Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e congestion control

Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e congestion control

[David P. Reed]

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On Thursday, August 11, 2022 10:29am, starlink-request@lists.bufferbloat.net said:



> From: Hesham ElBakoury <helbakoury@gmail.com>
> To: "David P. Reed" <dpreed@deepplum.com>,
> starlink@lists.bufferbloat.net
> Subject: Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e
> congestion control
> 
> Hi David,
> 
> I think someone such as Professor Hari who got many awards including the
> sigcomm 2021 life-achievement award or his student Venkat need to be
> educated on Fair Queuing. There are many publications and text books
> which describe FQ. The results of this paper is for network paths that
> do not use FQ or ECN. Venkat/Hari can provide more details.
 
I would think that he knows about FQ in AQM, too. He should.
My point is that this paper, which talks about *starvation*, doesn't mention FQ at all, even though it is well known to mitigate "starvation effects" - it was invented to solve exactly that problem!
I'd suggest at minimum that the paper should point out that it *excludes* FQ from consideration. And if possible, explain why it was excluded...
 
I can think of reasons for excluding FQ in the specific paper, but shouldn't the title and abstract say  it applies only narrowly: Proposed revised title: "Starvation in e2e congestion control if FQ is excluded within the network"
 
Particularly since the paper makes *broad* generalizations - the only 2-out-of-3 argument is stated as if it applies to ALL congestion control.
> 
> For the CAP theorem, do you think I can get C,A,P, if this is what I
> need ? if this is the case, then this theorem is wrong or has limited
> applicability, correct ?
 
It has limited applicability for sure. Yet, it has become fashionable to act as if it is a completely general truth.
 
The CAP theorem, in the limited space of its assumptions, appears to be correct. But because it is so easily trivialized, as encouraged by the "you can have any two of C A an P, but not 3" without any qualification, problems with the definitions of the words C A and P - serious problems indeed that matter to a first order in real distributed systems - it is often used to derive "impossibility".
 
I'll give you another example of a serious misuse of a theorem outside its range of applicability:
 
Shannon proved a channel capacity theorem: C = W log(S / N). The proof is mathematical, and correct.
But hiding in the assumptions are some very strong and rarely applicable conditions. It was a very useful result in founding information theory.
 
But... it is now called "Shannon's Law" and asserted to be true and applicable to ALL communications systems. 
 
This turns out not to be correct. And it is hardly ever correct in practice. An example of non-correct application turns out to be when multiple transmissions of electromagnetic waves occur at the same time. EE practice is to treat "all other signals" as Gaussian Noise. They are not - they never are.
So, later information theorists discovered that where there are multiple signals received by a single receiving antenna, and only a little noise (usually from the RF Front End of the receiver, not the environment) the Slepian-Wolf capacity theorem applies C = W log(\sum(S[i]. i=1,N) /W). That's a LOT more capacity than Shannon's Law predicts, especially in narrowband signalling.
And noise itself is actually "measurement error" at the receiver, which is rarely Gaussian, in fact it really is quite predictable and/or removable.
 
So a theorem can be correct (based on its assumptions) and inapplicable in most cases, because of its narrowness.
 
And this is why a limited (not very general) theorem of the 2-out-of-3 form is dangerous.
 
As for the CAP theorem, my Ph.D. thesis was in this very area - multi-copy consistency in distributed data systems. That was in 1978, 45 years ago.  I've followed that work since the time - both the pragmatics and the theory. I think I fully understand both the context and how the axioms chosen by Brewer simplify reality in radical ways.
 
C A and P are not booleans or binary quantities. So in a real sense the CAP theorem is always inapplicable. But worse, the proof structure falls apart as a mathematical proof if you assume any metric for C A or P that isn't homomorphic to boolean algebraic quantities.
 
And worse, there is no standard measure of C A and P that captures what matters on any dimension.
 
So, aside from an intuition that maybe C, A, and P trade off in some way in some model of reality, the theorem is meaningless, and not very useful.
 
I hope this helps understand what's behind my comments.
 
At core, a referee ought to have asked - how is this conclusion justified as a general conclusion about ALL e2e congestion control in all networks, when it is only shown in a narrow, unrealistic case?
 
