BBR congestion control algorithm. More...

#include "tcp-bbr.h"

Inheritance diagram for ns3::TcpBbr:

Collaboration diagram for ns3::TcpBbr:

Public Types
enum	BbrMode_t { BBR_STARTUP , BBR_DRAIN , BBR_PROBE_BW , BBR_PROBE_RTT }
	BBR has the following 4 modes for deciding how fast to send: More...

typedef WindowedFilter< DataRate, MaxFilter< DataRate >, uint32_t, uint32_t >	MaxBandwidthFilter_t
	Definition of max bandwidth filter.

Public Member Functions
	TcpBbr ()
	Constructor.

	TcpBbr (const TcpBbr &sock)
	Copy constructor.

void	CongControl (Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateConnection &rc, const TcpRateOps::TcpRateSample &rs) override
	Called when packets are delivered to update cwnd and pacing rate.

void	CongestionStateSet (Ptr< TcpSocketState > tcb, const TcpSocketState::TcpCongState_t newState) override
	Trigger events/calculations specific to a congestion state.

void	CwndEvent (Ptr< TcpSocketState > tcb, const TcpSocketState::TcpCAEvent_t event) override
	Trigger events/calculations on occurrence of congestion window event.

Ptr< TcpCongestionOps >	Fork () override
	Copy the congestion control algorithm across sockets.

std::string	GetName () const override
	Get the name of the congestion control algorithm.

uint32_t	GetSsThresh (Ptr< const TcpSocketState > tcb, uint32_t bytesInFlight) override
	Get the slow start threshold after a loss event.

bool	HasCongControl () const override
	Returns true when Congestion Control Algorithm implements CongControl.

virtual void	SetStream (uint32_t stream)
	Assign a fixed random variable stream number to the random variables used by this model.

Public Member Functions inherited from ns3::TcpCongestionOps
	TcpCongestionOps ()

	TcpCongestionOps (const TcpCongestionOps &other)
	Copy constructor.

	~TcpCongestionOps () override

virtual void	CongControl (Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateConnection &rc, const TcpRateOps::TcpRateSample &rs)
	Called when packets are delivered to update cwnd and pacing rate.

virtual void	CongestionStateSet (Ptr< TcpSocketState > tcb, const TcpSocketState::TcpCongState_t newState)
	Trigger events/calculations specific to a congestion state.

virtual void	CwndEvent (Ptr< TcpSocketState > tcb, const TcpSocketState::TcpCAEvent_t event)
	Trigger events/calculations on occurrence of congestion window event.

virtual Ptr< TcpCongestionOps >	Fork ()=0
	Copy the congestion control algorithm across sockets.

virtual std::string	GetName () const =0
	Get the name of the congestion control algorithm.

virtual uint32_t	GetSsThresh (Ptr< const TcpSocketState > tcb, uint32_t bytesInFlight)=0
	Get the slow start threshold after a loss event.

virtual bool	HasCongControl () const
	Returns true when Congestion Control Algorithm implements CongControl.

virtual void	IncreaseWindow (Ptr< TcpSocketState > tcb, uint32_t segmentsAcked)
	Congestion avoidance algorithm implementation.

virtual void	Init (Ptr< TcpSocketState > tcb)
	Set configuration required by congestion control algorithm.

virtual void	PktsAcked (Ptr< TcpSocketState > tcb, uint32_t segmentsAcked, const Time &rtt)
	Timing information on received ACK.

Public Member Functions inherited from ns3::Object
	Object ()
	Constructor.

	~Object () override
	Destructor.

void	AggregateObject (Ptr< Object > other)
	Aggregate two Objects together.

void	Dispose ()
	Dispose of this Object.

AggregateIterator	GetAggregateIterator () const
	Get an iterator to the Objects aggregated to this one.

TypeId	GetInstanceTypeId () const override
	Get the most derived TypeId for this Object.

template<typename T >
Ptr< T >	GetObject () const
	Get a pointer to the requested aggregated Object.

template<>
Ptr< Object >	GetObject () const
	Specialization of () for objects of type ns3::Object.

template<typename T >
Ptr< T >	GetObject (TypeId tid) const
	Get a pointer to the requested aggregated Object by TypeId.

template<>
Ptr< Object >	GetObject (TypeId tid) const
	Specialization of (TypeId tid) for objects of type ns3::Object.

void	Initialize ()
	Invoke DoInitialize on all Objects aggregated to this one.

bool	IsInitialized () const
	Check if the object has been initialized.

void	UnidirectionalAggregateObject (Ptr< Object > other)
	Aggregate an Object to another Object.

Public Member Functions inherited from ns3::SimpleRefCount< Object, ObjectBase, ObjectDeleter >
	SimpleRefCount ()
	Default constructor.

	SimpleRefCount (const SimpleRefCount &o)
	Copy constructor.

uint32_t	GetReferenceCount () const
	Get the reference count of the object.

SimpleRefCount &	operator= (const SimpleRefCount &o)
	Assignment operator.

void	Ref () const
	Increment the reference count.

void	Unref () const
	Decrement the reference count.

Public Member Functions inherited from ns3::ObjectBase
virtual	~ObjectBase ()
	Virtual destructor.

void	GetAttribute (std::string name, AttributeValue &value) const
	Get the value of an attribute, raising fatal errors if unsuccessful.

bool	GetAttributeFailSafe (std::string name, AttributeValue &value) const
	Get the value of an attribute without raising errors.

virtual TypeId	GetInstanceTypeId () const =0
	Get the most derived TypeId for this Object.

void	SetAttribute (std::string name, const AttributeValue &value)
	Set a single attribute, raising fatal errors if unsuccessful.

bool	SetAttributeFailSafe (std::string name, const AttributeValue &value)
	Set a single attribute without raising errors.

bool	TraceConnect (std::string name, std::string context, const CallbackBase &cb)
	Connect a TraceSource to a Callback with a context.

bool	TraceConnectWithoutContext (std::string name, const CallbackBase &cb)
	Connect a TraceSource to a Callback without a context.

bool	TraceDisconnect (std::string name, std::string context, const CallbackBase &cb)
	Disconnect from a TraceSource a Callback previously connected with a context.

bool	TraceDisconnectWithoutContext (std::string name, const CallbackBase &cb)
	Disconnect from a TraceSource a Callback previously connected without a context.

Static Public Member Functions
static TypeId	GetTypeId ()
	Get the type ID.

Static Public Member Functions inherited from ns3::TcpCongestionOps
static TypeId	GetTypeId ()
	Get the type ID.

Static Public Member Functions inherited from ns3::Object
static TypeId	GetTypeId ()
	Register this type.

Static Public Member Functions inherited from ns3::ObjectBase
static TypeId	GetTypeId ()
	Get the type ID.

Static Public Attributes
static const char *const	BbrModeName [BBR_PROBE_RTT+1]
	Literal names of BBR mode for use in log messages.

static const uint8_t	GAIN_CYCLE_LENGTH = 8
	The number of phases in the BBR ProbeBW gain cycle.

static const double	PACING_GAIN_CYCLE [] = {5.0 / 4, 3.0 / 4, 1, 1, 1, 1, 1, 1}
	BBR uses an eight-phase cycle with the given pacing_gain value in the BBR ProbeBW gain cycle.

