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

James M Snell <jasnell@gmail.com> Fri, 26 April 2013 20:55 UTC

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From: James M Snell <jasnell@gmail.com>
Date: Fri, 26 Apr 2013 13:54:16 -0700
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To: 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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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.)