Re: proposed WINDOW_UPDATE text for session flow control windows

Mark Nottingham <mnot@mnot.net> Tue, 26 February 2013 01:04 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 9828621E8127 for <ietfarch-httpbisa-archive-bis2Juki@ietfa.amsl.com>; Mon, 25 Feb 2013 17:04:19 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -9.551
X-Spam-Level:
X-Spam-Status: No, score=-9.551 tagged_above=-999 required=5 tests=[AWL=1.048, BAYES_00=-2.599, RCVD_IN_DNSWL_HI=-8]
Received: from mail.ietf.org ([64.170.98.30]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Le5PYZfoaw0D for <ietfarch-httpbisa-archive-bis2Juki@ietfa.amsl.com>; Mon, 25 Feb 2013 17:04:19 -0800 (PST)
Received: from frink.w3.org (frink.w3.org [128.30.52.56]) by ietfa.amsl.com (Postfix) with ESMTP id 091AE21E80B6 for <httpbisa-archive-bis2Juki@lists.ietf.org>; Mon, 25 Feb 2013 17:04:19 -0800 (PST)
Received: from lists by frink.w3.org with local (Exim 4.72) (envelope-from <ietf-http-wg-request@listhub.w3.org>) id 1UA8xE-0004Oy-Ou for ietf-http-wg-dist@listhub.w3.org; Tue, 26 Feb 2013 01:03:36 +0000
Resent-Date: Tue, 26 Feb 2013 01:03:36 +0000
Resent-Message-Id: <E1UA8xE-0004Oy-Ou@frink.w3.org>
Received: from maggie.w3.org ([128.30.52.39]) by frink.w3.org with esmtp (Exim 4.72) (envelope-from <mnot@mnot.net>) id 1UA8x5-0004Lg-Ep for ietf-http-wg@listhub.w3.org; Tue, 26 Feb 2013 01:03:27 +0000
Received: from mxout-07.mxes.net ([216.86.168.182]) by maggie.w3.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.72) (envelope-from <mnot@mnot.net>) id 1UA8uq-0001sS-ES for ietf-http-wg@w3.org; Tue, 26 Feb 2013 01:02:51 +0000
Received: from [192.168.1.80] (unknown [118.209.5.152]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) by smtp.mxes.net (Postfix) with ESMTPSA id D9C2B22E1F4; Mon, 25 Feb 2013 20:00:44 -0500 (EST)
Content-Type: text/plain; charset=us-ascii
Mime-Version: 1.0 (Mac OS X Mail 6.2 \(1499\))
From: Mark Nottingham <mnot@mnot.net>
In-Reply-To: <CABkgnnWgNHHHuCSXNpDQSVbaBTp=ZYnPH+MX9-_CXvaj4VD83w@mail.gmail.com>
Date: Tue, 26 Feb 2013 12:00:41 +1100
Cc: Roberto Peon <grmocg@gmail.com>, =?utf-8?Q?William_Chan_=28=E9=99=88=E6=99=BA=E6=98=8C=29?= <willchan@chromium.org>, Patrick McManus <mcmanus@ducksong.com>, HTTP Working Group <ietf-http-wg@w3.org>
Content-Transfer-Encoding: quoted-printable
Message-Id: <A89944B3-8BB6-4B09-AF80-4F2C683A14EF@mnot.net>
References: <CAA4WUYiH8tCF83=jsk_jsvhXkYvmJ+pPLFzhacAMq3O54z2YBw@mail.gmail.com> <CAOdDvNqCe3d7QerQaxiwdwJ+wC+4CGA4ZrLRYFY75nR2QFThog@mail.gmail.com> <CAA4WUYg2gn7Um1FZk3KBcP5aH=RpSCbYduFz3M+hZGQ_A4tsxQ@mail.gmail.com> <CAOdDvNqTNa=R1MzZe1mKZF34tW-=mhHnM_s_XPVzBBSEWHveVQ@mail.gmail.com> <CAA4WUYiW6xsT8g--1cL7HZTVYS_+5Y-WKpzfbx2JCLRqHXNgcQ@mail.gmail.com> <2595AFA8-9928-4511-B569-3DFC36B73C5C@mnot.net> <CAA4WUYg8ksyjKYmeX6YC3P1-iaRRSD_e5KDhpPw0d9i2CnvpSQ@mail.gmail.com> <CABkgnnU4=OYYZEkS7sfxWjXum+Mpx7RzUdJSzYa9a+UybESQYw@mail.gmail.com> <CAP+FsNcDxJeU=7+x8Jx5TO0hm_P2yCKPu7_tEZF0GEtjMbQ2Xg@mail.gmail.com> <CAA4WUYh1qU6HPbeZTsFTy7i5svxWS2dATgUNyaoGnzbMLkCELg@mail.gmail.com> <CABkgnnUH5_t4BesWz2K5gtR0k0+ve42k-EWEaObK_nteh9fOUw@mail.gmail.com> <CAP+FsNcZrQ072mQikMSnyFrKqN0yDYhh=-8G4848YxdO_M-_zw@mail.gmail.com> <CABkgnnU8Okqrq5POYZqDyFUoFzkQwjRAvQJQQ_jhCO9heaFYNA@mail.gmail.com> <CAP+FsNd5bCpcVg7Z9Q=D1goYZ2keGnxPmy2G79O+h5K6bSa=cA@mail.gmail.com> <CABkgnnWgNHHHuCSXNpDQSVbaBTp=ZYn PH+MX9-_CXvaj4VD83w@mail.gmail.com>
To: Martin Thomson <martin.thomson@gmail.com>
X-Mailer: Apple Mail (2.1499)
Received-SPF: pass client-ip=216.86.168.182; envelope-from=mnot@mnot.net; helo=mxout-07.mxes.net
X-W3C-Hub-Spam-Status: No, score=-4.3
X-W3C-Hub-Spam-Report: AWL=-2.392, BAYES_00=-1.9, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001
X-W3C-Scan-Sig: maggie.w3.org 1UA8uq-0001sS-ES bf7c181937b5e5993e416390ae9cb756
X-Original-To: ietf-http-wg@w3.org
Subject: Re: proposed WINDOW_UPDATE text for session flow control windows
Archived-At: <http://www.w3.org/mid/A89944B3-8BB6-4B09-AF80-4F2C683A14EF@mnot.net>
Resent-From: ietf-http-wg@w3.org
X-Mailing-List: <ietf-http-wg@w3.org> archive/latest/16815
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>