Protected Member Functions
uint32_t	AckAggregationCwnd ()
	Find Cwnd increment based on ack aggregation.

void	AdvanceCyclePhase ()
	Advances pacing gain using cycle gain algorithm, while in BBR_PROBE_BW state.

void	CheckCyclePhase (Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
	Checks whether to advance pacing gain in BBR_PROBE_BW state, and if allowed calls AdvanceCyclePhase ()

void	CheckDrain (Ptr< TcpSocketState > tcb)
	Checks whether its time to enter BBR_DRAIN or BBR_PROBE_BW state.

void	CheckFullPipe (const TcpRateOps::TcpRateSample &rs)
	Identifies whether pipe or BDP is already full.

void	CheckProbeRTT (Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
	This method handles the steps related to the ProbeRTT state.

void	EnterDrain ()
	Updates variables specific to BBR_DRAIN state.

void	EnterProbeBW ()
	Updates variables specific to BBR_PROBE_BW state.

void	EnterProbeRTT ()
	Updates variables specific to BBR_PROBE_RTT state.

void	EnterStartup ()
	Updates variables specific to BBR_STARTUP state.

void	ExitProbeRTT ()
	Called on exiting from BBR_PROBE_RTT state, it eithers invoke EnterProbeBW () or EnterStartup ()

uint32_t	GetBbrState ()
	Gets BBR state.

double	GetCwndGain ()
	Gets current cwnd gain.

double	GetPacingGain ()
	Gets current pacing gain.

void	HandleProbeRTT (Ptr< TcpSocketState > tcb)
	Handles the steps for BBR_PROBE_RTT state.

void	HandleRestartFromIdle (Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
	Updates pacing rate if socket is restarting from idle state.

uint32_t	InFlight (Ptr< TcpSocketState > tcb, double gain)
	Estimates the target value for congestion window.

void	InitFullPipe ()
	Initializes the full pipe estimator.

void	InitPacingRate (Ptr< TcpSocketState > tcb)
	Initializes the pacing rate.

void	InitRoundCounting ()
	Initializes the round counting related variables.

bool	IsNextCyclePhase (Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
	Checks whether to move to next value of pacing gain while in BBR_PROBE_BW.

void	ModulateCwndForProbeRTT (Ptr< TcpSocketState > tcb)
	Modulates congestion window in BBR_PROBE_RTT.

bool	ModulateCwndForRecovery (Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
	Modulates congestion window in CA_RECOVERY.

void	RestoreCwnd (Ptr< TcpSocketState > tcb)
	Helper to restore the last-known good congestion window.

void	SaveCwnd (Ptr< const TcpSocketState > tcb)
	Helper to remember the last-known good congestion window or the latest congestion window unmodulated by loss recovery or ProbeRTT.

void	SetBbrState (BbrMode_t state)
	Sets BBR state.

void	SetCwnd (Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
	Updates congestion window based on the network model.

void	SetPacingRate (Ptr< TcpSocketState > tcb, double gain)
	Updates pacing rate based on network model.

void	SetSendQuantum (Ptr< TcpSocketState > tcb)
	Updates send quantum based on the network model.

void	UpdateAckAggregation (Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
	Estimates max degree of aggregation.

void	UpdateBtlBw (Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
	Updates maximum bottleneck.

void	UpdateControlParameters (Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
	Updates control parameters congestion windowm, pacing rate, send quantum.

void	UpdateModelAndState (Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
	Updates BBR network model (Maximum bandwidth and minimum RTT).

void	UpdateRound (Ptr< TcpSocketState > tcb, const TcpRateOps::TcpRateSample &rs)
	Updates round counting related variables.

void	UpdateRTprop (Ptr< TcpSocketState > tcb)
	Updates minimum RTT.

void	UpdateTargetCwnd (Ptr< TcpSocketState > tcb)
	Updates target congestion window.

Protected Member Functions inherited from ns3::Object
	Object (const Object &o)
	Copy an Object.

virtual void	DoDispose ()
	Destructor implementation.

virtual void	DoInitialize ()
	Initialize() implementation.

virtual void	NotifyNewAggregate ()
	Notify all Objects aggregated to this one of a new Object being aggregated.

Protected Member Functions inherited from ns3::ObjectBase
void	ConstructSelf (const AttributeConstructionList &attributes)
	Complete construction of ObjectBase; invoked by derived classes.

virtual void	NotifyConstructionCompleted ()
	Notifier called once the ObjectBase is fully constructed.

Private Attributes
uint32_t	m_ackEpochAcked {0}
	Bytes ACked in sampling epoch.

uint32_t	m_ackEpochAckedResetThresh
	Max allowed val for m_ackEpochAcked, after which sampling epoch is reset.

Time	m_ackEpochTime {Seconds(0)}
	Starting of ACK sampling epoch time.

uint32_t	m_appLimited
	The index of the last transmitted packet marked as application-limited.

uint32_t	m_bandwidthWindowLength {0}
	A constant specifying the length of the BBR.BtlBw max filter window, default 10 packet-timed round trips.

double	m_cWndGain {0}
	The dynamic congestion window gain factor.

uint32_t	m_cycleIndex {0}
	Current index of gain cycle.

Time	m_cycleStamp {Seconds(0)}
	Last time gain cycle updated.

uint64_t	m_delivered {0}
	The total amount of data in bytes delivered so far.

uint32_t	m_extraAcked [2] {0, 0}
	Maximum excess data acked in epoch.

uint32_t	m_extraAckedGain {1}
	Gain factor for adding extra ack to cwnd.

uint32_t	m_extraAckedIdx {0}
	Current index in extra acked array.

uint32_t	m_extraAckedWinRtt {0}
	Age of extra acked in rtt.

uint32_t	m_extraAckedWinRttLength {5}
	Window length of extra acked window.

DataRate	m_fullBandwidth {0}
	Value of full bandwidth recorded.

uint32_t	m_fullBandwidthCount {0}
	Count of full bandwidth recorded consistently.

bool	m_hasSeenRtt {false}
	Have we seen RTT sample yet?

double	m_highGain {0}
	A constant specifying highest gain factor, default is 2.89.

bool	m_idleRestart {false}
	When restarting from idle, set it true.

bool	m_isInitialized {false}
	Set to true after first time initializtion variables.

bool	m_isPipeFilled {false}
	A boolean that records whether BBR has filled the pipe.

MaxBandwidthFilter_t	m_maxBwFilter
	Maximum bandwidth filter.

uint32_t	m_minPipeCwnd
	The minimal congestion window value BBR tries to target, default 4 Segment size.

uint32_t	m_nextRoundDelivered {0}
	Denotes the end of a packet-timed round trip.

double	m_pacingGain {0}
	The dynamic pacing gain factor.

bool	m_packetConservation {false}
	Enable/Disable packet conservation mode.

uint32_t	m_priorCwnd {0}
	The last-known good congestion window.

Time	m_probeRtPropStamp
	The wall clock time at which the current BBR.RTProp sample was obtained.

Time	m_probeRttDoneStamp {Seconds(0)}
	Time to exit from BBR_PROBE_RTT state.

Time	m_probeRttDuration {MilliSeconds(200)}
	A constant specifying the minimum duration for which ProbeRTT state, default 200 millisecs.

bool	m_probeRttRoundDone {false}
	True when it is time to exit BBR_PROBE_RTT.

uint32_t	m_roundCount {0}
	Count of packet-timed round trips.

bool	m_roundStart {false}
	A boolean that BBR sets to true once per packet-timed round trip.

Time	m_rtProp
	Estimated two-way round-trip propagation delay of the path, estimated from the windowed minimum recent round-trip delay sample.

bool	m_rtPropExpired {false}
	A boolean recording whether the BBR.RTprop has expired.

Time	m_rtPropFilterLen {Seconds(10)}
	A constant specifying the length of the RTProp min filter window, default 10 secs.

Time	m_rtPropStamp
	The wall clock time at which the current BBR.RTProp sample was obtained.

uint32_t	m_sendQuantum
	The maximum size of a data aggregate scheduled and transmitted together.

BbrMode_t	m_state {BbrMode_t::BBR_STARTUP}
	Current state of BBR state machine.

uint32_t	m_targetCWnd {0}
	Target value for congestion window, adapted to the estimated BDP.

uint32_t	m_txItemDelivered
	The number of bytes already delivered at the time of new packet transmission.

Ptr< UniformRandomVariable >	m_uv {nullptr}
	Uniform Random Variable.

Related Functions
(Note that these are not member functions.)
class	TcpBbrCheckGainValuesTest
	TcpBbrCheckGainValuesTest friend class (for tests).

