Re: [tsvwg] Transport Area Working Group (tsvwg) WG Virtual Meeting: 2020-02-20 CHANGED

Ingemar Johansson S <ingemar.s.johansson@ericsson.com> Tue, 11 February 2020 07:19 UTC

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From: Ingemar Johansson S <ingemar.s.johansson@ericsson.com>
To: "tsvwg@ietf.org" <tsvwg@ietf.org>
CC: Ingemar Johansson S <ingemar.s.johansson@ericsson.com>
Thread-Topic: Transport Area Working Group (tsvwg) WG Virtual Meeting: 2020-02-20 CHANGED
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Subject: Re: [tsvwg] Transport Area Working Group (tsvwg) WG Virtual Meeting: 2020-02-20 CHANGED
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Hi
I may have missed the info, is there a webEx link available yet ?

/Ingemar

> 
> > On Feb 6, 2020, at 20:35, IESG Secretary <iesg-secretary@ietf.org>
wrote:
> >
> > MEETING DETAILS HAVE CHANGED.  SEE LATEST DETAILS BELOW.
> >
> > The Transport Area Working Group (tsvwg) Working Group will hold
> > a virtual interim meeting on 2020-02-20 from 09:00 to 11:00
> America/New_York.
> >
> > Agenda:
> > 1. Agenda bashing (chairs - 5 min)
> > 2. Update on status and near-term plans for the set of L4S drafts (Bob?
- 5 min)
> >     - Chair request: Think about adding an explicit &quot;Open Issues /
Future
> Work&quot; type of section in the architecture draft to consolidate a list
of
> things still being worked in the context of TCP Prague and/or caveats and
> unknowns people should be aware of when deploying this Experimental work.
> > 3. Update on L4S &amp; TCP Prague implementation, test, evaluation
> (Greg/Bob/Koen? - 15 min)
> > 4. L4S Issues List Discussion (goal is to see if we can agree on what
more needs
> to be done on each issue to suffice for Experimental/Informational RFCs):
> >    4.1 Discuss status on (Bob - ~30 min):
> >          #16 on classic ECN interaction
> >          #21 CE codepoint semantics (closely related to #16)
> >          #20 ECT(1) codepoint usage
> >    4.2  Discuss plans forward to address (Bob - ~15 min):
> >           #26 on admission control
> >           #27 on terminology
> >           #22 on deployment feasibility
> >            #24 on evaluation &amp; testing results
> >     4.3 (We will try to handle the issues below by mailing list prior to
the
> meeting)
> >           If needed, discuss close-out of (~15 min):
> >           #25 on IPR
> >           #18 on loss detection in time-units
> >           #23 on implementation status
> >           #19 on the single codepoint
> >           #17 on FQ interaction
> > 5. SCE Update (Morton/Heist/etc. - ~30 min)
> >
> >
> > Information about remote participation:
> > Remote participation information will be obtained at the time of
approval.
> Plan to use IETF WebEx.
> >
> 
> 
> 
> ------------------------------
> 
> Message: 3
> Date: Mon, 10 Feb 2020 17:05:26 +0100
> From: Sebastian Moeller <moeller0@gmx.de>
> To: Pete Heist <pete@heistp.net>
> Cc: Dave Taht <dave@taht.net>et>, tsvwg@ietf.org
> Subject: Re: [tsvwg] rrul yet?
> Message-ID: <7D22D3D0-98BB-4EAF-B99A-3712C057EEBE@gmx.de>
> Content-Type: text/plain;	charset=utf-8
> 
> 
> 
> > On Feb 9, 2020, at 17:18, Pete Heist <pete@heistp.net> wrote:
> >
> >
> >> On Feb 9, 2020, at 4:34 AM, Dave Taht <dave@taht.net> wrote:
> >>
> >> Has anyone done a rrul style benchmark yet? (flooding the uplink and
> >> downlink with mixed traffic, especially one with asymmetric bandwidth)
> >>
> >> Probably my greatest concern with either approach was the gradual rate
> >> reduction stuff would be too gradual when the return path is inflated
> >> by other traffic.
> >
> > We have run rrul in a few different ways, one of which was a 50:1
asymmetric
> link with higher flow counts in the ?wrong' direction.
> >
> > With SCE, the existing multiplicative backoff CE signal is still
available as a
> backstop, when the SCE signal alone either isn?t enough or isn?t being
> responded to, without necessarily having to resort to drop. In a test like
this,
> you?ll typically see both heavy SCE marking and CE marks as well.
> 
> Okay, any information on how L4S' dualq and TCPPrague deal with the same
> load?
> 
> Best Regards
> 	Sebastian
> 
> 
> 
> ------------------------------
> 
> Message: 4
> Date: Mon, 10 Feb 2020 16:15:41 +0000
> From: Bob Briscoe <ietf@bobbriscoe.net>
> To: Sebastian Moeller <moeller0@gmx.de>
> Cc: G Fairhurst <gorry@erg.abdn.ac.uk>uk>, Ingemar Johansson S
> 	<ingemar.s.johansson@ericsson.com>om>, "tsvwg@ietf.org"
> <tsvwg@ietf.org>rg>,
> 	"tsvwg-chairs@ietf.org" <tsvwg-chairs@ietf.org>
> Subject: Re: [tsvwg] RTT-independence
> Message-ID: <d5376b53-2180-cf92-6f50-dc9cafcf9bfd@bobbriscoe.net>
> Content-Type: text/plain; charset="utf-8"; Format="flowed"
> 
> Sebastian,
> 
> On 30/12/2019 22:10, Sebastian Moeller wrote:
> > Dear Bob,
> >
> > summary to save the rest of the list some time:
> >
> > I argued that the current implementation of the dual queue coupled AQM
> (DQCAQM) fails to meet the required isolation quality between L4S two
queues
> to to merit rolling it out of the lab and into the real internet.
> >
> > The symptom is that in realistic scenarios of high bandwidth flows with
short
> RTTs L4S traffic demonstrably pummels/dominates the non-L4S traffics
> aggregate throughput. That fact is not under dispute as far as I can tell.
> The clue is in the subject of your sentence: "short RTTs L4S traffic
> demonstrably pummels/dominates..." This suggests that, by changing the
> behaviour of the subject of your sentence (the L4S traffic over short
> RTTs), the problem will be addressed. I know you don't want that to be
> the answer, but that doesn't mean it isn't the answer.
> 
> >
> > The L4S proponents argue, that this is working as designed, as this is a
side-
> effect of their under-explained choices of acceptable standing queue
"targets"
> for the two queues (1ms for the L4S-queue and 15ms for the non-L4S queue),
> which for short path RTTs in the limit creates an RTT imbalance of 1:15.