In my nearly 50 years of publishing in the computing and communications world, I've done a LOT of refereeing, and served on program committees as well. The obligation of a referee is to look at the conclusions of the paper, in the context of the state of the science, and figure out if the conclusion is supported by the paper's contents.
 
I'm not sure why this didn't happen here.
 
David
 
PS: compared to the post-publication comments to my first CS publication, in a letter to my mentor from Edsgar Dijkstra, I think I'm being gentle. It's motivated by getting the science right.
 
> 
> Thanks
> 
> Hesham


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Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e congestion control

[Ulrich Speidel]

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On 12/08/2022 7:34 am, David P. Reed via Starlink wrote:
>
> I'll give you another example of a serious misuse of a theorem outside 
> its range of applicability:
>
> Shannon proved a channel capacity theorem: C = W log(S / N). The proof 
> is mathematical, and correct.
>
Indeed.
>
> But hiding in the assumptions are some very strong and rarely 
> applicable conditions. It was a very useful result in founding 
> information theory.
>
> But... it is now called "Shannon's Law" and asserted to be true and 
> applicable to ALL communications systems.
>
...and it is. But it needs to be applied correctly.
>
> This turns out not to be correct. And it is hardly ever correct in 
> practice.
>
Ahem ... if it's proven, it's correct, even in practice ;-)
>
> An example of non-correct application turns out to be when multiple 
> transmissions of electromagnetic waves occur at the same time. EE 
> practice is to treat "all other signals" as Gaussian Noise. They are 
> not - they never are
>
Therein lies the problem. Correct theorem, incorrectly applied.
>
> .
>
> So, later information theorists discovered that where there are 
> multiple signals received by a single receiving antenna, and only a 
> little noise (usually from the RF Front End of the receiver, not the 
> environment) the Slepian-Wolf capacity theorem applies C = W 
> log(\sum(S[i]. i=1,N) /W).
>
Note: N here isn't the noise power (just the number of signals).
>
> That's a LOT more capacity than Shannon's Law predicts, especially in 
> narrowband signalling.
>
Only if you lump in correlated signals with noise, which is an incorrect 
(or rather, over-simplified) application of the Shannon-Hartley theorem.
>
> And noise itself is actually "measurement error" at the receiver, 
> which is rarely Gaussian, in fact it really is quite predictable 
> and/or removable.
>
Noise in the Shannon sense is random and therefore not predictable or 
correlated. Interference can be both predictable and correlated, and 
therefore can sometimes be removed / to an extent. Modelling 
interference as noise means not exploiting its inherent properties, and 
yes that means ending lower capacity. But that doesn't mean that either 
theorem is inapplicable - Shannon's fundamental limit still holds, even 
in the multi-user case, as long as the noise you plug in is the "little 
noise" from the RF front end and leave the interference out.

The point I guess is that models are just models, and the more you know 
about what it is that you are dealing with, the better you can model.

Which, I suppose, applies to managing queues also. The more you know 
what's in them and how it'll respond when you manage it, the better.

-- 
****************************************************************
Dr. Ulrich Speidel

School of Computer Science

Room 303S.594 (City Campus)

The University of Auckland
u.speidel@auckland.ac.nz  
http://www.cs.auckland.ac.nz/~ulrich/
****************************************************************



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Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e congestion control

[Ulrich Speidel]

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On 12/08/2022 8:22 am, Ulrich Speidel wrote:
>
>> And noise itself is actually "measurement error" at the receiver, 
>> which is rarely Gaussian, in fact it really is quite predictable 
>> and/or removable.
>>
> Noise in the Shannon sense is random and therefore not predictable or 
> correlated. Interference can be both predictable and correlated, and 
> therefore can sometimes be removed / to an extent. Modelling 
> interference as noise means not exploiting its inherent properties, 
> and yes that means ending lower capacity.
>
"ending up with lower capacity"

-- 

****************************************************************
Dr. Ulrich Speidel

School of Computer Science

Room 303S.594 (City Campus)

The University of Auckland
u.speidel@auckland.ac.nz  
http://www.cs.auckland.ac.nz/~ulrich/
****************************************************************



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Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e congestion control

[Livingood, Jason]

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IMO this is all good feedback for the authors to have. I don’t know them but will send them a note that this list may have feedback on the paper as well as for future research*.

JL

* I will also note that this research is the kind of thing a grant program I lead at work might be interested in for 2023.