Additional Inherited Members
Related Functions inherited from ns3::ObjectBase
static TypeId	GetObjectIid ()
	Ensure the TypeId for ObjectBase gets fully configured to anchor the inheritance tree properly.

Detailed Description

BBR congestion control algorithm.

This class implement the BBR (Bottleneck Bandwidth and Round-trip propagation time) congestion control type.

Config Paths

ns3::TcpBbr is accessible through the following paths with Config::Set and Config::Connect:

"/NodeList/[i]/$ns3::TcpL4Protocol/SocketList/[i]/CongestionOps/$ns3::TcpBbr"

Attributes

AckEpochAckedResetThresh: Max allowed val for m_ackEpochAcked, after which sampling epoch is reset
- Set with class: ns3::UintegerValue
- Underlying type: uint32_t 0:4294967295
- Initial value: 4096
- Flags: constructwriteread
BwWindowLength: Length of bandwidth windowed filter
- Set with class: ns3::UintegerValue
- Underlying type: uint32_t 0:4294967295
- Initial value: 10
- Flags: constructwriteread
ExtraAckedRttWindowLength: Window length of extra acked window
- Set with class: ns3::UintegerValue
- Underlying type: uint32_t 0:4294967295
- Initial value: 5
- Flags: constructwriteread
HighGain: Value of high gain
- Set with class: ns3::DoubleValue
- Underlying type: double -1.79769e+308:1.79769e+308
- Initial value: 2.89
- Flags: constructwriteread
ProbeRttDuration: Time to be spent in PROBE_RTT phase
- Set with class: ns3::TimeValue
- Underlying type: Time +9.22337e+18ns:+9.22337e+18ns
- Initial value: +2e+08ns
- Flags: constructwriteread
RttWindowLength: Length of RTT windowed filter
- Set with class: ns3::TimeValue
- Underlying type: Time +9.22337e+18ns:+9.22337e+18ns
- Initial value: +1e+10ns
- Flags: constructwriteread
Stream: Random number stream (default is set to 4 to align with Linux results)
- Set with class: ns3::UintegerValue
- Underlying type: uint32_t 0:4294967295
- Initial value: 4
- Flags: constructwrite

No TraceSources are defined for this type.
Size of this type is 360 bytes (on a 64-bit architecture).

Definition at line 45 of file tcp-bbr.h.

Member Typedef Documentation

◆ MaxBandwidthFilter_t

typedef WindowedFilter<DataRate, MaxFilter<DataRate>, uint32_t, uint32_t> ns3::TcpBbr::MaxBandwidthFilter_t

Definition of max bandwidth filter.

Definition at line 90 of file tcp-bbr.h.

Member Enumeration Documentation

◆ BbrMode_t

enum ns3::TcpBbr::BbrMode_t

BBR has the following 4 modes for deciding how fast to send:

Enumerator
BBR_STARTUP	Ramp up sending rate rapidly to fill pipe.
BBR_DRAIN	Drain any queue created during startup.
BBR_PROBE_BW	Discover, share bw: pace around estimated bw.
BBR_PROBE_RTT	Cut inflight to min to probe min_rtt.

Definition at line 78 of file tcp-bbr.h.

Constructor & Destructor Documentation

◆ TcpBbr() [1/2]

ns3::TcpBbr::TcpBbr ( )

Constructor.

Definition at line 82 of file tcp-bbr.cc.

References m_uv, and NS_LOG_FUNCTION.

◆ TcpBbr() [2/2]

ns3::TcpBbr::TcpBbr ( const TcpBbr & sock )

Copy constructor.

Parameters

sock	The socket to copy from.

Definition at line 89 of file tcp-bbr.cc.

References NS_LOG_FUNCTION.

Member Function Documentation

◆ AckAggregationCwnd()

uint32_t ns3::TcpBbr::AckAggregationCwnd ( )

protected

Find Cwnd increment based on ack aggregation.

Returns: uint32_t aggregate cwnd.

Definition at line 476 of file tcp-bbr.cc.

References ns3::WindowedFilter< T, Compare, TimeT, TimeDeltaT >::GetBest(), ns3::DataRate::GetBitRate(), m_extraAcked, m_extraAckedGain, m_isPipeFilled, and m_maxBwFilter.

Referenced by UpdateTargetCwnd().

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◆ AdvanceCyclePhase()

void ns3::TcpBbr::AdvanceCyclePhase ( )

protected

Advances pacing gain using cycle gain algorithm, while in BBR_PROBE_BW state.

Definition at line 255 of file tcp-bbr.cc.

References GAIN_CYCLE_LENGTH, m_cycleIndex, m_cycleStamp, m_pacingGain, ns3::Simulator::Now(), NS_LOG_FUNCTION, and PACING_GAIN_CYCLE.

Referenced by CheckCyclePhase(), and EnterProbeBW().

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◆ CheckCyclePhase()

void ns3::TcpBbr::CheckCyclePhase	(	Ptr< TcpSocketState >	tcb,
		const TcpRateOps::TcpRateSample &	rs
	)

protected

Checks whether to advance pacing gain in BBR_PROBE_BW state, and if allowed calls AdvanceCyclePhase ()

Parameters

tcb	the socket state.
rs	rate sample.

Definition at line 284 of file tcp-bbr.cc.

References AdvanceCyclePhase(), BBR_PROBE_BW, IsNextCyclePhase(), m_state, and NS_LOG_FUNCTION.

Referenced by UpdateModelAndState().

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◆ CheckDrain()

void ns3::TcpBbr::CheckDrain ( Ptr< TcpSocketState > tcb )

protected

Checks whether its time to enter BBR_DRAIN or BBR_PROBE_BW state.

Parameters

tcb	the socket state.

Definition at line 339 of file tcp-bbr.cc.

References BBR_DRAIN, BBR_STARTUP, EnterDrain(), EnterProbeBW(), InFlight(), m_isPipeFilled, m_state, and NS_LOG_FUNCTION.

Referenced by UpdateModelAndState().

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◆ CheckFullPipe()

void ns3::TcpBbr::CheckFullPipe ( const TcpRateOps::TcpRateSample & rs )

protected

Identifies whether pipe or BDP is already full.

Parameters

rs	rate sample.

Definition at line 294 of file tcp-bbr.cc.

References ns3::WindowedFilter< T, Compare, TimeT, TimeDeltaT >::GetBest(), ns3::DataRate::GetBitRate(), m_fullBandwidth, m_fullBandwidthCount, ns3::TcpRateOps::TcpRateSample::m_isAppLimited, m_isPipeFilled, m_maxBwFilter, m_roundStart, NS_LOG_DEBUG, and NS_LOG_FUNCTION.

Referenced by UpdateModelAndState().

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◆ CheckProbeRTT()

void ns3::TcpBbr::CheckProbeRTT	(	Ptr< TcpSocketState >	tcb,
		const TcpRateOps::TcpRateSample &	rs
	)

protected

This method handles the steps related to the ProbeRTT state.

Parameters

tcb	the socket state.
rs	rate sample.

Definition at line 440 of file tcp-bbr.cc.

References BBR_PROBE_RTT, EnterProbeRTT(), HandleProbeRTT(), ns3::TcpRateOps::TcpRateSample::m_delivered, m_idleRestart, m_probeRttDoneStamp, m_rtPropExpired, m_state, NS_LOG_FUNCTION, SaveCwnd(), and ns3::Seconds().

Referenced by UpdateModelAndState().

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◆ CongControl()

void ns3::TcpBbr::CongControl	(	Ptr< TcpSocketState >	tcb,
		const TcpRateOps::TcpRateConnection &	rc,
		const TcpRateOps::TcpRateSample &	rs
	)

overridevirtual

Called when packets are delivered to update cwnd and pacing rate.

This function mimics the function cong_control in Linux. It is allowed to change directly cWnd and pacing rate.

