hear about this problem enough that I think its worth seeing if this
can be m ade a consensus mvp
 c] my belief that websockets is a transitional technology - it will be
around for years but some kind of native http will supplant it.

ymmv (more than usual on this one!)

-P



>
>
> Given that you’re doing the full Upgrade-to-WebSockets dance inside the
> tunneled connection, why don’t you just say that you’re CONNECTing to an
> HTTP/1.1 tunnel?  That’s then treated as HTTP/1.1 over TCP, which is fully
> allowed to do Upgrade itself.  If you’re sure that’s the path you want,
> then simply say in the HTTP/2 layer that you’re doing HTTP/1.1 inside the
> stream.  Incidentally, that might be a nice alternative for dealing with
> HTTP_1_1_REQUIRED responses, too!
>
>
>
> *From:* Patrick McManus [mailto:pmcmanus@mozilla.com]
> *Sent:* Monday, October 16, 2017 5:16 AM
> *To:* Andy Green <andy@warmcat.com>
> *Cc:* Martin Thomson <martin.thomson@gmail.com>; Patrick McManus <
> pmcmanus@mozilla.com>; hybi <hybi@ietf.org>; Cory Benfield <
> cory@lukasa.co.uk>; Patrick McManus <mcmanus@ducksong.com>; HTTP Working
> Group <ietf-http-wg@w3.org>
> *Subject:* Re: [hybi] New Version Notification for
> draft-mcmanus-httpbis-h2-websockets-00.txt
>
>
>
>
>
>
>
> On Mon, Oct 16, 2017 at 12:44 AM, Andy Green <andy@warmcat.com> wrote:
>
>
> You can probably pipeline the CONNECT + ws handshake though, Patrick shows
> them sequentially and I didn't think about it myself.
>
>
>
> right. The example is just for clarity and cannot show all expressions of
> h2 flows.
>
>
>
> CONNECT + DATA before the response headers is pretty much the h2 analog of
> TCP Fast Open. The devil is in the details.. That's a general CONNECT +
> DATA issue not limited to the protocol upgrade described here so I don't
> think its worth discussion in a websockets rfc.
>
>
>
> I think the path to success here hinges on a very tight scoping of work
> and therefore optimizing handshake latency is a non-goal of this effort.
>
>
>
>
>
> Still only two round trips.
>
>
>  - SETTINGS                      - SETTINGS
>  - GET /index.html
>                  - 200 HEADERS + DATA
>
>  - :method CONNECT
>  - DATA ws handshake
>                   - 200 HEADERS
>                   - DATA ws handshake final
>                   - DATA...
>
>  - DATA ...             - DATA...
>
> With the part of the pipelining that is legal for ws, two round trips
> before the client can start to send data and 1.5 before the server can send
> data... if it's true then you're right it's not so bad.
>
> Were you concerned that the client needs to learn that the server
> supports websockets and not just :protocol?
>
>
> No I just followed Patrick's sequencing; he shows them serialized.  But
> you're right at least the CONNECT + ws handshake can probably be pipelined.
>
> That's also going to be a variation from normal h2 HEADERS flow if I
> understood it, on one stream there will be END_HEADERs coming twice (for
> the CONNECT and the ws handshake separately)
>
> Anyway you are right, it makes any difference with PUSH_PROMISE probably
> not worth the effort.
>
> -Andy
>
>
>
Received on Monday, 16 October 2017 21:32:12 UTC

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