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From: Andy Parkins <andyparkins@gmail.com>
To: bitcoin-development@lists.sourceforge.net
Date: Fri, 5 Aug 2011 14:03:05 +0100
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Subject: Re: [Bitcoin-development] Double spend detection to speed up
	transaction trust
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On 2011 August 05 Friday, Matt Corallo wrote:
> On Fri, 2011-08-05 at 12:58 +0100, Andy Parkins wrote:
> > I don't really see that "number of connections" is the relevant metric.
>=20
> Number of connections is something that needs serious thought.  Too many
> and you fill everyone's connection slots and no one can make
> connections.  Too few and you don't have a network but just a bunch of
> islands which would also cause serious problems.
> If you aren't relaying, each connection takes almost no bandwidth, so
> the question is how many do you need to be considered secure.

I'm arguing that "number of connection slots" isn't the best metric; so tha=
t=20
wouldn't matter.  Just keep accepting incoming connections (with some sanit=
y=20
limit of course) until you've allocated your bandwidth, not your number of=
=20
connections.

If I connect to a thousand nodes and never send anything, I'm not using up=
=20
very much of their resources.  If _they_ want to use up resources by relayi=
ng,=20
then that is their choice, but again they can do that based on bandwidth=20
calculations rather than connection counts.  If I am sending, then that add=
s=20
to their bandwidth and gets included in whatever limit they've chosen.

=46or example: the client could simply maintain an average bandwidth over a=
ll=20
connections.  If that average is less than threshold0, then make new outgoi=
ng=20
connections.  If that average exceeds threshold1, then stop accepting incom=
ing=20
connections.  If it exceeds threshold2, start dropping established incoming=
=20
connections.  If it exceeds theshold3, start dropping established outgoing=
=20
connections.

The actual rules don't matter so much; I'm just saying bandwidth is a bette=
r=20
metric than connection count.  If you limit by connection count, then you'l=
l=20
just end up filled with non-relaying listeners, since they (in the future)=
=20
will be the most commonplace.  You'll have no incoming relays, and therefor=
e=20
nothing to forward, so your bandwidth will be zero, but your connection cou=
nt=20
at maximum -- you've locked yourself out.


Andy
=2D-=20
Dr Andy Parkins
andyparkins@gmail.com

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