Re: Cascading Failures Could Crash the Global Internet

[Marshall Eubanks <tme () multicasttech com>]

Hello;

A packet switched network can be engineered against cascading failures
in a way that's hard for a circuit switched network. Every time you see a
random wait in a protocol, it's a good bet that the protocol writers 
were trying to
protect against the tight coupling that leads to cascading failures.

Regards
Marshall Eubanks

On Sunday, February 9, 2003, at 10:07  AM, Jack Bates wrote:

> From: "Stewart, William C (Bill), SALES"
>
> > I think the key is that the failures described in the paper
> > are caused by overload rather than other things -
> > too much demand for power blows out the generator,
> > and without it, the grid tries to get the power from the next
> > nearest generators, which overload and fail, and try to pull an
> > even large amount from the _next_ nearest, etc.
> > So the bit about heterogeneity is probably referring to
> > the fact that some nodes are bigger or better-connected than others,
> > and are more likely to blow out a bunch of their neighbors when
> > they fail and shed a big load.
> >
> > That's not really how Internet systems usually fail.
>
>  A prime example of this theory was the large network I was using back 
> when
> IE5 first came out. They had one circuit bad which overloaded an ATM 
> circuit
> at another NAP causing it to generate bit errors. Shutting down the 
> second
> circuit overloaded both MAE circuits effectively shutting down the 
> network.
> However, it required manual intervention to create full failure, 
> otherwise
> TCP would pull back to being useless, effectively killing all 
> connections
> going that path, but not causing an issue with other paths until the 
> manual
> intervention of shutting down the cirucit.
>
> While in theory it was still a cascade failure, it was also poor
> planning/policy on the part of the network to not be able to compensate 
> in
> case of failure. The information provided may be partially inaccurate 
> and is
> only hearsay concerning actual outages and effects when various
> interventions were tried; no hard fact. Thus it could be taken as 
> solely my
> conjecture and not actual fact.
>
> -Jack