Summary: DHT Survey

This was a good overview: there isn't much to say about it because most of the material is straightforward.  The authors follow the evolution of search over P2P overlays, from the naive broadcast search of gnutella, to the hierarchical broadcast approach of kazaa, to the forwarding approach of Freenet.  From here, academic answers to the forwarding approach like Chord and Pastry enforce structure over the overlay to allow them to make certain guarantees about robustness and performance.  These solutions are quite similar: all offer name-host hash mapping, resolving gets and puts by routing towards the node responsible for a given key.  They differ in the underlying topological structure of the overlay that is used to bound the complexity of lookup, storage and stabilization operations.  The notions of unidirectionality and symmetry as axes around which to classify the various DHT implementations goes a long way in explaining the practical differences between them.