Parameters

tcb	internal congestion state
rc	Rate information for the connection
rs	Rate sample (over a period of time) information

Reimplemented from ns3::TcpCongestionOps.

Definition at line 697 of file tcp-bbr.cc.

References m_delivered, m_txItemDelivered, NS_LOG_FUNCTION, UpdateControlParameters(), and UpdateModelAndState().

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◆ CongestionStateSet()

void ns3::TcpBbr::CongestionStateSet	(	Ptr< TcpSocketState >	tcb,
		const TcpSocketState::TcpCongState_t	newState
	)

overridevirtual

Trigger events/calculations specific to a congestion state.

This function mimics the notification function set_state in Linux. The function does not change the congestion state in the tcb; it notifies the congestion control algorithm that this state is about to be changed. The tcb->m_congState variable must be separately set; for example:

m_congestionControl->CongestionStateSet (m_tcb, TcpSocketState::CA_RECOVERY);

m_tcb->m_congState = TcpSocketState::CA_RECOVERY;

ns3::TcpSocketState::CA_RECOVERY

@ CA_RECOVERY

CWND was reduced, we are fast-retransmitting.

Definition: tcp-socket-state.h:88

Parameters

tcb	internal congestion state
newState	new congestion state to which the TCP is going to switch

Reimplemented from ns3::TcpCongestionOps.

Definition at line 709 of file tcp-bbr.cc.

References ns3::TcpSocketState::CA_LOSS, ns3::TcpSocketState::CA_OPEN, ns3::TcpSocketState::CA_RECOVERY, EnterStartup(), InitFullPipe(), InitPacingRate(), InitRoundCounting(), m_ackEpochAcked, m_ackEpochTime, m_extraAcked, m_extraAckedIdx, m_extraAckedWinRtt, m_isInitialized, m_minPipeCwnd, m_packetConservation, m_priorCwnd, m_roundStart, m_rtProp, m_rtPropStamp, m_sendQuantum, m_targetCWnd, ns3::Time::Max(), ns3::Simulator::Now(), NS_LOG_DEBUG, NS_LOG_FUNCTION, and SaveCwnd().

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◆ CwndEvent()

void ns3::TcpBbr::CwndEvent	(	Ptr< TcpSocketState >	tcb,
		const TcpSocketState::TcpCAEvent_t	event
	)

overridevirtual

Trigger events/calculations on occurrence of congestion window event.

This function mimics the function cwnd_event in Linux. The function is called in case of congestion window events.

Parameters

tcb	internal congestion state
event	the event which triggered this function

Reimplemented from ns3::TcpCongestionOps.

Definition at line 752 of file tcp-bbr.cc.

References BBR_PROBE_BW, BBR_PROBE_RTT, ns3::TcpSocketState::CA_EVENT_COMPLETE_CWR, ns3::TcpSocketState::CA_EVENT_TX_START, ExitProbeRTT(), m_ackEpochAcked, m_ackEpochTime, m_appLimited, m_idleRestart, m_packetConservation, m_probeRttDoneStamp, m_probeRttRoundDone, m_rtPropStamp, m_state, ns3::Simulator::Now(), NS_LOG_DEBUG, NS_LOG_FUNCTION, RestoreCwnd(), and SetPacingRate().

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◆ EnterDrain()

void ns3::TcpBbr::EnterDrain ( )

protected

Updates variables specific to BBR_DRAIN state.

Definition at line 319 of file tcp-bbr.cc.

References BBR_DRAIN, m_cWndGain, m_highGain, m_pacingGain, NS_LOG_FUNCTION, and SetBbrState().

Referenced by CheckDrain().

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◆ EnterProbeBW()

void ns3::TcpBbr::EnterProbeBW ( )

protected

Updates variables specific to BBR_PROBE_BW state.

Definition at line 328 of file tcp-bbr.cc.

References AdvanceCyclePhase(), BBR_PROBE_BW, GAIN_CYCLE_LENGTH, ns3::UniformRandomVariable::GetValue(), m_cWndGain, m_cycleIndex, m_pacingGain, m_uv, NS_LOG_FUNCTION, and SetBbrState().

Referenced by CheckDrain(), and ExitProbeRTT().

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◆ EnterProbeRTT()

void ns3::TcpBbr::EnterProbeRTT ( )

protected

Updates variables specific to BBR_PROBE_RTT state.

Definition at line 367 of file tcp-bbr.cc.

References BBR_PROBE_RTT, m_cWndGain, m_pacingGain, NS_LOG_FUNCTION, and SetBbrState().

Referenced by CheckProbeRTT().

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◆ EnterStartup()

void ns3::TcpBbr::EnterStartup ( )

protected

Updates variables specific to BBR_STARTUP state.

Definition at line 196 of file tcp-bbr.cc.

References BBR_STARTUP, m_cWndGain, m_highGain, m_pacingGain, NS_LOG_FUNCTION, and SetBbrState().

Referenced by CongestionStateSet(), and ExitProbeRTT().

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◆ ExitProbeRTT()

void ns3::TcpBbr::ExitProbeRTT ( )

protected

Called on exiting from BBR_PROBE_RTT state, it eithers invoke EnterProbeBW () or EnterStartup ()

Definition at line 397 of file tcp-bbr.cc.

References EnterProbeBW(), EnterStartup(), m_isPipeFilled, and NS_LOG_FUNCTION.

Referenced by CwndEvent(), and HandleProbeRTT().

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◆ Fork()

Ptr< TcpCongestionOps > ns3::TcpBbr::Fork ( )

overridevirtual

Copy the congestion control algorithm across sockets.

Returns: a pointer of the copied object

Implements ns3::TcpCongestionOps.

Definition at line 792 of file tcp-bbr.cc.

◆ GetBbrState()

uint32_t ns3::TcpBbr::GetBbrState ( )

protected

Gets BBR state.

Returns: returns BBR state.

Definition at line 663 of file tcp-bbr.cc.

References m_state, and NS_LOG_FUNCTION.

◆ GetCwndGain()

double ns3::TcpBbr::GetCwndGain ( )

protected

Gets current cwnd gain.

Returns: returns current cwnd gain.

Definition at line 670 of file tcp-bbr.cc.

References m_cWndGain, and NS_LOG_FUNCTION.

◆ GetName()

std::string ns3::TcpBbr::GetName ( ) const

overridevirtual

Get the name of the congestion control algorithm.

Returns: A string identifying the name

Implements ns3::TcpCongestionOps.

Definition at line 684 of file tcp-bbr.cc.

◆ GetPacingGain()

double ns3::TcpBbr::GetPacingGain ( )

protected

Gets current pacing gain.

Returns: returns current pacing gain.

Definition at line 677 of file tcp-bbr.cc.

References m_pacingGain, and NS_LOG_FUNCTION.

◆ GetSsThresh()

uint32_t ns3::TcpBbr::GetSsThresh	(	Ptr< const TcpSocketState >	tcb,
		uint32_t	bytesInFlight
	)

overridevirtual

Get the slow start threshold after a loss event.

Is guaranteed that the congestion control state (TcpAckState_t) is changed BEFORE the invocation of this method. The implementer should return the slow start threshold (and not change it directly) because, in the future, the TCP implementation may require to instantly recover from a loss event (e.g. when there is a network with an high reordering factor).

Parameters

tcb	internal congestion state
bytesInFlight	total bytes in flight

Returns: Slow start threshold

Implements ns3::TcpCongestionOps.

Definition at line 784 of file tcp-bbr.cc.

References NS_LOG_FUNCTION, and SaveCwnd().

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◆ GetTypeId()

TypeId ns3::TcpBbr::GetTypeId ( )

static

Get the type ID.

Returns: the object TypeId

Definition at line 36 of file tcp-bbr.cc.

