Transcript Peer-to-peer systems

Peer-to-peer systems
”Sharing is caring”
Why P2P?
Client-server systems limited by
management and bandwidth
 P2P uses network resources at the edges
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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
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Early use
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
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Next generation
Three generations of P2P systems
 Napster
 Second generation – large improvements.
Freenet or Kazaa
 P2P middleware – Pastry and Tapestry

Napster
Created in 1999 by Shawn Fanning
 Centralized index
 Shut down 2001
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Routing overlay and GUID
Network in the application layer
 Globally Unique Identifiers
 Addition and removal
 Secure against tampering
 Spreads out the GUID
 Bittorrent and trackers
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Middleware – Pastry
Prefix routing
 128-bit GUID
 No clashing
 Uses UDP
 Sets up routing table using GUID and IP
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Middleware – Tapestry
Message distribution similar to Pastry
 DOLR (Distributed Object Location and
Routing)
 Replicas
 160-bit
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Unstructured P2P
No structure for placement, routing or
searching
 No topological order
 Ad hoc
 Connect to nearest neighbour
 Flooding
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