[p2p-hackers] Paradigma Question: DHT's or Small World?

[Rita H. Wouhaybi]

Alexander Löser wrote:
> Hey all,
> structured overlay networks  based on DHT's, such as Pastry and  Chord
> among others, have been investigated in the past to construct scalable
> and performance orientated peer-to-peer networks.  However, unstructured
> networks, such as Gnutella or Kazaa,  are still widely used among the
> file sharing community. Recently researchers proposed extensions to
> unstructured networks  networks based on the small world idea: peers
> dynamically create shortcuts to other peers based on their interests.
> Over a while peers with the same interests became direct neighbors
> through its shortcuts and build interest based clusters.   Hence peers
> no longer flood messages but partly route it's queries via a interested
> based/semantic  overlay.  Examples are described in [1] [2] among
> others.
> 
> Comparing small world and DHT  approaches is a difficult task, since
> simulations usually differ in scenarios, data sets or simulation
> methodology.    I'm interested in scenarios and arguments PRO small
> world overlays for unstructured networks. Does anybody now actual
> theoretic or practical work that compares both approaches in different
> scenarios (high churn, no super peers, key word based search, meta data
> based search)?  Which scenarios or arguments support small world
> approaches for unstructured networks?
> 
> Alex
> 
> 
> 
> 
> [1] Gia - Making Gnutella like P2P Systems Scalable
> http://berkeley.intel-research.net/sylvia/1103-chawathe.pdf
> http://seattle.intel-research.net/people/yatin/publications/talks/sigcomm2003-gia.ppt
> 
> [2]  Efficient Content Location Using Interest Based Locality in
> Peer-to-Peer Systems
> http://www.ieee-infocom.org/2003/papers/53_01.PDF
> --
> ___________________________________________________________
> 
>   Alexander Löser
>   Technische Universitaet Berlin
>   hp: http://cis.cs.tu-berlin.de/~aloeser/
>   office: +49- 30-314-25551
>   fax   : +49- 30-314-21601
> ___________________________________________________________
> 
> 
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Interesting discussion Alex.

>From the practical and system challenges that faced researchers working on DHTs (long time for the network to become stable, updates and maintenance for nodes join and leave, high cost of messaging when adding an object to the network, ..), it has become the norm to think about the application when trying to decide to use structured (DHTs) or unstructured (gnutella-like) p2p topologies. That is probably one of the reasons why people did not compare both structures in an analysis similar to what you are asking for. Thus, small world and power-law have emerged to bridge the gap between a total random network and a "rigid" DHT. Note that super-peers in Kazaa and Gnutella do actually help the network become more like a small-world. We also have worked in this area and created a power-law distribution P2P network that might interest you: 
- Rita H. Wouhaybi, and Andrew T. Campbell, "Phenix: Supporting Resilient Low-Diameter Peer-to-Peer Topologies", IEEE INFOCOM'2004, Hong Kong, China, March 7-11, 2004. 


Rita H. Wouhaybi
rita at comet.columbia.edu
http://comet.columbia.edu/~rita/
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