References m_ackEpochAckedResetThresh, m_bandwidthWindowLength, m_extraAckedWinRttLength, m_highGain, m_probeRttDuration, m_rtPropFilterLen, ns3::MakeDoubleAccessor(), ns3::MakeTimeAccessor(), ns3::MakeTimeChecker(), ns3::MakeUintegerAccessor(), ns3::MilliSeconds(), ns3::Seconds(), ns3::TypeId::SetParent(), and SetStream().

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◆ HandleProbeRTT()

void ns3::TcpBbr::HandleProbeRTT ( Ptr< TcpSocketState > tcb )

protected

Handles the steps for BBR_PROBE_RTT state.

Parameters

tcb	the socket state.

Definition at line 411 of file tcp-bbr.cc.

References ExitProbeRTT(), m_appLimited, m_delivered, m_minPipeCwnd, m_nextRoundDelivered, m_probeRttDoneStamp, m_probeRttDuration, m_probeRttRoundDone, m_roundStart, m_rtPropStamp, ns3::Simulator::Now(), NS_LOG_FUNCTION, RestoreCwnd(), and ns3::Seconds().

Referenced by CheckProbeRTT().

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◆ HandleRestartFromIdle()

void ns3::TcpBbr::HandleRestartFromIdle	(	Ptr< TcpSocketState >	tcb,
		const TcpRateOps::TcpRateSample &	rs
	)

protected

Updates pacing rate if socket is restarting from idle state.

Parameters

tcb	the socket state.
rs	rate sample.

Definition at line 205 of file tcp-bbr.cc.

References BBR_PROBE_BW, m_idleRestart, ns3::TcpRateOps::TcpRateSample::m_isAppLimited, m_state, NS_LOG_FUNCTION, and SetPacingRate().

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◆ HasCongControl()

bool ns3::TcpBbr::HasCongControl ( ) const

overridevirtual

Returns true when Congestion Control Algorithm implements CongControl.

Returns: true if CC implements CongControl function

This function is the equivalent in C++ of the C checks that are used in the Linux kernel to see if an optional function has been defined. Since CongControl is optional, not all congestion controls have it. But, from the perspective of TcpSocketBase, the behavior is different if CongControl is present. Therefore, this check should return true for any congestion controls that implements the CongControl optional function.

Reimplemented from ns3::TcpCongestionOps.

Definition at line 690 of file tcp-bbr.cc.

References NS_LOG_FUNCTION.

◆ InFlight()

uint32_t ns3::TcpBbr::InFlight	(	Ptr< TcpSocketState >	tcb,
		double	gain
	)

protected

Estimates the target value for congestion window.

Parameters

tcb	the socket state.
gain	cwnd gain.

Returns: returns congestion window based on max bandwidth and min RTT.

Definition at line 237 of file tcp-bbr.cc.

References BBR_PROBE_BW, ns3::WindowedFilter< T, Compare, TimeT, TimeDeltaT >::GetBest(), m_cycleIndex, m_maxBwFilter, m_rtProp, m_sendQuantum, m_state, ns3::Time::Max(), and NS_LOG_FUNCTION.

Referenced by CheckDrain(), IsNextCyclePhase(), and UpdateTargetCwnd().

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◆ InitFullPipe()

void ns3::TcpBbr::InitFullPipe ( )

protected

Initializes the full pipe estimator.

Definition at line 158 of file tcp-bbr.cc.

References m_fullBandwidth, m_fullBandwidthCount, m_isPipeFilled, and NS_LOG_FUNCTION.

Referenced by CongestionStateSet().

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◆ InitPacingRate()

void ns3::TcpBbr::InitPacingRate ( Ptr< TcpSocketState > tcb )

protected

Initializes the pacing rate.

Parameters

tcb	the socket state.

Definition at line 167 of file tcp-bbr.cc.

References ns3::DataRate::GetBitRate(), ns3::Time::GetSeconds(), m_bandwidthWindowLength, m_hasSeenRtt, m_maxBwFilter, m_pacingGain, ns3::Time::Max(), ns3::MilliSeconds(), NS_LOG_FUNCTION, and NS_LOG_WARN.

Referenced by CongestionStateSet(), and SetPacingRate().

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◆ InitRoundCounting()

void ns3::TcpBbr::InitRoundCounting ( )

protected

Initializes the round counting related variables.

Definition at line 149 of file tcp-bbr.cc.

References m_nextRoundDelivered, m_roundCount, m_roundStart, and NS_LOG_FUNCTION.

Referenced by CongestionStateSet().

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◆ IsNextCyclePhase()

bool ns3::TcpBbr::IsNextCyclePhase	(	Ptr< TcpSocketState >	tcb,
		const TcpRateOps::TcpRateSample &	rs
	)

protected

Checks whether to move to next value of pacing gain while in BBR_PROBE_BW.

Parameters

tcb	the socket state.
rs	rate sample.

Returns: true if want to move to next value otherwise false.

Definition at line 264 of file tcp-bbr.cc.

References InFlight(), ns3::TcpRateOps::TcpRateSample::m_bytesLoss, m_cycleStamp, m_pacingGain, ns3::TcpRateOps::TcpRateSample::m_priorInFlight, m_rtProp, ns3::Simulator::Now(), and NS_LOG_FUNCTION.

Referenced by CheckCyclePhase().

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◆ ModulateCwndForProbeRTT()

void ns3::TcpBbr::ModulateCwndForProbeRTT ( Ptr< TcpSocketState > tcb )

protected

Modulates congestion window in BBR_PROBE_RTT.

Parameters

tcb	the socket state.

Definition at line 553 of file tcp-bbr.cc.

References BBR_PROBE_RTT, m_minPipeCwnd, m_state, and NS_LOG_FUNCTION.

Referenced by SetCwnd().

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◆ ModulateCwndForRecovery()

bool ns3::TcpBbr::ModulateCwndForRecovery	(	Ptr< TcpSocketState >	tcb,
		const TcpRateOps::TcpRateSample &	rs
	)

protected

Modulates congestion window in CA_RECOVERY.

Parameters

tcb	the socket state.
rs	rate sample.

Returns: true if congestion window is updated in CA_RECOVERY.

Definition at line 535 of file tcp-bbr.cc.

References ns3::TcpRateOps::TcpRateSample::m_ackedSacked, ns3::TcpRateOps::TcpRateSample::m_bytesLoss, m_packetConservation, and NS_LOG_FUNCTION.

Referenced by SetCwnd().

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◆ RestoreCwnd()

void ns3::TcpBbr::RestoreCwnd ( Ptr< TcpSocketState > tcb )

protected

Helper to restore the last-known good congestion window.

Parameters

tcb	the socket state.

Definition at line 390 of file tcp-bbr.cc.

References m_priorCwnd, and NS_LOG_FUNCTION.

Referenced by CwndEvent(), and HandleProbeRTT().

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◆ SaveCwnd()

void ns3::TcpBbr::SaveCwnd ( Ptr< const TcpSocketState > tcb )

protected

Helper to remember the last-known good congestion window or the latest congestion window unmodulated by loss recovery or ProbeRTT.

Parameters

tcb	the socket state.

Definition at line 376 of file tcp-bbr.cc.

References BBR_PROBE_RTT, ns3::TcpSocketState::CA_RECOVERY, m_priorCwnd, m_state, and NS_LOG_FUNCTION.

Referenced by CheckProbeRTT(), CongestionStateSet(), and GetSsThresh().

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◆ SetBbrState()

void ns3::TcpBbr::SetBbrState ( BbrMode_t state )

protected

Sets BBR state.

Parameters

state BBR state.

Definition at line 654 of file tcp-bbr.cc.

References BbrModeName, m_state, ns3::Simulator::Now(), NS_LOG_DEBUG, and NS_LOG_FUNCTION.

Referenced by EnterDrain(), EnterProbeBW(), EnterProbeRTT(), and EnterStartup().

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◆ SetCwnd()

void ns3::TcpBbr::SetCwnd	(	Ptr< TcpSocketState >	tcb,
		const TcpRateOps::TcpRateSample &	rs
	)

protected

Updates congestion window based on the network model.

