reserved bit from Flags field | Re: new type number versus repurpose of existing field | … | Re: Setting to disable HTTP/2 Priorities

Kari Hurtta <hurtta-ietf@elmme-mailer.org> Fri, 09 August 2019 05:30 UTC

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To: HTTP Working Group <ietf-http-wg@w3.org>
Date: Fri, 9 Aug 2019 08:26:49 +0300 (EEST)
From: Kari Hurtta <hurtta-ietf@elmme-mailer.org>
CC: Kari Hurtta <hurtta-ietf@elmme-mailer.org>, Matthew Kerwin <matthew@kerwin.net.au>, HTTP Working Group <ietf-http-wg@w3.org>, Lucas Pardue <lucaspardue.24.7@gmail.com>, Brad Lassey <lassey@chromium.org>, Dmitri Tikhonov <dtikhonov@litespeedtech.com>
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Subject: reserved bit from Flags field | Re: new type number versus repurpose of existing field | =?UTF-8?Q?=E2=80=A6_=7C_Re:_Setting_to_disable_HTTP/2?= Priorities
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> <  ⋯ >
> > > In Montreal we also discussed a possible experiment where the H2 PRIORITY
> > > frame contents would be repurposed, which requires a compatible server to
> > > read it correctly. In this case the signal would be more like "will send in
> > > an RFC7540-incompatible format".

> 
> Yes, it makes sense to allocate new type number for PRIORITY when frame
> content is repurposed.
> 
> Also is make sense to allocate new type number for HEADERS when 
> "Stream Dependency" or "Weight" field of HEADERS frame conrent is repurposed.
> 
> That avaind dance about on what point on time change of  "Stream Dependency" / "Weight" field"
> field happens.

Then there is also third possibility:

Invent new field for new stype priority information (say "PRIORITY2").

Indicate presense of PRIORITY2 field with (currently) reserved bit from Flags field (which
is on part 9-octet header of all frames).

There is unused flags bit available for both HEADERS and PRIORITY frame.


And fourth possibility is indicate repurpose of current "Stream Dependency" / "Weight" field"
with (currently) reserved bit from Flags field.

These possibilities also avoid dance on what point on time change of  "Stream Dependency" / "Weight" field"
field happens.

/ Kari Hurtta