Re: [Bloat] Animation

Re: [Bloat] Animation

[Daniel Brooks]

I saw the video that Richard posted, and I agree that it needs to be
accompanied by an explanation. Text is the simplest way to go, and
subtitles can be abused for this purpose, so I converted the video to a
WebM file and put it up on my webserver at
http://db48x.net/bufferbloat/. I then used universalsubtitles.org to add
subtitles to it; You can check them out at
http://universalsubtitles.org/en/videos/qstl1K7mdGuq/. The subtitles are
also supposed to show up on db48x.net but for the moment there's a snag.

Anyone can edit these subtitles right in the browser, so I encourage
anyone who has an idea for improvements to simply do so. Consider the
existing subtitles to be a first draft. Similarly, if there is any other
information we can sync to the video in order to produce a better
presentation then suggest it here in the list and I'll implement
it. Syncing text, images, whole webpages, and audio to the video is
practically trivial, so don't be shy. If someone wants to record a
spoken explanation that would be wonderful.

db48x

Re: [Bloat] Animation

[Jim Gettys]

On 03/01/2011 02:22 AM, Daniel Brooks wrote:
> I saw the video that Richard posted, and I agree that it needs to be
> accompanied by an explanation. Text is the simplest way to go, and
> subtitles can be abused for this purpose, so I converted the video to a
> WebM file and put it up on my webserver at
> http://db48x.net/bufferbloat/. I then used universalsubtitles.org to add
> subtitles to it; You can check them out at
> http://universalsubtitles.org/en/videos/qstl1K7mdGuq/. The subtitles are
> also supposed to show up on db48x.net but for the moment there's a snag.
>
> Anyone can edit these subtitles right in the browser, so I encourage
> anyone who has an idea for improvements to simply do so. Consider the
> existing subtitles to be a first draft. Similarly, if there is any other
> information we can sync to the video in order to produce a better
> presentation then suggest it here in the list and I'll implement
> it. Syncing text, images, whole webpages, and audio to the video is
> practically trivial, so don't be shy. If someone wants to record a
> spoken explanation that would be wonderful.
>
> db48x

The big problem I see (with the original simulation) is that it chooses 
a very unlikely situation to simulate; a number of hops with identical 
throughput, and the queues therefore growing at multiple hops.

Almost always, there will be (for a simple path such as that being 
simulated in this case) a single hop which is the bottleneck, and the 
queues grow on either side of that hop.

Given the original NS2 script, it should be easy to re-run with 
something much more "typical".

Another point we need to get across is that the bottleneck moves and 
therefore where the queues grow: e.g. when your 802.11 bandwidth drops 
below that of your broadband bandwidth and it shifts to your host and 
home router.

Anyone care to take the original ns2 script and regenerate video for the 
typical cases we know happen most often?
			- Jim

Re: [Bloat] Animation

[Eric Raymond]

John W. Linville <linville@tuxdriver.com>:
> On Tue, Feb 08, 2011 at 07:54:57AM +0100, Richard Scheffenegger wrote:
> 
> > I've created a simplistic simulation of bufferbloat with ns2-2.34.
> > 
> > http://www.bufferbloat.net/attachments/15/nam00000.avi
> 
> Looks good -- I _think_ I almost understand what I'm seeing... :-)

That's my reaction, too.  (a) it needs a narrative voicover, badly, and (b) 
the graphics need to be less abstract.
-- 
		<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>

Re: [Bloat] Animation

[John W. Linville]

On Tue, Feb 08, 2011 at 07:54:57AM +0100, Richard Scheffenegger wrote:

> I've created a simplistic simulation of bufferbloat with ns2-2.34.
> 
> http://www.bufferbloat.net/attachments/15/nam00000.avi

Looks good -- I _think_ I almost understand what I'm seeing... :-)

> The animation is released under CC 3.0 - I explicitly invite you to
> ie. voice over the animation, use parts of it (ie. time-lapse for
> beverity) etc.

I hope someone does this.  If nothing else, maybe even just an
accompanying script or some text overlay during the animation would
be nice.

