Struct RttEma 

pub struct RttEma {
    pub srtt_ns: u64,
    pub rttvar_ns: u64,
    pub sample_count: u64,
}

Jacobson/Karels RTT EMA: smoothed SRTT + smoothed RTTVAR with sample-count tracking. Mirrors RFC 6298 §2 with α = 1/8 and β = 1/4.

The deadline-derivation formula SRTT + 4·RTTVAR follows the canonical Karn/Partridge recommendation for retransmission timeout. Self::is_warm gates the per-tier fallback so cold EMAs (fewer than three samples) fall through to coarser priors.

Fields

srtt_ns: u64

Smoothed round-trip time, nanoseconds.

rttvar_ns: u64

Smoothed round-trip-time variance, nanoseconds.

sample_count: u64

Count of samples observed.

Implementations

impl RttEma

pub fn observe(&mut self, sample_ns: u64)

Observe a round-trip sample. Updates SRTT + RTTVAR using Jacobson’s α = 1/8 / β = 1/4 weights.

pub fn observe_with_alpha_beta( &mut self, sample_ns: u64, alpha_shift: u8, beta_shift: u8, )

Observe a round-trip sample with a smaller learning rate. Used by the global prior to dampen the influence of any one peer’s bursty samples on the cross-runtime estimate.

alpha_shift = log2(1/α), beta_shift = log2(1/β). Values of (3, 2) match the Jacobson recommendation (α=1/8, β=1/4); larger shifts (e.g. (6, 5)) make the EMA more conservative.

pub fn budget_ns(&self) -> u64

Recommended budget: SRTT + 4·RTTVAR per RFC 6298 §2.3.

pub fn is_warm(&self) -> bool

“Warm” once we have three samples - gates the fallback hierarchy so very-fresh EMAs don’t poison budgets.

Trait Implementations

impl Clone for RttEma

fn clone(&self) -> RttEma

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for RttEma

impl Debug for RttEma

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

Formats the value using the given formatter.

impl Default for RttEma

fn default() -> RttEma

Returns the “default value” for a type.