From: Starlink <starlink-bounces@lists.bufferbloat.net> on behalf of "David P. Reed via Starlink" <starlink@lists.bufferbloat.net>
Reply-To: "David P. Reed" <dpreed@deepplum.com>
Date: Thursday, August 11, 2022 at 15:34
To: "starlink@lists.bufferbloat.net" <starlink@lists.bufferbloat.net>
Subject: Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e congestion control




On Thursday, August 11, 2022 10:29am, starlink-request@lists.bufferbloat.net said:

> From: Hesham ElBakoury <helbakoury@gmail.com>
> To: "David P. Reed" <dpreed@deepplum.com>,
> starlink@lists.bufferbloat.net
> Subject: Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e
> congestion control
>
> Hi David,
>
> I think someone such as Professor Hari who got many awards including the
> sigcomm 2021 life-achievement award or his student Venkat need to be
> educated on Fair Queuing. There are many publications and text books
> which describe FQ. The results of this paper is for network paths that
> do not use FQ or ECN. Venkat/Hari can provide more details.



I would think that he knows about FQ in AQM, too. He should.

My point is that this paper, which talks about *starvation*, doesn't mention FQ at all, even though it is well known to mitigate "starvation effects" - it was invented to solve exactly that problem!

I'd suggest at minimum that the paper should point out that it *excludes* FQ from consideration. And if possible, explain why it was excluded...



I can think of reasons for excluding FQ in the specific paper, but shouldn't the title and abstract say  it applies only narrowly: Proposed revised title: "Starvation in e2e congestion control if FQ is excluded within the network"



Particularly since the paper makes *broad* generalizations - the only 2-out-of-3 argument is stated as if it applies to ALL congestion control.

>
> For the CAP theorem, do you think I can get C,A,P, if this is what I
> need ? if this is the case, then this theorem is wrong or has limited
> applicability, correct ?



It has limited applicability for sure. Yet, it has become fashionable to act as if it is a completely general truth.



The CAP theorem, in the limited space of its assumptions, appears to be correct. But because it is so easily trivialized, as encouraged by the "you can have any two of C A an P, but not 3" without any qualification, problems with the definitions of the words C A and P - serious problems indeed that matter to a first order in real distributed systems - it is often used to derive "impossibility".



I'll give you another example of a serious misuse of a theorem outside its range of applicability:



Shannon proved a channel capacity theorem: C = W log(S / N). The proof is mathematical, and correct.

But hiding in the assumptions are some very strong and rarely applicable conditions. It was a very useful result in founding information theory.



But... it is now called "Shannon's Law" and asserted to be true and applicable to ALL communications systems.



This turns out not to be correct. And it is hardly ever correct in practice. An example of non-correct application turns out to be when multiple transmissions of electromagnetic waves occur at the same time. EE practice is to treat "all other signals" as Gaussian Noise. They are not - they never are.

So, later information theorists discovered that where there are multiple signals received by a single receiving antenna, and only a little noise (usually from the RF Front End of the receiver, not the environment) the Slepian-Wolf capacity theorem applies C = W log(\sum(S[i]. i=1,N) /W). That's a LOT more capacity than Shannon's Law predicts, especially in narrowband signalling.

And noise itself is actually "measurement error" at the receiver, which is rarely Gaussian, in fact it really is quite predictable and/or removable.



So a theorem can be correct (based on its assumptions) and inapplicable in most cases, because of its narrowness.



And this is why a limited (not very general) theorem of the 2-out-of-3 form is dangerous.



As for the CAP theorem, my Ph.D. thesis was in this very area - multi-copy consistency in distributed data systems. That was in 1978, 45 years ago.  I've followed that work since the time - both the pragmatics and the theory. I think I fully understand both the context and how the axioms chosen by Brewer simplify reality in radical ways.



C A and P are not booleans or binary quantities. So in a real sense the CAP theorem is always inapplicable. But worse, the proof structure falls apart as a mathematical proof if you assume any metric for C A or P that isn't homomorphic to boolean algebraic quantities.



And worse, there is no standard measure of C A and P that captures what matters on any dimension.



So, aside from an intuition that maybe C, A, and P trade off in some way in some model of reality, the theorem is meaningless, and not very useful.



I hope this helps understand what's behind my comments.



