Most people would probably agree Gnutella being 'true' or 'pure' p2p. The network seems to keep living and breathing indefinitely on a voluntary population of private computers. Public entry points (websites with fresh listings of peers in the network) are still needed for the newcomers to find their way into the network but for the active users it is usually possible to reconnect without any external help. This is possible because each Gnutella client maintains a list of active peers (often called 'host cache') which it memorizes between sessions. When reconnecting, the client scans through its memorized host cache to find an active peer. Even if most of the listed peers would have gone offline it is enough to find one that is still alive and with the help of that peer you are back in the network in no time.
On the other hand, Napster and OpenNap are definitely
not pure p2p even if they utilize p2p technology to provide content into the network and to distribute it between peers. All messaging and crucial control traffic goes through the servers and should the servers go down, only ongoing transfers will finish. Left on their own, the users become virtually disconnected from each other, not being able to message each other or initiate new transfers.
Morpheus is a borderline case. People seem to be able to reconnect to the network without Music City's entry point servers and the network itself might also remain functional without Music City's supporting server farm. However, there does not seem to be any easy mechanism for the user to feed new peer addresses into the client in case they would be needed. This would prevent newcomers (who have yet no memorized peer listings) and less active users (with outdated peer lists) from entering the network. If such a mechanism is provided (either by MC or by a friendly hacker), Morpheus could be considered pure p2p. Similar remarks apply to WinMX's WPNP which also uses public servers to help people getting connected.
- tg
