Struct RateController 

pub struct RateController { /* private fields */ }

The AIMD controller: a usage signal and a received rate in, a target bitrate out.

Additive versus multiplicative increase

Climbing multiplicatively is fast but overshoots, which on a path already known to be near its limit means congesting it again immediately. So the controller climbs multiplicatively only while it is far from the rate that last caused a backoff, and switches to additive — one packet per round trip — as it approaches. Upstream does the same; it is the difference between probing for capacity and hammering at a known ceiling.

Implementations

impl RateController

pub fn new(initial: f64, min: f64, max: f64) -> Self

A controller starting at initial, clamped to min..=max.

One clamp, from configuration — see D3. Upstream clamps in two places with two different hard-coded ranges, and they disagree.

pub fn with_decrease_factor(self, decrease_factor: f64) -> Self

How hard to back off, as a fraction of the received rate.

pub fn target(&self) -> f64

The current target, in bits per second.

pub fn state(&self) -> RateControlState

What the controller is doing.

pub fn update( &mut self, now: Instant, usage: Usage, received: Option<f64>, ) -> f64

Fold in a usage signal and the rate the far end is receiving.

received is None when the window holds too little to say; the controller then holds rather than guessing, because every action it could take needs a rate to compute from.

Trait Implementations

impl Clone for RateController

fn clone(&self) -> RateController

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for RateController

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.