(I have
> also argued that 15ms is the wrong value in theoretical grounds and so far
this
> has not been disproven with facts/data).
> 15ms comes from the amplitude of the sawteeth of typical traffic at
> typical Internet bottlenecks over typical paths. "Traffic" might be
> multiple flows or single flows, but an AQM has to work well for the
> cases where the user wants to use the bandwidth they are paying for,
> including for single long-lived flows (OS updates, video uploads, etc).
> "Traffic" might use Cubic, Reno or other CCs but the user doesn't
> control the CC the other end uses, so the AQM has to work for typical
> cases and not be awful for worst cases. "Bottlenecks" might be anywhere,
> but they are most often in access links where there is not much flow
> multiplexing. With Reno, Cubic etc, the sawtooth amplitude depends on
> the RTT of the path. So "paths" might be between a customer in a large
> urban conurbation and a CDN in the same or a nearby conurbation, or a
> path might be half way round the globe, but the common case these days
> is an urban customer and a CDN.
> 
> One can argue whether the number is 10ms, 15ms, 20ms or whatever, but
> there is an operating point below which more and more traffic badly
> underutilizes the link. Whatever, this is not a theoretical question, it
> is a commercial question for ISPs when setting the target parameter of
> their AQM. You have to look at what ISPs do, not what you think they
> should do.
> 
> >
> > The L4S team seems to accept though that this situation is sub-optimal
and
> argues that by increasing the RTT-independence of all flows admitted to
the L4S
> queue the problem can be ameliorated.
> Correct.
> >
> > While I am all for increased RTT-independence, I fail to see how this
can be
> considered a general solution for the problem that the DQCAQM simply fails
to
> do the one thing exists to do.
> The DualQ Coupled AQM merely gives out signals. It doesn't schedule
> throughput of anything in normal circumstances. The throughput that a
> flow takes depends on its response to those signals.
> 
> >
> > Even if this would work for TCP Prague (and the increased RTT
independence is
> not even deomstrated reliably for TCP Prague so far) that still will only
solve this
> issue for flows with that congestion controller, this exercise needs to be
> repeated for all transports aimed for the L4S queue.
> The point of the CC requirements (including the RTT independence
> requirement) in draft-ietf-ecn-l4s-id is that any CC is meant to comply
> if it wants to apply the ECT(1) codepoint.
> 
> The point of TCP Prague is to be a reference implementation that
> satisfies those requirements (that statement is not meant to discourage
> others from producing better reference implementations). Then people
> implementing other transport protocols can either a) copy the precise
> details, b) copy the general idea, or c) find other ways to satisfy the
> requirements.
> 
> When the requirements were written, it was known to be hard to precisely
> satisfy all of them at once. That was also the message from the paper
> "Resolving Tensions between Congestion Control Scaling Requirements
> <https://protect2.fireeye.com/v1/url?k=09b7b188-5563bd79-09b7f113-
> 864685b2085c-023bb76d36ac29ea&q=1&e=7766affd-61a2-4b4c-857e-
> a020626cbd8f&u=http%3A%2F%2Fbobbriscoe.net%2Fpubs.html%23ccdi_tr>"
> and the presentations of it
> in ICCRG at the time (also linked via the link I've just given, and all
> these are also linked via the L4S landing page
> <https://protect2.fireeye.com/v1/url?k=7b10ba36-27c4b6c7-7b10faad-
> 864685b2085c-db7c8b7a04b8ef32&q=1&e=7766affd-61a2-4b4c-857e-
> a020626cbd8f&u=https%3A%2F%2Friteproject.eu%2Fdctth%2F>). Some of the
> requirements are already
> written with some wriggle room (e.g. the case in point uses the
> weasel-words highlighted "MUST *reduce* or eliminate RTT bias over as
> wide a range of RTTs *as possible*"). The implementation and testing
> exercises we're going through will allow us to be able to suggest to the
> community how best to soften (or harden) any requirement that is
> unnecessarily ambitious (or permissive).
> 
> 
> >
> > If on the other hand the DQCAQM simply is fixed to deliver robust and
reliable
> equitable bandwidth sharing between the two queues* then TCP Prague and
all
> other transports intended for the L4S queue can take their sweet tome to
> develop more RTT-independence.
> The problem is not just between L & C flows. it's also between long-RTT
> L and short-RTT L flows. And the problem appears when you cut out
> queuing delay with any shared-queue AQM, not just the DualQ Coupled AQM.
> >
> > I am no engineer, but I can easily recognize which of the two options
promises
> robust isolation and which just promises an on-going whack-a-mole.
> I don't know how to persuade someone about where it's best to apply a
> solution, if that person is only prepared to countenance applying
> solutions in the network, even though the problem stems from end system
> behaviour.
> 
> >
> >
> >
> > *) Say under congestion no class gets more than double the bandwidth of
the
> other, ideally obviously exactly 50%
> Per class throughput has very little to do with per-flow throughput when
> users can arbitrarily vary the number of flows per class.
> 
> 
> 
> Bob
> >
> >
> > more below in-line, mostly for Bob.
> >
> >> On Dec 30, 2019, at 00:25, Bob Briscoe <ietf@bobbriscoe.net> wrote:
> >>
> >> Sebastian,
> >>
> >> On 18/12/2019 08:11, Sebastian Moeller wrote:
> >>> Hi Bob,
> >>>   more below in-line.
> >>>
> >>>
> >>>> On Dec 18, 2019, at 01:23, Bob Briscoe <in@bobbriscoe.net>
> >>>>   wrote:
> >>>>
> >>>> Sebastian,
> >>>>
> >>>> I wanted to pick up your point about RTT-independence that you
recently
> said has never been responded to.
> >>>>
> >>>> I have changed the subject line, because this is not an L4S vs SCE
issue.
> With a shared queue it is just as much an issue for SCE as for L4S. With
an FQ
> scheduler, it is just as much a non-issue for L4S as for SCE.
> >>>>
> >>>>
> >>>> On 20/11/2019 14:18, Sebastian Moeller wrote:
> >>>>
> >>>>> Dear Koen, dear all,
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>> On Nov 20, 2019, at 13:40, De Schepper, Koen (Nokia - BE/Antwerp)
> <koen.de_schepper@nokia-bell-labs.com>
> >>>>>>
> >>>>>>   wrote:
> >>>>>>
> >>>>>>
> >>>>>> One of these opportunities here is to make L4S_TCP less RTT
dependent.
