Peer To Peer Systems

#cse6603

• An overlay organizes:
  • the way different sites communicate with each other
  • the storing of data objects at the different sites.
• Overlays provide a method for retrieving objects, and typically support two basic operations using a key value pair:
  • Set: Insert the key-value tuple in the overlay.
  • Get: lookup and return the corresponding value using key.
• Overlays are typically represented as a graph,
  • Sites as nodes,
  • Edges connecting these sites,
  • Categorized into:
    • Unstructured overlays.
    • Structured overlays.

Unstructured Overlays

No specific structure on logical graph between the peers.

• Napster
• Gnutella

Structured Overlays

• Impose a well-defined data structure on the various peers.

See, Distributed Hash Tables (DHTs)

See, Consistent Hashing