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Re: SYN_REPLY

From: James M Snell <jasnell@gmail.com>
Date: Mon, 25 Feb 2013 20:51:45 -0800
Message-ID: <CABP7RbfBbatzzSRv+SFgOxx58ftS2LmAs8c0tkOEYXgetv27AQ@mail.gmail.com>
To: William Chan (陈智昌) <willchan@chromium.org>
Cc: Roberto Peon <grmocg@gmail.com>, Martin Thomson <martin.thomson@gmail.com>, HTTP Working Group <ietf-http-wg@w3.org>
"Combining SYN_REPLY and HEADERS" isn't quite the right terminology
here but I believe there is some optimization that we can get by
eliminating SYN_REPLY and using SYN_STREAM to signal responses. If the
outbound SYN_STREAM has the same opaque-id as the inbound SYN_STREAM,
then it's a reply. That ought to be easy enough to coordinate and
gives us good consistency with SYN_STREAMS for pushes. That gives us
the potential option of allowing servers to prioritize response
traffic.

For right now, however, I'd say it's likely best to leave SYN_REPLY as
it is and do some experimentation to figure out if this optimization
really does make sense. We can pull SYN_REPLY out in the next
iteration.

On Mon, Feb 25, 2013 at 8:42 PM, William Chan (陈智昌)
<willchan@chromium.org> wrote:
> Fully agreed it's more general. I think that unless we go all the way with
> ditching SYN_STREAM too (which I disagree with), then I think it's a net
> loss (primarily due to more difficulty in grokking the spec) to save a frame
> type value and combine SYN_REPLY and HEADERS into one.
>
>
> On Mon, Feb 25, 2013 at 8:39 PM, Roberto Peon <grmocg@gmail.com> wrote:
>>
>> HEADERS can be used for arbitrary other key-value metadata, in
>> other-than-HTTP semantic layers so it more general a name than SYN_REPLY.
>>
>> It is cheap either way, and I don't care either way :)
>> -=R
>>
>>
>> On Mon, Feb 25, 2013 at 8:36 PM, William Chan (陈智昌)
>> <willchan@chromium.org> wrote:
>>>
>>> It's kinda nice when reading the spec to have a symmetric
>>> SYN_STREAM&SYN_REPLY. Is there a reason to prefer the HEADERS name over the
>>> SYN_REPLY name? One main use case with HEADERS was for server push, but now
>>> that we're opting to use a PUSH_PROMISE frame rather than a SYN_STREAM as
>>> our "promise", we don't need HEADERS since we'll just send a SYN_STREAM when
>>> we need it.
>>>
>>> How important is supporting stuff like chunked extension headers and http
>>> trailers? I guess we need to support it for backwards compatibility reasons
>>> with HTTP/1.X? I guess if we need that, then a HEADERS name might be more
>>> "general", but it is somewhat hurtful for the common case where all the
>>> headers come back in a single reply.
>>>
>>> If no one has other comments about this, then don't worry about my
>>> concerns and move forward anyways. I'm more lamenting the assymetry of
>>> SYN_STREAM and HEADERS. I suspect it'll confuse people. Honestly, despite
>>> the "wastefulness" of a frame type, maybe it's better for clarity's sake to
>>> burn a frame type (they're cheap). I think the code cost is cheap too.
>>>
>>>
>>> On Thu, Feb 21, 2013 at 4:09 PM, Roberto Peon <grmocg@gmail.com> wrote:
>>>>
>>>> Indeed, on re-reading the first message, that is what you're proposing.
>>>>
>>>> Seems reasonable to me.
>>>> -=R
>>>>
>>>>
>>>> On Thu, Feb 21, 2013 at 4:07 PM, Roberto Peon <grmocg@gmail.com> wrote:
>>>>>
>>>>>
>>>>>> > SYN_REPLY doesn't have one, because it doesn't need to declare
>>>>>> > priority--
>>>>>> > the SYN_STREAM already did that, and it is almost always a waste to
>>>>>> > include
>>>>>> > a priority field in SYN_REPLY.
>>>>>>
>>>>>> Agree.  So what does SYN_REPLY actually do then?
>>>>>>
>>>>> It contains a HEADERS block and little else. If you're arguing to elide
>>>>> SYN_REPLY given HEADERS, then sure, I can see that-- the frame fields are
>>>>> the same now that we've removed the 'in-reply-to' field.
>>>>>
>>>>> -=R
>>>>
>>>>
>>>
>>
>
Received on Tuesday, 26 February 2013 04:52:32 GMT

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