At core, a referee ought to have asked - how is this conclusion justified as a general conclusion about ALL e2e congestion control in all networks, when it is only shown in a narrow, unrealistic case?



In my nearly 50 years of publishing in the computing and communications world, I've done a LOT of refereeing, and served on program committees as well. The obligation of a referee is to look at the conclusions of the paper, in the context of the state of the science, and figure out if the conclusion is supported by the paper's contents.



I'm not sure why this didn't happen here.



David



PS: compared to the post-publication comments to my first CS publication, in a letter to my mentor from Edsgar Dijkstra, I think I'm being gentle. It's motivated by getting the science right.



>
> Thanks
>
> Hesham

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Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e congestion control

[Hesham ElBakoury]

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I already notified the authors.

Hesham

On 8/12/2022 7:21 AM, Livingood, Jason via Starlink wrote:
>
> IMO this is all good feedback for the authors to have. I don’t know 
> them but will send them a note that this list may have feedback on the 
> paper as well as for future research*.
>
> JL
>
> * I will also note that this research is the kind of thing a grant 
> program I lead at work might be interested in for 2023.
>
> *From: *Starlink <starlink-bounces@lists.bufferbloat.net> on behalf of 
> "David P. Reed via Starlink" <starlink@lists.bufferbloat.net>
> *Reply-To: *"David P. Reed" <dpreed@deepplum.com>
> *Date: *Thursday, August 11, 2022 at 15:34
> *To: *"starlink@lists.bufferbloat.net" <starlink@lists.bufferbloat.net>
> *Subject: *Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e 
> congestion control
>
> On Thursday, August 11, 2022 10:29am, 
> starlink-request@lists.bufferbloat.net said:
>
> > From: Hesham ElBakoury <helbakoury@gmail.com>
> > To: "David P. Reed" <dpreed@deepplum.com>,
> > starlink@lists.bufferbloat.net
> > Subject: Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e
> > congestion control
> >
> > Hi David,
> >
> > I think someone such as Professor Hari who got many awards including the
> > sigcomm 2021 life-achievement award or his student Venkat need to be
> > educated on Fair Queuing. There are many publications and text books
> > which describe FQ. The results of this paper is for network paths that
> > do not use FQ or ECN. Venkat/Hari can provide more details.
>
> I would think that he knows about FQ in AQM, too. He should.
>
> My point is that this paper, which talks about *starvation*, doesn't 
> mention FQ at all, even though it is well known to mitigate 
> "starvation effects" - it was invented to solve exactly that problem!
>
> I'd suggest at minimum that the paper should point out that it 
> *excludes* FQ from consideration. And if possible, explain why it was 
> excluded...
>
> I can think of reasons for excluding FQ in the specific paper, but 
> shouldn't the title and abstract say  it applies only narrowly: 
> Proposed revised title: "Starvation in e2e congestion control if FQ is 
> excluded within the network"
>
> Particularly since the paper makes *broad* generalizations - the only 
> 2-out-of-3 argument is stated as if it applies to ALL congestion control.
>
> >
> > For the CAP theorem, do you think I can get C,A,P, if this is what I
> > need ? if this is the case, then this theorem is wrong or has limited
> > applicability, correct ?
>
> It has limited applicability for sure. Yet, it has become fashionable 
> to act as if it is a completely general truth.
>
> The CAP theorem, in the limited space of its assumptions, appears to 
> be correct. But because it is so easily trivialized, as encouraged by 