> There have been many working implementations for less RTT-dependent CCs in
> the past. One that is widely deployed is Cubic, which is doing this for
getting
> more throughput for longer RTTs. The only reason why it didn?t fly for
lower
> RTTs on the current Internet is that they would hurt themselves (get lower
> throughput, competing with Reno).
> >>>>>>
> >>>>>>
> >>>>> 	[SM] Looking at the pfifo_fast results in H?iland-J?rgensen
T, Hurtig P,
> Brunstrom A (2015) The Good, the Bad and the WiFi: Modern AQMs in a
> residential setting. Computer Networks 89:90?106. For Cubic/pfifo_fast
(linux
> former default combination), I fail to see a strong indicator that cubic
is RTT
> invariant or getting more thoughput at longer RTTs (except for the 10ms
versus
> 50ms "hump"). What paper/data should I be looking at instead?
> >>>>>
> >>>>>
> >>>>>
> >>>>>>
> >>>>>> As we are able to define a new independent behavior and the RTT
> dependence in L4S is taken serious (some even call it a show stopper) this
is even
> a must do opportunity for L4S. It is all a matter of perspective:
show-stopper <->
> opportunity.
> >>>>>>
> >>>>>>
> >>>>> 	[SM] I believe that working on more RTT independence is
worth-while
> but no replacement for fixing the isolation system as it it is that
equitable
> isolation from existing traffic that basically gives you the slate
clean-"green
> field" development opportunity, no?
> >>>>>
> >>>> [BB] RTT-dependence is caused by the end-system, and should be solved
in
> the end-system (whether or not FQ is also deployed to solve it in some
places).
> >>>>
> >>> 	[SM] I fully agree, and that is also a convincing argument, why
> increasing RTT independence can not be the solution for the observed
isolation
> failure of the dual queue coupled AQM, glad that you agree.
> >> [BB] There is no convincing argument yet. This is an opening sentence,
from
> which neither I nor you can make any convincing argument. Please work
through
> the whole argument below...
> > 	[SM] I disagree, the argument is, since " RTT-dependence is caused
by
> the end-system[s]" and needs to be addressed in the end-systems  we can
not
> assume higher RTT-independence as a means to ameliorate deficiencies in
L4S's
> chosen class separator, the DQCAQM, unless you are willing to post-pone
the
> L4S experiment/roll-out until all end-points are changes to have a higher
RTT-
> independence. Also what is missing is actual data demonstrating, that this
will
> bring the worst case sharing of the DQCAQM into the acceptable range.
> >
> >>
> >>>
> >>>
> >>>
> >>>> Importantly, RTT-dependence only needs to be addressed in the newly
> deployed scalable (L4S or SCE) end-systems, not pre-existing end-systems
like
> Reno & Cubic, as I'll now explain.
> >>>>
> >>>> The problem is due to the tiny RTT you can get when you have both a
tiny
> base RTT and a tiny queue. For example:
> >>>>
> >>>> Base RTT/ms
> >>>> Queue/ms
> >>>> Total RTT/ms
> >>>> Close Scalable flow:	2.5
> >>>> 0.5
> >>>> 3
> >>>> Distant Scalable flow:	100
> >>>> 0.5
> >>>> 100.5
> >>>> Close Classic flow:	2.5
> >>>> 15
> >>>> 7.5
> >>>>
> >>> 	[SM] Note, 15 + 2.5 = 17.5, a typo for sure. If I am wrong and you
really
> ment 7.5, please elaborate why you only add 1/3 of the queueing delay, as
I
> assume we are talking about saturating traffic here.
> >>>
> >>>
> >>>
> >>>> Distant Classic flow:	100
> >>>> 15
> >>>> 105
> >>>>
> >>> 	[SM] 15 + 105 = 120
> >>>
> >>>
> >>>> If all the above flows were RTT-dependent, the lowest 3ms RTT ('Close
> Scalable') would be the potential hog. For example against 105ms ('Distant
> Classic') if they were both 'window fair' like Reno, the throughput ratio
would be
> 105:3 = 35:1
> >> [BB] Sorry, I screwed up that table. I decided to use a 5ms queue
instead of a
> 15ms queue at the last minute (in order to use the worst case for my
argument),
> however I only changed the totals, and omitted to change the queue itself.
> Here's the corrected table:
> >>
> >>
> >>
> >> Base RTT/ms
> >> Queue/ms
> >> Total RTT/ms
> >> Close Scalable flow:	2.5
> >> 0.5
> >> 3
> >> Distant Scalable flow:	100
> >> 0.5
> >> 100.5
> >> Close Classic flow:	2.5
> >> 5.0
> >> 7.5
> >> Distant Classic flow:	100
> >> 5.0
> >> 105
> >>
> >> All the arguments that followed remain the same though, because they
relied
> on the totals not the constituent parts of the totals.
> > 	[SM] Thanks for fixing the numbers, but as I already conceded below
> "but your point still stands", meaning I well understood the gist of your
> argument.
> >
> >
> >>> 	[SM] I am not convinced that "window fairness" is in reality a
useful
> property, throughput fairness seems much more desirable.
> >> [BB] 'Window fairness' is not a useful property, it's just a property
of a large
> class of congestion controls. The word 'fairness' sounds intrinsically
like people
> should think it is desirable. So I try to avoid using it, and if I do, I
try to always
> put it in quotes.
> > 	[SM] Why bother? I have read a few of your opinion pieces arguing
> against flow fairness, and hence understand where you come from. I tend to
> think that rough equality is the best of all achievable bad splits, I
happily concede
> it to be rarely "optimal". But as you have realized yourself, for any
arbitrary hop
> on a path there typically is insufficient information available to
actually optimize
> the bandwidth distribution between all active flows in any meaningful way;
out
> of the two options, "anything goes" and "try to equalize by some relative
> objective measure",you seem to prefer the former while I prefer the
latter.
> >
> >>>> Whereas the Close vs Distant Classic case is cushioned by the 15ms
queue.
> RTT ratio = 105:7.5 = 14:1, which was the Internet status quo pre-L4S (or
SCE).
> >>>>
> >>> 	[SM] If I fill in the modified numbers from above I get 115 / 17.5
~
> 6.6:1, but your point still stands.
> >>>
> >> [BB] Please now revisit the arguments below without the distraction of
the
> typos.
> >>>> So why is it enough for only scalable flows to reduce their RTT
> dependence? Assuming they do, the lowest 3ms RTT ('Close Scalable')
doesn't go
> much faster than 'Distant Scalable'. If it's no longer a hog in relation
to Distant
> Scalable, it's no longer a hog in relation to any of the other flows.
