Analysis for QUIC in libp2p

• Configuration we may use

  There are many configurations, but I think there only 5 we may use

  • max_idle_timeout: the maximum duration of inactivity in ms to accept before timing out the connection. We may use this to control how long a connection will be kept alive.
    • e.g. If max_idle_timeout is 10s, and we only receive keep-alive messages in this 10s, then after 10s, the connection will be closed.
  • keep_alive_interval: Period of inactivety before sending a keep-alive packet. Must be set lower than the max_idle_timeout of both peers to be effective.
  • max_concurrent_stream_limit: Maximum number of incoming bidirectional streams that may be open concurrently by the remote peer.
    • As in QUIC, stream/connection and file descriptor are not 1-1 relation but M-N relation (M streams/connections match N file descriptor, M > N).
  • client_tls_config: set client TLS configuration
  • server_tls_config: set server TLS configuration

• Transport implementation details:

  • Listener

    struct Listener {
      endpoint: quinn::Endpoint,
      // Cloned from the socket used to create a Endpoint.
      // Use for hole punching, support NAT.
      socket: UdpSocket,
      ...
    }
    

    • listener contains a quinn endpoint, note that an endpoint corresponds to a single UDP socket, may host many connections, and may act as both client and server for different connections. May be cloned to obtain another handle to the same endpoint.
    • NAT is also supported. I think this is important, because if users run a light node on their mobile devices, the NAT can help us provide the functionality.

  • Transport

    struct Transport {
      listeners: SelectAll<Listener>
      ...
    }
    

    • For a new address, the transport will create a new listener(endpoint) for this address, a single listener(endpoint) can connect to multiple remote addresses when sending or receiving data.
    • No connection pool employed to manage connections.

• In summary, for mixnet V1, libp2p's QUIC is good enough. And it also help us solve the NAT problem.