> the "you can have any two of C A an P, but not 3" without any 
> qualification, problems with the definitions of the words C A and P - 
> serious problems indeed that matter to a first order in real 
> distributed systems - it is often used to derive "impossibility".
>
> I'll give you another example of a serious misuse of a theorem outside 
> its range of applicability:
>
> Shannon proved a channel capacity theorem: C = W log(S / N). The proof 
> is mathematical, and correct.
>
> But hiding in the assumptions are some very strong and rarely 
> applicable conditions. It was a very useful result in founding 
> information theory.
>
> But... it is now called "Shannon's Law" and asserted to be true and 
> applicable to ALL communications systems.
>
> This turns out not to be correct. And it is hardly ever correct in 
> practice. An example of non-correct application turns out to be when 
> multiple transmissions of electromagnetic waves occur at the same 
> time. EE practice is to treat "all other signals" as Gaussian Noise. 
> They are not - they never are.
>
> So, later information theorists discovered that where there are 
> multiple signals received by a single receiving antenna, and only a 
> little noise (usually from the RF Front End of the receiver, not the 
> environment) the Slepian-Wolf capacity theorem applies C = W 
> log(\sum(S[i]. i=1,N) /W). That's a LOT more capacity than Shannon's 
> Law predicts, especially in narrowband signalling.
>
> And noise itself is actually "measurement error" at the receiver, 
> which is rarely Gaussian, in fact it really is quite predictable 
> and/or removable.
>
> So a theorem can be correct (based on its assumptions) and 
> inapplicable in most cases, because of its narrowness.
>
> And this is why a limited (not very general) theorem of the 2-out-of-3 
> form is dangerous.
>
> As for the CAP theorem, my Ph.D. thesis was in this very area - 
> multi-copy consistency in distributed data systems. That was in 1978, 
> 45 years ago.  I've followed that work since the time - both the 
> pragmatics and the theory. I think I fully understand both the context 
> and how the axioms chosen by Brewer simplify reality in radical ways.
>
> C A and P are not booleans or binary quantities. So in a real sense 
> the CAP theorem is always inapplicable. But worse, the proof structure 
> falls apart as a mathematical proof if you assume any metric for C A 
> or P that isn't homomorphic to boolean algebraic quantities.
>
> And worse, there is no standard measure of C A and P that captures 
> what matters on any dimension.
>
> So, aside from an intuition that maybe C, A, and P trade off in some 
> way in some model of reality, the theorem is meaningless, and not very 
> useful.
>
> I hope this helps understand what's behind my comments.
>
> At core, a referee ought to have asked - how is this conclusion 
> justified as a general conclusion about ALL e2e congestion control in 
> all networks, when it is only shown in a narrow, unrealistic case?
>
> In my nearly 50 years of publishing in the computing and 
> communications world, I've done a LOT of refereeing, and served on 
> program committees as well. The obligation of a referee is to look at 
> the conclusions of the paper, in the context of the state of the 
> science, and figure out if the conclusion is supported by the paper's 
> contents.
>
> I'm not sure why this didn't happen here.
>
> David
>
> PS: compared to the post-publication comments to my first CS 
> publication, in a letter to my mentor from Edsgar Dijkstra, I think 
> I'm being gentle. It's motivated by getting the science right.
>
> >
> > Thanks
> >
> > Hesham
>
>
> _______________________________________________
> Starlink mailing list
> Starlink@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/starlink

