Re: Fractal models of Big-I Internet

[Vern Paxson]

> Given that real world systems that exhibit fractal behaviors can now often
> be modelled mathematically, do you know of anyone who has attempted to
> apply such fractal models to Internet traffic?

There have been several studies presenting strong evidence that Internet
traffic in general, and also that of some individual protocols (of particular
interest: HTTP), have a fractal structure.  This is still a major research
area, though.  One of the important unanswered questions is whether the
fractal structure is a good model for behavior on short time scales (10-100
msec).  Best guess (IMHO :-) is that it isn't.  So there's a major question
of how to put together a model that deals with both the short-term and
long-term dynamics, along with major questions as to what's the *right*
fractal model.  Unfortunately, the math gets hairy fast, and the Internet
is tremendously diverse.

> When designing protocols
> do researchers take this fractal nature into account?

This also is a research frontier.  Some work's been done though.  One study
that comes to mind is that by Sugih Jamin of USC (now at U Michigan) and
colleagues, on the impact of fractal traffic on admission control schemes.
I don't know of any protocols being designed with fractal traffic in mind.
I'm right now in the middle of analyzing a bunch of end-to-end data to try
to build up some sort of model of congestion time scales.  One thing I'll
be looking for is a link between the measurements and fractal models.  I'm
hoping to present some results at the first 1997 NANOG.

		Vern
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