[e2e] simulation using self-similar traffic

[Polly Huang]

Soo-hyeong,

This depends a lot on what metrics you're interested and how you 
generate the self-similar traffic.

According to Crovella and Lipsky's chapter in 'Self-similar Network
Traffic and Performance Evaluation' edited by Park and Willinger, if
you're measuring average throughput and using heavy-tailed file sizes 
with a small alpha, say 1.2, you'll need to simulate 10^12 samples to 
get 2-digit accuracy.  This is not feasible in practice (at least with 
ns-2).  

However, the above applies specifically to 'average' throughput. 
For metrics like 90% quantile of the throughput, I have been using 
the following heuristics:
1. plot the 90% quantile of the file sizes for different numbers of
   samples (using MATLAB or Splus, see the attached ps for example)
2. identify where the value converges
3. simulate at minimum that amount of samples

This might not be sufficient theoretically but necessary intuitively.
And I hope this helps.

-Polly

On Tue, 3 Apr 2001, Soo-hyeong Lee wrote:

> 
> Hello,
> 
> Could you please tell me how long should I run a simulation to obtain a sufficiently confident result when using a self-similar traffic trace?
> I want to show the performance of a scheme in the 'general' case which consists of mixture of busy period and silent period.
> However, a self-similar traffic trace can have very long busy period and very long silent period with unnegligible probability. Then any fixed simulation time can be entirely filled with either busy period or silent period with unnegligible probability.
> Is there any recommendation on simulation time (or how many independent simulations should be run) to yield something like 90% confidence interval.
> 
> Thanks and regards.
> 
> Soo-hyeong
> 
> 
> 


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