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Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e congestion control

[Dave Taht]

btw, it won best student paper at sigcomm. twitter thread here:

https://twitter.com/VenkatArun95/status/1555200399652814850

On Thu, Aug 11, 2022 at 12:34 PM David P. Reed via Starlink
<starlink@lists.bufferbloat.net> wrote:
>
>
>
> On Thursday, August 11, 2022 10:29am, starlink-request@lists.bufferbloat.net said:
>
> > From: Hesham ElBakoury <helbakoury@gmail.com>
> > To: "David P. Reed" <dpreed@deepplum.com>,
> > starlink@lists.bufferbloat.net
> > Subject: Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e
> > congestion control
> >
> > Hi David,
> >
> > I think someone such as Professor Hari who got many awards including the
> > sigcomm 2021 life-achievement award or his student Venkat need to be
> > educated on Fair Queuing. There are many publications and text books
> > which describe FQ. The results of this paper is for network paths that
> > do not use FQ or ECN. Venkat/Hari can provide more details.
>
>
>
> I would think that he knows about FQ in AQM, too. He should.
>
> My point is that this paper, which talks about *starvation*, doesn't mention FQ at all, even though it is well known to mitigate "starvation effects" - it was invented to solve exactly that problem!
>
> I'd suggest at minimum that the paper should point out that it *excludes* FQ from consideration. And if possible, explain why it was excluded...
>
>
>
> I can think of reasons for excluding FQ in the specific paper, but shouldn't the title and abstract say  it applies only narrowly: Proposed revised title: "Starvation in e2e congestion control if FQ is excluded within the network"
>
>
>
> Particularly since the paper makes *broad* generalizations - the only 2-out-of-3 argument is stated as if it applies to ALL congestion control.
>
> >
> > For the CAP theorem, do you think I can get C,A,P, if this is what I
> > need ? if this is the case, then this theorem is wrong or has limited
> > applicability, correct ?
>
>
>
> It has limited applicability for sure. Yet, it has become fashionable to act as if it is a completely general truth.
>
>
>
> The CAP theorem, in the limited space of its assumptions, appears to be correct. But because it is so easily trivialized, as encouraged by the "you can have any two of C A an P, but not 3" without any qualification, problems with the definitions of the words C A and P - serious problems indeed that matter to a first order in real distributed systems - it is often used to derive "impossibility".
>
>
>
> I'll give you another example of a serious misuse of a theorem outside its range of applicability:
>
>
>
> Shannon proved a channel capacity theorem: C = W log(S / N). The proof is mathematical, and correct.
>
> But hiding in the assumptions are some very strong and rarely applicable conditions. It was a very useful result in founding information theory.
>
>
>
> But... it is now called "Shannon's Law" and asserted to be true and applicable to ALL communications systems.
>
>
>
> This turns out not to be correct. And it is hardly ever correct in practice. An example of non-correct application turns out to be when multiple transmissions of electromagnetic waves occur at the same time. EE practice is to treat "all other signals" as Gaussian Noise. They are not - they never are.
>
> So, later information theorists discovered that where there are multiple signals received by a single receiving antenna, and only a little noise (usually from the RF Front End of the receiver, not the environment) the Slepian-Wolf capacity theorem applies C = W log(\sum(S[i]. i=1,N) /W). That's a LOT more capacity than Shannon's Law predicts, especially in narrowband signalling.
>
> And noise itself is actually "measurement error" at the receiver, which is rarely Gaussian, in fact it really is quite predictable and/or removable.
>
>
>
> So a theorem can be correct (based on its assumptions) and inapplicable in most cases, because of its narrowness.
>
>
>
> And this is why a limited (not very general) theorem of the 2-out-of-3 form is dangerous.
>
>
>
> As for the CAP theorem, my Ph.D. thesis was in this very area - multi-copy consistency in distributed data systems. That was in 1978, 45 years ago.  I've followed that work since the time - both the pragmatics and the theory. I think I fully understand both the context and how the axioms chosen by Brewer simplify reality in radical ways.
>
>
>
> C A and P are not booleans or binary quantities. So in a real sense the CAP theorem is always inapplicable. But worse, the proof structure falls apart as a mathematical proof if you assume any metric for C A or P that isn't homomorphic to boolean algebraic quantities.
>
>
>
> And worse, there is no standard measure of C A and P that captures what matters on any dimension.
>
>
>
> So, aside from an intuition that maybe C, A, and P trade off in some way in some model of reality, the theorem is meaningless, and not very useful.
>
>
>
> I hope this helps understand what's behind my comments.
>
>
>
> At core, a referee ought to have asked - how is this conclusion justified as a general conclusion about ALL e2e congestion control in all networks, when it is only shown in a narrow, unrealistic case?
>
>
>
> In my nearly 50 years of publishing in the computing and communications world, I've done a LOT of refereeing, and served on program committees as well. The obligation of a referee is to look at the conclusions of the paper, in the context of the state of the science, and figure out if the conclusion is supported by the paper's contents.
>
>
>
> I'm not sure why this didn't happen here.
>
>
>
> David
>
>
>
> PS: compared to the post-publication comments to my first CS publication, in a letter to my mentor from Edsgar Dijkstra, I think I'm being gentle. It's motivated by getting the science right.
>
>
>
> >
> > Thanks
> >
> > Hesham
>
> _______________________________________________
> Starlink mailing list
> Starlink@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/starlink



-- 
FQ World Domination pending: https://blog.cerowrt.org/post/state_of_fq_codel/
Dave Täht CEO, TekLibre, LLC

Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e congestion control

[David P. Reed]

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Two things:
 
1) Do they understand Fair Queuing among flows? I actually doubt it or they would have commented on it, to be intellectually honest.
But maybe they will publish another paper that includes that? I get really frustrated when reviewers don't force papers to address well-known contradictory evidence. What are reviewers and referees who are expert in the field for if not that? (my crankiness is justified, I believe, by my commitment to research quality. But hey, maybe MIT CSAIL faculty and SIGCOMM don't care about quality? Or maybe there's been nothing published about FQ?
 
