Days: A Performant Discrete-Event Simulator for Network Simulations

Days is a discrete-event network simulator written in Rust. It models network components as actors (async coroutines) that communicate via message passing, with pluggable schedulers, flow models (packet distributions, TCP, optional DCQCN), and optional link-layer PFC support.

Quick start

cargo run --release --bin days -- configs/simple.toml

Simulation outputs are written under log_path (default: ./output/) as CSV files.

Documentation

All design and configuration documentation lives under docs/:

cd docs/
bun install
bun dev

Alternatively, one can directly visit the documentation website.

Examples

• Config-driven runs: cargo run --release --bin days -- configs/tcp_simple.toml
• Rust examples: cargo run --release --example basic

Tests

cargo nextest run --all-features

Feature flags

• l2 / l2_pfc: optional L2/PFC pipeline
• dcqcn: DCQCN flow type and models
• lean: additional DCQCN event logging for the Lean checker
• test: extra assertions and test helpers