> >>>>
> >>> 	[SM] That seem strictly depend on your definition of hog 105/120 is
not
> equal still giving L4S an IMHO (hard to justify) edge over standard
compliant
> traffic. But I am happy to be convinced by actual empirical numbers.
> >> [BB] Oh dear. What is so important to you about such precise rate
equality?
> > 	[SM] Please remember that this is not a pure discussion about the
> desirability of higher RTT-independence (I am all for it), but rather
about the fact
> that it is a red herring to bring up RTT-independence as explanation for
the fact
> that the current implementation of dual queue coupled AQM does not seem to
> meet what both the L4S-arch and the dualQ I.D.'s "promise" to the reader.
The
> only fact that both are not wrong is because they hedge their bets by
attaching
> specific conditions (and fail to mention that dualQ will make sure the
required
> RTT equality will require shorter true RTTs for the non-L4S queue). Hence
the
> text might be technically correct, but it is also misleading.
> > 	So my point is that you need to fix the well-documented deficiencies
in
> the dual queue coupled AQM. AND here I, and I assume most casual readers
of
> the L4S I.D.s will expect equitable sharing between the two traffic
classes. I am
> sure that most reviewers will not see that as strictly as I do, and will
accept a
> fudge factor of say 1:2, but 1:8 and worse is simply an indication that
either the
> implementation or the design are not up for the intended purpose...
> >
> >
> >> Please be prepared to set aside your preconceptions about rate
equality.
> > 	[SM] No, I will not, as far as I understand the rationale behind the
dual
> queue coupled AQM is to allow exposing the internet to the more
> "aggressive"/nimble 1/p type congestion controllers, and to be fit for
roll-out
> the current guarantees that dual queue AQM will give, namely "not
completely
> starving" non L4S-traffic is simply too weak.
> > 	The discussion I am leading here is not about what L4S's AQM does
> inside each of the two traffic classes, but purely between them, so I am
NOT
> talking about flow-fairness at all, but inter-class-fairness. And as I
already
> indicated, even equitable sharing between classes will give the initially
rare L4S
> traffic already a considerable boost over packets in the non-L4S queue,
which I
> consider undesirable, but this is not a discussion about my preferences,
but
> about whether the L4S experiment is sufficiently cautious and safe enough
for
> the rest of the internet to being exposed to L4S traffic.
> >
> >
> >> Please re-read the reference at {Note 1}. No-one has ever been able to
justify
> a goal of equal flow-rates, except for starvation avoidance (when rough
rate
> equality is sufficient).
> > 	[SM] I read that note, but it fully failed to convince me. You seem
to
> argue that equitable sharing prohibits more optimal traffic splits, and I
fully
> agree, but at the same time it also prohibits more pessimal traffic
splits, and
> given that the congested hop typically has no reasonable means to assign
> "valence" to the flows, I prefer predictable "good enough" sharing over
> "anything goes". And with that let's put that discussion to rest, given
your
> dogmatic position regarding this topic, I am sure that I will not be able
to
> convince you, and equally you will not be able to convince me of your
position,
> as I have read quite a lot of your prose on that topic already and am
still not
> convinced that "potentially optimal, but also potentially pessimal" is
preferable
> to "mostly good enough and rarely really bad".
> >
> >
> >> Congestion levels have to be high for starvation to be a concern. So,
the
> lower congestion is, the less important rate equality becomes.
> >>
> >> There's a lot more to this, so please read and try really hard to
understand
> /all/ the points in that reference at {Note 1}.
> >>
> >> For instance 'rate fairness' is also not a useful goal because, like
'window
> fairness', it makes the comparison in inappropriate units - if you try to
say what
> is 'fair' at each instant without taking account of congestion over time,
you'll get
> a much worse outcome (see the first argument in section 2.1.1 of the
reference
> at {Note 1}).
> >>
> >> I recall that you (if my memory serves me correctly) dismissed that
argument
> in section 2.1.1  because you couldn't see how to calculate the correct
shares at
> any one time. You'd need to read the references for that. But even if you
can't
> work out the perfect solution, doesn't mean you cannot see that, for flows
with
> different volumes, highly unequal flow rates give much shorter flow
completion
> times than equal flow rates. The idea is to start you questioning your
belief in
> equal flow rates.
> > 	[SM] Your leap of faith is that I follow you in accepting
"completion
> time" as the relevant measure, which I do not. BTW, the intermediate hop
really
> has little way to figure out whether a given flow is (close to being)
finished or
> not or whether a sparse flow switches into bulk capacity-seeking mode
later. In
> the light of all that uncertainty I still consider the outcome in b) quite
reasonable
> and good enough. But I really disliked reading that editorial and will
stop
> discussing it further.
> >
> >
> >> Nonetheless, compared to 'window fairness', 'rate fairness' is a more
useful
> /baseline/ on which to build other more useful behaviours, because at
least it
> avoids starvation.
> >>
> >> So, please understand that the reason I prefer an RTT-independent
> congestion control is not because I believe 'rate fairness' is a desirable
goal. In
> the presence of very shallow queues, 'rate-fairness' is just less
undesirable than
> 'window fairness', because 'rate-fairness' avoids starvation.
> > 	[SM] Bob, while I agree with very little in the above, this is
orthogonal
> to the question that I am really concerned about, so I will let this pass,
as it only
> distracts from the fact that I am not claiming the dual queue coupled AQM
is
> broken because it does not do flow-queueing, to repeat myself, it is
BROKEN,
> because it fails to properly ISOLATE the two traffic types you classify
all packets
> into. So the property I see lacking is class-fairness not flow-fairness.
> >
> >
> >>
> >>>> So the worst case reverts to the Close Classic flow, which isn't so
bad
> because the total RTT is cushioned by the queue. So we will be no worse
off
> than we were before L4S or SCE.
> >>>>
> >>>>
> >>>> You will see we explained this at the end of Section V.B 'Congestion
> Control Roadmap' in the draft journal paper about L4S that we posted
earlier
> this year:
> >>>> ?`Data Centre to the Home?: Deployable Ultra-Low Latency for All?
> >>>>
> >>>> But is RTT-independent TCP Prague real? No, not quite yet. At the
time we
> designed this, we simulated it, but we're now working on it again,
including
> implementing it in Linux, so you should see results soon. The approach to
RTT-
> independence that we suggest is explained in section 3.2 of a paper we
> presented to the iccrg back in Jul 2017.
> >>>> ?Resolving Tensions Between Congestion Control Scaling Requirements?
