Quickstart

Run the built-in config examples

The repository ships with runnable TOML configs in configs/.

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

Useful variations:

# TCP example
RUST_LOG=info cargo run -- configs/tcp_simple.toml

# Fat-tree topology examples
RUST_LOG=info cargo run -- configs/fattree.toml
RUST_LOG=info cargo run -- configs/tcp_fattree.toml
RUST_LOG=info cargo run -- configs/bbr_fattree.toml

Output artifacts

By default, Days writes periodic reports to CSV files under log_path (see /docs/configuration/logging):

• sources.csv: per-source send statistics
• sinks.csv: per-sink receive statistics
• switches.csv: per-scheduler (port) statistics
• pfc.csv: PFC port statistics (only with --features l2_pfc)
• dcqcn_events.csv: DCQCN event trace (only with --features dcqcn,lean)
• cubic_events.csv: TCP CUBIC event trace (only with --features lean)
• drr_events.csv: DRR event trace (only with --features lean)
• wfq_events.csv: WFQ event trace (only with --features lean)

Debugging

Increase log verbosity with RUST_LOG:

RUST_LOG=debug cargo run -- configs/simple.toml

Mental model

At a high level, Days runs this pipeline for each flow:

PacketSource -> (host) PacketSwitch -> [Scheduler per hop] -> ... -> PacketSwitch -> PacketSink

Packets carry the current simulation timestamp (Packet.time) and accumulate queueing delay. Most components avoid querying the global simulation clock, using packet timestamps instead (see /docs/architecture/time-concurrency).