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Introduction to subp2p

subp2p is the foundational peer-to-peer networking layer of the SUBFROST ecosystem. It is built on top of the powerful and flexible libp2p framework, providing a secure and robust foundation for all other SUBFROST components to communicate with each other.

Core Concepts​

At its core, subp2p is responsible for:

  • Peer Discovery: Finding and connecting to other peers on the network.
  • Transport: Establishing secure and reliable communication channels between peers.
  • Stream Multiplexing: Allowing multiple independent streams of communication to coexist over a single connection.
  • Protocol Negotiation: Allowing peers to agree on which protocols to use for communication.

Key Features​

subp2p leverages the rich feature set of libp2p and extends it with SUBFROST-specific functionality.

Multi-Transport Support​

subp2p supports multiple transport protocols, allowing it to operate in a variety of network environments:

  • TCP: The standard transport protocol for most internet traffic.
  • QUIC: A modern, encrypted transport protocol that provides faster connection establishment and better performance on lossy networks.
  • WebTransport: A new protocol based on HTTP/3 and QUIC that allows for secure, multiplexed communication between web clients and servers. This is the primary transport used by SUBFROST, as it allows subp2p nodes to run directly in the browser and to be easily proxied behind standard web servers and CDNs like Cloudflare.

Peer Discovery​

subp2p uses multiple mechanisms for peer discovery:

  • mDNS: Multicast DNS allows peers to discover each other on a local network without the need for a central server.
  • Kademlia DHT: A distributed hash table (DHT) is used for discovering peers on the public internet. Peers can publish their contact information to the DHT, and other peers can query the DHT to find them.

Secure and Private Communication​

All communication on the subp2p network is encrypted and authenticated using modern cryptographic protocols. subp2p uses noise for its encrypted handshake, ensuring that all communication between peers is private and secure.

Network Address Translation (NAT) Traversal​

subp2p incorporates several mechanisms for NAT traversal, allowing peers behind firewalls and NATs to connect to each other:

  • AutoNAT: Allows a peer to discover its own public IP address.
  • Hole Punching (DCUtR): Allows two peers behind NATs to establish a direct connection with the help of a relay.
  • Circuit Relay: When a direct connection cannot be established, subp2p can use a relay peer to forward traffic between two peers.

SUBFROSTNetworkBehaviour​

The heart of a subp2p node is the SUBFROSTNetworkBehaviour. This is a composite libp2p NetworkBehaviour that combines all the different protocols and behaviors used by SUBFROST:

  • gossipsub: For pub/sub messaging.
  • mdns: For local peer discovery.
  • kademlia: For distributed peer discovery and content routing.
  • relay_client and relay_server: For circuit relaying.
  • dcutr: For direct connection upgrade through NATs.
  • identify: For discovering the public address of a peer.
  • autonat: For determining if a peer is behind a NAT.
  • ping: For checking the liveness of a peer.
  • request_response: For simple request-response interactions.
  • proxy_stream: A custom protocol for creating generic, proxied duplex streams between peers.

This modular and extensible architecture allows subp2p to provide a rich set of networking capabilities that can be easily leveraged by higher-level applications in the SUBFROST ecosystem.

subp2p in SUBFROST​

The subfrost-cli uses subp2p to connect to the SUBFROST network and to communicate with other peers. When you run the subfrost-cli, it creates a subp2p node and joins the SUBFROST network. This allows it to:

  • Discover other peers: The subfrost-cli uses the Kademlia DHT to discover other peers on the network.
  • Communicate with other peers: The subfrost-cli uses gossipsub to broadcast messages to the network and request_response to send direct messages to other peers.
  • Participate in FROST signing ceremonies: The subfrost-cli uses subp2p to communicate with other signers during FROST signing ceremonies.

Creating a subp2p Node​

Here is an example of how to create a subp2p node:

use subp2p::Subp2p;

// Create a new subp2p node
let mut subp2p = Subp2p::new().await?;

// Listen on a random TCP port
subp2p.listen_on("/ip4/0.0.0.0/tcp/0".parse()?).await?;

// Start the event loop
loop {
    let event = subp2p.next_event().await;
    println!("New event: {:?}", event);
}