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What is Discovery & Routing

Peer discovery and routing protocols are used to discover and announce services to other peers and find a peer's location, respectively.

2 min read

Overview

Peer discovery and routing are two essential aspects of P2P networking. In a P2P network, each node must be able to discover and communicate with other nodes without the need for a central server.

Peer discovery

Peer discovery is the process of finding and announcing services to other available peers in a P2P network. Peer discovery can be done using various protocols, such as broadcasting a message to all peers in the network or using a bootstrap node to provide a list of known peers.

Peer routing

Peer routing, on the other hand, refers to finding a specific peer's location in the network. This is typically done by maintaining a routing table or a similar data structure that keeps track of the network topology.

Different algorithms can be used to find the "closest" neighboring peers to a given peer ID. A peer may use a routing algorithm to find the location of a specific peer and then use that information to discover new peers in the vicinity. Additionally, a peer may use both peer routing and peer discovery mechanisms in parallel to find new peers and route data to them.

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Note

In practice, the distinction between peer routing and peer discovery is not always clear-cut, and it's worth noting that in a real-world implementation, discovery and routing usually happen concurrently.

Discovery and routing in libp2p

libp2p provides a set of modules for different network-level functionality, including peer discovery and routing. Peers in libp2p can discover other peers using various mechanisms, such as exchanging peer multiaddresses over the network, querying a directory service, or using a distributed hash table (DHT) to store and retrieve information about available peers.

These methods include, but are not limited to:

  • Rendezvous: a protocol that allows peers to exchange peer multiaddresses in a secure and private manner.
  • mDNS: a multicast Domain Name System (DNS) protocol that allows peers to discover other peers on the local network.
  • DHT: Distributed Hash Table, libp2p uses a DHT called Kademlia, it assigns each piece of content a unique identifier and stores the content on the peer whose identifier is closest to the content's identifier.