Re: [tsvwg] L4S drafts: Next Steps

Sebastian Moeller <> Fri, 19 March 2021 22:22 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id E14FF3A1235 for <>; Fri, 19 Mar 2021 15:22:22 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -1.648
X-Spam-Status: No, score=-1.648 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=no autolearn_force=no
Authentication-Results: (amavisd-new); dkim=pass (1024-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id OtuXBi0YOuIx for <>; Fri, 19 Mar 2021 15:22:21 -0700 (PDT)
Received: from ( []) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id AD4203A1232 for <>; Fri, 19 Mar 2021 15:22:20 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple;; s=badeba3b8450; t=1616192494; bh=EtvNg4yktJkqXXpfqLvaa4exTKolINs4JzgzNIqCB40=; h=X-UI-Sender-Class:Subject:From:In-Reply-To:Date:Cc:References:To; b=O//Y+ajg/alKf4NeJYdEyg9+rQcoTqZEiE/FYHGJB+0wW1GeYkbB5KzogSQGkGG3P YJHJwbd17iXoPoLJXR0mlZj1kBxT9r5rMaVexQq9z6qMeyv3FrA/2D6ZOmPk48318G +eWG24ZWOrnMuRty30BI810mQML2Oq9U6uMww5QE=
X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c
Received: from [] ([]) by (mrgmx104 []) with ESMTPSA (Nemesis) id 1MTRMi-1lFj1u1oi4-00Tj8S; Fri, 19 Mar 2021 23:21:34 +0100
Content-Type: text/plain; charset="us-ascii"
Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.17\))
From: Sebastian Moeller <>
In-Reply-To: <>
Date: Fri, 19 Mar 2021 23:21:31 +0100
Cc: Jonathan Morton <>, "" <>
Content-Transfer-Encoding: quoted-printable
Message-Id: <>
References: <> <> <> <> <> <> <> <> <> <>
To: Bob Briscoe <>
X-Mailer: Apple Mail (2.3445.104.17)
X-Provags-ID: V03:K1:DeO34FWafMrAbfraGWJM1a5AsmQLAZfuKF+8p09fl67sQPRj67t RAzGPcQKm/XanplP3bGYhJQvg1FuYxOmc5OVR4gBECtbBRy6uEcTTnS4KcAjE6hwWyGerwv 6Cismz5V6+jfI8aMGJTOhZP/kzXyIpUg1fKrP0AEjqm7p8mC1VYjChFtf+AcAGVqC/2Z5BR mu9NLHxuZUojhxmc+O70g==
X-UI-Out-Filterresults: notjunk:1;V03:K0:Umg+mktMsn4=:PKFPtEZuWrHJK8v2e1f4P9 UeiiTLkAz52CRbTQiMvgIChNus1gAw2N6QGzIUN63XRDkVcs7UUm4Z+JIe8JTmn63DcsHsP8m A3+EvAn/v4pYcgHv5Z69ZxD57sB55PqEd9/uS7B0mlYhwu4mGq3Z4J07mnE0MLv+wySbqwHNT e9N1llnIa+RVSPbw5kFhRCgDL2Q3mSbj4ngUm+kAJM7UvA+PpO3mTWcl9YxBH6A1GACpPjrHK bJg8rLtVsGgXTt2XEU/aikpYAY/Q54a0xg0vjlS8e4yF1P2GqaSzjE4JNdgdxeEEPOfA29Jw0 /nkBITWgTdtdEUf9ZzM3//1BKn7BmzUwBdwo+H6QbS5ml18zpEzvokXK8cgvdCCBzXIxaOy+A w1urIw0s0qCbtG1le/4GWmzVicR8EiOa6i0zjF3BaADvLHdm3J97a+yMetlXaGmnX+8rez2JN 0I+ueW8gd8IXiYPCUkQVsGxGnBhj5RQeYBO0P4aRcX33sVjxFlpAt6lsrs02JcIei7oIixbtb Yxr7ZbW5gsO5os552HicRt2RuUiu5i6VREy7aG6VepmkoWig+EjBk2SNNCuYjc7QtZ8drmH5Q 00TMRWmcT1BTLeHHVVBFQJsde9MIioxXs30HUM1hHm5Nm87cEVDQ3Hn+PkbuWpZjRcR8TktEM f0kU77KBCbZKT3Kau6tBq7polojhkQZOknHU3HETKXNsihnf9rNkL7IskZH6gE48HLTSLU31v 2din+csgA+BnUW8RpZ8q7W928E0OxevBkc4YdNmPx7uswHCY1BnI/Y5HqAVv0s+ufF4Qsnaih aYDvnVLJfHiMLayzCbkMEtb/7sO198Y+xjg7fIJHuzD8Ug6WZLYiXgkRx5QsQGd0rrrfLUJuM R6dGPJTeAuple8PIx4VHK9zQA6W/eNlEDI2wICFL+jCaZEWOsM+0HNd0dGroAHZ2uxzr5dI8C UcsOBlewMS0ID1B2itDXjDKP0XyHbQ47ce1LzgBpaOQtnD4D3pUvJb12euQ3XiYPYm/Pkv9EI T24XWVkb0SlBYBqQTZp8tlwRsrZGgMf3Oqpz4c/MRyUw7eLb8g1Y+bVYdSFvUA/x8fG3R2LrL V1ChzNsKmLWy3IWgsQxTk2GaTCmg/kiHN39OHxjQRUOYI9BbY/FmgaRWgaFZ3jvmQzzfGmifw ZQ4Ihem7dFLASK+bZbukMcowYityQRBIe6UnGyA/SGIz+NC7vKeJJIyN2sEmEimTNey6M=
Archived-At: <>
Subject: Re: [tsvwg] L4S drafts: Next Steps
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Transport Area Working Group <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Fri, 19 Mar 2021 22:22:23 -0000

