An implementation of TCP Westwood and Westwood+. More...

#include "tcp-westwood.h"

Inheritance diagram for ns3::TcpWestwood:

Collaboration diagram for ns3::TcpWestwood:

Public Types
enum	FilterType { NONE , TUSTIN }
	Filter type (None or Tustin) More...

enum	ProtocolType { WESTWOOD , WESTWOODPLUS }
	Protocol variant (Westwood or Westwood+) More...

Public Member Functions
	TcpWestwood (const TcpWestwood &sock)
	Copy constructor. More...

	TcpWestwood (void)

virtual	~TcpWestwood (void)

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

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

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

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

	TcpNewReno (const TcpNewReno &sock)
	Copy constructor. More...

	~TcpNewReno ()

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

virtual void	IncreaseWindow (Ptr< TcpSocketState > tcb, uint32_t segmentsAcked)
	Try to increase the cWnd following the NewReno specification. More...

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

	TcpCongestionOps (const TcpCongestionOps &other)
	Copy constructor. More...

virtual	~TcpCongestionOps ()

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. More...

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

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

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

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

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

virtual	~Object ()
	Destructor. More...

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

void	Dispose (void)
	Dispose of this Object. More...

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

virtual TypeId	GetInstanceTypeId (void) const
	Get the most derived TypeId for this Object. More...

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

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

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

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

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

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

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

	SimpleRefCount (const SimpleRefCount &o[[maybe_unused]])
	Copy constructor. More...

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

SimpleRefCount &	operator= ([[maybe_unused]] const SimpleRefCount &o)
	Assignment operator. More...

void	Ref (void) const
	Increment the reference count. More...

void	Unref (void) const
	Decrement the reference count. More...

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Protected Attributes
uint32_t	m_ackedSegments
	The number of segments ACKed between RTTs. More...

EventId	m_bwEstimateEvent
	The BW estimation event for Westwood+. More...

TracedValue< DataRate >	m_currentBW
	Current value of the estimated BW. More...

enum FilterType	m_fType
	0 for none, 1 for Tustin More...

bool	m_IsCount
	Start keeping track of m_ackedSegments for Westwood+ if TRUE. More...

Time	m_lastAck
	The last ACK time. More...

DataRate	m_lastBW
	Last bandwidth sample after being filtered. More...

DataRate	m_lastSampleBW
	Last bandwidth sample. More...

enum ProtocolType	m_pType
	0 for Westwood, 1 for Westwood+ More...

Private Member Functions
void	EstimateBW (const Time &rtt, Ptr< TcpSocketState > tcb)
	Estimate the network's bandwidth. More...

void	UpdateAckedSegments (int acked)
	Update the total number of acknowledged packets during the current RTT. More...

Additional Inherited Members
Protected Member Functions inherited from ns3::TcpNewReno
virtual void	CongestionAvoidance (Ptr< TcpSocketState > tcb, uint32_t segmentsAcked)
	NewReno congestion avoidance. More...

virtual uint32_t	SlowStart (Ptr< TcpSocketState > tcb, uint32_t segmentsAcked)
	Tcp NewReno slow start algorithm. More...

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

virtual void	DoDispose (void)
	Destructor implementation. More...

virtual void	DoInitialize (void)
	Initialize() implementation. More...

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

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

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

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

Detailed Description

An implementation of TCP Westwood and Westwood+.

Westwood and Westwood+ employ the AIAD (Additive Increase/Adaptive Decrease) congestion control paradigm. When a congestion episode happens, instead of halving the cwnd, these protocols try to estimate the network's bandwidth and use the estimated value to adjust the cwnd. While Westwood performs the bandwidth sampling every ACK reception, Westwood+ samples the bandwidth every RTT.

The two main methods in the implementation are the CountAck (const TCPHeader&) and the EstimateBW (int, const, Time). The CountAck method calculates the number of acknowledged segments on the receipt of an ACK. The EstimateBW estimates the bandwidth based on the value returned by CountAck and the sampling interval (last ACK inter-arrival time for Westwood and last RTT for Westwood+).

