Tcp sender buffer. More...

#include "tcp-tx-buffer.h"

Inheritance diagram for ns3::TcpTxBuffer:

Collaboration diagram for ns3::TcpTxBuffer:

Public Member Functions
	TcpTxBuffer (uint32_t n=0)
	Constructor. More...

virtual	~TcpTxBuffer (void)

bool	Add (Ptr< Packet > p)
	Append a data packet to the end of the buffer. More...

uint32_t	Available (void) const
	Returns the available capacity of this buffer. More...

uint32_t	BytesInFlight (uint32_t dupThresh, uint32_t segmentSize) const
	Return total bytes in flight. More...

Ptr< Packet >	CopyFromSequence (uint32_t numBytes, const SequenceNumber32 &seq)
	Copy data from the range [seq, seq+numBytes) into a packet. More...

Ptr< const TcpOptionSack >	CraftSackOption (const SequenceNumber32 &seq, uint8_t available) const
	Craft a SACK block. More...

void	DiscardUpTo (const SequenceNumber32 &seq)
	Discard data up to but not including this sequence number. More...

uint32_t	GetRetransmitsCount (void) const
	Return the number of segments in the sent list that have been transmitted more than once, without acknowledgment. More...

SequenceNumber32	HeadSequence (void) const
	Get the sequence number of the buffer head. More...

bool	IsHeadRetransmitted () const
	Check if the head is retransmitted. More...

bool	IsLost (const SequenceNumber32 &seq, uint32_t dupThresh, uint32_t segmentSize) const
	Check if a segment is lost per RFC 6675. More...

uint32_t	MaxBufferSize (void) const
	Get the maximum buffer size. More...

bool	NextSeg (SequenceNumber32 *seq, uint32_t dupThresh, uint32_t segmentSize, bool isRecovery) const
	Get the next sequence number to transmit, according to RFC 6675. More...

void	ResetLastSegmentSent ()
	Take the last segment sent and put it back into the un-sent list (at the beginning) More...

void	ResetScoreboard ()
	Reset the Scoreboard from all SACK informations. More...

void	ResetSentList (uint32_t keepItems=1)
	Reset the sent list. More...

void	SetHeadSequence (const SequenceNumber32 &seq)
	Set the head sequence of the buffer. More...

void	SetMaxBufferSize (uint32_t n)
	Set the maximum buffer size. More...

void	SetSentListLost ()
	Set the entire sent list as lost (typically after an RTO) More...

uint32_t	Size (void) const
	Returns total number of bytes in this buffer. More...

uint32_t	SizeFromSequence (const SequenceNumber32 &seq) const
	Returns the number of bytes from the buffer in the range [seq, tailSequence) More...

SequenceNumber32	TailSequence (void) const
	Get the sequence number of the buffer tail (plus one) More...

bool	Update (const TcpOptionSack::SackList &list)
	Update the scoreboard. 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...

SimpleRefCount &	operator= (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::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...

Private Types
typedef std::list< TcpTxItem * >	PacketList
	container for data stored in the buffer More...

Private Member Functions
std::pair< TcpTxBuffer::PacketList::const_iterator, SequenceNumber32 >	GetHighestSacked () const
	Find the highest SACK byte. More...

TcpTxItem *	GetNewSegment (uint32_t numBytes)
	Get a block of data not transmitted yet and move it into SentList. More...

TcpTxItem *	GetPacketFromList (PacketList &list, const SequenceNumber32 &startingSeq, uint32_t numBytes, const SequenceNumber32 &requestedSeq, bool *listEdited) const
	Get a block (which is returned as Packet) from a list. More...

