# Cascading Failures Could Crash the Global Internet

I believe the comments about heterogenous networks has to do with a
measurement called assortivitiy that is used in statistical mechanics.
A homogenous network is when nodes connect preferentially to nodes like
them. In a heterogenous network they connect to nodes that are not
like them. For networks like the Intneret and the electric grid it is
measured by the number of connections a node has.

The kicker, that the author's are alluding to, is that the more
heterogenous a network is the more vulnerable it is to targeted
attack. By taking out a highly connected node - lots of poorly
connected nodes that use it as a hub are lost. The AS network had the
highest heterogenous score of real-world tested networks, so lots of
folks on that bandwagon.

That said I don't think the tolerance parameter they set up in the
paper makes much sense when applied to the Internet at the AS level.
Basically it says once traffic exceeds a certain threshold the node
will fail and cause cascades across the network. You guys are the
experts but that does not sound overly realistic.

"sgorman1" == sgorman1 <sgorman1@gmu.edu> writes:

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

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.