Struct Vegas

pub(crate) struct Vegas {
    params: VegasParams,
    bdp: BdpEstimator,
    cwnd: CongestionWindow,
    num_cell_until_sendme: u32,
    num_sendme_until_cwnd_update: u32,
    num_sendme_per_cwnd: u32,
    num_inflight: u32,
    is_blocked_on_chan: bool,
}

Congestion control Vegas algorithm.

TCP Vegas control algorithm estimates the queue lengths at relays by subtracting the current BDP estimate from the current congestion window.

This object implements CongestionControlAlgorithm trait used by the [‘CongestionControl’].

Spec: prop324 section 3.3 (TOR_VEGAS) C-tor: Split between congestion_control_vegas.c and the congestion_control_t struct.

Fields

params: VegasParams

Congestion control parameters.

bdp: BdpEstimator

Bandwidth delay product. C-tor: “bdp”

cwnd: CongestionWindow

Congestion window. C-tor: “cwnd”, “cwnd_inc_pct_ss”, “cwnd_inc”, “cwnd_min”, “cwnd_inc_rate”, “cwnd_full”,

num_cell_until_sendme: u32

Number of cells expected before we send a SENDME resulting in more data.

num_sendme_until_cwnd_update: u32

The number of SENDME until we will acknowledge a congestion event again. C-tor: “next_cc_event”

num_sendme_per_cwnd: u32

Counts down until we process a cwnd worth of SENDME acks. Used to track full cwnd status. C-tor: “next_cwnd_event”

num_inflight: u32

Number of cells in-flight (sent but awaiting SENDME ack). C-tor: “inflight”

is_blocked_on_chan: bool

Indicate if we noticed we were blocked on channel during an algorithm run. This is used to notice a change from blocked to non-blocked in order to reset the num_sendme_per_cwnd. C-tor: “blocked_chan”

Implementations

impl Vegas

pub(crate) fn new( params: &VegasParams, state: &State, cwnd: CongestionWindow, ) -> Self

Create a new Vegas from the specified parameters, state, and cwnd.

Trait Implementations

impl Clone for Vegas

fn clone(&self) -> Vegas

Returns a copy of the value.

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

Performs copy-assignment from source.

impl CongestionControlAlgorithm for Vegas

fn sendme_received( &mut self, state: &mut State, rtt: &mut RoundtripTimeEstimator, signals: CongestionSignals, ) -> Result<()>

Called when a SENDME cell is received.

This is where the Vegas algorithm magic happens entirely. For every SENDME we get, the entire state is updated which usually result in the congestion window being changed.

An error is returned if there is a protocol violation with regards to flow or congestion control.

Spec: prop324 section 3.3 (TOR_VEGAS) C-tor: congestion_control_vegas_process_sendme() in congestion_control_vegas.c

fn uses_stream_sendme(&self) -> bool

Return true iff this algorithm uses stream level SENDMEs.

fn is_next_cell_sendme(&self) -> bool

Return true iff the next cell is expected to be a SENDME.

fn can_send(&self) -> bool

Return true iff a cell can be sent on the wire according to the congestion control algorithm.

fn cwnd(&self) -> Option<&CongestionWindow>

Return the congestion window object. The reason is returns an Option is because not all algorithm uses one and so we avoid acting on it if so.

fn sendme_sent(&mut self) -> Result<()>

Inform the algorithm that we just sent a SENDME.

fn data_received(&mut self) -> Result<bool>

Inform the algorithm that we just got a DATA cell.

fn data_sent(&mut self) -> Result<()>

Inform the algorithm that we just sent a DATA cell.

fn inflight(&self) -> Option<u32>

Available on crate feature conflux only.

Return the number of in-flight cells (sent but awaiting SENDME ack).

impl Debug for Vegas

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

Formats the value using the given formatter.