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Re: [hybi] WebSocket subprotocol parameters

Tobias Oberstein <tobias.oberstein@tavendo.de> Mon, 20 January 2014 11:26 UTC

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From: Tobias Oberstein <tobias.oberstein@tavendo.de>
To: Takeshi Yoshino <tyoshino@google.com>
Date: Mon, 20 Jan 2014 03:26:03 -0800
Thread-Topic: [hybi] WebSocket subprotocol parameters
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Cc: Julian Reschke <julian.reschke@gmx.de>, "hybi@ietf.org" <hybi@ietf.org>
Subject: Re: [hybi] WebSocket subprotocol parameters
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Hi Takeshi,

thanks alot for digging out these posts!

In retrospect, I think it's a pity that we did not specify "qvalue-like" grammer for Sec-WebSocket-Protocol as we did for Sec-WebSocket-Extension.

The latter provides a lot of useful flexibility … eg as used in "permessage-deflate".

Hacks like having subprotocols like this

wamp.2.json
wamp.2.msgpack
wamp.2.json.batched
wamp.2.msgpack.batched
..

negotiated only works for "discrete value parameters" (json/msgpack, batched/unbatched), but breaks down quite quickly.

As Julian pointed out, making Sec-WebSocket-Protocol using the same "qvalue-grammer" as Sec-WebSocket-Extension
would be a significant change to the RFC6455, and break existing code.

It would also possibly require changes to the WS API in JavaScript to be useful.

Mmh. Too bad;(

/Tobias




Von: Takeshi Yoshino [mailto:tyoshino@google.com]
Gesendet: Montag, 20. Januar 2014 09:36
An: Tobias Oberstein
Cc: Julian Reschke; hybi@ietf.org
Betreff: Re: [hybi] WebSocket subprotocol parameters

On Fri, Jan 17, 2014 at 10:01 PM, Tobias Oberstein <tobias.oberstein@tavendo.de<mailto:tobias.oberstein@tavendo.de>> wrote:
> > Was there any good reason disallowing parameters for "Sec-WebSocket-
> Protocol"?
>
> I think that was discussed and the decision was made on purpose. For details
> you'll have to visit the mailing list archives though.
I can't find it .. searching the Hybi archives is a pain ..

I can't recall such discussion.

In this thread, Brodie used an example similar to that, but the main topic of the post was to update the spec to include multiple subprotocol offer mechanism.
http://www.ietf.org/mail-archive/web/hybi/current/msg04467.html

In this long thread, what character should be used for subprotocol is discussed. Some people preferred more liberal rule, but no one discussed qvalue-like grammar.
http://www.ietf.org/mail-archive/web/hybi/current/msg00913.html

Subprotocol History FYI:

We added the constraint "U+0021 ..  U+007E" from
http://tools.ietf.org/html/draft-hixie-thewebsocketprotocol-31 -> 32

Single value -> multiple value (SP-separated)
http://tools.ietf.org/html/draft-ietf-hybi-thewebsocketprotocol-02 -> 03

We made it follow 1#(token | quoted-string) ABNF from
http://tools.ietf.org/html/draft-ietf-hybi-thewebsocketprotocol-03 -> 04

Changed from (token | quoted-string) to token
http://tools.ietf.org/html/draft-ietf-hybi-thewebsocketprotocol-07

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