Subject: [PCN] simulation efforts

From: ken carlberg <[email-masked]>
Date: Wed, 21 Mar 2007 10:26:36 +0100

One thing that occurred to me after seeing the simulation  
presentations is that if these efforts are relying on Poisson to  
represent inter-arrival rates, it would be nice if they could use  
other representations.  the journal papers of the last few years  
having been using other strategies (self similar, brown noise, heavy  
tail) and so our confidence level in the results would improve if  
something other than poisson is used.

cheers,

-ken

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---

From: "Anna Charny \(acharny\)" <[email-masked]>
Date: Wed, 21 Mar 2007 08:06:27 -0400

Hello Ken,

A few notes on simulation models we used. Given that the charter
constrains us to non-elastic real-time traffic, we concentrated on
modeling voip and video only.

1) Voip *packet* arrivals:  we have simulated a subset of actual
encodings and plan to simulate other encodings as well as their mix.  So
for *packet* arrival models for voip we seem to be in reasonable shape.
There are also a few papers suggesting how to model aggregate voip
traffic - but we have not done so because our interest has been in
simulating specific call reaction to pcn rather than aggregate voip
queuing in the core.

2) Voip *call* arrivals: 
For voice call arrivals Poisson  seems not an unreasonable assumption,
based on the classic telephony experience. Of course things may change
with voip, but we have not found any studies that argued for a
non-Poisson *call* arrival models for voice.  To be on the safe side we
also tried what we called "Batch Poisson" - Poisson arrivals for some of
our simulations (a burstier-than Poisson model when a batch of flows
arrive near-simultaneously, but the batches arrive according to the
Poisson)- and our intent is to expand the simulation study to cover a
broader range of "batch sizes" traffic types.  If anyone is aware of any
study that suggests other  voip *call* arrival distributions please do
let us know. 

3) Video *packet* arrivals:
There is a vast amount of work on modeling video packet arrival models.
We did not get to simulating any of those, but we did not use Poisson
packet arrival assumption either. Instead, we used real video traces,
and we also simulated an extremely rough on-off traffic model with an
MPEG-2-like peak-to-mean ratio, with exponentially distributed on-off
intervals. It is clearly not a reasonable video model, but it likely to
be more challenging for the algorithms and was used as a stress-test.
Our plan is to find more real video traces for simulation.

4) It is less clear what a reasonable models for video *call* arrivals
are and we would appreciate any pointers on that.  We used Poisson call
arrivals for video simply for the lack of clarity of what a better model
might be and for the lack of time to try anything else.  Unlike studies
of packet arrival models for video, we did not find any that studied
*session/call* arrival distributions. If we just missed the relevant
work, please do let us know.  

Any specific input to simulation assumptions is very welcome. In
general, this simulation effort is quite time-consuming, so more
volunteers in the WG to share the work would be very welcome.

Anna 

> -----Original Message-----
> From: ken carlberg [mailto:[email-masked]] 
> Sent: Wednesday, March 21, 2007 5:27 AM
> To: [email-masked]
> Subject: [PCN] simulation efforts
> 
> presentations is that if these efforts are relying on Poisson 
> to represent inter-arrival rates, it would be nice if they 
> could use other representations.  the journal papers of the 
> last few years having been using other strategies (self 
> similar, brown noise, heavy
> tail) and so our confidence level in the results would 
> improve if something other than poisson is used.
> 
> cheers,
> 
> -ken
> 
>

---

From: Michael Menth <[email-masked]>
Date: Wed, 21 Mar 2007 18:30:27 +0100

Hi Anna,

my Ex-colleague Oliver Rose did quite a good on video modeling in the 
1990ies. You can find his PhD thesis and a zip-file with tons of traces 
on the following page:
http://www.iai.inf.tu-dresden.de/ms/rose/rose.html

Best wishes (already from home),

    Michael

-- 
Dr. Michael Menth, Assistant Professor
University of Wuerzburg, Institute of Computer Science
Am Hubland, D-97074 Wuerzburg, Germany, room B206
phone: (+49)-931/888-6644, fax: (+49)-931/888-6632
mailto:[email-masked]
http://www3.informatik.uni-wuerzburg.de/research/ngn

---

From: "Anna Charny \(acharny\)" <[email-masked]>
Date: Wed, 21 Mar 2007 21:28:16 -0400

Hello Michael,

Thank you for the pointers. We do keep Oliver Rose's traces in mind for
the future use - for the moment we have been using MPEG-4 traces from
http://www.tkn.tu-berlin.de/research/trace/trace.html.

One thing to note is that to the best of my knowledge, Oliver Rose's
work is not about modelling video *flow arrivals* - rather it is about
modelling traffic within a video flow.  However, it is the flow arrival
model that we are missing (as I mentioned, in the absense of better
knowledge we have been using Poisson and plan to use Poisson burst
arrival (BATCH) for video flow arrival). 

Thank you also for the introduction to Oliver Rose.  Oliver, we would
appreciate any insight you might share regarding video *flow* arrival
models.

