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ns3::TcpWestwoodPlus Class Reference

An implementation of TCP Westwood+. More...

#include "tcp-westwood-plus.h"

+ Inheritance diagram for ns3::TcpWestwoodPlus:
+ Collaboration diagram for ns3::TcpWestwoodPlus:

Public Types

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

Public Member Functions

 TcpWestwoodPlus ()
 
 TcpWestwoodPlus (const TcpWestwoodPlus &sock)
 Copy constructor.
 
 ~TcpWestwoodPlus () override
 
Ptr< TcpCongestionOpsFork () override
 Copy the congestion control algorithm across sockets.
 
uint32_t GetSsThresh (Ptr< const TcpSocketState > tcb, uint32_t bytesInFlight) override
 Get the slow start threshold after a loss event.
 
void PktsAcked (Ptr< TcpSocketState > tcb, uint32_t packetsAcked, const Time &rtt) override
 Timing information on received ACK.
 
- Public Member Functions inherited from ns3::TcpNewReno
 TcpNewReno ()
 
 TcpNewReno (const TcpNewReno &sock)
 Copy constructor.
 
 ~TcpNewReno () override
 
Ptr< TcpCongestionOpsFork () 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.
 
void IncreaseWindow (Ptr< TcpSocketState > tcb, uint32_t segmentsAcked) override
 Try to increase the cWnd following the NewReno specification.
 
- 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< TcpCongestionOpsFork ()=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< ObjectGetObject () 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< ObjectGetObject (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.
 
SimpleRefCountoperator= (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::TcpNewReno
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.
 

Protected Attributes

uint32_t m_ackedSegments
 The number of segments ACKed between RTTs.
 
EventId m_bwEstimateEvent
 The BW estimation event for Westwood+.
 
TracedValue< DataRatem_currentBW
 Current value of the estimated BW.
 
FilterType m_fType
 0 for none, 1 for Tustin
 
bool m_IsCount
 Start keeping track of m_ackedSegments for Westwood+ if TRUE.
 
Time m_lastAck
 The last ACK time.
 
DataRate m_lastBW
 Last bandwidth sample after being filtered.
 
DataRate m_lastSampleBW
 Last bandwidth sample.
 

Private Member Functions

void EstimateBW (const Time &rtt, Ptr< TcpSocketState > tcb)
 Estimate the network's bandwidth.
 
void UpdateAckedSegments (int acked)
 Update the total number of acknowledged packets during the current RTT.
 

Additional Inherited Members

- Protected Member Functions inherited from ns3::TcpNewReno
virtual void CongestionAvoidance (Ptr< TcpSocketState > tcb, uint32_t segmentsAcked)
 NewReno congestion avoidance.
 
virtual uint32_t SlowStart (Ptr< TcpSocketState > tcb, uint32_t segmentsAcked)
 Tcp NewReno slow start algorithm.
 
- 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.
 

Detailed Description

An implementation of TCP Westwood+.

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 RTT).

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

Config Paths

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

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

Attributes

TraceSources

Size of this type is 144 bytes (on a 64-bit architecture).

Definition at line 67 of file tcp-westwood-plus.h.

Member Enumeration Documentation

◆ FilterType

Filter type (None or Tustin)

Enumerator
NONE 
TUSTIN 

Definition at line 87 of file tcp-westwood-plus.h.

Constructor & Destructor Documentation

◆ TcpWestwoodPlus() [1/2]

ns3::TcpWestwoodPlus::TcpWestwoodPlus ( )

Definition at line 66 of file tcp-westwood-plus.cc.

References NS_LOG_FUNCTION.

◆ TcpWestwoodPlus() [2/2]

ns3::TcpWestwoodPlus::TcpWestwoodPlus ( const TcpWestwoodPlus sock)

Copy constructor.

Parameters
sockthe object to copy

Definition at line 78 of file tcp-westwood-plus.cc.

References NS_LOG_FUNCTION, and NS_LOG_LOGIC.

◆ ~TcpWestwoodPlus()

ns3::TcpWestwoodPlus::~TcpWestwoodPlus ( )
override

Definition at line 90 of file tcp-westwood-plus.cc.

