tendermint/spec/p2p/v0.34

Peer-to-Peer Communication

This document describes the implementation of the peer-to-peer (p2p) communication layer in Tendermint.

It is part of an effort to produce a high-level specification of the operation of the p2p layer adopted in production Tendermint networks.

This documentation, therefore, considers the releases 0.34.* of Tendermint, more specifically, the branch v0.34.x of this repository.

Overview

A Tendermint network is composed of multiple Tendermint instances, hereafter called nodes, that interact by exchanging messages.

Tendermint assumes a partially-connected network model. This means that a node is not assumed to be directly connected to every other node in the network. Instead, each node is directly connected to a subset of other nodes in the network, hereafter called its peers.

The peer-to-peer (p2p) communication layer is responsible for establishing connections between nodes in a Tendermint network, for managing the communication between a node and its peers, and for intermediating the exchange of messages between peers in Tendermint protocols.

Contents

The documentation follows the organization of the p2p package of Tendermint, which implements the following abstractions:

• Transport: establishes secure and authenticated connections with peers;
• Switch: responsible for dialing peers and accepting connections from peers, for managing established connections, and for routing messages between the reactors and peers, that is, between local and remote instances of the Tendermint protocols;
• PEX Reactor: a reactor is the implementation of a protocol which exchanges messages through the p2p layer. The PEX reactor manages the Address Book and implements both the PEX protocol and the Peer Manager role.
  • Peer Exchange protocol: enables nodes to exchange peer addresses, thus implementing a peer discovery service;
  • Address Book: stores discovered peer addresses and quality metrics associated to peers with which the node has interacted;
  • Peer Manager: defines when and to which peers a node should dial, in order to establish outbound connections;
• Finally, Types and Configuration provide a list of existing types and configuration parameters used by the p2p layer implementation.

Further References

Existing documentation referring to the p2p layer:

• https://github.com/tendermint/tendermint/tree/main/spec/p2p: p2p-related configuration flags; overview of connections, peer instances, and reactors; overview of peer discovery and node types; peer identity, secure connections and peer authentication handshake.
• https://github.com/tendermint/tendermint/tree/main/spec/p2p/messages: message types and channel IDs of Block Sync, Mempool, Evidence, State Sync, PEX, and Consensus reactors.
• https://docs.tendermint.com/v0.34/tendermint-core: the p2p layer configuration and operation is documented in several pages. This content is not necessarily up-to-date, some settings and concepts may refer to the release v0.35, that was discontinued.
• https://github.com/tendermint/tendermint/tree/master/docs/tendermint-core/pex: peer types, peer discovery, peer management overview, address book and peer ranking. This documentation refers to the release v0.35, that was discontinued.