Re: Design Issue: HEADERS+PRIORITY "MUST be used" for each stream that is created??

James M Snell <jasnell@gmail.com> Sun, 28 April 2013 06:20 UTC

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Date: Sat, 27 Apr 2013 23:17:51 -0700
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From: James M Snell <jasnell@gmail.com>
To: Roberto Peon <grmocg@gmail.com>
Cc: ietf-http-wg@w3.org, Martin Thomson <martin.thomson@gmail.com>
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Subject: Re: Design Issue: HEADERS+PRIORITY "MUST be used" for each stream that is created??
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Minor correction on my note... I meant to say we don't really seem to have
a good reason to allow data frames *without* preceding header bearing
frames.
On Apr 27, 2013 2:44 PM, "Roberto Peon" <grmocg@gmail.com> wrote:

> The WS case may actually require headers as we do need to announce (per WS
> 'connection') the URL of the endpoint to which it is attaching/connecting.
> -=R
>
>
> On Fri, Apr 26, 2013 at 1:54 PM, James M Snell <jasnell@gmail.com> wrote:
>
>> Well, until that case is made, we don't have very many good reasons to
>> allow DATA frames with preceding headers-bearing frames. Also, keep in
>> mind that it's perfectly legal to send a HEADERS frame with an empty
>> set of HEADERS. It the WebSockets case does not require any preceding
>> headers (which I rather doubt), it would still be simple enough to
>> send an empty HEADERS frame to establish the stream before sending the
>> DATA frames.
>>
>>
>> On Fri, Apr 26, 2013 at 1:49 PM, Martin Thomson
>> <martin.thomson@gmail.com> wrote:
>> > On 26 April 2013 13:43, James M Snell <jasnell@gmail.com> wrote:
>> >> I think I disagree on that point and say that I think it's much safer
>> >> if we require that streams be initiated with only headers-bearing
>> >> frames.
>> >>
>> >> Imagine, for instance, that a sender sends along a DATA frame with a
>> >> new, previously unused stream identifier. Without an associated
>> >> headers frame I have absolutely no context with which to determine
>> >> what I need to do with that DATA frame. Likewise if I receive an
>> >> RST_STREAM that references a previously unused stream identifier. If
>> >> there's absolutely nothing that I can reliably do with it, or not
>> >> reliable way that I can interpret it without additional context, then
>> >> we should not allow it.
>> >
>> > I believe that this is exactly the scenario that the websockets
>> > binding will take advantage of.  (Maybe there is some need to expose
>> > some header information there, but that's a case that needs to be made
>> > for that specific use of the framing layer.)
>>
>>
>