Parameters

tcb	the socket state.
rs	rate sample

Definition at line 563 of file tcp-bbr.cc.

References ns3::TcpSocketState::CA_RECOVERY, ns3::TcpRateOps::TcpRateSample::m_ackedSacked, m_isPipeFilled, m_minPipeCwnd, m_targetCWnd, ModulateCwndForProbeRTT(), ModulateCwndForRecovery(), NS_LOG_FUNCTION, and UpdateTargetCwnd().

Referenced by UpdateControlParameters().

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◆ SetPacingRate()

void ns3::TcpBbr::SetPacingRate	(	Ptr< TcpSocketState >	tcb,
		double	gain
	)

protected

Updates pacing rate based on network model.

Parameters

tcb	the socket state.
gain	pacing gain.

Definition at line 219 of file tcp-bbr.cc.

References ns3::WindowedFilter< T, Compare, TimeT, TimeDeltaT >::GetBest(), ns3::DataRate::GetBitRate(), InitPacingRate(), m_hasSeenRtt, m_isPipeFilled, m_maxBwFilter, ns3::Time::Max(), and NS_LOG_FUNCTION.

Referenced by CwndEvent(), HandleRestartFromIdle(), and UpdateControlParameters().

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◆ SetSendQuantum()

void ns3::TcpBbr::SetSendQuantum ( Ptr< TcpSocketState > tcb )

protected

Updates send quantum based on the network model.

Parameters

tcb	the socket state.

Definition at line 462 of file tcp-bbr.cc.

References m_sendQuantum, and NS_LOG_FUNCTION.

Referenced by UpdateControlParameters().

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◆ SetStream()

void ns3::TcpBbr::SetStream ( uint32_t stream )

virtual

Assign a fixed random variable stream number to the random variables used by this model.

Parameters

stream first stream index to use

Definition at line 142 of file tcp-bbr.cc.

References m_uv, NS_LOG_FUNCTION, and ns3::RandomVariableStream::SetStream().

Referenced by GetTypeId().

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◆ UpdateAckAggregation()

void ns3::TcpBbr::UpdateAckAggregation	(	Ptr< TcpSocketState >	tcb,
		const TcpRateOps::TcpRateSample &	rs
	)

protected

Estimates max degree of aggregation.

Parameters

tcb	the socket state.
rs	rate sample.

Definition at line 491 of file tcp-bbr.cc.

References ns3::WindowedFilter< T, Compare, TimeT, TimeDeltaT >::GetBest(), ns3::DataRate::GetBitRate(), ns3::Time::GetSeconds(), ns3::TcpRateOps::TcpRateSample::m_ackedSacked, m_ackEpochAcked, m_ackEpochAckedResetThresh, m_ackEpochTime, ns3::TcpRateOps::TcpRateSample::m_delivered, m_extraAcked, m_extraAckedGain, m_extraAckedIdx, m_extraAckedWinRtt, m_extraAckedWinRttLength, m_maxBwFilter, m_roundStart, and ns3::Simulator::Now().

Referenced by UpdateModelAndState().

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◆ UpdateBtlBw()

void ns3::TcpBbr::UpdateBtlBw	(	Ptr< TcpSocketState >	tcb,
		const TcpRateOps::TcpRateSample &	rs
	)

protected

Updates maximum bottleneck.

Parameters

tcb	the socket state.
rs	rate sample.

Definition at line 614 of file tcp-bbr.cc.

References ns3::WindowedFilter< T, Compare, TimeT, TimeDeltaT >::GetBest(), ns3::TcpRateOps::TcpRateSample::m_deliveryRate, ns3::TcpRateOps::TcpRateSample::m_isAppLimited, m_maxBwFilter, m_roundCount, NS_LOG_FUNCTION, ns3::WindowedFilter< T, Compare, TimeT, TimeDeltaT >::Update(), and UpdateRound().

Referenced by UpdateModelAndState().

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◆ UpdateControlParameters()

void ns3::TcpBbr::UpdateControlParameters	(	Ptr< TcpSocketState >	tcb,
		const TcpRateOps::TcpRateSample &	rs
	)

protected

Updates control parameters congestion windowm, pacing rate, send quantum.

Parameters

tcb	the socket state.
rs	rate sample.

Definition at line 645 of file tcp-bbr.cc.

References m_pacingGain, NS_LOG_FUNCTION, SetCwnd(), SetPacingRate(), and SetSendQuantum().

Referenced by CongControl().

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◆ UpdateModelAndState()

void ns3::TcpBbr::UpdateModelAndState	(	Ptr< TcpSocketState >	tcb,
		const TcpRateOps::TcpRateSample &	rs
	)

protected

Updates BBR network model (Maximum bandwidth and minimum RTT).

Parameters

tcb	the socket state.
rs	rate sample.

Definition at line 632 of file tcp-bbr.cc.

References CheckCyclePhase(), CheckDrain(), CheckFullPipe(), CheckProbeRTT(), NS_LOG_FUNCTION, UpdateAckAggregation(), UpdateBtlBw(), and UpdateRTprop().

Referenced by CongControl().

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◆ UpdateRound()

void ns3::TcpBbr::UpdateRound	(	Ptr< TcpSocketState >	tcb,
		const TcpRateOps::TcpRateSample &	rs
	)

protected

Updates round counting related variables.

Parameters

tcb	the socket state.
rs	rate sample.

Definition at line 597 of file tcp-bbr.cc.

References m_delivered, m_nextRoundDelivered, m_packetConservation, ns3::TcpRateOps::TcpRateSample::m_priorDelivered, m_roundCount, m_roundStart, and NS_LOG_FUNCTION.

Referenced by UpdateBtlBw().

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◆ UpdateRTprop()

void ns3::TcpBbr::UpdateRTprop ( Ptr< TcpSocketState > tcb )

protected

Updates minimum RTT.

Parameters

tcb	the socket state.

Definition at line 355 of file tcp-bbr.cc.

References m_rtProp, m_rtPropExpired, m_rtPropFilterLen, m_rtPropStamp, ns3::Simulator::Now(), NS_LOG_FUNCTION, and ns3::Seconds().

Referenced by UpdateModelAndState().

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◆ UpdateTargetCwnd()

void ns3::TcpBbr::UpdateTargetCwnd ( Ptr< TcpSocketState > tcb )

protected

Updates target congestion window.

Parameters

tcb	the socket state.

Definition at line 469 of file tcp-bbr.cc.

References AckAggregationCwnd(), InFlight(), m_cWndGain, m_targetCWnd, and NS_LOG_FUNCTION.

Referenced by SetCwnd().

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Friends And Related Function Documentation

◆ TcpBbrCheckGainValuesTest

friend class TcpBbrCheckGainValuesTest

friend

TcpBbrCheckGainValuesTest friend class (for tests).

Definition at line 121 of file tcp-bbr.h.

Member Data Documentation

◆ BbrModeName

const char *const ns3::TcpBbr::BbrModeName

static

Initial value:

= {
    "BBR_STARTUP",
    "BBR_DRAIN",
    "BBR_PROBE_BW",
    "BBR_PROBE_RTT",
}

Literal names of BBR mode for use in log messages.

Definition at line 95 of file tcp-bbr.h.

Referenced by SetBbrState().

◆ GAIN_CYCLE_LENGTH

const uint8_t ns3::TcpBbr::GAIN_CYCLE_LENGTH = 8

static

The number of phases in the BBR ProbeBW gain cycle.

Definition at line 51 of file tcp-bbr.h.

Referenced by AdvanceCyclePhase(), and EnterProbeBW().

◆ m_ackEpochAcked

uint32_t ns3::TcpBbr::m_ackEpochAcked {0}

private

Bytes ACked in sampling epoch.

Definition at line 403 of file tcp-bbr.h.

Referenced by CongestionStateSet(), CwndEvent(), and UpdateAckAggregation().

