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IpfsDHT

• implementation of Kademlia with S/Kademlia, Coral and mainlineDHT modifications
  • used to implement the base Routing module
  • BitTorrent DHT spec - https://github.com/libp2p/specs/blob/master/kad-dht/README.md
• https://github.com/libp2p/go-libp2p-kad-dht
• Distance
  • XOR(sha256(key1), sha256(key2))
• Replication Parameter k
  • amount of replication is governed by it
  • recommended value for k is 20
• Concurrency parameter α
  • concurrency of node and value lookups are limited by this param
  • default value of 3
  • each lookup process can perform no more than 3 inflight requests, at any given time
• Node ID
  • spec - https://github.com/libp2p/specs/blob/master/peer-ids/peer-ids.md
  • IDs are base58btc encoded (base58-bitcoin) - used to WIF for bitcoin address

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Client/Server mode

• Server mode
  • unrestricted nodes; Internet, publicly routable nodes, e.g. servers in a datacenter
  • nodes advertise the libp2p Kademlia protocol identifier via the identify protocol
  • accept incoming streams using the Kademlia protocol identifier
• Client mode
  • restricted nodes; those with intermittent availability, high latency, low bandwidth, low CPU/RAM/Storage; non-publicly routable nodes, e.g. laptops behind a NAT and firewall.
  • nodes do not advertise support for the libp2p Kademlia protocol identifier.
  • nodes do not offer the Kademlia protocol identifier for incoming streams.
• Nodes add another node to their routing table if and only if that node operates in server mode.
  • allows restricted nodes to utilize the DHT (query the DHT), without decreasing the quality of the distributed hash table (without polluting the routing tables)

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Identify protocol

• https://github.com/libp2p/specs/tree/master/identify
• used to exchange basic information with other peers in the network, including addresses, public keys, and capabilities
• 2 variations of the protocol:
  • identify
    • protocol id /ipfs/id/1.0.0
    • used to query remote peers for their information
    • works by opening a stream to the remote peer you want to query, using /ipfs/id/1.0.0 as the protocol id string
    • peer being identified responds by returning an Identify message and closes the stream
    message Identify {
        optional string protocolVersion = 5;
        optional string agentVersion = 6;
        optional bytes publicKey = 1;
        repeated bytes listenAddrs = 2;
        optional bytes observedAddr = 4;
        repeated string protocols = 3;
    }
    
  • identify/push
    • protocol id /ipfs/id/push/1.0.0
    • used to inform known peers about changes that occur at runtime
    • When a peer’s basic information changes, for example, because they’ve obtained a new public listen address

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related repos

• DHT - github.com/libp2p/go-libp2p-kad-dht
• KBUCKET - github.com/libp2p/go-libp2p-kbucket
• MULTIADDRESS - github.com/multiformats/go-multiaddr

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Tools

• libp2p-lookup
  • Small helper tool
  • takes as input a peer ID or address and prints the output of the libp2p-identify protocol
  • https://github.com/mxinden/libp2p-lookup
• nebula
  • https://github.com/dennis-tra/nebula
  • A libp2p DHT crawler, monitor, and measurement tool that exposes timely information about DHT networks.
  • https://discuss.libp2p.io/t/nebula-libp2p-dht-crawler/950
  • DHT crawler that also monitors the liveness and availability of peers
  • crawler connects to the standard DHT bootstrap nodes and then recursively follows all entries in their k-buckets until all peers have been visited

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Major TODO’s remaining that we need for initial protocol implementation

• get DHT k/v ops (put/get) to function
• how to get GF bootstrap nodes to function (so we dont use IPFS bootstrap nodes)