Member Function Documentation

◆ EstimateBW()

void ns3::TcpWestwoodPlus::EstimateBW ( const Time rtt,
Ptr< TcpSocketState tcb 
)
private

Estimate the network's bandwidth.

Parameters
[in]rttthe RTT estimation.
[in]tcbthe socket state.

Definition at line 116 of file tcp-westwood-plus.cc.

References ns3::Time::GetSeconds(), ns3::Time::IsZero(), m_ackedSegments, m_currentBW, m_fType, m_IsCount, m_lastBW, m_lastSampleBW, NS_ASSERT, NS_LOG_FUNCTION, NS_LOG_LOGIC, and TUSTIN.

Referenced by PktsAcked().

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◆ Fork()

Ptr< TcpCongestionOps > ns3::TcpWestwoodPlus::Fork ( )
overridevirtual

Copy the congestion control algorithm across sockets.

Returns
a pointer of the copied object

Reimplemented from ns3::TcpNewReno.

Definition at line 156 of file tcp-westwood-plus.cc.

◆ GetSsThresh()

uint32_t ns3::TcpWestwoodPlus::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
tcbinternal congestion state
bytesInFlighttotal bytes in flight
Returns
Slow start threshold

Reimplemented from ns3::TcpNewReno.

Definition at line 145 of file tcp-westwood-plus.cc.

References m_currentBW, and NS_LOG_LOGIC.

◆ GetTypeId()

TypeId ns3::TcpWestwoodPlus::GetTypeId ( )
static

Get the type ID.

Returns
the object TypeId

Definition at line 46 of file tcp-westwood-plus.cc.

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

Referenced by TcpFastRetrTestSuite::TcpFastRetrTestSuite().

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◆ PktsAcked()

void ns3::TcpWestwoodPlus::PktsAcked ( Ptr< TcpSocketState tcb,
uint32_t  segmentsAcked,
const Time rtt 
)
overridevirtual

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
tcbinternal congestion state
segmentsAckedcount of segments acked
rttlast rtt

Reimplemented from ns3::TcpCongestionOps.

Definition at line 95 of file tcp-westwood-plus.cc.

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

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◆ UpdateAckedSegments()

void ns3::TcpWestwoodPlus::UpdateAckedSegments ( int  acked)
private

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

Parameters
[in]ackedthe number of packets the currently received ACK acknowledges

Member Data Documentation

◆ m_ackedSegments

uint32_t ns3::TcpWestwoodPlus::m_ackedSegments
protected

The number of segments ACKed between RTTs.

Definition at line 121 of file tcp-westwood-plus.h.

Referenced by EstimateBW(), and PktsAcked().

◆ m_bwEstimateEvent

EventId ns3::TcpWestwoodPlus::m_bwEstimateEvent
protected

The BW estimation event for Westwood+.

Definition at line 123 of file tcp-westwood-plus.h.

Referenced by PktsAcked().

◆ m_currentBW

TracedValue<DataRate> ns3::TcpWestwoodPlus::m_currentBW
protected

Current value of the estimated BW.

Definition at line 116 of file tcp-westwood-plus.h.

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

◆ m_fType

FilterType ns3::TcpWestwoodPlus::m_fType
protected

0 for none, 1 for Tustin

Definition at line 119 of file tcp-westwood-plus.h.

Referenced by EstimateBW(), and GetTypeId().

◆ m_IsCount

bool ns3::TcpWestwoodPlus::m_IsCount
protected

Start keeping track of m_ackedSegments for Westwood+ if TRUE.

Definition at line 122 of file tcp-westwood-plus.h.

Referenced by EstimateBW(), and PktsAcked().

◆ m_lastAck

Time ns3::TcpWestwoodPlus::m_lastAck
protected

The last ACK time.

Definition at line 124 of file tcp-westwood-plus.h.

◆ m_lastBW

DataRate ns3::TcpWestwoodPlus::m_lastBW
protected

Last bandwidth sample after being filtered.

Definition at line 118 of file tcp-westwood-plus.h.

Referenced by EstimateBW().

◆ m_lastSampleBW

DataRate ns3::TcpWestwoodPlus::m_lastSampleBW
protected

Last bandwidth sample.

Definition at line 117 of file tcp-westwood-plus.h.

Referenced by EstimateBW().


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