◆ m_ackEpochAckedResetThresh

uint32_t ns3::TcpBbr::m_ackEpochAckedResetThresh

private

Initial value:

{

1 << 17}

Max allowed val for m_ackEpochAcked, after which sampling epoch is reset.

Definition at line 399 of file tcp-bbr.h.

Referenced by GetTypeId(), and UpdateAckAggregation().

◆ m_ackEpochTime

Time ns3::TcpBbr::m_ackEpochTime {Seconds(0)}

private

Starting of ACK sampling epoch time.

Definition at line 402 of file tcp-bbr.h.

Referenced by CongestionStateSet(), CwndEvent(), and UpdateAckAggregation().

◆ m_appLimited

uint32_t ns3::TcpBbr::m_appLimited

private

Initial value:

{

0}

The index of the last transmitted packet marked as application-limited.

Definition at line 391 of file tcp-bbr.h.

Referenced by CwndEvent(), and HandleProbeRTT().

◆ m_bandwidthWindowLength

uint32_t ns3::TcpBbr::m_bandwidthWindowLength {0}

private

A constant specifying the length of the BBR.BtlBw max filter window, default 10 packet-timed round trips.

Definition at line 353 of file tcp-bbr.h.

Referenced by GetTypeId(), and InitPacingRate().

◆ m_cWndGain

double ns3::TcpBbr::m_cWndGain {0}

private

The dynamic congestion window gain factor.

Definition at line 356 of file tcp-bbr.h.

Referenced by EnterDrain(), EnterProbeBW(), EnterProbeRTT(), EnterStartup(), GetCwndGain(), and UpdateTargetCwnd().

◆ m_cycleIndex

uint32_t ns3::TcpBbr::m_cycleIndex {0}

private

Current index of gain cycle.

Definition at line 382 of file tcp-bbr.h.

Referenced by AdvanceCyclePhase(), EnterProbeBW(), and InFlight().

◆ m_cycleStamp

Time ns3::TcpBbr::m_cycleStamp {Seconds(0)}

private

Last time gain cycle updated.

Definition at line 381 of file tcp-bbr.h.

Referenced by AdvanceCyclePhase(), and IsNextCyclePhase().

◆ m_delivered

uint64_t ns3::TcpBbr::m_delivered {0}

private

The total amount of data in bytes delivered so far.

Definition at line 390 of file tcp-bbr.h.

Referenced by CongControl(), HandleProbeRTT(), and UpdateRound().

◆ m_extraAcked

uint32_t ns3::TcpBbr::m_extraAcked[2] {0, 0}

private

Maximum excess data acked in epoch.

Definition at line 396 of file tcp-bbr.h.

Referenced by AckAggregationCwnd(), CongestionStateSet(), and UpdateAckAggregation().

◆ m_extraAckedGain

uint32_t ns3::TcpBbr::m_extraAckedGain {1}

private

Gain factor for adding extra ack to cwnd.

Definition at line 395 of file tcp-bbr.h.

Referenced by AckAggregationCwnd(), and UpdateAckAggregation().

◆ m_extraAckedIdx

uint32_t ns3::TcpBbr::m_extraAckedIdx {0}

private

Current index in extra acked array.

Definition at line 401 of file tcp-bbr.h.

Referenced by CongestionStateSet(), and UpdateAckAggregation().

◆ m_extraAckedWinRtt

uint32_t ns3::TcpBbr::m_extraAckedWinRtt {0}

private

Age of extra acked in rtt.

Definition at line 397 of file tcp-bbr.h.

Referenced by CongestionStateSet(), and UpdateAckAggregation().

◆ m_extraAckedWinRttLength

uint32_t ns3::TcpBbr::m_extraAckedWinRttLength {5}

private

Window length of extra acked window.

Definition at line 398 of file tcp-bbr.h.

Referenced by GetTypeId(), and UpdateAckAggregation().

◆ m_fullBandwidth

DataRate ns3::TcpBbr::m_fullBandwidth {0}

private

Value of full bandwidth recorded.

Definition at line 374 of file tcp-bbr.h.

Referenced by CheckFullPipe(), and InitFullPipe().

◆ m_fullBandwidthCount

uint32_t ns3::TcpBbr::m_fullBandwidthCount {0}

private

Count of full bandwidth recorded consistently.

Definition at line 375 of file tcp-bbr.h.

Referenced by CheckFullPipe(), and InitFullPipe().

◆ m_hasSeenRtt

bool ns3::TcpBbr::m_hasSeenRtt {false}

private

Have we seen RTT sample yet?

Definition at line 404 of file tcp-bbr.h.

Referenced by InitPacingRate(), and SetPacingRate().

◆ m_highGain

double ns3::TcpBbr::m_highGain {0}

private

A constant specifying highest gain factor, default is 2.89.

Definition at line 357 of file tcp-bbr.h.

Referenced by EnterDrain(), EnterStartup(), and GetTypeId().

◆ m_idleRestart

bool ns3::TcpBbr::m_idleRestart {false}

private

When restarting from idle, set it true.

Definition at line 372 of file tcp-bbr.h.

Referenced by CheckProbeRTT(), CwndEvent(), and HandleRestartFromIdle().

◆ m_isInitialized

bool ns3::TcpBbr::m_isInitialized {false}

private

Set to true after first time initializtion variables.

Definition at line 388 of file tcp-bbr.h.

Referenced by CongestionStateSet().

◆ m_isPipeFilled

bool ns3::TcpBbr::m_isPipeFilled {false}

private

A boolean that records whether BBR has filled the pipe.

Definition at line 358 of file tcp-bbr.h.

Referenced by AckAggregationCwnd(), CheckDrain(), CheckFullPipe(), ExitProbeRTT(), InitFullPipe(), SetCwnd(), and SetPacingRate().

◆ m_maxBwFilter

MaxBandwidthFilter_t ns3::TcpBbr::m_maxBwFilter

private

Maximum bandwidth filter.

Definition at line 352 of file tcp-bbr.h.

Referenced by AckAggregationCwnd(), CheckFullPipe(), InFlight(), InitPacingRate(), SetPacingRate(), UpdateAckAggregation(), and UpdateBtlBw().

◆ m_minPipeCwnd

uint32_t ns3::TcpBbr::m_minPipeCwnd

private

Initial value:

{

0}

The minimal congestion window value BBR tries to target, default 4 Segment size.

Definition at line 359 of file tcp-bbr.h.

Referenced by CongestionStateSet(), HandleProbeRTT(), ModulateCwndForProbeRTT(), and SetCwnd().

◆ m_nextRoundDelivered

uint32_t ns3::TcpBbr::m_nextRoundDelivered {0}

private

Denotes the end of a packet-timed round trip.

Definition at line 363 of file tcp-bbr.h.

Referenced by HandleProbeRTT(), InitRoundCounting(), and UpdateRound().

◆ m_pacingGain

double ns3::TcpBbr::m_pacingGain {0}

private

The dynamic pacing gain factor.

Definition at line 355 of file tcp-bbr.h.

Referenced by AdvanceCyclePhase(), EnterDrain(), EnterProbeBW(), EnterProbeRTT(), EnterStartup(), GetPacingGain(), InitPacingRate(), IsNextCyclePhase(), and UpdateControlParameters().

◆ m_packetConservation

bool ns3::TcpBbr::m_packetConservation {false}

private

Enable/Disable packet conservation mode.

Definition at line 370 of file tcp-bbr.h.

Referenced by CongestionStateSet(), CwndEvent(), ModulateCwndForRecovery(), and UpdateRound().

◆ m_priorCwnd

uint32_t ns3::TcpBbr::m_priorCwnd {0}

private

The last-known good congestion window.

Definition at line 371 of file tcp-bbr.h.

Referenced by CongestionStateSet(), RestoreCwnd(), and SaveCwnd().