> >>>>
> >>> 	[SM] At this point I want to see real numbers from empirical
testing,
> thanks for the references though.
> > 	[SM] And I still do.
> >
> >>>
> >>>
> >>>> All the above papers are available via the L4S landing page:
> >>>> https://protect2.fireeye.com/v1/url?k=302ff051-6cfbfca0-302fb0ca-
> 864685b2085c-e81006a26e005f11&q=1&e=7766affd-61a2-4b4c-857e-
> a020626cbd8f&u=https%3A%2F%2Friteproject.eu%2Fdctth%2F%23papers
> >>>>>> I'm also not against the recent vibrant energy, interest and
engagement
> of people, but I think we can better use this energy in making things
work. As
> you noticed, we can use the help to speed things up on the open source
part.
> >>>>>>
> >>>>>>
> >>>>> 	[SM]... while at the same time requesting help for
implementation and
> dealing with the consequences of said "code point and requirements".
> >>>>>
> >>>> If you recall, when I asked you not to keep repeating other people's
> arguments without adding anything, you said the RTT-dependence point was
> your contribution to the debate.
> >>>>
> >>> 	[SM] Then we miscommunicated, my point is, that if you fix the dual
> queue couplked AQM than you can tackle the worthy goal of less RTT
> dependence at your own sweet time.
> >> [BB] You never say what you mean by 'fix the dualQ coupled AQM'.
> > 	[SM] I did not have the impression that I left that in doubt, but I
am
> happy to state this explicitly. Under congestion the dual queue coupled
AQM
> needs to strictly maintain inter-class equality just as a casual reader
expects it to
> do. That is, under load and independent of the number os flows and their
RTT
> make-up egress rate of the AQM needs to be equal on a sufficiently small
time-
> scale.
> >
> >
> >> I am not going to know what you mean because, from my perspective, the
> AQM does what it was designed to do very well.
> > 	[SM] That was my suspicion as well, that we are not simply talking
about
> an implementation bug, but rather about a deep-rooted design decision
behind
> the dual queue coupled AQM. But when bringing this up with Koen, he seemed
> to argue that he also is concerned about class inequalities (say at
extremely
> short RTTs) so I am at a loss, is the failure to share equitable between
the
> classes considered as "working as intended" or considered something that
> should be fixed?
> >
> >
> >> It doesn't determine per-flow shares of capacity.
> > 	[SM] We are talking per-class sharing here, please do not confuse
these
> two they are conceptually quite different, and I am NOT, to repeat myself,
> blubbering on about the fact that there is no flow-queueing inside any of
the
> two queues. Your AQM, your rules, as long as you do not completely pummel
my
> non-L4S thoughput I am willing to live and let live.
> >
> >
> >> It merely emits congestion signals. Per-flow shares of capacity are
> determined by each sender's response to those signals.
> >>
> >> You clearly want the AQM to do something different, but you don't say
what.
> I assume you don't mean just "replace it with FQ" {Note 2}.
> > 	[SM] No, Bob I do not propose that. I have wielded the term
"equitable
> sharing" quite a lot, and at least in my humble opinion it was always
clear that
> this is about sharing between the two queues. I am not trying to change
your
> project to do flow-fair queueing inside of each of the two queues at all;
I am
> trying to save the rest of the internet (including my own access link)
from the
> negative side-effects I expect from your experiment.
> >
> >
> >>>> The L4S team identified this problem in early 2015 during testing
with
> diverse RTTs.
> >>>>
> >>> 	[SM] And then opted to keep pushing for internet-wide roll-out of
L4S
> with this issue unsolved, color me not impressed.
> >> [BB] We were pushing for Internet-wide roll-out of the /network/ part
of L4S.
> > 	[SM] Which contains the arguably not-working-as-it-should dual queue
> coupled AQM, exactly the right tome to voice concerns and objections,
IMHO.
> >
> >
> >> We were from network companies and we thought others would do the end-
> system parts - hence the Prague requirements. We thought DCTCP was a
> sufficient starting point for others to build on. Once I realized that
wasn't
> happening (except in Google) without a reference implementation, I left
> CableLabs and got funding to hire folks to work on TCP Prague with me.
> > 	[SM] So you really set out to spend the ECT(1) codepoint on the
intuition
> that there potentially might be users interested in using such a system
initially?
> >
> >
> >>>
> >>>
> >>>> When the Prague requirements were first agreed, we (Koen in
particular)
> insisted that this should be included as a basic safety requirement, even
tho
> some people said it wasn't important.
> >>>> The WG has so far kept it as a MUST requirement, justified by the
> potentially large discrepancy in rates that can result, articulated here:
> >>>>
> >>>>
https://tools.ietf.org/html/draft-ietf-tsvwg-ecn-l4s-id-08#appendix-A.1.5
> >>>>
> >>>>
> >>>> What I wanted to show by this email is that a significant amount of
work
> has been done on this, the problem is well-understood and solutions are in
> progress. RTT-independent congestion controls have been produced before -
> not that I'm belittling how hard it is to resolve the tension between
requirements
> identified in the 'Tensions' paper above.
> >>>>
> >>> 	[SM] To repeat myself, this all supports the thesis that making RTT-
> independence the mechanism by which L4S equitably shares with standards-
> compliant traffic at the current state is premature.
> >> [BB] It is not premature to develop an RTT-independence solution that
we
> have shown to work in simulations, and that we know has been implemented
> successfully in other congestion controllers in the past.
> > 	[SM] Bob, in the context of dual queue coupled AQ's short-comings,
> RTT-independence is a red herring. Even if you achieve RTT-independence
for
> TCP-Prague, unless you enforce to only allow TCP-Prague into the L4S-queue
> (which would also allow to get rid of the abuse of ETC(1) as leaky
classifier code
> point) you are not fixing the generic isolation failure of the dual queue
coupled
> AQM, so hurrah for TCP Prague gaining RTT-independence in the future but
that
> does not remove my objection or your AQM's issue.
> >
> >
> >>> I very much would like to see the dual queue coupled AQM fixed, and
once
> RTT independence (for all users of the L4S queue) is functional then the
AQM can
> be changed again.
> >> [BB] If you mean that we should bias the signals emitted by the DualQ
to
> counterbalance the incorrect response of RTT-dependent senders, that would
> create a nightmare "incremental undeployment" problem.
> > 	[SM] No, I mean that if your current design does not work at rather
> normal (given the closeness of CDNs to the edge) short RTT you should be
given
> the chance to redesign your AQM. If you insist upon the AQM sharing to be
> driven by RTT dependent mechanisms, the onus is on you to remedy this.
