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Re: Stream State and PRIORITY Frames

From: Scott Mitchell <scott.k.mitch1@gmail.com>
Date: Wed, 18 Jan 2017 17:21:13 -0800
Message-ID: <CAFn2buB_RpbwaTzDgYUNt0e9=vFyu--SYgSLBrfAd1Tf0b1_nQ@mail.gmail.com>
To: Martin Thomson <martin.thomson@gmail.com>
Cc: Tatsuhiro Tsujikawa <tatsuhiro.t@gmail.com>, HTTP Working Group <ietf-http-wg@w3.org>
On Tue, Jan 17, 2017 at 2:43 PM, Scott Mitchell <scott.k.mitch1@gmail.com>
wrote:

> From my perspective I would like to see two clarifications:
>
> 1. It is clear to me that PRIORITY doesn't impact state.
>

Just to clarify ... it is clear that a PRIORITY frame doesn't impact the
state of the stream  it is carrying priority information for. The impacts
PRIORITY frames have on other streams is not clear due to the wording in
section 5.1.1.


> However Section 5.1.1 states "first use of a new stream identifier" which
> makes no reference to stream state. If stream state is important/implied
> here better to be specific about it. I don't think the one-off example
> below this text is sufficient to convey the intended implications of this
> statement.
>
> 2. Section 5.1.2 states "Streams in either of the 'reserved' states do
> not count toward the stream limit." which seems to conflict with section
> 8.2.2 "A client can use the SETTINGS_MAX_CONCURRENT_STREAMS setting to
> limit the number of responses that can be concurrently pushed by a server.".
> These two statements appear to contradict each other. Since
> SETTINGS_MAX_CONCURRENT_STREAMS is really the only mechanism to limit
> resources due to server push I'm assuming section 5.1.2 is overly
> restrictive.
>
>
> On Tue, Jan 17, 2017 at 2:27 PM, Martin Thomson <martin.thomson@gmail.com>
> wrote:
>
>> On 18 January 2017 at 01:37, Tatsuhiro Tsujikawa <tatsuhiro.t@gmail.com>
>> wrote:
>> > If my understanding is correct, this only refers to the new stream ID
>> used
>> > by HEADERS, and PUSH_PROMISE frames which open or reserve streams.  The
>> > example text following that statement uses HEADERS which opens new
>> stream.
>> > PRIORITY frame does not change stream state, and there is no reason to
>> close
>> > all unused streams lower than bearing stream ID.  That said, I agree
>> that
>> > this is not crystal clear in the document.  In practice, this is
>> probably
>> > rather rare case.
>>
>> This is, I think, the expectation.
>>
>> I think that we probably want to clarify the point by explicitly
>> saying that PRIORITY doesn't affect stream states.  We say that it can
>> be sent in any state, but we don't also mention that important point.
>> Do people here agree that an erratum on this point is appropriate
>> here?
>>
>
>
Received on Thursday, 19 January 2017 01:21:47 UTC

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