# irtt-stats

Statistics aggregation over [`irtt-client`](https://crates.io/crates/irtt-client)
events: loss/duplicate/late accounting, RTT and one-way-delay timing, and
inter-packet delay variation (IPDV), as cumulative and rolling snapshots.

## Relationship to irtt-client

This crate does not open sessions or drive sockets. Feed it the `ClientEvent`
stream produced by an `irtt-client` `Client`, `AsyncClient`, or managed
session via `StatsCollector::process`, and read back a `Snapshot`.

Generic timing accumulation and count-window storage come from
`measurement-stats`. `TimeStats` remains available from `irtt_stats` as a
re-export. Event interpretation, IPDV pairing, loss, and snapshot reconstruction
remain here.

A `StatsCollector` has one sequence/IPDV namespace and one packet count, both
scoped to a single target. A managed session covering multiple targets needs
one collector per target — as the `irtt-rs` CLI does — since a target's
sequence numbers start over at zero and feeding two targets into one
collector would pair up unrelated probes.

## Retention modes

`StatsConfig::finite()` retains exact timing samples for its cumulative
snapshot, so every metric with samples reports an exact median there —
retention grows with the probe count. `StatsConfig::continuous()` keeps
bounded running statistics instead (no exact median) plus a bounded
4096-entry adjacent-sequence IPDV store per target, for long-running or
unbounded sessions. Rolling-window snapshots are always running-only and
report no medians, whichever `StatsConfig` produced them.

An enabled time-based rolling window has no event-count cap, including in
continuous mode. It expires only on new events, anchored at the maximum observed
normalized timestamp, with events exactly at the cutoff retained. Retained events
are replayed in arrival order; backdated events cannot move the window backwards.
Reading a snapshot does not advance time. Use count-based rolling storage for a
hard bound on retained events. The memory estimate excludes time-window storage.

Exact snapshots sort a temporary copy of each metric's retained samples, adding
O(n) scratch memory and O(n log n) computation for that metric. The retention
estimate is not peak snapshot or allocator accounting.

See `examples/` in the repository for a runnable comparison of both modes.

## Documentation

Full API documentation is on [docs.rs/irtt-stats](https://docs.rs/irtt-stats).

## Project

Part of [irtt-rs](https://github.com/Lochnair/irtt-rs), an independent Rust
implementation of an IRTT-compatible protocol stack.