congestion

Documentation

Index

• type Bandwidth
  • func BandwidthFromDelta(bytes protocol.ByteCount, delta time.Duration) Bandwidth
• type Clock
• type Cubic
  • func NewCubic(clock Clock) *Cubic
  • func (c *Cubic) CongestionWindowAfterAck(ackedBytes protocol.ByteCount, currentCongestionWindow protocol.ByteCount, ...) protocol.ByteCount
  • func (c *Cubic) CongestionWindowAfterPacketLoss(currentCongestionWindow protocol.ByteCount) protocol.ByteCount
  • func (c *Cubic) OnApplicationLimited()
  • func (c *Cubic) Reset()
  • func (c *Cubic) SetNumConnections(n int)
• type DefaultClock
  • func (DefaultClock) Now() time.Time
• type HybridSlowStart
  • func (s *HybridSlowStart) IsEndOfRound(ack protocol.PacketNumber) bool
  • func (s *HybridSlowStart) OnPacketAcked(ackedPacketNumber protocol.PacketNumber)
  • func (s *HybridSlowStart) OnPacketSent(packetNumber protocol.PacketNumber)
  • func (s *HybridSlowStart) Restart()
  • func (s *HybridSlowStart) ShouldExitSlowStart(latestRTT time.Duration, minRTT time.Duration, ...) bool
  • func (s *HybridSlowStart) StartReceiveRound(lastSent protocol.PacketNumber)
  • func (s *HybridSlowStart) Started() bool
• type PrrSender
  • func (p *PrrSender) CanSend(congestionWindow, bytesInFlight, slowstartThreshold protocol.ByteCount) bool
  • func (p *PrrSender) OnPacketAcked(ackedBytes protocol.ByteCount)
  • func (p *PrrSender) OnPacketLost(priorInFlight protocol.ByteCount)
  • func (p *PrrSender) OnPacketSent(sentBytes protocol.ByteCount)
• type RTTStats
  • func NewRTTStats() *RTTStats
  • func (r *RTTStats) ExpireSmoothedMetrics()
  • func (r *RTTStats) LatestRTT() time.Duration
  • func (r *RTTStats) MeanDeviation() time.Duration
  • func (r *RTTStats) MinRTT() time.Duration
  • func (r *RTTStats) OnConnectionMigration()
  • func (r *RTTStats) SmoothedOrInitialRTT() time.Duration
  • func (r *RTTStats) SmoothedRTT() time.Duration
  • func (r *RTTStats) UpdateRTT(sendDelta, ackDelay time.Duration, now time.Time)
• type SendAlgorithm
• type SendAlgorithmWithDebugInfo
  • func NewCubicSender(clock Clock, rttStats *RTTStats, reno bool, ...) SendAlgorithmWithDebugInfo

Types

type Bandwidth

type Bandwidth uint64

Bandwidth of a connection

const (
	// BitsPerSecond is 1 bit per second
	BitsPerSecond Bandwidth = 1
	// BytesPerSecond is 1 byte per second
	BytesPerSecond = 8 * BitsPerSecond
)

func BandwidthFromDelta

func BandwidthFromDelta(bytes protocol.ByteCount, delta time.Duration) Bandwidth

BandwidthFromDelta calculates the bandwidth from a number of bytes and a time delta

type Clock

type Clock interface {
	Now() time.Time
}

A Clock returns the current time

type Cubic

type Cubic struct {
	// contains filtered or unexported fields
}

Cubic implements the cubic algorithm from TCP

func NewCubic

func NewCubic(clock Clock) *Cubic

NewCubic returns a new Cubic instance

func (*Cubic) CongestionWindowAfterAck

func (c *Cubic) CongestionWindowAfterAck(
	ackedBytes protocol.ByteCount,
	currentCongestionWindow protocol.ByteCount,
	delayMin time.Duration,
	eventTime time.Time,
) protocol.ByteCount

CongestionWindowAfterAck computes a new congestion window to use after a received ACK. Returns the new congestion window in packets. The new congestion window follows a cubic function that depends on the time passed since last packet loss.

func (*Cubic) CongestionWindowAfterPacketLoss

func (c *Cubic) CongestionWindowAfterPacketLoss(currentCongestionWindow protocol.ByteCount) protocol.ByteCount

CongestionWindowAfterPacketLoss computes a new congestion window to use after a loss event. Returns the new congestion window in packets. The new congestion window is a multiplicative decrease of our current window.

func (*Cubic) OnApplicationLimited

func (c *Cubic) OnApplicationLimited()

OnApplicationLimited is called on ack arrival when sender is unable to use the available congestion window. Resets Cubic state during quiescence.

func (*Cubic) Reset

func (c *Cubic) Reset()

Reset is called after a timeout to reset the cubic state

func (*Cubic) SetNumConnections

func (c *Cubic) SetNumConnections(n int)

SetNumConnections sets the number of emulated connections

type DefaultClock

type DefaultClock struct{}

DefaultClock implements the Clock interface using the Go stdlib clock.

func (DefaultClock) Now

func (DefaultClock) Now() time.Time

Now gets the current time

type HybridSlowStart

type HybridSlowStart struct {
	// contains filtered or unexported fields
}

HybridSlowStart implements the TCP hybrid slow start algorithm

func (*HybridSlowStart) IsEndOfRound

func (s *HybridSlowStart) IsEndOfRound(ack protocol.PacketNumber) bool

IsEndOfRound returns true if this ack is the last packet number of our current slow start round.

func (*HybridSlowStart) OnPacketAcked

func (s *HybridSlowStart) OnPacketAcked(ackedPacketNumber protocol.PacketNumber)

OnPacketAcked gets invoked after ShouldExitSlowStart, so it's best to end the round when the final packet of the burst is received and start it on the next incoming ack.

