Re: Design Issue: Separate HEADERS and PRIORITY Frames, Eliminate HEADERS+PRIORITY

William Chan (陈智昌) <willchan@chromium.org> Tue, 21 May 2013 16:34 UTC

Return-Path: <ietf-http-wg-request@listhub.w3.org>
X-Original-To: ietfarch-httpbisa-archive-bis2Juki@ietfa.amsl.com
Delivered-To: ietfarch-httpbisa-archive-bis2Juki@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 1675A21F98E3 for <ietfarch-httpbisa-archive-bis2Juki@ietfa.amsl.com>; Tue, 21 May 2013 09:34:03 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -9.259
X-Spam-Level:
X-Spam-Status: No, score=-9.259 tagged_above=-999 required=5 tests=[AWL=0.417, BAYES_00=-2.599, FM_FORGED_GMAIL=0.622, HTML_MESSAGE=0.001, MIME_8BIT_HEADER=0.3, RCVD_IN_DNSWL_HI=-8]
Received: from mail.ietf.org ([12.22.58.30]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id iTkQXUOuKfb2 for <ietfarch-httpbisa-archive-bis2Juki@ietfa.amsl.com>; Tue, 21 May 2013 09:33:58 -0700 (PDT)
Received: from frink.w3.org (frink.w3.org [128.30.52.56]) by ietfa.amsl.com (Postfix) with ESMTP id 2586021F98DF for <httpbisa-archive-bis2Juki@lists.ietf.org>; Tue, 21 May 2013 09:33:57 -0700 (PDT)
Received: from lists by frink.w3.org with local (Exim 4.72) (envelope-from <ietf-http-wg-request@listhub.w3.org>) id 1UepVG-0008EE-MT for ietf-http-wg-dist@listhub.w3.org; Tue, 21 May 2013 16:33:34 +0000
Resent-Date: Tue, 21 May 2013 16:33:34 +0000
Resent-Message-Id: <E1UepVG-0008EE-MT@frink.w3.org>
Received: from maggie.w3.org ([128.30.52.39]) by frink.w3.org with esmtp (Exim 4.72) (envelope-from <willchan@google.com>) id 1UepV4-0008B6-MP for ietf-http-wg@listhub.w3.org; Tue, 21 May 2013 16:33:22 +0000
Received: from mail-qe0-f54.google.com ([209.85.128.54]) by maggie.w3.org with esmtps (TLS1.0:RSA_ARCFOUR_SHA1:16) (Exim 4.72) (envelope-from <willchan@google.com>) id 1UepUz-0005lQ-7b for ietf-http-wg@w3.org; Tue, 21 May 2013 16:33:22 +0000
Received: by mail-qe0-f54.google.com with SMTP id i11so510631qej.13 for <ietf-http-wg@w3.org>; Tue, 21 May 2013 09:32:51 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type; bh=L9LwJJLQ92viiMSfea0vd0H16BOM1wDIno9FL/ZVXmw=; b=DLrRXrz4cQViVHxLEhGiWZH2c3abzePKLMC+qaXAXRH7sE+fJajQokF2CeNYq5i902 Lwncmxfv0pnfL4AV2opQ1E3q8fqBcXMS+aiTnOgthjPHOBq5QNw98fCOPWiLtMevty5L E2ieIoRqiznH9226CnwMJLfYTDsiHE199NbfR7QR4chRBTmfNF3xa9U3/v5FoyTuE88S yVf0FGnVeECDuCp9X0pmBQ1SBYcv5sdtGqZA6AOmfgG86qujAUOCsW/te6Ot3Pvs9fX7 LPCj79Kwy9SczbdO3PhVlFZpTjoTbi62I1s2fm3/fLzo0+YakX9Zdl0/GCTXdtwQqcZA 3y4g==
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type; bh=L9LwJJLQ92viiMSfea0vd0H16BOM1wDIno9FL/ZVXmw=; b=F+gO3Rdm+TSraa2rH0z+XGGJV2TX4jQunSGuE6sMme9R+nI7X6S6G6WAceMpznGEKd 8ahwf0Fs719DZNzqcInO7hp2t57kld0MdssgGy/MRBwDrkbKIJDAYFyTPNhMnK0ftnpA nE2yw7x7Gjp8LiO+tjbTm9txo/9YxeaTUWRX8=
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :x-gm-message-state; bh=L9LwJJLQ92viiMSfea0vd0H16BOM1wDIno9FL/ZVXmw=; b=ogUb/cC+qxbS8Zj7sI9rxCfgRzQGjyru3Qy9p5rJiFOxL+UR8CF+dInAsHwr6ogDFT qH0er2Da7eCjCglG6Vy2SrUD+O/ENgztqy7kZgPdPeLGc+at416CfB5TH0q1LF810yFK koxbVXFm9WkxfHUJ5M9uTcOr5FqWIwlb3QWj9mCoPENKAg24hgMDkivy0QiJnAo/rVqO xRYgLKkyi/sz4yW0m/mC7kopTwQk7lBktBhYcTwUzPMwh7O8A5gGxTpkkJbpfYLhUiIZ UepEcwKkO8wZFjFnZF/cDeHUZ+QDNZHUK7xHZR2HaUH/LB/niAI3CIB9lwfvtcGz8EDy dQJw==
MIME-Version: 1.0
X-Received: by 10.49.116.206 with SMTP id jy14mr3510989qeb.32.1369153971318; Tue, 21 May 2013 09:32:51 -0700 (PDT)
Sender: willchan@google.com
Received: by 10.229.217.19 with HTTP; Tue, 21 May 2013 09:32:50 -0700 (PDT)
In-Reply-To: <CABP7RbfX_H_7dwM7ExL5qJgpV5JN1NYyv9tqnu_E23qGk63mWg@mail.gmail.com>
References: <CABP7RbfX_H_7dwM7ExL5qJgpV5JN1NYyv9tqnu_E23qGk63mWg@mail.gmail.com>
Date: Tue, 21 May 2013 13:32:50 -0300
X-Google-Sender-Auth: gHhssp_nx8O00n9mQi58dqQeY0w
Message-ID: <CAA4WUYhDhoS+BNknRnYLAOXfWzumcjkWnQnM=NkNM8oqqE=atw@mail.gmail.com>
From: =?UTF-8?B?V2lsbGlhbSBDaGFuICjpmYjmmbrmmIwp?= <willchan@chromium.org>
To: James M Snell <jasnell@gmail.com>
Cc: "ietf-http-wg@w3.org" <ietf-http-wg@w3.org>
Content-Type: multipart/alternative; boundary=047d7b6d7ae01a899d04dd3d0001
X-Gm-Message-State: ALoCoQlj761a5UsJT37zIC5+Kv2HzER/KKSaJDJKnOxiOOEBdN1Cux4dpfR0O+B7NYXU5H9uke4TkpiBvvW7++BMo6RQtuYBSVbGmaJGtJ3vEmAtK5BCEc/+DD+uwG4c/Qkyf2XTsgViVrVrfBQzNcMWTbyYJ4k8UV6ZZy3ie5wxkht3oRNdWR5FlJqJ6LSVW3tzUKQwNp8n
Received-SPF: pass client-ip=209.85.128.54; envelope-from=willchan@google.com; helo=mail-qe0-f54.google.com
X-W3C-Hub-Spam-Status: No, score=-4.1
X-W3C-Hub-Spam-Report: AWL=-2.198, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_LOW=-0.7, RP_MATCHES_RCVD=-1.07, SPF_PASS=-0.001
X-W3C-Scan-Sig: maggie.w3.org 1UepUz-0005lQ-7b 0e55f371b1a2b20dfe7f002176748f17
X-Original-To: ietf-http-wg@w3.org
Subject: Re: Design Issue: Separate HEADERS and PRIORITY Frames, Eliminate HEADERS+PRIORITY
Archived-At: <http://www.w3.org/mid/CAA4WUYhDhoS+BNknRnYLAOXfWzumcjkWnQnM=NkNM8oqqE=atw@mail.gmail.com>
Resent-From: ietf-http-wg@w3.org
X-Mailing-List: <ietf-http-wg@w3.org> archive/latest/18055
X-Loop: ietf-http-wg@w3.org
Resent-Sender: ietf-http-wg-request@w3.org
Precedence: list
List-Id: <ietf-http-wg.w3.org>
List-Help: <http://www.w3.org/Mail/>
List-Post: <mailto:ietf-http-wg@w3.org>
List-Unsubscribe: <mailto:ietf-http-wg-request@w3.org?subject=unsubscribe>

