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Re: Cascading Failures Could Crash the Global Internet
From: <sgorman1 () gmu edu>
Date: Sat, 08 Feb 2003 09:24:06 -0800

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.
----- Original Message -----
From: Douglas Denault <doug () safeport com>
Date: Saturday, February 8, 2003 7:31 am
Subject: Re: Cascading Failures Could Crash the Global Internet

The model proposed makes several assumptions. My question is about:

  Many real-world networks are heterogeneous and as such are 
expected to
  undergo large-scale cascades if some vital nodes are attacked.

on page 3. I do not get the basis for this assumption. So any help 
for a 60's
educated math major would be appreciated.

On Thu, 6 Feb 2003 sgorman1 () gmu edu wrote:

The paper is avaibable on the Los Alamos site free of charge:


----- Original Message -----
From: Sean Donelan <sean () donelan com>
Date: Thursday, February 6, 2003 12:43 pm
Subject: Cascading Failures Could Crash the Global Internet

Sigh, there are differences between tightly coupled networks, 
such as
the electric power grid and loosely couple networks like the 
But there are also some similarities, such as electric grids 
use DC
interconnections to limit how far AC disturbances propagate; the
Internet uses AS interconnections to limit IGP disturbances from


The actual article requires payment to read

Douglas Denault
doug () safeport com
Voice: 301-469-8766
 Fax: 301-469-0601

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