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Peer-to-peer systems. ” S haring is caring ”. Why P2P?. Client-server systems limited by management and bandwidth P2P uses network resources at the edges. Characteristics of P2P. All nodes have the same capabilities and responsibilities No central control needed
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Peer-to-peer systems ”Sharing is caring”
Why P2P? • Client-server systems limited by management and bandwidth • P2P usesnetworkresourcesat the edges
Characteristics of P2P • All nodes have the same capabilities and responsibilities • No central control needed • Offers more or less anonymity • Data placement algorithm • Does not rely on any one node
Earlyuse • Xerox Grapevine • Lamport’s algorithm, Bayou storage system and classless interdomain IP routing algorithm • Need a large number of broadband users • 1999 in the US and by 2004 worldwide with over 100 million users
Next generation • Three generations of P2P systems • Napster • Second generation – largeimprovements. Freenet or Kazaa • P2P middleware – Pastry and Tapestry
Napster • Created in 1999 by ShawnFanning • Centralized index • Shutdown 2001
Routingoverlay and GUID • Network in the applicationlayer • GloballyUniqueIdentifiers • Addition and removal • Secureagainsttampering • Spreadsout the GUID • Bittorrent and trackers
Middleware – Pastry • Prefix routing • 128-bit GUID • No clashing • Uses UDP • Sets up routing table using GUID and IP
Middleware – Tapestry • Message distribution similar to Pastry • DOLR (DistributedObjectLocation and Routing) • Replicas • 160-bit
Unstructured P2P • No structure for placement, routing or searching • No topological order • Ad hoc • Connect to nearestneighbour • Flooding