> >
> >
> >> Then, no-one would ever be able to fix any of these broken     (RTT-
> dependent) congestion controllers because, during the transition, the
> counterbalances added to AQMs would remain in the network and cause RTT-
> unfairness in the opposite direction. So reverse engineering the AQM to
counter
> broken senders would freeze both into the Internet for ever.
> > 	[SM] Realistically, what you call "broken senders" is the reality in
the
> internet, the exact reality your new system be better compatible with to
merit
> roll-out in the first place.
> >
> >> So, please accept that is not the way it's going to happen. The DualQ
Coupled
> AQM does not need to be fixed because it isn't broken - it is very much
working
> as intended.
> > 	[SM] So I have you on record, that the equitable sharing failure at
short
> RTTs is a property that you designed into the AQM on purpose? Again that
> seems to contradict my interpretation of Koen's words on this matter, but
I am
> easily confused anyway.
> >
> >
> >> Network deployments take years and remain for years. End system
> deployments can continuously evolve.
> >>
> >> My point at the start was that RTT-dependence is an aspect of the way
> DCTCP senders respond to the signals emitted by queues. So the correct
place to
> fix RTT-dependence is in those senders.
> >
> > 	[SM] And I fully agree. Except that I draw the obvious logical
conclusion,
> that hence increasing RTT-independence can NOT be the solution to the
unequal
> between-class sharing of the dual queue coupled AQM. That is my point for
> some time now, and a rather explicit point.
> >
> >>
> >>>
> >>>
> >>>> So I ask you to take a more constructive approach. Banging on your
> keyboard in the style of "ner ner ne ner ner, I found a problem with L4S"
doesn't
> help anyone,
> >>>>
> >>> 	[SM] Let me be blunt, without the deserved push-back on the lists,
> "peaceful coexistence with single queue RFC3168 AQMs" would not have been
> tackled, the gist of the presentatuins so far has always been to ask the
room,
> but do we ned to care for this at all? So IMHO pointing out L4S current
short
> comings is important as otherwise little progress on the difficult issues
would
> happen at all.
> >> [BB] The concerns about single-queue RFC3168 AQMs did indeed succeed in
> redirecting my attention from RTT-independence, which I would otherwise
still
> be focusing on. Olivier at least is still working on that.
> > 	[SM] Look, all of these issues come from a list of important issues
that
> the L4S project itself created :
> >
> >
> > Requirements
> >
> > L4S-ECN Packet Identification: ECT(1)
> >
> > Accurate ECN TCP feedback
> >
> > Reno-friendly on loss
> >
> > Reno-friendly if Classic ECN bottleneck
> >
> > Reduce RTT dependence
> >
> > Scale down to fractional window
> >
> > Detecting loss in units of time
> >
> > I can understand if you prefer working on some of them more than on
others,
> but complaining that woking to make sure your design meets your own
> REQUIREMENTS seems odd. Or I am misreading your words and all you are
> saying is that you are dedicating time to this?
> >
> >> I am concerned that still no-one has yet found a single-queue RFC3168
AQM
> deployed on the public Internet, or a network operator who wants one. No
> doubt there are some out there, but I have no idea how large or small the
> problem really is.
> > 	[SM] IMHO the prevalence of single queue RFC3168 AQM is irrelevant,
> this is a point of contention that was correctly identified in the TCP
Prague
> requirements and needs a proper solution instead of trying to argue it
away.
> >
> >> It would be preferable if you would at least gather data to help
prioritize this
> work, by quantifying the prevalence and impact of these problems. But I
can't
> stop you just repeating known problems in email after email with no data
to
> support your invective.
> > 	[SM] @Chairs, I do not want to appear to touchy, butI take offense
in
> this, as long as Bob repeats the same points over and over again (instead
of
> shutting me up with data), I do not seem him getting the right to complain
that I
> also repeat my position instead of doing his research for him.
> >
> >
> >>>> when the problem you've "found" exists with any low latency shared
> queue, including an SCE-based solution.
> >>>>
> >>> 	[SM] Well, the something called "dual queue" AQM certainly needs to
at
> least behave as if it had two queues in my book.
> >> [BB] It does. The L queue isolates its traffic from the latency of the
other, and
> they each emit different but coupled levels of congestion signals.
> > 	[SM] The problem I see is that fine time scales Bandwidth and
latency
> are inter-twined and pretending that they are orthogonal does not really
help (at
> any point in time typical links will only allow to transmit 1 packet that
than hogs
> the link for its transmission time).
> >
> >
> >>> L4S versus SCE is red herring here,
> >> [BB] What I said was not pitting L4S against SCE. Quite the opposite.
> >>
> >> I said that an SCE transport also needs to be RTT-independent, for the
cases
> where it runs over a single queue SCE AQM (e.g. CNQ). I do not see any
work
> being done on RTT-independence in SCE transports at all. And I do not see
you
> criticising anyone for not having done this.
> > 	[SM] The current status is that L4S will pummel standards-compliant
> traffic in this condition, while SCE will yield too generously, the latter
restricts
> the fall-out of too high RTT-dependence to the SCE flows themselves, the
> former will simply bully its way through. Note how the SCE way is both
safe for
> roll-out and carries an in-built incentive to address this issue, while
the L4S
> approach is not safe (from the viewpoint of the existing non-L4S internet)
and
> carries no real incentive to fix this, after all if I make my L4S-endpoint
sender
> less RTT independent at short RTTs I can get an advantage over both
non-L4S as
> well as TCP Prague traffic.
> >
> >
> >>> my current issue is that the current implementation of L4S's reference
AQM
> does not work as it should and as a normal reader would understand from
> reading the dualQ ID, IMHO that needs to be fixed.
> >> [BB] Which text in the aqm-dualq-coupled draft gives this wrong
impression?
> It clearly says:
> >>        For the
> >>        public Internet an L4S transport has to comply with the
> >>        requirements in Section 4 of [
> >> I-D.ietf-tsvwg-ecn-l4s-id
> >> ] (aka.
> >>        the 'Prague L4S requirements').
> > 	[SM] I have cited these before, but here again:
> > "This specification defines `DualQ Coupled Active Queue Management
> >     (AQM)', which enables these Scalable congestion controls to safely
> >     co-exist with Classic Internet traffic."
> > "Analytical study and implementation testing of the Coupled AQM have
> >     shown that Scalable and Classic flows competing under similar
> >     conditions run at roughly the same rate."