2) I absolutely hate folks who invent "theorems" that say you can have "any two of three" properties. It's become popular in computer systems research, but it actually creates a huge intellectual mess.
The CAP theorem, for example has some very peculiar definitions in order to make C, A, and P "independent" axes. Of course they are NOT independent in engineering practice. In fact, they aren't even "binary" - there's no "yes" or "no" to C, A or P - they are not even spectra that map to some increasing sequence.
Yes, you can't always get what you want. But you can almost always get what you need, and that is never a specific two out of three.
Especially not in queue management algorithms.
Goddamn cutesy anti-intellectuals.
 

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Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e congestion control

[David Lang]

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To quote from Tom Clancy (Hunt for Red Octover IIRC), it's possible to both 
increase security and increase access as a marine at a gate beats a padlock for 
both

In computer security especially there are many examples of things that increase 
security while decreasing error, increasing availablity, and (overall) 
decreasing cost.

sometimes it's 'pick 2', but all to frequently people actually opt for 'none of 
the above' (i.e. sub-optimal in all areas)

David Lang

On Mon, 8 Aug 2022, David P. Reed via Starlink wrote:

> 2) I absolutely hate folks who invent "theorems" that say you can have "any two of three" properties. It's become popular in computer systems research, but it actually creates a huge intellectual mess.
> The CAP theorem, for example has some very peculiar definitions in order to make C, A, and P "independent" axes. Of course they are NOT independent in engineering practice. In fact, they aren't even "binary" - there's no "yes" or "no" to C, A or P - they are not even spectra that map to some increasing sequence.
> Yes, you can't always get what you want. But you can almost always get what you need, and that is never a specific two out of three.
> Especially not in queue management algorithms.
> Goddamn cutesy anti-intellectuals.

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Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e congestion control

[Dave Taht]

On Mon, Aug 8, 2022 at 3:37 PM David Lang via Starlink
<starlink@lists.bufferbloat.net> wrote:
>
> To quote from Tom Clancy (Hunt for Red Octover IIRC), it's possible to both
> increase security and increase access as a marine at a gate beats a padlock for
> both

OT, dlang - how'd the wifi at SCALE go?

> In computer security especially there are many examples of things that increase
> security while decreasing error, increasing availablity, and (overall)
> decreasing cost.
>
> sometimes it's 'pick 2', but all to frequently people actually opt for 'none of
> the above' (i.e. sub-optimal in all areas)

OT also, but a really good read:
http://alexmckenzie.weebly.com/seeking-high-imp-reliability.html

>
> David Lang
>
> On Mon, 8 Aug 2022, David P. Reed via Starlink wrote:
>
> > 2) I absolutely hate folks who invent "theorems" that say you can have "any two of three" properties. It's become popular in computer systems research, but it actually creates a huge intellectual mess.
> > The CAP theorem, for example has some very peculiar definitions in order to make C, A, and P "independent" axes. Of course they are NOT independent in engineering practice. In fact, they aren't even "binary" - there's no "yes" or "no" to C, A or P - they are not even spectra that map to some increasing sequence.
> > Yes, you can't always get what you want. But you can almost always get what you need, and that is never a specific two out of three.
> > Especially not in queue management algorithms.
> > Goddamn cutesy anti-intellectuals._______________________________________________
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> Starlink@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/starlink
> _______________________________________________
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> Starlink@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/starlink



-- 
FQ World Domination pending: https://blog.cerowrt.org/post/state_of_fq_codel/
Dave Täht CEO, TekLibre, LLC

Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e congestion control

[Hesham ElBakoury]

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Hi David,

I think someone such as Professor Hari who got many awards including the 
sigcomm 2021 life-achievement award or his student Venkat need to be 
educated on Fair Queuing. There are many publications and text books 
which describe FQ. The results of this paper is for network paths that 
do not use FQ or ECN. Venkat/Hari can provide more details.

For the CAP theorem, do you think I can get C,A,P, if this is what I 
need ? if this is the case, then this theorem is wrong or has limited 
applicability, correct ?