func (*HybridSlowStart) OnPacketSent

func (s *HybridSlowStart) OnPacketSent(packetNumber protocol.PacketNumber)

OnPacketSent is called when a packet was sent

func (*HybridSlowStart) Restart

func (s *HybridSlowStart) Restart()

Restart the slow start phase

func (*HybridSlowStart) ShouldExitSlowStart

func (s *HybridSlowStart) ShouldExitSlowStart(latestRTT time.Duration, minRTT time.Duration, congestionWindow protocol.ByteCount) bool

ShouldExitSlowStart should be called on every new ack frame, since a new RTT measurement can be made then. rtt: the RTT for this ack packet. minRTT: is the lowest delay (RTT) we have seen during the session. congestionWindow: the congestion window in packets.

func (*HybridSlowStart) StartReceiveRound

func (s *HybridSlowStart) StartReceiveRound(lastSent protocol.PacketNumber)

StartReceiveRound is called for the start of each receive round (burst) in the slow start phase.

func (*HybridSlowStart) Started

func (s *HybridSlowStart) Started() bool

Started returns true if started

type PrrSender

type PrrSender struct {
	// contains filtered or unexported fields
}

PrrSender implements the Proportional Rate Reduction (PRR) per RFC 6937

func (*PrrSender) CanSend

func (p *PrrSender) CanSend(congestionWindow, bytesInFlight, slowstartThreshold protocol.ByteCount) bool

CanSend returns if packets can be sent

func (*PrrSender) OnPacketAcked

func (p *PrrSender) OnPacketAcked(ackedBytes protocol.ByteCount)

OnPacketAcked should be called after a packet was acked

func (*PrrSender) OnPacketLost

func (p *PrrSender) OnPacketLost(priorInFlight protocol.ByteCount)

OnPacketLost should be called on the first loss that triggers a recovery period and all other methods in this class should only be called when in recovery.

func (*PrrSender) OnPacketSent

func (p *PrrSender) OnPacketSent(sentBytes protocol.ByteCount)

OnPacketSent should be called after a packet was sent

type RTTStats

type RTTStats struct {
	// contains filtered or unexported fields
}

RTTStats provides round-trip statistics

func NewRTTStats

func NewRTTStats() *RTTStats

NewRTTStats makes a properly initialized RTTStats object

func (*RTTStats) ExpireSmoothedMetrics

func (r *RTTStats) ExpireSmoothedMetrics()

ExpireSmoothedMetrics causes the smoothed_rtt to be increased to the latest_rtt if the latest_rtt is larger. The mean deviation is increased to the most recent deviation if it's larger.

func (*RTTStats) LatestRTT

func (r *RTTStats) LatestRTT() time.Duration

LatestRTT returns the most recent rtt measurement. May return Zero if no valid updates have occurred.

func (*RTTStats) MeanDeviation

func (r *RTTStats) MeanDeviation() time.Duration

MeanDeviation gets the mean deviation

func (*RTTStats) MinRTT

func (r *RTTStats) MinRTT() time.Duration

MinRTT Returns the minRTT for the entire connection. May return Zero if no valid updates have occurred.

func (*RTTStats) OnConnectionMigration

func (r *RTTStats) OnConnectionMigration()

OnConnectionMigration is called when connection migrates and rtt measurement needs to be reset.

func (*RTTStats) SmoothedOrInitialRTT

func (r *RTTStats) SmoothedOrInitialRTT() time.Duration

SmoothedOrInitialRTT returns the EWMA smoothed RTT for the connection. If no valid updates have occurred, it returns the initial RTT.

func (*RTTStats) SmoothedRTT

func (r *RTTStats) SmoothedRTT() time.Duration

SmoothedRTT returns the EWMA smoothed RTT for the connection. May return Zero if no valid updates have occurred.

func (*RTTStats) UpdateRTT

func (r *RTTStats) UpdateRTT(sendDelta, ackDelay time.Duration, now time.Time)

UpdateRTT updates the RTT based on a new sample.

type SendAlgorithm

type SendAlgorithm interface {
	TimeUntilSend(bytesInFlight protocol.ByteCount) time.Duration
	OnPacketSent(sentTime time.Time, bytesInFlight protocol.ByteCount, packetNumber protocol.PacketNumber, bytes protocol.ByteCount, isRetransmittable bool)
	GetCongestionWindow() protocol.ByteCount
	MaybeExitSlowStart()
	OnPacketAcked(number protocol.PacketNumber, ackedBytes protocol.ByteCount, priorInFlight protocol.ByteCount, eventTime time.Time)
	OnPacketLost(number protocol.PacketNumber, lostBytes protocol.ByteCount, priorInFlight protocol.ByteCount)
	SetNumEmulatedConnections(n int)
	OnRetransmissionTimeout(packetsRetransmitted bool)
	OnConnectionMigration()

	// Experiments
	SetSlowStartLargeReduction(enabled bool)
}

A SendAlgorithm performs congestion control and calculates the congestion window

type SendAlgorithmWithDebugInfo

type SendAlgorithmWithDebugInfo interface {
	SendAlgorithm
	BandwidthEstimate() Bandwidth

	HybridSlowStart() *HybridSlowStart
	SlowstartThreshold() protocol.ByteCount
	RenoBeta() float32
	InRecovery() bool
}

SendAlgorithmWithDebugInfo adds some debug functions to SendAlgorithm

func NewCubicSender

func NewCubicSender(clock Clock, rttStats *RTTStats, reno bool, initialCongestionWindow, initialMaxCongestionWindow protocol.ByteCount) SendAlgorithmWithDebugInfo

NewCubicSender makes a new cubic sender