> > "without compromising the performance of
> >     the Classic traffic"
> > "the Coupled AQM that addresses throughput equivalence between
> >        Classic (e.g.  Reno, Cubic) flows and L4S flows (that satisfy the
> >        Prague L4S requirements)."
> > "For safe co-existence, under stationary conditions, a Scalable flow
> >     has to run at roughly the same rate as a Reno TCP flow (all other
> >     factors being equal)."
> > "Nonetheless, coupled marking ensures that giving priority to L4S
> >     traffic still leaves the right amount of spare scheduling time for
> >     Classic flows to each get equivalent throughput to DCTCP flows (all
> >     other factors such as RTT being equal)."
> >
> >
> > None of this indicates that at short RTTs L4S traffic will
dominate/pummel
> non-L4S traffic at short RTT paths, and nothing indicates that this is
made worse
> by a severely under-explained set of latency targets for the two queues.
Is that
> clear enough?
> >
> >
> > 	[SM] And I note that not even TCP Prague seems to comply with all of
> these L4S requirements yet...
> > 	Look, in my discipline the onus to demonstrate that something new
and
> wonderful works and has no/little/acceptable side-effects is on the person
> proposing the new thing. So with that background I very much like to see a
> working-in-the-lab-as-designed-and-as-considered-safe version first before
> even contemplating inflicting this on the wider internet. As it stands the
dual
> queue coupled AQM is willing to give both a latency and a bandwidth
advantage
> to any flow willing to set ECT(1), I am quite troubled that I seem to be
the only
> person that sees this as an obvious unsafe design...
> >
> >>
> >> That clearly does not promise that the dualQ will behave as intended
for a
> transport in the L queue that is RTT-dependent, i.e. that does not satisfy
the
> stated requirements for that queue.
> > 	[SM] Which IMHO is another problem, thanks for highlighting this.
But
> also if the class-isolation is fixed that will also solve this issue.
> >
> >
> >> Whatever, I notice that Appendix C assumes an RTT-dependent L4S
transport,
> which will need to be changed once we have empirical results for RTT-
> independent transports. And that assumption needs to be called out in the
> interim. I've made a note-to-self to do both these.
> >>
> >>> I do not believe that the not yet solved RTT-independence goal is the
best
> approach to solve the issue, but you are free to spend your time as you
please.
> >> It would help if you argued against the fairly straightforward
reasoning
> (above, starting "So why is it enough for..."), rather than just generally
saying
> you don't believe it.
> > 	[SM] Well, I do not buy your "reasoning" what I see is you trying to
shut
> me up instead of engaging in a discussions of the points I bring and I do
not
> appreciate that.
> >
> >
> >>>
> >>>
> >>>> Instead you could have read all the papers referenced from the L4S
landing
> page, \\
> >>>>
> >>> 	[SM} Regrettably, I have read quite a lot of that material, and I
typically
> see too much hype and too little critical analysis for my taste.
> >>>
> >>>
> >>>> understood how much everyone already understands the problem,
> >>>>
> >>> 	[SM] I have no beef with your understanding of the issues, my
complaint
> is that you do not act upon long-standing well-documented show-stopper
> issues. Not every documented bug can be dressed as a feature.
> >> [BB] When you consider something to be an important bug, but I argue it
is
> an important feature, the proper approach is to try to understand why
> something you thought was an accepted truth is being questioned.
> > 	[SM] Bob, please re-read my arguments under the light that I am in
no
> way trying to make you do flow-fair queueing inside of your two queues.
All I
> want is that the network side of L4S is robust and reliable and does not
harm the
> rest of the internet (well, my emphasis is on the latter part, as I have
severe
> doubts that L4S will in reality work as intended anyway).
> >
> >> Instead, what you've typed is effectively an accusation that I am a
charlatan
> with evil intent.
> > 	[SM] I fail to see such an accusation in my mails could you please
point
> out a specific instance, so I can try to avoid this in the future.
> >
> >> This frequent descent into personal slurs does not move anything
forwards.
> > 	[SM] It seems I offended you, since that was not my intention, I
offer
> my apology for all phrases that you consider offensive. But that does not
one
> iota affect my criticism.
> >
> >
> >> Think of all the material about FQ-CoDel. Is that hype, or is it
enthusiasm
> about good results? To a sceptical reader who has not repeated the results
> themselves, I'm sure it seems like extreme hype.
> > 	[SM] You are really comparing the hype content of a single 25 page
RFC
> versus a triplet of 35
(https://tools.ietf.org/html/draft-ietf-tsvwg-l4s-arch-04),
> 49 (https://tools.ietf.org/html/draft-ietf-tsvwg-aqm-dualq-coupled-10),
and 42
> page monsters
(https://tools.ietf.org/html/draft-ietf-tsvwg-ecn-l4s-id-08),
> really?
> >
> >> I would ask you to presume the L4S results are all genuine until proven
> otherwise (of course, you should also hold a degree of scepticism in
reserve).
> Then perhaps you would read enthusiasm as enthusiasm, rather than as hype.
> >>
> >> (Nonetheless, I am making an editorial pass through the drafts damping
down
> the enthusiasm/hype.)
> > 	[SM] Thanks.
> >
> >> Regards
> >>
> >>
> >>
> >> Bob
> >>
> >> {Note 1}: These arguments for allowing rate inequality are developed
> properly in "Per-Flow Scheduling and the End-to-End Argument". I wrote it
this
> summer specially for readers who believe in per-flow scheduling and who
missed
> the debates in the research and IETF communities about this over the past
dozen
> years.
> >>
> >> {Note 2} I would never introduce per-flow rate controls into the
network
> anyway.
> > 	[SM] I know, but luckily that is not at issue here, we are merely
talking
> about per-class rate controls...
> >
> >
> >> Because I do not want to be to blame for a future where high-rate
> applications (AR, VR, holographic, light-field, remote viewing, etc) have
to ask
> permission from the network, just in order to maintain a certain amount of
> throughput in the presence of FQ with varying numbers of competing flows
> (when there is plenty of bandwidth so that a less than equal share is
still
> nowhere near starvation).
> >> I do not think proponents of per-flow scheduling want such a
politically
> distasteful shift of control towards network operators either, so I don't
know
> why they choose not to see that they are pushing the Internet in this
direction.
> >>
> >> The main reason the early L4S proponents sunk years into developing the
> dualQ coupled AQM was to provide a way to do low latency without FQ.
> > 	[SM] It still remains to be seen, whether they succeeded though.
> >
> > Best Regards
> > 	Sebastian
> >
> >
> >>
> >>
> >>
> >>> Best Regards
> >>> 	Sebastian
> >>>
> >>>
> >>>
> >>>> how much has already been done to solve it, and then you could have
tried
> to work out the details of a full solution.