Thanks

Hesham

On 8/8/2022 2:39 PM, David P. Reed via Starlink wrote:
>
> Two things:
>
> 1) Do they understand Fair Queuing among flows? I actually doubt it or 
> they would have commented on it, to be intellectually honest.
>
> But maybe they will publish another paper that includes that? I get 
> really frustrated when reviewers don't force papers to address 
> well-known contradictory evidence. What are reviewers and referees who 
> are expert in the field for if not that? (my crankiness is justified, 
> I believe, by my commitment to research quality. But hey, maybe MIT 
> CSAIL faculty and SIGCOMM don't care about quality? Or maybe there's 
> been nothing published about FQ?
>
> 2) I absolutely hate folks who invent "theorems" that say you can have 
> "any two of three" properties. It's become popular in computer systems 
> research, but it actually creates a huge intellectual mess.
>
> The CAP theorem, for example has some very peculiar definitions in 
> order to make C, A, and P "independent" axes. Of course they are NOT 
> independent in engineering practice. In fact, they aren't even 
> "binary" - there's no "yes" or "no" to C, A or P - they are not even 
> spectra that map to some increasing sequence.
>
> Yes, you can't always get what you want. But you can almost always get 
> what you need, and that is never a specific two out of three.
>
> Especially not in queue management algorithms.
>
> Goddamn cutesy anti-intellectuals.
>
>
> _______________________________________________
> Starlink mailing list
> Starlink@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/starlink

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Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e congestion control

[Dave Taht]

This paper among others is being presented aug 22.

https://conferences.sigcomm.org/sigcomm/2022/program.html

Remote attendance at this sigcomm is $350.

There are a few other papers of note, in particular I have higher hopes for

"Cebinae: scalable in-network fairness augmentation" which starts off
with cites of a lot of papers I found influential (like them or
no)....

and google finally documenting how they've been using the ipv6
flowheader intelligently with
"PLB (Protective Load Balancing)"

[Starlink] SIGCOMM MIT paper: Starvation in e2e congestion control

[Dave Taht]

Perhaps it's obvious to the authors that FQ opens up new possibilities
for delay based convergence. Otherwise, pretty good:

"We prove that when two flows using the same CCA share a bottleneck
link, if the non-congestive delay variations exceed double the
difference between the maximum and minimum queueing delay at
equilibrium, then there are patterns of non-congestive delay where one
flow will get arbitrarily low throughput compared to the other. Our
theorem shows that CCAs have
to choose at most two out of three properties: high through put,
convergence to a small and bounded delay range, and no starvation."

Paper: http://people.csail.mit.edu/venkatar/cc-starvation.pdf

Article: https://news.mit.edu/2022/algorithm-computer-network-bandwidth-0804



-- 
FQ World Domination pending: https://blog.cerowrt.org/post/state_of_fq_codel/
Dave Täht CEO, TekLibre, LLC

Re: [Starlink] SIGCOMM MIT paper: Starvation in e2e congestion control

[Venkat Arun]

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Hi Dave,

Yes definitely, when fair-queuing is present, the onus is no longer on the
congestion control algorithm to ensure fairness. In fact, if buffer-sharing
is implemented correctly, FQ can even stand against adversarial congestion
control algorithms. We have good reason to believe that end-to-end
congestion control algorithms can provably work (i.e. achieve high
utilization, bounded delay and fairness) in the presence of FQ.

Cheers,
Venkat

On Fri, Aug 5, 2022 at 12:36 AM Dave Taht <dave.taht@gmail.com> wrote:

> Perhaps it's obvious to the authors that FQ opens up new possibilities
> for delay based convergence. Otherwise, pretty good:
>
> "We prove that when two flows using the same CCA share a bottleneck
> link, if the non-congestive delay variations exceed double the
> difference between the maximum and minimum queueing delay at
> equilibrium, then there are patterns of non-congestive delay where one
> flow will get arbitrarily low throughput compared to the other. Our
> theorem shows that CCAs have
> to choose at most two out of three properties: high through put,
> convergence to a small and bounded delay range, and no starvation."
>
> Paper: http://people.csail.mit.edu/venkatar/cc-starvation.pdf
>
> Article:
> https://news.mit.edu/2022/algorithm-computer-network-bandwidth-0804
>
>
>
> --
> FQ World Domination pending:
> https://blog.cerowrt.org/post/state_of_fq_codel/
> Dave Täht CEO, TekLibre, LLC
>

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