Re: Bandwidth distribution (was: Re: AllowInvalidNodes entry, exit, ... ?)

[Scott Bennett <bennett@xxxxxxxxxx>]

     On Wed, 20 Aug 2008 18:19:40 +0200 Sven Anderson <sven@xxxxxxxxxxx>
wrote:
>Am 18.08.2008 um 16:43 schrieb macintoshzoom:
>
>> Using "valid nodes" I have noticed too many times mu browsing is =20
>> going to the same exit nodes .... yes fast, but always the same tor =20=
>
>> exit nodes "club".
>
>this is not really a surprise if you look at the distribution of the =20
>bandwidth. I did some graphs for the bandwidth distribution of =20
>yesterday.
>
>As you can see in [1] the distribution of bandwidth over the exit =20
>nodes follows a power-law (aka Pareto, Zipf, heavy/long tail, ...), =20
>like so many other distributions. In the double-logarithmic plot this =20=
>
>is expressed in a linear relation. In this case the linearity starts =20
>between 20 and 30 kB/s. (The bandwidth of the exit nodes is =20
>exponentially binned which results in the equidistant data points.)
>
>These power-law distributions have the well-known characteristic of =20
>many small values and very few big values, also referred to as 90/10 =20
>or 80/20 rule. In plot [2] you can see the cumulative distribution =20
>function (CDF) over the ranked exit nodes. As you can see, the 30 =20
>biggest exit nodes are holding 50% of the total tor exit bandwidth, =20
>and the 100 biggest hold 70%. While this is still quite moderate it =20
>shows how often you will see the top 30, even if the exit node =20
>selection would only be based on bandwidth. But the "Fast" and =20
>"Stable" flags of course increase this effect.
>
>So there's no conspiracy, it's a natural law.
>
>[1] http://sven.anderson.de/misc/en_bw_dist.pdf
>[2] http://sven.anderson.de/misc/en_bw_cdf.pdf
>
     Very nicely done.  I was just curious, though, what other flags you
used, if any.  Running?  Not BadExit?
     Thanks much for the graphs!


                                  Scott Bennett, Comm. ASMELG, CFIAG
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