> >>>>
> >>>>
> >>>> Regards
> >>>>
> >>>>
> >>>>
> >>>> Bob
> >>>>
> >>>>
> >>>>
> >>>>> Best Regards
> >>>>> 	Sebastian
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>>
> >>>>>> Regards,
> >>>>>> Koen.
> >>>>>>
> >>>>>> From: Ingemar Johansson S
> >>>>>>
> >>>>>> <ingemar.s.johansson@ericsson.com>
> >>>>>>
> >>>>>>
> >>>>>> Sent: Wednesday, November 20, 2019 11:50 AM
> >>>>>> To: Kyle Rose
> >>>>>>
> >>>>>> <krose@krose.org>rg>; Ingemar Johansson S
> <ingemar.s.johansson@ericsson.com>
> >>>>>>
> >>>>>>
> >>>>>> Cc: Sebastian Moeller
> >>>>>>
> >>>>>> <moeller0@gmx.de>de>; G Fairhurst <gorry@erg.abdn.ac.uk>uk>;
> tsvwg@ietf.org; tsvwg-chairs@ietf.org; De Schepper, Koen (Nokia -
> BE/Antwerp) <koen.de_schepper@nokia-bell-labs.com>om>;
> 4bone@gndrsh.dnsmgr.net; Ingemar Johansson S
> <ingemar.s.johansson@ericsson.com>
> >>>>>>
> >>>>>>
> >>>>>> Subject: RE: [tsvwg] L4S vs SCE
> >>>>>>
> >>>>>> Hi
> >>>>>>
> >>>>>> So given the imagined outcome that L4S fails.. two scenarios
> >>>>>>
> >>>>>> If other SDOs or developers don?t pick up L4S then things are quite
> simple I guess, just declare the L4S drafts as deprecated, or is there
more to do ?
> >>>>>>
> >>>>>> But, if e.g. 3GPP somehow thinks that this is a good idea and
adopts it..
> Will the IETF send a message (LS?) to 3GPP with the message ?please stop
using
> L4S?, is this even a reasonable scenario?. After all, the fact that it is
picked up by
> other SDOs, speaks against a failure ?
> >>>>>>
> >>>>>> /Ingemar
> >>>>>>
> >>>>>> From: Kyle Rose
> >>>>>>
> >>>>>> <krose@krose.org>
> >>>>>>
> >>>>>>
> >>>>>> Sent: den 20 november 2019 11:14
> >>>>>> To: Ingemar Johansson S
> >>>>>>
> >>>>>> <ingemar.s.johansson=40ericsson.com@dmarc.ietf.org>
> >>>>>>
> >>>>>>
> >>>>>> Cc: Sebastian Moeller
> >>>>>>
> >>>>>> <moeller0@gmx.de>de>; G Fairhurst <gorry@erg.abdn.ac.uk>uk>;
> tsvwg@ietf.org; Ingemar Johansson S <ingemar.s.johansson@ericsson.com>om>;
> tsvwg-chairs@ietf.org; De Schepper, Koen (Koen)
> <koen.de_schepper@nokia.com>om>; 4bone@gndrsh.dnsmgr.net
> >>>>>>
> >>>>>>
> >>>>>> Subject: Re: [tsvwg] L4S vs SCE
> >>>>>>
> >>>>>> On Wed, Nov 20, 2019 at 6:04 PM Ingemar Johansson S
> >>>>>>
> >>>>>> <ingemar.s.johansson=40ericsson.com@dmarc.ietf.org>
> >>>>>>
> >>>>>>   wrote:
> >>>>>>
> >>>>>>
> >>>>>>>        How do you expect an industry/commercial roll-out of L4S
> >>>>>>> technology to behave, if the L4S experiment should terminated
without
> >>>>>>> adoption as a standard track RFC? Are they supposed to phase-out
> using
> >>>>>>> ECT(1) as well, or is it understood that deployed L4S instances
continue
> using
> >>>>>>> L4S methods?
> >>>>>>>
> >>>>>>>
> >>>>>> [IJ] The premise would be that L4S is declared a failure. I doubt
that
> anybody has a good enough crystal ball to predict what happens. First it
is
> necessary to come to the conclusion that L4S is a failure and I would
argue that
> we are not yet there and I don't currently see that coming. Before that
possible
> event I don't see it meaningful to speculate.
> >>>>>>
> >>>>>> I'm going to have to go ahead and disagree with you strongly here.
> Given the potential consequences of cleaning up after a failed experiment
> without a plan worked out beforehand, this blithe approach is simply not
> acceptable.
> >>>>>>
> >>>>>> In lots of cases, experiments are easy to terminate in an obvious
way:
> for example, in one typical case, a code point can simply be abandoned, or
(even
> better) a pollutable experimental code point returned to the available
pool after
> some time. If that were the case here, it would not be difficult to
enumerate a
> sequence of steps required to do so. It doesn't appear that's the case,
however,
> so all the more reason to make sure we address this as part of the
experiment
> setup.
> >>>>>>
> >>>>>> A launch escape system of the necessary complexity should be a
> requirement of any experimental deployment. In this case, that might
> circumscribe the scope of the experiment itself.
> >>>>>>
> >>>>>> Kyle
> >>>>>>
> >>>>>>
> >>>> --
> >>>>
> ________________________________________________________________
> >>>> Bob Briscoe
> >>>>
> >>>> https://protect2.fireeye.com/v1/url?k=0d356c44-51e160b5-0d352cdf-
> 864685b2085c-6879b90e0589441a&q=1&e=7766affd-61a2-4b4c-857e-
> a020626cbd8f&u=http%3A%2F%2Fbobbriscoe.net%2F
> >> --
> >>
> ________________________________________________________________
> >> Bob Briscoe
> >> https://protect2.fireeye.com/v1/url?k=e92fb07e-b5fbbc8f-e92ff0e5-
> 864685b2085c-e5743c5216f4903d&q=1&e=7766affd-61a2-4b4c-857e-
> a020626cbd8f&u=http%3A%2F%2Fbobbriscoe.net%2F
> 
> --
> ________________________________________________________________
> Bob Briscoe
https://protect2.fireeye.com/v1/url?k=b340fa0c-
> ef94f6fd-b340ba97-864685b2085c-9f0d0e713b3189d6&q=1&e=7766affd-61a2-
> 4b4c-857e-a020626cbd8f&u=http%3A%2F%2Fbobbriscoe.net%2F
> 
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