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## Re: Cascading Failures Could Crash the Global Internet

• From: Douglas Denault
• Date: Sat Feb 08 18:25:42 2003

I believe the answer meant heterogenous has a meaning in a statistical context.
As I was a Real Variables guy I, was weak on statistics (of my day). Math guys
love to use perfectly good English words giving them different meanings.

Assuming that the given definition is correct, the applicability of the
assumption to the backbone is still not clear to me. While not doubting the
mathematical model, it seems to me there is little empirical evidence to support
it in this context. Or I am in the second half of your second point.

On 8 Feb 2003, Michael Lamoureux wrote:

>  "sgorman1" == sgorman1  <sgorman1@gmu.edu> writes:
>
> sgorman1> I believe the comments about heterogenous networks has to do
> sgorman1> with a measurement called assortivitiy that is used in
> sgorman1> statistical mechanics.  A homogenous network is when nodes
> sgorman1> connect preferentially to nodes like them.  In a
> sgorman1> heterogenous network they connect to nodes that are not like
> sgorman1> them.  For networks like the Intneret and the electric grid
> sgorman1> it is measured by the number of connections a node has.
>
> sgorman1> The kicker, that the author's are alluding to, is that the
> sgorman1> more heterogenous a network is the more vulnerable it is to
> sgorman1> targeted attack.  By taking out a highly connected node -
> sgorman1> lots of poorly connected nodes that use it as a hub are
> sgorman1> lost.  The AS network had the highest heterogenous score of
> sgorman1> real-world tested networks, so lots of folks on that
> sgorman1> bandwagon.
>
> I don't see how the fact that a network is homogeneous or
> heterogeneous has anything to do with how well connected it is.  The
> only possible sense to this I can see is that, statistically, you are
> more likely to have a platform that the attacker has a viable attack
> for if you have lots of different platforms.  But at the same time, if
> the attacker only has one exploit (or whatever attack vector), then
> you are also in a MUCH better position than someone who's network is
> made up 100% of that platform.  I'm still not sure how having a
> homogeneous network helps.
>
> Either you aren't explaining it well, or I'm being stupid.  I consider
> both possibilities to be equally likely at this point.   ;-)
>
>
> IMHO,
> Michael
>

_____
Douglas Denault
doug@safeport.com
Voice: 301-469-8766
Fax: 301-469-0601