Transport abstraction

Platform / build: Iroh is in blvm default features (Linux x86_64 release artifacts use the same default set; portable Windows/aarch64 CI omits several defaults). Quinn requires the quinn feature (source build). All release binaries default to TCP-capable builds; set transport_preference in config. See Release process: Build variants.

Overview

Multiple network transport protocols (TCP for Bitcoin P2P compatibility and QUIC) share one abstraction so the node can run both at once.

Architecture

NetworkManager
 └── Transport Trait (abstraction)
 ├── TcpTransport (Bitcoin P2P compatible)
 ├── QuinnTransport (direct QUIC)
 └── IrohTransport (QUIC with NAT traversal)

Transport Types

Transport Comparison

TCP Transport

Traditional TCP transport for Bitcoin P2P protocol compatibility:

• Uses standard TCP sockets
• Maintains Bitcoin wire protocol format
• Compatible with standard Bitcoin nodes
• Default transport for backward compatibility
• No built-in encryption (TLS optional)
• No connection multiplexing

Quinn QUIC Transport

Direct QUIC transport using the Quinn library:

• QUIC protocol benefits (multiplexing, encryption, connection migration)
• SocketAddr-based addressing (similar to TCP)
• Lower latency and better congestion control
• Built-in TLS encryption
• Stream multiplexing over single connection
• Optional feature flag: quinn

Iroh Transport

QUIC-based transport using Iroh for P2P networking:

• Public key-based peer identity
• NAT traversal support via DERP (Distributed Endpoint Relay Protocol)
• Decentralized peer discovery
• Built-in encryption and multiplexing
• Connection migration support
• Optional feature flag: iroh

Performance Characteristics

TCP Transport:

• Latency: Standard (RTT-dependent)
• Throughput: Standard (TCP congestion control)
• Connection Overhead: Low (no encryption by default)
• Use Case: Bitcoin P2P compatibility, standard networking

Quinn QUIC Transport:

• Latency: Lower (0-RTT connection establishment)
• Throughput: Higher (better congestion control)
• Connection Overhead: Moderate (built-in encryption)
• Use Case: Modern applications, improved performance

Iroh QUIC Transport:

• Latency: Lower (0-RTT + DERP routing)
• Throughput: Higher (QUIC + optimized routing)
• Connection Overhead: Higher (DERP relay overhead)
• Use Case: NAT traversal, decentralized networking

Transport Abstraction

Transport Trait

The Transport trait is the shared interface:

#![allow(unused)]
fn main() {
pub trait Transport: Send + Sync {
 fn connect(&self, addr: TransportAddr) -> Result<Box<dyn TransportConnection>>;
 fn listen(&self, addr: TransportAddr) -> Result<Box<dyn TransportListener>>;
 fn transport_type(&self) -> TransportType;
}
}

TransportAddr

Unified address type supporting all transports:

#![allow(unused)]
fn main() {
pub enum TransportAddr {
 Tcp(SocketAddr),
 Quinn(SocketAddr),
 Iroh(Vec<u8>), // Public key bytes
}
}

TransportType

Runtime transport selection:

#![allow(unused)]
fn main() {
pub enum TransportType {
 Tcp,
 Quinn,
 Iroh,
}
}

Transport Selection

Transport Preference

Runtime preference for transport selection:

• TcpOnly: Use only TCP transport
• IrohOnly: Use only Iroh transport
• Hybrid: Prefer Iroh if available, fallback to TCP

Feature Negotiation

Peers negotiate transport capabilities during connection:

• Service flags indicate transport support
• Automatic fallback if preferred transport unavailable
• Transport-aware message routing

Protocol Adapter

The ProtocolAdapter handles message serialization between:

• Consensus-proof NetworkMessage types
• Transport-specific wire formats (TCP Bitcoin P2P vs Iroh message format)

Message Bridge

The MessageBridge bridges blvm-consensus message processing with transport layer:

• Converts messages to/from transport formats
• Processes incoming messages
• Generates responses

Network Manager Integration

The NetworkManager supports multiple transports:

• Runtime transport selection
• Transport-aware peer management
• Unified message routing
• Automatic transport fallback

Benefits

1. Backward Compatibility: TCP transport maintains Bitcoin P2P compatibility
2. Modern Protocols: QUIC support for improved performance
3. Flexibility: Runtime transport selection
4. Unified Interface: Single API for all transports
5. NAT Traversal: Iroh transport enables NAT traversal
6. Extensible: Easy to add new transport types

Usage

Configuration

NodeConfig uses top-level keys (see config/mod.rs, TransportPreferenceConfig). Example:

listen_addr = "0.0.0.0:8333"
transport_preference = "hybrid" # TOML serde: tcponly | irohonly | quinnonly | hybrid | all

P2P listen address is listen_addr, not a nested [network.tcp] table. quinn / iroh must be enabled in the binary for non-TCP preferences to work.

Code Example

TransportAddr wraps TCP / optional Quinn / optional Iroh addresses. Wire-up is via NetworkManager and the running node: see crate examples and integration tests rather than copying a minimal new/connect snippet here.

Components

The transport abstraction includes:

• Transport trait definitions
• TCP transport implementation
• Quinn QUIC transport (optional)
• Iroh QUIC transport (optional)
• Protocol adapter for message conversion
• Message bridge for unified routing
• Network manager integration

Source

• transport.rs
• tcp_transport.rs
• quinn_transport.rs
• iroh_transport.rs
• protocol.rs
• protocol_adapter.rs
• message_bridge.rs
• mod.rs