Enum CongestionController 

pub enum CongestionController {
    Aimd {
        window: f64,
        min_window: f64,
        max_window: f64,
        additive_increase: f64,
        multiplicative_decrease: f64,
        ssthresh: f64,
    },
    Cubic {
        window: f64,
        min_window: f64,
        max_window: f64,
        w_max: f64,
        acks_since_loss: u64,
        c: f64,
        beta: f64,
        ssthresh: f64,
    },
    Fixed {
        window: f64,
    },
}

Consumer-side congestion control algorithm.

Each variant carries its own internal state. The caller drives events (on_data, on_congestion_mark, on_timeout) and reads the current window via window().

Variants

Algorithm	Best for	Behaviour
Aimd	General-purpose, matches NFD consumers	Linear increase, multiplicative decrease
Cubic	High-bandwidth, long-RTT links	Cubic function ramp-up after loss
Fixed	Benchmarks, known-capacity links	Constant window, no adaptation

Variants

Aimd

Additive-Increase Multiplicative-Decrease.

Standard algorithm used by ndncatchunks. Window grows by additive_increase / window per ack (≈ +1 per RTT) and is multiplied by multiplicative_decrease on congestion/timeout.

Fields

window: f64

min_window: f64

max_window: f64

additive_increase: f64

multiplicative_decrease: f64

ssthresh: f64

Slow-start threshold. While window < ssthresh, window grows by 1.0 per ack (exponential); above it, grows additively.

Cubic

CUBIC (RFC 8312).

Concave/convex window growth based on time since last loss event. More aggressive ramp-up than AIMD on high-bandwidth links.

Fields

window: f64

min_window: f64

max_window: f64

w_max: f64

Window size at last loss event.

acks_since_loss: u64

Ack count since last loss event (proxy for time).

c: f64

CUBIC scaling constant (default: 0.4).

beta: f64

Multiplicative decrease factor (default: 0.7).

ssthresh: f64

Fixed

Fixed window — no adaptation.

Fields

window: f64

Implementations

impl CongestionController

pub fn aimd() -> Self

AIMD with standard parameters (matches ndncatchunks).

pub fn cubic() -> Self

CUBIC with standard parameters (RFC 8312).

pub fn fixed(window: f64) -> Self

Fixed window (no adaptation).

pub fn with_window(self, w: f64) -> Self

Set the initial and current window size.

For Cubic, this also updates w_max to match so the cubic formula’s “recovery target” reflects the user’s intent. Without this, a caller that does cubic().with_window(N).with_ssthresh(N) for large N would leave w_max at its tiny default value (2.0), and the first on_data() call would take the cubic branch (since window >= ssthresh) and collapse the window back toward w_max = 2. See the cubic_does_not_collapse_at_large_initial_window regression test.

pub fn with_min_window(self, w: f64) -> Self

Set the minimum window (floor after decrease). Ignored by Fixed.

pub fn with_max_window(self, w: f64) -> Self

Set the maximum window (ceiling). Ignored by Fixed.

pub fn with_additive_increase(self, ai: f64) -> Self

Set AIMD additive increase per RTT (default: 1.0). Only affects AIMD.

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

Set AIMD/CUBIC multiplicative decrease factor (default: 0.5 for AIMD, 0.7 for CUBIC).

pub fn with_cubic_c(self, c_val: f64) -> Self

Set CUBIC scaling constant C (default: 0.4). Only affects CUBIC.

pub fn with_ssthresh(self, ss: f64) -> Self

Set the slow-start threshold.

By default ssthresh is f64::MAX (unbounded slow start). Setting this to the initial window size prevents the exponential ramp from overshooting the link capacity on the first flow.

pub fn window(&self) -> f64

Current window size (number of Interests allowed in flight).

Callers should use window().floor() as usize for the actual limit.

pub fn on_data(&mut self)

A Data packet was received successfully (no congestion mark).

pub fn on_congestion_mark(&mut self)

A CongestionMark was received on a Data packet.

Reduces the window but does NOT trigger retransmission — the Data was delivered successfully, only the sending rate should decrease.

pub fn on_timeout(&mut self)

An Interest timed out (no Data received within lifetime).

More aggressive reduction than congestion mark since timeout indicates actual packet loss, not just queue buildup.

pub fn reset(&mut self)

Reset to initial state (e.g. on route change or new flow).

Trait Implementations

impl Clone for CongestionController

fn clone(&self) -> CongestionController

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for CongestionController

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

Formats the value using the given formatter.

impl Default for CongestionController

fn default() -> Self

Default: AIMD with standard parameters.