Hi Bob,

i believe nobody is asking for rocks (nor shrubberies) here, this is really about a convincing demonstration that the whole L4S design, consisting of network and protocol bits actually behaves like a coherent design and not two disjoint sub-projects that will never really harmonize? ATM what I see is you off-loading problems in the network bits by claiming the protocol will need to fix this up (RTT-bias comes to mind), and currently not even a single protocol convincingly demonstrates that the requirements a) can be met, and that b) doing so results in an L4S system that performs as promised without causing a safety issue for the existing internet.

	As it stands not even TCP Prague meaningfully fulfills the L4S transport requirements*, so we have zero proof that these requirements are actually feasible (I am simply going to ignore the questionnaire you send around, as neither party claimed, let alone demonstrated that their protocol actually meets all the requirements; these are essentially mere pre-implementation judgements whether people see conceptual stumbling blocks a priori, but as we all know the devil is in the details, so...)

Best Regards

*) Partly because these requirements are unclear and impossible to fulfill, the RTT-bias thing comes to mind again, where you require the impossible from transport protocols (as that essentially requires faster than light travel) to fix up grave misdesigns in L4S' network bits core, the AQM which makes RTT-bias considerably worse as compared to the status quo (as seen in Pete's data))

> On Mar 11, 2021, at 23:07, Bob Briscoe <> wrote:
> Jonathan,
> The concern is requiring unnecessary work to prove things that are "bring me a different rock" exercises.
> Bob
> On 11/03/2021 21:35, Jonathan Morton wrote:
>>> On 11 Mar, 2021, at 11:18 pm, Bob Briscoe <> wrote:
>>> Where does the concern about transport protocol independence come from? No-one expects that to be a problem for L4S implementers.
>> If it's not expected to be a problem, then there shouldn't be any difficulty meeting the requirement, should there?
>> I think the concern arises because there is not yet even *one* complete implementation that meets *all* of the necessary requirements (including, for example, good behaviour when encountering an RFC-3168 AQM).  This points to the likely difficulty of a second implementer's task in replicating the feat.
>>  - Jonathan Morton
> -- 
> ________________________________________________________________
> Bob Briscoe