TcpTxItem *	GetTransmittedSegment (uint32_t numBytes, const SequenceNumber32 &seq)
	Get a block of data previously transmitted. More...

bool	IsLost (const SequenceNumber32 &seq, const PacketList::const_iterator &segment, uint32_t dupThresh, uint32_t segmentSize) const
	Check if a segment is lost per RFC 6675. More...

void	MergeItems (TcpTxItem &t1, TcpTxItem &t2) const
	Merge two TcpTxItem. More...

void	SplitItems (TcpTxItem &t1, TcpTxItem &t2, uint32_t size) const
	Split one TcpTxItem. More...

Private Attributes
PacketList	m_appList
	Buffer for application data. More...

TracedValue< SequenceNumber32 >	m_firstByteSeq
	Sequence number of the first byte in data (SND.UNA) More...

std::pair< PacketList::const_iterator, SequenceNumber32 >	m_highestSack
	Highest SACK byte. More...

uint32_t	m_maxBuffer
	Max number of data bytes in buffer (SND.WND) More...

PacketList	m_sentList
	Buffer for sent (but not acked) data. More...

uint32_t	m_sentSize
	Size of sent (and not discarded) segments. More...

uint32_t	m_size
	Size of all data in this buffer. More...

Friends
std::ostream &	operator<< (std::ostream &os, TcpTxBuffer const &tcpTxBuf)
	Output operator. More...

Additional Inherited Members
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

Tcp sender buffer.

The class keeps track of all data that the application wishes to transmit to the other end. When the data is acknowledged, it is removed from the buffer. The buffer has a maximum size, and data is not saved if the amount exceeds the limit. Packets can be added to the class through the method Add(). An important thing to remember is that all the data managed is strictly sequential. It can be divided into blocks, but all the data follow a strict ordering. That order is managed through SequenceNumber.

In other words, this buffer contains numbered bytes (e.g., 1,2,3), and the class is allowed to return only ordered (using "<" as operator) subsets (e.g. 1,2 or 2,3 or 1,2,3).

The data structure underlying this is composed by two distinct packet lists. The first (SentList) is initially empty, and it contains the packets returned by the method CopyFromSequence. The second (AppList) is initially empty, and it contains the packets coming from the applications, but that are not transmitted yet as segments. To discover how the chunks are managed and retrieved from these lists, check CopyFromSequence documentation.

The head of the data is represented by m_firstByteSeq, and it is returned by HeadSequence(). The last byte is returned by TailSequence(). In this class, we also store the size (in bytes) of the packets inside the SentList in the variable m_sentSize.

SACK management

The SACK information is usually saved in a data structure referred as scoreboard. In this implementation, the scoreboard is developed on top of the existing classes. In particular, instead of keeping raw pointers to packets in TcpTxBuffer we added the capability to store some flags associated with every segment sent. This is done through the use of the class TcpTxItem: instead of storing a list of packets, we store a list of TcpTxItem. Each item has different flags (check the corresponding documentation) and maintaining the scoreboard is a matter of travelling the list and set the SACK flag on the corresponding segment sent.

Inefficiencies

The algorithms outlined in RFC 6675 are full of inefficiencies. In particular, traveling all the sent list each time it is needed to compute the bytes in flight is expensive. We try to overcome the issue by maintaining a pointer to the highest sequence SACKed; in this way, we can avoid traveling all the list in some cases. Another option could be keeping a count of each critical value (e.g., the number of packets sacked). However, this would be different from the algorithms in RFC. There are some other possible improvements; if you wish, take a look and try to add some earlier exit conditions in the loops.

See also: Size; SizeFromSequence; CopyFromSequence

Config Paths

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

"/NodeList/[i]/$ns3::TcpL4Protocol/SocketList/[i]/TxBuffer"

No Attributes are defined for this type.

TraceSources

UnackSequence: First unacknowledged sequence number (SND.UNA)
Callback signature: ns3::SequenceNumber32TracedValueCallback

Size of this type is 120 bytes (on a 64-bit architecture).

Definition at line 126 of file tcp-tx-buffer.h.

Member Typedef Documentation

typedef std::list<TcpTxItem*> ns3::TcpTxBuffer::PacketList

private

container for data stored in the buffer

Definition at line 338 of file tcp-tx-buffer.h.