Hopefully you/we can clarify the issue for knuckle-dragging "layer 2"
guys like me that have been trained into the "don't drop packets"
mentality.  Some of the recent writings have been good for this too.
But a lot of the posts on this list and the blogs have amounted to a
URL with a comment like "the problem here is obvious" -- leaving me
to squint and scratch my head...

Given my associations with Linux and wireless, I am interested in
working on this problem.  Still, I (and presumably others) may need
some hand-holding!

John
-- 
John W. Linville		Someday the world will need a hero, and you
linville@tuxdriver.com			might be all we have.  Be ready.

[Bloat] Animation

[Richard Scheffenegger]

Hi,

I've created a simplistic simulation of bufferbloat with ns2-2.34.

http://www.bufferbloat.net/attachments/15/nam00000.avi


Since bandwidth x latency x time-per-frame are scale invariant (if each 
frame represents less time, the simulatied bandwidth goes up / latency goes 
down), I choose parameters which fit best with good graphical results.

Perhaps one should add some line-graphs next to the sender, showing the 
evolution of the congestion window, or the bandwidth utilized.

The simulated tcp stack was an older variant of Linux.

The animation is released under CC 3.0 - I explicitly invite you to ie. 
voice over the animation, use parts of it (ie. time-lapse for beverity) etc.

Best regards,
   Richard


----- Original Message ----- 
From: "Jim Gettys" <jg@freedesktop.org>
To: <esr@thyrsus.com>
Cc: "Eric Raymond" <esr@snark.thyrsus.com>; <bloat@lists.bufferbloat.net>
Sent: Monday, February 07, 2011 8:56 PM
Subject: Re: [Bloat] Overview modifications


> On 02/06/2011 03:20 PM, Eric Raymond wrote:
>> Jim Gettys<jg@freedesktop.org>:
>>>> Change in progress -- append to the "Hating" paragraph the following
>>>> sentence: "Lossy networks such as wireless actually show less chaotic
>>>> behavior under load than clean ones."  Is this correct and adequate?
>>>
>>> It's not chaotic behaviour.  In fact, it is much more worrying: it
>>> is periodic (oscillatory) behaviour.  Chaos is good, in this case.
>>
>> Dave also says my take is wrong and is promising to suggest a correction.
>> I have enough other stuff to do that I'll wait on that.
>>
>>> My nightmare, is that as traffic shifts over more and more to
>>> saturated links as XP retires, we end up with self synchronising
>>> behaviour on a local, regional or global scale, and havoc ensues,
>>> and parts/all of the Internet stop working. Whether these fears are
>>> justified, I do not know.
>>>
>>> Think: we may be a column of soldiers in cadence approaching a bridge...
>>
>> New graphs at the end of "From Highway to Network":
>>
>>      We also have some worries about the future.  For various reasons
>>      (including the gradual retirement of Windows XP) more and more
>>      Internet traffic is now running over saturated links.  In this new
>>      environment, we think there is a possibility that bufferbloat 
>> cascades
>>      and defects in management strategies might produce 
>> self-synchronising
>>      behaviour in network traffic - packet floods and network resonance 
>> on
>>      a local, regional or global scale that could be a greater threat to
>>      the Internet than the congestion-driven near-collapse of the NSF
>>      backbone in 1986.
>
> It's not just bufferbloat: a number of network technologies are bunching 
> up packets and injecting them into the Internet with periodic bursts. 
> Unfortunately, I don't have good references to this; I gather this is true 
> of both wireless and wired technologies.
>
>>
>>      This is a classic "black swan" situation in Nassim Taleb's sense; in
>>      today's Internet-dependent economy there is a potential for nearly
>>      inacalculable havoc in the worst case, but we don't even know in
>>      principle how to estimate the overall risk.  Bufferbloat mitigation
>>      might keep us out of some very serious trouble, and is worth 
>> pursuing
>>      on those grounds alone.
>
> It's actually a general fear of any periodic behaviour; I'm just spooked 
> to see it in such long period TCP traffic.
>
> Van warned me about time based congestion phenomena in general.
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