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Peer to Peer

  • Each peer assigned GUID
  • Virtually round structure
  • Two main algo
    • Chord
    • Kademelia

Kademelia

  • Kademlia is not a consensus algorithm, it’s a DHT
  • It is a way to structure p2p networks, and to store and look up data on them, which means it can tolerate a whole lot more failures than Raft can
  • It is usually used to store data that never changes
  • Many implementations don’t necessarily replicate data and by themselves, it doesn’t have any consistency guarantees
  • Kademelia has xor matrics
    • b | a
  • Each node has a routing table
    • It contains more info on nodes closer to it
  • When finding just need binary lookup
  • Leaving is simple in kademelia
  • In case of a crash ping

Chord

  • Each Node Operations

    • Join
    • Leave
    • Copy routing table
    • Find closed

  • Chord GUID Distance

    • (b-a + 2^n) % 2^n
    • 7 to 8 and 8 to 7 not same

  • For Kademelia order doesn't matter

  • Each node has a successor and a predecessor

  • The successor to a node is the next node in the identifier circle in a clockwise direction. The predecessor is counterclockwise.

  • If there is a node for each possible ID, the successor of node 0 is node 1, and the predecessor of node 0 is node 2^m - 1; however, normally there are "holes" in the sequence.

  • The successor of node 153 may be node 167 (and nodes from 154 to 166 do not exist); in this case, the predecessor of node 167 will be node 153

References