A Discrete-Event Network Simulator
API
ns3::TcpWestwood Class Reference

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 (void)
 
 TcpWestwood (const TcpWestwood &sock)
 Copy constructor. More...
 
virtual ~TcpWestwood (void)
 
virtual Ptr< TcpCongestionOpsFork ()
 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...
 
- 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<typename T >
Ptr< T > GetObject (void) const
 Get a pointer to the requested aggregated Object. More...
 
template<typename T >
Ptr< T > GetObject (TypeId tid) const
 Get a pointer to the requested aggregated Object by TypeId. 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)
 Copy constructor. More...
 
uint32_t GetReferenceCount (void) const
 Get the reference count of the object. More...
 
SimpleRefCountoperator= (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< double > 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...
 
double m_lastBW
 Last bandwidth sample after being filtered. More...
 
double 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...
 

Detailed Description

An implementation of TCP Westwood and Westwood+.


Introspection did not find any typical Config paths.

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+).


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

Size of this type is 112 bytes (on a 64-bit architecture).

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

Member Enumeration Documentation

◆ FilterType

Filter type (None or Tustin)

Enumerator
NONE 
TUSTIN 

Definition at line 96 of file tcp-westwood.h.

◆ ProtocolType

Protocol variant (Westwood or Westwood+)

Enumerator
WESTWOOD 
WESTWOODPLUS 

Definition at line 87 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
sockthe object to copy

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

References NS_LOG_FUNCTION, and NS_LOG_LOGIC().

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◆ ~TcpWestwood()

ns3::TcpWestwood::~TcpWestwood ( void  )
virtual

Definition at line 91 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]rttthe RTT estimation.
[in]tcbthe socket state.

Definition at line 126 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_lastBW, m_lastSampleBW, m_pType, ns3::TcpSocketState::m_segmentSize, NONE, NS_ASSERT, NS_LOG_FUNCTION, NS_LOG_LOGIC(), TUSTIN, 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 174 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
tcbinternal congestion state
bytesInFlighttotal bytes in flight
Returns
Slow start threshold

Reimplemented from ns3::TcpNewReno.

Definition at line 161 of file tcp-westwood.cc.

References m_currentBW, max, NS_LOG_LOGIC(), and NS_UNUSED.

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◆ 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
tcbinternal congestion state
segmentsAckedcount of segments acked
rttlast rtt

Reimplemented from ns3::TcpCongestionOps.

Definition at line 96 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]ackedthe 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 133 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 135 of file tcp-westwood.h.

Referenced by PktsAcked().

◆ m_currentBW

TracedValue<double> ns3::TcpWestwood::m_currentBW
protected

Current value of the estimated BW.

Definition at line 127 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 131 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 134 of file tcp-westwood.h.

Referenced by EstimateBW(), and PktsAcked().

◆ m_lastBW

double ns3::TcpWestwood::m_lastBW
protected

Last bandwidth sample after being filtered.

Definition at line 129 of file tcp-westwood.h.

Referenced by EstimateBW().

◆ m_lastSampleBW

double ns3::TcpWestwood::m_lastSampleBW
protected

Last bandwidth sample.

Definition at line 128 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 130 of file tcp-westwood.h.

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


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