Merit Network
Can't find what you're looking for? Search the Mail Archives.
  About Merit   Services   Network   Resources & Support   Network Research   News   Events   Home

Discussion Communities: Merit Network Email List Archives

North American Network Operators Group

Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: Cascading Failures Could Crash the Global Internet

  • From: sgorman1
  • Date: Sat Feb 08 20:36:36 2003

Ya - that pretty much sums it up - interesting model dubious 
application in reality.

Homogenous, in this context, does not mean similar platform 
connectivity, but nodes with same degree connecting to each other.  It 
is more likely for a node with ten connections to connect to other 
nodes with ten connections than one with one or two connections.  The 
Internet is heterogenous.  So, take UUnet as your nodes at the AS level 
and lets say it has 1700 or so connections to other AS's.  Most of 
those other AS's would not not also have 1700 connections, thus it is 

Lots of problems in applying that to cascading failures in reality - 
making AS701 disappear, BGP allowing a cascading traffic failure 
from "having to redistribute" AS701's traffic etc etc.  Hope that makes 
it more clear, but it is just my interpretation of someone elses work.  

----- Original Message -----
From: Douglas Denault <>
Date: Saturday, February 8, 2003 3:23 pm
Subject: Re: Cascading Failures Could Crash the Global Internet

> 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  <> 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
> Voice: 301-469-8766
>  Fax: 301-469-0601

Discussion Communities

About Merit | Services | Network | Resources & Support | Network Research
News | Events | Contact | Site Map | Merit Network Home

Merit Network, Inc.