Thank you in advance,
Anna 

> From: Michael Menth [mailto:[email-masked]] 
> Sent: Wednesday, March 21, 2007 1:30 PM
> To: Anna Charny (acharny)
> Cc: ken carlberg; [email-masked]; Prof. Dr. Oliver Rose
> Subject: Re: [PCN] simulation efforts
> 
> Hi Anna,
> 
> my Ex-colleague Oliver Rose did quite a good on video 
> modeling in the 1990ies. You can find his PhD thesis and a 
> zip-file with tons of traces on the following page:
> > encodings and plan to simulate other encodings as well as 
> their mix.  
> > So for *packet* arrival models for voip we seem to be in 
> reasonable shape.
> > non-Poisson *call* arrival models for voice.  To be on the 
> safe side 
> > we also tried what we called "Batch Poisson" - Poisson arrivals for 
> > some of our simulations (a burstier-than Poisson model when 
> a batch of 
> > flows arrive near-simultaneously, but the batches arrive 
> according to 
> > the
> > broader range of "batch sizes" traffic types.  If anyone is 
> aware of 
> > any study that suggests other  voip *call* arrival distributions 
> > please do let us know.
> >
> > intervals. It is clearly not a reasonable video model, but 
> it likely 
> > to be more challenging for the algorithms and was used as a 
> stress-test.
> > are and we would appreciate any pointers on that.  We used Poisson 
> > call arrivals for video simply for the lack of clarity of what a 
> > better model might be and for the lack of time to try 
> anything else.  
> > Unlike studies of packet arrival models for video, we did 
> not find any 
> > that studied
> University of Wuerzburg, Institute of Computer Science Am 
> Hubland, D-97074 Wuerzburg, Germany, room B206

---

From: Michael Menth <[email-masked]>
Date: Thu, 22 Mar 2007 08:45:23 +0100

Hello Anna,

Anna Charny (acharny) wrote:
> modelling traffic within a video flow.  
Yes, that's true. As far as I know Oliver developed a model to generate 
artificial traffic having the same statistical properties (including 
inter-frame correlations) as video traffic. That's nice for simulations 
as it avoids artifacts due to repetitions of the same video trace.

> However, it is the flow arrival
I think whatever we assume is not realistic. I would use an arrival 
process that allows a simple parameterization of the burstiness. This 
yields if-then-results and doesn't pretend to capture the reality by the 
simulation of a "typical video arrival process". So you might go either 
with a batch arrival process for videos (but these are already 
artificially strong flash crowds) or you might use a Gamma-distributed 
interarrival time as this allows you to control its mean and variance 
independently of each other without having arrivals that exactly the 
same time. For a suitable choice of the parameters you get Poisson arrivals.

> appreciate any insight you might share regarding video *flow* arrival
He didn't do that.

Best wishes,

    Michael

>>> For voice call arrivals Poisson  seems not an unreasonable 
>>>       
>> assumption, 
>>     
>>> based on the classic telephony experience. Of course things 
>>>       
>> may change 
>>     
>>> Poisson)- and our intent is to expand the simulation study 
>>>       
>> to cover a 
>>     
>>> There is a vast amount of work on modeling video packet 
>>>       
>> arrival models.
>>     
>>> We did not get to simulating any of those, but we did not 
>>>       
>> use Poisson 
>>     
>>> packet arrival assumption either. Instead, we used real 
>>>       
>> video traces, 
>>     
>>> and we also simulated an extremely rough on-off traffic 
>>>       
>> model with an 
>>     
>>> MPEG-2-like peak-to-mean ratio, with exponentially 
>>>       
>> distributed on-off 
>>     
>>> 4) It is less clear what a reasonable models for video 
>>>       
>> *call* arrivals 
>>     
>>> *session/call* arrival distributions. If we just missed the 
>>>       
>> relevant 
>>     
>>>> having been using other strategies (self similar, brown 
>>>>         
>> noise, heavy
>>

---

From: "Jozef Babiarz" <[email-masked]>
Date: Thu, 22 Mar 2007 08:01:23 -0400

Anna, Michael,
The video source model we used in our simulation is based on video
streaming model 1 from B. Maglaris, D. Anastassiou, P. Sen, G. Karlsson
and J. Robbins, "Performance Models of Statistical Multiplexing in
Packet Video Communications", IEEE Transactions on Communications, 36,
pp. 834-844, July 1988. The selection of this model is for its
simplicity and ability to approximate the burstness and dependence of
the video source. The simulation is not required and does not attempt to
model accurate video codec processing. For more details see page 53
http://standards.nortel.com/pcn/Simulation_EPCN.pdf

This model assumes that the video source will generate constantly f
frames per second with each frame of a fixed size of p non-compressed
pixels, and the compressed bits per pixel of the frames can be modeled
by a first-order autoregressive Markov process with sequence of
independent Gaussian random variables with configured mean and variance.

In our simulation, the original parameters from the paper are used for
now, while, parameters f and p are configurable. The paper suggests that
with the original parameters, a bell-like shaped distribution is
produced. From simulation, it is found that the peak data rate is about
1.5 times of what is estimated using the Gaussian assumption.

Regards, Joe
email:[email-masked]
Telephone:613-763-6098
-----Original Message-----
From: Michael Menth [mailto:[email-masked]] 
Sent: March 22, 2007 3:45 AM
To: Anna Charny (acharny)
Cc: [email-masked]; Prof. Dr. Oliver Rose
Subject: Re: [PCN] simulation efforts

Hello Anna,

same time. For a suitable choice of the parameters you get Poisson
arrivals.

He didn't do that.

Best wishes,

    Michael