◆ m_probeRtPropStamp

Time ns3::TcpBbr::m_probeRtPropStamp

private

Initial value:

{

Seconds(0)}

ns3::Seconds

Time Seconds(double value)

Construct a Time in the indicated unit.

Definition: nstime.h:1326

The wall clock time at which the current BBR.RTProp sample was obtained.

Definition at line 366 of file tcp-bbr.h.

◆ m_probeRttDoneStamp

Time ns3::TcpBbr::m_probeRttDoneStamp {Seconds(0)}

private

Time to exit from BBR_PROBE_RTT state.

Definition at line 368 of file tcp-bbr.h.

Referenced by CheckProbeRTT(), CwndEvent(), and HandleProbeRTT().

◆ m_probeRttDuration

Time ns3::TcpBbr::m_probeRttDuration {MilliSeconds(200)}

private

A constant specifying the minimum duration for which ProbeRTT state, default 200 millisecs.

Definition at line 364 of file tcp-bbr.h.

Referenced by GetTypeId(), and HandleProbeRTT().

◆ m_probeRttRoundDone

bool ns3::TcpBbr::m_probeRttRoundDone {false}

private

True when it is time to exit BBR_PROBE_RTT.

Definition at line 369 of file tcp-bbr.h.

Referenced by CwndEvent(), and HandleProbeRTT().

◆ m_roundCount

uint32_t ns3::TcpBbr::m_roundCount {0}

private

Count of packet-timed round trips.

Definition at line 361 of file tcp-bbr.h.

Referenced by InitRoundCounting(), UpdateBtlBw(), and UpdateRound().

◆ m_roundStart

bool ns3::TcpBbr::m_roundStart {false}

private

A boolean that BBR sets to true once per packet-timed round trip.

Definition at line 362 of file tcp-bbr.h.

Referenced by CheckFullPipe(), CongestionStateSet(), HandleProbeRTT(), InitRoundCounting(), UpdateAckAggregation(), and UpdateRound().

◆ m_rtProp

Time ns3::TcpBbr::m_rtProp

private

Initial value:

{

Time::Max()}

ns3::Time::Max

static Time Max()

Maximum representable Time Not to be confused with Max(Time,Time).

Definition: nstime.h:297

Estimated two-way round-trip propagation delay of the path, estimated from the windowed minimum recent round-trip delay sample.

Definition at line 376 of file tcp-bbr.h.

Referenced by CongestionStateSet(), InFlight(), IsNextCyclePhase(), and UpdateRTprop().

◆ m_rtPropExpired

bool ns3::TcpBbr::m_rtPropExpired {false}

private

A boolean recording whether the BBR.RTprop has expired.

Definition at line 383 of file tcp-bbr.h.

Referenced by CheckProbeRTT(), and UpdateRTprop().

◆ m_rtPropFilterLen

Time ns3::TcpBbr::m_rtPropFilterLen {Seconds(10)}

private

A constant specifying the length of the RTProp min filter window, default 10 secs.

Definition at line 384 of file tcp-bbr.h.

Referenced by GetTypeId(), and UpdateRTprop().

◆ m_rtPropStamp

Time ns3::TcpBbr::m_rtPropStamp

private

Initial value:

{

Seconds(0)}

The wall clock time at which the current BBR.RTProp sample was obtained.

Definition at line 386 of file tcp-bbr.h.

Referenced by CongestionStateSet(), CwndEvent(), HandleProbeRTT(), and UpdateRTprop().

◆ m_sendQuantum

uint32_t ns3::TcpBbr::m_sendQuantum

private

Initial value:

{

0}

The maximum size of a data aggregate scheduled and transmitted together.

Definition at line 379 of file tcp-bbr.h.

Referenced by CongestionStateSet(), InFlight(), and SetSendQuantum().

◆ m_state

BbrMode_t ns3::TcpBbr::m_state {BbrMode_t::BBR_STARTUP}

private

Current state of BBR state machine.

Definition at line 351 of file tcp-bbr.h.

Referenced by CheckCyclePhase(), CheckDrain(), CheckProbeRTT(), CwndEvent(), GetBbrState(), HandleRestartFromIdle(), InFlight(), ModulateCwndForProbeRTT(), SaveCwnd(), and SetBbrState().

◆ m_targetCWnd

uint32_t ns3::TcpBbr::m_targetCWnd {0}

private

Target value for congestion window, adapted to the estimated BDP.

Definition at line 373 of file tcp-bbr.h.

Referenced by CongestionStateSet(), SetCwnd(), and UpdateTargetCwnd().

◆ m_txItemDelivered

uint32_t ns3::TcpBbr::m_txItemDelivered

private

Initial value:

{

0}

The number of bytes already delivered at the time of new packet transmission.

Definition at line 393 of file tcp-bbr.h.

Referenced by CongControl().

◆ m_uv

Ptr<UniformRandomVariable> ns3::TcpBbr::m_uv {nullptr}

private

Uniform Random Variable.

Definition at line 389 of file tcp-bbr.h.

Referenced by TcpBbr(), EnterProbeBW(), and SetStream().

◆ PACING_GAIN_CYCLE

const double ns3::TcpBbr::PACING_GAIN_CYCLE = {5.0 / 4, 3.0 / 4, 1, 1, 1, 1, 1, 1}

static

BBR uses an eight-phase cycle with the given pacing_gain value in the BBR ProbeBW gain cycle.

Definition at line 57 of file tcp-bbr.h.

Referenced by AdvanceCyclePhase().

The documentation for this class was generated from the following files:

src/internet/model/tcp-bbr.h
src/internet/model/tcp-bbr.cc

Public Types

Public Member Functions

Static Public Member Functions

Static Public Attributes

Protected Member Functions

Private Attributes

Related Functions

Additional Inherited Members

Detailed Description

Config Paths

Attributes

Member Typedef Documentation

◆ MaxBandwidthFilter_t

Member Enumeration Documentation

◆ BbrMode_t

Constructor & Destructor Documentation

◆ TcpBbr() [1/2]

◆ TcpBbr() [2/2]

Member Function Documentation

◆ AckAggregationCwnd()

◆ AdvanceCyclePhase()

◆ CheckCyclePhase()

◆ CheckDrain()

◆ CheckFullPipe()

◆ CheckProbeRTT()

◆ CongControl()

◆ CongestionStateSet()

◆ CwndEvent()

◆ EnterDrain()

◆ EnterProbeBW()

◆ EnterProbeRTT()

◆ EnterStartup()

◆ ExitProbeRTT()

◆ Fork()

◆ GetBbrState()

◆ GetCwndGain()

◆ GetName()

◆ GetPacingGain()

◆ GetSsThresh()

◆ GetTypeId()

◆ HandleProbeRTT()

◆ HandleRestartFromIdle()

◆ HasCongControl()

◆ InFlight()

◆ InitFullPipe()

◆ InitPacingRate()

◆ InitRoundCounting()

◆ IsNextCyclePhase()

◆ ModulateCwndForProbeRTT()

◆ ModulateCwndForRecovery()

◆ RestoreCwnd()

◆ SaveCwnd()

◆ SetBbrState()

◆ SetCwnd()

◆ SetPacingRate()

◆ SetSendQuantum()

◆ SetStream()

◆ UpdateAckAggregation()

◆ UpdateBtlBw()

◆ UpdateControlParameters()

◆ UpdateModelAndState()

◆ UpdateRound()

◆ UpdateRTprop()

◆ UpdateTargetCwnd()

Friends And Related Function Documentation

◆ TcpBbrCheckGainValuesTest

Member Data Documentation

◆ BbrModeName

◆ GAIN_CYCLE_LENGTH

◆ m_ackEpochAcked

◆ m_ackEpochAckedResetThresh

◆ m_ackEpochTime

◆ m_appLimited

◆ m_bandwidthWindowLength

◆ m_cWndGain

◆ m_cycleIndex

◆ m_cycleStamp

◆ m_delivered

◆ m_extraAcked

◆ m_extraAckedGain