Subject: [tcpm] IW10 & queuebloat

From: Bob Briscoe <[email-masked]>
Date: Fri, 30 Mar 2012 09:57:21 +0100

Jerry,

In the tcpm meeting just now, you blamed large buffers for the 
bufferbloat problem. Not so...

With a good AQM (loss or ECN), a large* buffer beyond the AQM 
threshold is good, not evil.

The problem is actually queuebloat, not bufferbloat. (The buffer is 
the memory set aside for the queue. The queue is how much of the 
memory is used to store packets or frames.)

The blame for large AQM thresholds lies primarily with TCP's cc algo. 
DCTCP shows the way forward, and highlights that NewReno TCP sawteeth 
are to blame for large average queues, and constraining how low an 
AQM threshold can go without harming utilisation.

I predicted nearly a year ago, that the term "bufferbloat" would 
confuse people by seeming to point the finger of blame at the wrong thing:
<http://www.mail-archive.com/[email-masked]/msg00215.html>
When it starts to mislead experts in the field, I get worried.

_____
* Large, but not bloated - see the above URL.

==Relevance to IW10==
I would like to see experiments with IW10 in a simulation modelling 
how the Internet is likely to be in future (with more DCTCP-like 
protocols and shallower AQM) rather than just how the Internet is 
now. I'm not saying whether IW10 is good or bad for "queuebloat", 
because I haven't done such experiments. Intuitively it may be OK, 
but I don't trust my intuition in this case.

Bob

________________________________________________________________
Bob Briscoe,                                BT Innovate & Design

---

From: Jerry Chu <[email-masked]>
Date: Fri, 30 Mar 2012 03:50:00 -0700

Bob,

On Fri, Mar 30, 2012 at 1:57 AM, Bob Briscoe <[email-masked]> wrote:

> Jerry,
>
> In the tcpm meeting just now, you blamed large buffers for the bufferbloat
> problem. Not so...
>

Stanford researchers have shown that backbone routers do not need large
buffers to maintain high utilization. Yes it's the bloated average queue
size that is the culprit and one can have large buffers but small average
queue
size if an adequate AQM is deployment. But most home/edge routers with
large buffers do not have adequate AQM, hence my statement.

> With a good AQM (loss or ECN), a large* buffer beyond the AQM threshold is
> good, not evil.
>
> The problem is actually queuebloat, not bufferbloat. (The buffer is the
> memory set aside for the queue. The queue is how much of the memory is used
> to store packets or frames.)
>

Specifically with the "loss-based", not "delayed-based" CC algorithms.

> DCTCP shows the way forward, and highlights that NewReno TCP sawteeth are
> to blame for large average queues, and constraining how low an AQM
> threshold can go without harming utilisation.
>

Yes there has been discussion about why ECN has not see deployment widely,
and how to fix it.

>
> I predicted nearly a year ago, that the term "bufferbloat" would confuse
> people by seeming to point the finger of blame at the wrong thing:
> <http://www.mail-archive.com/[email-masked]/**msg00215.html<http://www.mail-archive.com/[email-masked]/msg00215.html>
> >

To some of us the term "bufferbloat" itself already implies no AQM,... etc
so
no worry, we are not confused.

> I would like to see experiments with IW10 in a simulation modelling how
> the Internet is likely to be in future (with more DCTCP-like protocols and
> shallower AQM) rather than just how the Internet is now. I'm not saying
> whether IW10 is good or bad for "queuebloat", because I haven't done such
> experiments.

Did I just hear a volunteer? ;-)

Best,

Jerry

> Intuitively it may be OK, but I don't trust my intuition in this case.
>
>
> Bob
>
>
> ______________________________**______________________________**____

---

From: Bob Briscoe <[email-masked]>
Date: Fri, 30 Mar 2012 14:22:15 +0100

Jerry,

At 11:50 30/03/2012, Jerry Chu wrote:
>Bob,
>
>On Fri, Mar 30, 2012 at 1:57 AM, Bob Briscoe 
><<mailto:[email-masked]>[email-masked]> wrote:
>==Relevance to IW10==
>because I haven't done such experiments.
>
>

I'd love to see the people who are making the proposal pay for the research ;)
Seriously, we have other priorities for our stretched resources, but 
would love to see this done.

Bob

---

From: Mark Allman <[email-masked]>
Date: Fri, 30 Mar 2012 10:28:40 -0400

With all due respect Bob, 

Bob:
> > I would like to see experiments with IW10 in a simulation
> > modelling how the Internet is likely to be in future (with more
> > DCTCP-like protocols and shallower AQM) rather than just how the
> > Internet is now. I'm not saying whether IW10 is good or bad for
> > "queuebloat", because I haven't done such experiments.

> I'd love to see the people who are making the proposal pay for the

Surely the bar for getting something standardized these days is not
assessing how a proposal measures up to someone's notion of "how the
Internet is likely to be in [the] future".

Put another way, I don't think you'd appreciate this bar being applied
to your proposals and my volumous notions about the future Internet,
would you?  (Hint: I am *full* of (ahem) "vision".)

Silliness.

Dear TCPM chairs, Can we please WGLC IW10?  We have been talking about
it for eons.  There is much empirical / simulation / testbed assessment
of it.  The pros and cons have been discussed to death.  Everyone will
never agree with it.  But, lets put a stake in the ground and see where
we're at WRT WG consensus.  If we have consensus then lets move it.  If
we don't have consensus then lets table it.  It is time.

allman

---

From: Yuchung Cheng <[email-masked]>
Date: Fri, 30 Mar 2012 10:41:08 -0700

> would you?  (Hint: I am *full* of (ahem) "vision".)
nod

> we don't have consensus then lets table it.  It is time.

A gentle reminder the intended status is experimental which calls for more
experiments like what Bob and others are suggesting.

>
> allman
>
>
>
>
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