We discussed this previously and Roberto and I were both against the
removal of the priority field from the HEADERS+PRIORITY frame:
http://lists.w3.org/Archives/Public/ietf-http-wg/2013JanMar/1065.html, even
considering stream reprioritization.

I support adding a new additional PRIORITY frame for stream
reprioritization. That said, I'm in no hurry to write anything into the
spec. On the SPDY end we're planning on experimenting with prioritization
and when we have something to present with detailed explanations why, we
will do so. We presented the general ideas previously in the last interim
meeting and haven't finished implementation and experimentation.

Unless there's a reason this needs to be in the current http/2 draft sooner
rather than later, I'd rather punt on this discussion until we have
implementation experience that can guide this debate. I believe everyone
recognizes that people are interested in reprioritization. If we need to
put something in the spec, let's just add a new frame and then revisit
changing HEADERS+PRIORITY later.


On Tue, May 21, 2013 at 1:10 PM, James M Snell <jasnell@gmail.com> wrote:

> https://github.com/http2/http2-spec/issues/99
>
> With regards to the discussion over stream re-prioritization, I suggest:
>
> 1. Drop the HEADERS+PRIORITY frame type.
> 2. Create a new separate PRIORITY frame type whose payload is the
> Priority value, no frame-specific flags.
> 3. The PRIORITY frame becomes the only way to set/change the priority
> for a stream.
>
> If it is necessary to allow an endpoint to establish the priority of
> stream prior to actually initiating the stream, we can allow sending a
> PRIORITY frame before the initial HEADERS frame. Doing so would
> effectively reserve the stream id (in the same general manner
> PUSH_PROMISE does).
>
> The advantages of this approach are:
>
> 1. It eliminates any possible confusion and complexity about when to
> use HEADERS+PRIORITY vs. HEADERS
> 2. It provides a single way of setting/change stream priority (as
> opposed to using HEADERS+PRIORITY plus a separate CHANGE-PRIORITY
> frame)
>
>