Implementation of the TCP Hybla algorithm. More...

#include "tcp-hybla.h"

Inheritance diagram for ns3::TcpHybla:

Collaboration diagram for ns3::TcpHybla:

Public Member Functions
	TcpHybla ()
	Create an unbound tcp socket.

	TcpHybla (const TcpHybla &sock)
	Copy constructor.

	~TcpHybla () override

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

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

void	PktsAcked (Ptr< TcpSocketState > tcb, uint32_t segmentsAcked, 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< 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.

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

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

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, bool permissive=false) 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.

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 Member Functions
void	CongestionAvoidance (Ptr< TcpSocketState > tcb, uint32_t segmentsAcked) override
	NewReno congestion avoidance.

uint32_t	SlowStart (Ptr< TcpSocketState > tcb, uint32_t segmentsAcked) override
	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.

Private Member Functions
void	RecalcParam (const Ptr< TcpSocketState > &tcb)
	Recalculate algorithm parameters.

Private Attributes
double	m_cWndCnt
	cWnd integer-to-float counter

TracedValue< double >	m_rho
	Rho parameter.

Time	m_rRtt
	Reference RTT.

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

Detailed Description

Implementation of the TCP Hybla algorithm.

The key idea behind TCP Hybla is to obtain for long RTT connections the same instantaneous transmission rate of a reference TCP connection with lower RTT. With analytical steps, it is shown that this goal can be achieved by modifying the time scale, in order for the throughput to be independent from the RTT. This independence is obtained through the use of a coefficient rho.

This coefficient is used to calculate both the slow start threshold and the congestion window when in slow start and in congestion avoidance, respectively.

More information: http://dl.acm.org/citation.cfm?id=2756518

Definition at line 36 of file tcp-hybla.h.

Constructor & Destructor Documentation

◆ TcpHybla() [1/2]

ns3::TcpHybla::TcpHybla ( )

Create an unbound tcp socket.

Definition at line 39 of file tcp-hybla.cc.

References NS_LOG_FUNCTION.

◆ TcpHybla() [2/2]

ns3::TcpHybla::TcpHybla ( const TcpHybla & sock )

Copy constructor.

Parameters

sock	the object to copy

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

References NS_LOG_FUNCTION.

◆ ~TcpHybla()

ns3::TcpHybla::~TcpHybla ( )

override

Definition at line 55 of file tcp-hybla.cc.

References NS_LOG_FUNCTION.

Member Function Documentation

◆ CongestionAvoidance()

void ns3::TcpHybla::CongestionAvoidance	(	Ptr< TcpSocketState >	tcb,
		uint32_t	segmentsAcked )

overrideprotectedvirtual

NewReno congestion avoidance.

During congestion avoidance, cwnd is incremented by roughly 1 full-sized segment per round-trip time (RTT).

Parameters

tcb	internal congestion state
segmentsAcked	count of segments acked

Reimplemented from ns3::TcpNewReno.

Definition at line 114 of file tcp-hybla.cc.

References m_cWndCnt, m_rho, NS_ASSERT, NS_LOG_FUNCTION, and NS_LOG_INFO.

◆ Fork()

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

overridevirtual

Copy the congestion control algorithm across sockets.

Returns: a pointer of the copied object

Implements ns3::TcpCongestionOps.

Definition at line 155 of file tcp-hybla.cc.

References ns3::Object::CopyObject.

◆ GetName()

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

overridevirtual

Get the name of the congestion control algorithm.

Returns: A string identifying the name

Implements ns3::TcpCongestionOps.

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

◆ GetTypeId()

TypeId ns3::TcpHybla::GetTypeId ( )

static

Get the type ID.

Returns: the object TypeId

Definition at line 21 of file tcp-hybla.cc.

References m_rho, m_rRtt, ns3::MakeTimeAccessor(), ns3::MakeTimeChecker(), ns3::MakeTraceSourceAccessor(), ns3::MilliSeconds(), and ns3::TypeId::SetParent().

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◆ PktsAcked()

void ns3::TcpHybla::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

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

Reimplemented from ns3::TcpCongestionOps.

Definition at line 72 of file tcp-hybla.cc.

References NS_LOG_DEBUG, NS_LOG_FUNCTION, and RecalcParam().

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◆ RecalcParam()

void ns3::TcpHybla::RecalcParam ( const Ptr< TcpSocketState > & tcb )

private

Recalculate algorithm parameters.

Parameters

tcb	the socket state.

Definition at line 61 of file tcp-hybla.cc.

References ns3::Time::GetMilliSeconds(), m_rho, m_rRtt, NS_ASSERT, NS_LOG_DEBUG, and NS_LOG_FUNCTION.

Referenced by PktsAcked().

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◆ SlowStart()

uint32_t ns3::TcpHybla::SlowStart	(	Ptr< TcpSocketState >	tcb,
		uint32_t	segmentsAcked )

overrideprotectedvirtual

Tcp NewReno slow start algorithm.

Defined in RFC 5681 as

‍During slow start, a TCP increments cwnd by at most SMSS bytes for each ACK received that cumulatively acknowledges new data. Slow start ends when cwnd exceeds ssthresh (or, optionally, when it reaches it, as noted above) or when congestion is observed. While traditionally TCP implementations have increased cwnd by precisely SMSS bytes upon receipt of an ACK covering new data, we RECOMMEND that TCP implementations increase cwnd, per:
cwnd += min (N, SMSS)                      (2)
where N is the number of previously unacknowledged bytes acknowledged in the incoming ACK.

The ns-3 implementation respect the RFC definition. Linux does something different:

u32 tcp_slow_start(struct tcp_sock *tp, u32 acked)
{
  u32 cwnd = tp->snd_cwnd + acked;
 
  if (cwnd > tp->snd_ssthresh)
    cwnd = tp->snd_ssthresh + 1;
  acked -= cwnd - tp->snd_cwnd;
  tp->snd_cwnd = min(cwnd, tp->snd_cwnd_clamp);
 
  return acked;
}

As stated, we want to avoid the case when a cumulative ACK increases cWnd more than a segment size, but we keep count of how many segments we have ignored, and return them.

Parameters

tcb	internal congestion state
segmentsAcked	count of segments acked

Returns: the number of segments not considered for increasing the cWnd

Reimplemented from ns3::TcpNewReno.

Definition at line 84 of file tcp-hybla.cc.

References m_rho, NS_ASSERT, NS_LOG_FUNCTION, and NS_LOG_INFO.

Member Data Documentation

◆ m_cWndCnt

double ns3::TcpHybla::m_cWndCnt

private

cWnd integer-to-float counter

Definition at line 70 of file tcp-hybla.h.

Referenced by CongestionAvoidance().

◆ m_rho

TracedValue<double> ns3::TcpHybla::m_rho

private

Rho parameter.

Definition at line 68 of file tcp-hybla.h.

Referenced by CongestionAvoidance(), GetTypeId(), RecalcParam(), and SlowStart().

◆ m_rRtt

Time ns3::TcpHybla::m_rRtt

private

Reference RTT.

Definition at line 69 of file tcp-hybla.h.

Referenced by GetTypeId(), and RecalcParam().

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

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

Public Member Functions

Static Public Member Functions

Protected Member Functions

Private Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ TcpHybla() [1/2]

◆ TcpHybla() [2/2]

◆ ~TcpHybla()

Member Function Documentation

◆ CongestionAvoidance()

◆ Fork()

◆ GetName()

◆ GetTypeId()

◆ PktsAcked()

◆ RecalcParam()

◆ SlowStart()

Member Data Documentation

◆ m_cWndCnt

◆ m_rho

◆ m_rRtt