[p2p-hackers] clustering

Lemon Obrien lemonobrien at yahoo.com
Sat Mar 11 21:19:50 UTC 2006

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

  this is why you have a relay/super node...to be the go between between A nad C; this is also why creating p2p systems is very difficult...b/c you'll have to test this along with tons of other different senarios.

Michael J Freedman <mfreed at cs.nyu.edu> wrote:
  On Fri, 10 Mar 2006, Jeff Rose wrote:

> Date: Fri, 10 Mar 2006 11:08:57 +0100
> From: Jeff Rose 
> Reply-To: Peer-to-peer development. 

> To: Peer-to-peer development. 

> 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.)


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.


www.michaelfreedman.org www.coralcdn.org
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You don't get no juice unless you squeeze
Lemon Obrien, the Third.
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