Days

Days is a high-performance discrete-event network simulator written in Rust. It models a network as a graph of actors (stackless coroutines) that communicate via message passing (packets and control messages). Simulations can run on a single-threaded runtime (minimal overhead) or a multi-threaded runtime (parallel execution).

What you get

• Config-driven experiments: run a simulation from a single TOML file (topology, traffic, switch discipline, logging).
• Pluggable queueing/scheduling: FIFO, DRR, WRR, WFQ, Static Priority, Virtual Clock.
• Transport and congestion control models:
  • Packet-distribution traffic sources (arrival + size distributions)
  • TCP sources with Reno, CUBIC, and BBR congestion control
  • Optional DCQCN (feature-gated)
• Optional link-layer models: PFC/802.1Qbb (feature-gated and runtime-configured).
• Structured outputs: CSV reports for sources/sinks/switches (and optional PFC/DCQCN traces).

Quick start

From the repo root:

RUST_LOG=info cargo run --release -- configs/simple.toml

Output CSV files are written under the configured log_path (default: ./output/).

Where to go next

• Start running simulations: /docs/quickstart
• Learn how configuration maps to code: /docs/configuration/overview
• Understand the simulator architecture: /docs/architecture/overview
• Dive into core components (packets, switches, schedulers, flows): /docs/components/packet