Opening as:
  https://github.com/http2/http2-spec/issues/44
... and marking as ready for the editors to have a kick at it.

Regards,


On 21/02/2013, at 10:00 AM, Martin Thomson <martin.thomson@gmail.com> wrote:

> On 20 February 2013 14:52, Roberto Peon <grmocg@gmail.com> wrote:
>> I'm afraid of simply sending a large window size, because I suspect that
>> simple implementations will mess it up for objects > 31 bits in size.
> 
> Yes. Absolutely.
> 
>> If we don't have a SETTINGS thing, then we're requiring flow control for the
>> first RT for any stream.
> 
> Yes, that's the implication.  Though a client is always able to
> disable flow control without consequence, because it speaks first,
> before the server sends anything.  It's only servers that need to
> worry about having it on briefly.  The consequences are minimal - they
> just don't receive as many packets as they possibly could - but then
> that is always true for two reasons: TCP INIT CWD and the time it
> takes to send the WINDOW_UPDATE.
> 
>> I like the flag solely because it is difficult to do by accident, unlike
>> using zero (which is technically fine otherwise)
> 
> I don't believe in accidents, but I see your point.
> 
>> The other thing to consider is when, if ever, one can transition from
>> flow-control disabled to requiring its use again.
>> Even if we don't allow this, it will require text explaining it.
> 
> I thought about this.  The obvious choice is to start again from zero
> when a WINDOW_UPDATE comes in.  The problem is knowing (at the
> receiver end) when counting started.  Once you stop counting, that's
> the real difficulty.  I believe that once it's off, flow control will
> need to stay off.

--
Mark Nottingham   http://www.mnot.net/