On Mon, 4 Mar 2002, Tom Scott wrote:
> was typo. this url works:
> http://partner.unispherenetworks.com/rrg/
>
> Regarding Group B, I'd like to draw attention to section 10.9:
>
> Is it possible to apply a control theory framework, and analyze the
> stability of the control system of the whole network domain, for e.g.
> convergence speed and the frequency response, and then use the
> results from that analysis to set the timers and other protocol
> parameters.
>
> Control theory could also play a part is QoS Routing, by modifying
> current link state protocols with link costs dependent on load.
> Control theory is used to increase the stability of such systems.
>
> At best, it might be possible to construct a new totally dynamical
> routing protocol solely on a control theoretic basis as opposed to
> the current protocols which are based in graph theory and static in
> nature.
>
> Solution is ASM model:
>
> http://www.eecs.umich.edu/gasm
Is this related to Dina Katabi's congestion control work in her
thesis?
http://ana.lcs.mit.edu/dina/dkpub.html
Good stuff, but imo the main problem with applying control theory
widely in the Internet is that traditional control theory isn't very
good at being subverted and having the things it is using as control
inputs _lie_ for their own ends. So, if you have state concerning
utilisation in the routers (and state is expensive) tracking this -
can you trust that state? It's always cheaper not to store the state
and just make up a convenient lie on the spot.
The problem with applying the abstract state machine model to the
network is that you've really got a whole bunch of machines which
don't (can't!) trust each other. (also why many bright-eyed ideas to
load more information onto BGP data between ASs are doomed to
failure...)
The other problem is that you have to fall back to TCP congestion, as
Dina's PCP does, to preserve the current anti-congestion collapse
status quo.
OTOH, right now we're simply trusting all endhosts to implement given
heuristics effectively, which is equally flawed (Savage
exploits, DOS attacks etc.)
L.
sure, it's possible. But is it useful?
<L.Wood@surrey.ac.uk>PGP<http://www.ee.surrey.ac.uk/Personal/L.Wood/>
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