WARNING: this TCP model lacks validation and regression tests; use with caution.

Config Paths

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

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

Attributes

FilterType: Use this to choose no filter or Tustin's approximation filter
- Set with class: ns3::EnumValue
- Underlying type:
- Initial value: Tustin
- Flags: construct write read
ProtocolType: Use this to let the code run as Westwood or WestwoodPlus
- Set with class: ns3::EnumValue
- Underlying type:
- Initial value: Westwood
- Flags: construct write read

TraceSources

EstimatedBW: The estimated bandwidth
Callback signature: ns3::TracedValueCallback::DataRate

Size of this type is 128 bytes (on a 64-bit architecture).

Definition at line 66 of file tcp-westwood.h.

Member Enumeration Documentation

◆ FilterType

enum ns3::TcpWestwood::FilterType

Filter type (None or Tustin)

Enumerator
NONE
TUSTIN

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

◆ ProtocolType

enum ns3::TcpWestwood::ProtocolType

Protocol variant (Westwood or Westwood+)

Enumerator
WESTWOOD
WESTWOODPLUS

Definition at line 86 of file tcp-westwood.h.

Constructor & Destructor Documentation

◆ TcpWestwood() [1/2]

ns3::TcpWestwood::TcpWestwood ( void )

Definition at line 67 of file tcp-westwood.cc.

References NS_LOG_FUNCTION.

◆ TcpWestwood() [2/2]

ns3::TcpWestwood::TcpWestwood ( const TcpWestwood & sock )

Copy constructor.

Parameters

sock	the object to copy

Definition at line 79 of file tcp-westwood.cc.

References NS_LOG_FUNCTION, and NS_LOG_LOGIC.

◆ ~TcpWestwood()

ns3::TcpWestwood::~TcpWestwood ( void )

virtual

Definition at line 92 of file tcp-westwood.cc.

Member Function Documentation

◆ EstimateBW()

void ns3::TcpWestwood::EstimateBW	(	const Time &	rtt,
		Ptr< TcpSocketState >	tcb
	)

private

Estimate the network's bandwidth.

Parameters

[in]	rtt	the RTT estimation.
[in]	tcb	the socket state.

Definition at line 127 of file tcp-westwood.cc.

References sample-rng-plot::alpha, ns3::Time::GetSeconds(), ns3::Time::IsZero(), m_ackedSegments, m_currentBW, m_fType, m_IsCount, m_lastAck, m_lastBW, m_lastSampleBW, m_pType, ns3::TcpSocketState::m_segmentSize, ns3::Simulator::Now(), NS_ABORT_MSG_IF, NS_ASSERT, NS_LOG_FUNCTION, NS_LOG_LOGIC, TUSTIN, WESTWOOD, and WESTWOODPLUS.

Referenced by PktsAcked().

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◆ Fork()

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

virtual

Copy the congestion control algorithm across sockets.

Returns: a pointer of the copied object

Reimplemented from ns3::TcpNewReno.

Definition at line 182 of file tcp-westwood.cc.

◆ GetSsThresh()

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

virtual

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 implementator 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

Reimplemented from ns3::TcpNewReno.

Definition at line 169 of file tcp-westwood.cc.

References m_currentBW, max, and NS_LOG_LOGIC.

◆ GetTypeId()

TypeId ns3::TcpWestwood::GetTypeId ( void )

static

Get the type ID.

Returns: the object TypeId

Definition at line 47 of file tcp-westwood.cc.

References m_currentBW, m_fType, m_pType, ns3::MakeEnumAccessor(), ns3::MakeEnumChecker(), ns3::MakeTraceSourceAccessor(), NONE, ns3::TypeId::SetParent(), TUSTIN, WESTWOOD, and WESTWOODPLUS.

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◆ PktsAcked()

void ns3::TcpWestwood::PktsAcked	(	Ptr< TcpSocketState >	tcb,
		uint32_t	segmentsAcked,
		const Time &	rtt
	)

virtual

Timing information on received ACK.

