Re: Quick review for draft-svirid-websocket2-over-http2 (Was: Re: Draft HTTPbis Agenda For Seoul IETF 97)

Kazuho Oku <> Thu, 20 October 2016 00:54 UTC

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From: Kazuho Oku <>
Date: Thu, 20 Oct 2016 09:48:45 +0900
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To: Ilari Liusvaara <>
Cc: Van Catha <>, HTTP Working Group <>
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Subject: Re: Quick review for draft-svirid-websocket2-over-http2 (Was: Re: Draft HTTPbis Agenda For Seoul IETF 97)
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2016-10-20 1:50 GMT+09:00 Ilari Liusvaara <>:
> On Wed, Oct 19, 2016 at 10:03:18AM -0400, Van Catha wrote:
>> I am particularly interest in the future of 2 way binary streaming.  So the
>> topics of WebSocket, Streams API and other related. I have even put forward
>> a draft related to the WebSocket part.
> Some quick review comments:
> - The handshake seems to negotiate compression and then the frames
>   contain compression method indicator. Are there really multiple
>   compression methods available on per-frame basis, or should the
>   compression just be 1 bit (compressed or not)?
> - The abbrevations in frame diagram are bit difficult to understand
>   (have those be expanded in above text?).
> - Somebody needs to try what this does against many HTTP/2 origins
>   that don't support WebSockets2 and against intermediaries with
>   custom server that actually supports it. Just to see what the
>   heck happens (if it is nasty, one might need to use SETTINGS to
>   signal support, either for WebSockets directly or for some sort
>   of strict scheme).

That's a good point.

In case of H2O, all schemes are handling equally at the protocol
layer. In other words, whatever the :scheme is, the server is designed
to wait for a request, and then send response.

My understanding is that the HTTP/2 specification is written in mind
to allow such implementations, and that it would be a violation of
HTTP/2 to introduce different interactions by using :scheme as an
indicator. For example, transition of the stream states described in
section 5.1 is not restricted to specific schemes.

So if we are to start using the HTTP/2 framing layer to transmit
websocket or other bi-directional communication, I think we should
require negotiation using SETTINGS frame. Also, it might be beneficial
to use a frame type other than DATA to convey bi-directional
information to avoid potential issues (since the transition of the
stream states are mostly related to how DATA frames are handled).

> - What is "valid UTF-8" exactly? E.g. does it contain encodings for
>   Unicode noncharacters?
> -Ilari

Kazuho Oku