Structured vs Unstructured

Unstructured P2P networks

• Formed when the overlay links are established arbitrarily.

• If a peer wants to find a desired piece of data in the network, the query has to be flooded through the network to find as many peers as possible that share the data.

  • The queries may not always be resolved.

    • If a peer is looking for rare data shared by only a few other peers, then it is highly unlikely that the search will be successful

  • Flooding causes a high amount of signaling traffic in the network.

  • Gnutella and FastTrack/KaZaa, BitTorrent.

Structured P2P networks

• Globally consistent protocol (logic) to ensure that any node can efficiently route a search to some peer that has the desired file, even if the file is extremely rare.

• The most common type of structured P2P network is the Distributed Hash Table (DHT).

  • A variant of consistent hashing is used to assign ownership of each file to a particular peer.

  • Chord, Pastry, Tapestry, CAN, Tulip, Kadmelia, BitTorrent (trackerless), IPFS.