[9fans] What is TFT? (was: Hangar 18 Weekly Social - May 22, 2003)

[Jim Choate <ravage@einstein.ssz.com>]

On Sun, 18 May 2003, northern snowfall wrote:

> >We are
> >a tit-for-tat group of computer hobbyist of a wide range of skills
> >intent on building the next computing infra-structure using Open Source
> >technology.
> >
> I gotta know... what is a "tit-for-tat" computer group. Not to
> sound potentially condescending, I really want to know.

Tit For Tat (TFT) is a strategy from game theory. It is considered one of
the strongest approaches to resolving situations where two or more parties
must decide via a 'iterated prisoners dilemma' what to do on the next
turn. There are several variants.

In short, it means you get to use my stuff because I get to use your
stuff. You abuse it you get dropped like a hot potato. At least for the SSZ
and Open Forge site we capture all traffic over the network via sniffer
and can review it for any strangeness. Another technique we use is that we
export our namespace resources read only, except in very special cases to
particular individuals or node operators.

We couple this with a 'small worlds' network approach; the number of
connections per node is limited to ln(number of nodes). Which has some
very strong characteristics, though it does have the weakness of getting
it off the ground. It's a network application of the 'Kevin Bacon Game' or
the 'Six Degrees of Seperation' theory. Studies of the Internet indicate
that it's degree of freedom with respect to small world networks is
somewhere between 17 and 21. This means that no two sites are farther away
than that many hops (which takes us into spanning tree theories from
graph theory).

The utility of the small world model with respect to 'next neighbor' in
the network is that you probably know that person as something other than
a stranger. So there is a two fold factor being used: familiarity breeds
trust, and it makes it reasonably easy to back track problems. An
additional feature is that in tests small world networks seem to exhibit
the least amount of congestion under heavy load.

You will find several references on the Hangar 18 website to books that
discuss these topics. A visit to Google will also turn up quite a few hits
on these topics. I can particularly suggest the arXiv repository
(eg xyz.lanl.gov).

I sent out a 'suggested reading' list this morning to several of the lists
and one of these goes into TFT with applications to animal cooperation to
some degree. It's not on the H18 list. The book was,

Cooperation Among Animals - An Evolutionary Approach
L.A. Dugatkin
ISBN 0-19-508621-x

If you want to learn more than get some books on game theory, graph
theory, and network theory. A book on psychology and group cooperation can
be usefull as well.

Ta ta.


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      We are all interested in the future for that is where you and I
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      ravage@ssz.com                            jchoate@open-forge.org
      www.ssz.com                               www.open-forge.org
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