The function is called every time an ACK is received (only one time also for cumulative ACKs) and contains timing information. It is optional (congestion controls need not implement it) and the default implementation does nothing.

Parameters

tcb	internal congestion state
segmentsAcked	count of segments acked
rtt	last rtt

Reimplemented from ns3::TcpCongestionOps.

Definition at line 97 of file tcp-westwood.cc.

References ns3::EventId::Cancel(), EstimateBW(), ns3::Time::IsZero(), m_ackedSegments, m_bwEstimateEvent, m_IsCount, m_pType, NS_LOG_FUNCTION, NS_LOG_WARN, ns3::Simulator::Schedule(), WESTWOOD, and WESTWOODPLUS.

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◆ UpdateAckedSegments()

void ns3::TcpWestwood::UpdateAckedSegments ( int acked )

private

Update the total number of acknowledged packets during the current RTT.

Parameters

[in] acked the number of packets the currently received ACK acknowledges

Member Data Documentation

◆ m_ackedSegments

uint32_t ns3::TcpWestwood::m_ackedSegments

protected

The number of segments ACKed between RTTs.

Definition at line 132 of file tcp-westwood.h.

Referenced by EstimateBW(), and PktsAcked().

◆ m_bwEstimateEvent

EventId ns3::TcpWestwood::m_bwEstimateEvent

protected

The BW estimation event for Westwood+.

Definition at line 134 of file tcp-westwood.h.

Referenced by PktsAcked().

◆ m_currentBW

TracedValue<DataRate> ns3::TcpWestwood::m_currentBW

protected

Current value of the estimated BW.

Definition at line 126 of file tcp-westwood.h.

Referenced by EstimateBW(), GetSsThresh(), and GetTypeId().

◆ m_fType

enum FilterType ns3::TcpWestwood::m_fType

protected

0 for none, 1 for Tustin

Definition at line 128 of file tcp-westwood.h.

Referenced by EstimateBW(), and GetTypeId().

◆ m_IsCount

bool ns3::TcpWestwood::m_IsCount

protected

Start keeping track of m_ackedSegments for Westwood+ if TRUE.

Definition at line 133 of file tcp-westwood.h.

Referenced by EstimateBW(), and PktsAcked().

◆ m_lastAck

Time ns3::TcpWestwood::m_lastAck

protected

The last ACK time.

Definition at line 135 of file tcp-westwood.h.

Referenced by EstimateBW().

◆ m_lastBW

DataRate ns3::TcpWestwood::m_lastBW

protected

Last bandwidth sample after being filtered.

Definition at line 128 of file tcp-westwood.h.

Referenced by EstimateBW().

◆ m_lastSampleBW

DataRate ns3::TcpWestwood::m_lastSampleBW

protected

Last bandwidth sample.

Definition at line 127 of file tcp-westwood.h.

Referenced by EstimateBW().

◆ m_pType

enum ProtocolType ns3::TcpWestwood::m_pType

protected

0 for Westwood, 1 for Westwood+

Definition at line 128 of file tcp-westwood.h.

Referenced by EstimateBW(), GetTypeId(), and PktsAcked().

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

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

Public Types

Public Member Functions

Static Public Member Functions

Protected Attributes

Private Member Functions

Additional Inherited Members

Detailed Description

Config Paths

Attributes

TraceSources

Member Enumeration Documentation

◆ FilterType

◆ ProtocolType

Constructor & Destructor Documentation

◆ TcpWestwood() [1/2]

◆ TcpWestwood() [2/2]

◆ ~TcpWestwood()

Member Function Documentation

◆ EstimateBW()

◆ Fork()

◆ GetSsThresh()

◆ GetTypeId()

◆ PktsAcked()

◆ UpdateAckedSegments()

Member Data Documentation

◆ m_ackedSegments

◆ m_bwEstimateEvent

◆ m_currentBW

◆ m_fType

◆ m_IsCount

◆ m_lastAck

◆ m_lastBW

◆ m_lastSampleBW

◆ m_pType