On Fri, 10 Mar 2006, Jeff Rose wrote:

Date: Fri, 10 Mar 2006 11:08:57 +0100
From: Jeff Rose <[EMAIL PROTECTED]>
Reply-To: Peer-to-peer development. <p2p-hackers@zgp.org>
To: Peer-to-peer development. <p2p-hackers@zgp.org>
Subject: Re: [p2p-hackers] clustering

It seems like people are always putting arbitrary restrictions on p2p systems and simulations in terms of connectivity, but is this really necessary? Unless you are trying to use NATed nodes (assume we can punch or route through a neighbor),just about any pair of computers on the internet can be neighbors. In essence the internet is a fully connected overlay graph.

The problem is that "just about every" and "every" node being able to communicate are not quite the same thing. Indeed, it's precisely the difference in these two assumptions which actually raises a lot of problems when actually deploying DHTs in the wide-area.

We recently presented a short paper at WORLDS '05 which discusses the real-world problems that arises from non-transitivity in Internet routing:

  A can speak to B, B can speak to C, but A can't speak to C

as we all independently discovered from running CoralCDN, OpenDHT, and i3. (Firewalls and NATs are actually an easier problem that this, as they express routing constraints much more symmetrically.)

  http://www.scs.stanford.edu/mfreed/docs/ntr-worlds05.pdf

I sent an email about this paper to this mailing list a few months ago, and my apologies for the repeat. However, as our main audience for this paper was actually meant to be the hacker community, as opposed to the academic one, I thought it bears re-mention.

--mike

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www.michaelfreedman.org                              www.coralcdn.org
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