Constructor & Destructor Documentation

ns3::TcpTxBuffer::TcpTxBuffer ( uint32_t n = 0 )

Constructor.

Parameters

n	initial Sequence number to be transmitted

Definition at line 114 of file tcp-tx-buffer.cc.

ns3::TcpTxBuffer::~TcpTxBuffer ( void )

virtual

Definition at line 119 of file tcp-tx-buffer.cc.

References ns3::Packet::GetSize(), m_appList, ns3::TcpTxItem::m_packet, m_sentList, m_sentSize, and m_size.

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Member Function Documentation

bool ns3::TcpTxBuffer::Add ( Ptr< Packet > p )

Append a data packet to the end of the buffer.

Parameters

p	The packet to be appended to the Tx buffer

Returns: Boolean to indicate success

Definition at line 186 of file tcp-tx-buffer.cc.

References Available(), ns3::Packet::Copy(), ns3::Packet::GetSize(), m_appList, m_firstByteSeq, ns3::TcpTxItem::m_packet, m_size, NS_LOG_FUNCTION, NS_LOG_INFO, and NS_LOG_WARN.

Referenced by TcpTxBufferTestCase::TestNewBlock(), TcpTxBufferTestCase::TestNextSeg(), and TcpTxBufferTestCase::TestUpdateScoreboardWithCraftedSACK().

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uint32_t ns3::TcpTxBuffer::Available ( void ) const

Returns the available capacity of this buffer.

Returns: available capacity in this Tx window

Definition at line 169 of file tcp-tx-buffer.cc.

References m_maxBuffer, and m_size.

Referenced by Add().

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uint32_t ns3::TcpTxBuffer::BytesInFlight	(	uint32_t	dupThresh,
		uint32_t	segmentSize
	)		const

Return total bytes in flight.

The routine follows the "SetPipe" function in RFC 6675 and assumes that SACK is enabled for the session

Parameters

dupThresh	duplicate ACK threshold
segmentSize	segment size

Returns: total bytes in flight

Definition at line 929 of file tcp-tx-buffer.cc.

References ns3::Packet::GetSize(), IsLost(), m_firstByteSeq, ns3::TcpTxItem::m_lost, ns3::TcpTxItem::m_packet, ns3::TcpTxItem::m_retrans, ns3::TcpTxItem::m_sacked, and m_sentList.

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Ptr< Packet > ns3::TcpTxBuffer::CopyFromSequence	(	uint32_t	numBytes,
		const SequenceNumber32 &	seq
	)

Copy data from the range [seq, seq+numBytes) into a packet.

In the following, we refer to the block [seq, seq+numBytes) simply as "block". We check the boundary of the block, and divide the possibilities in three cases:

the block have already been transmitted (managed in GetTransmittedSegment)
the block have not been transmitted yet (managed in GetNewSegment)

The last case is when the block is partially transmitted and partially not transmitted. We trick this case by requesting the portion not transmitted from GetNewSegment, and then calling GetTransmittedSegment with the full block range.

Parameters

numBytes	number of bytes to copy
seq	start sequence number to extract

Returns: a packet

Definition at line 227 of file tcp-tx-buffer.cc.

References ns3::Packet::Copy(), ns3::TracedValue< T >::Get(), GetNewSegment(), ns3::Packet::GetSize(), GetTransmittedSegment(), m_firstByteSeq, ns3::TcpTxItem::m_lastSent, ns3::TcpTxItem::m_lost, ns3::TcpTxItem::m_packet, ns3::TcpTxItem::m_retrans, m_sentSize, min, ns3::Simulator::Now(), NS_ABORT_MSG_UNLESS, NS_ASSERT, NS_LOG_DEBUG, NS_LOG_ERROR, NS_LOG_FUNCTION, and SizeFromSequence().

Referenced by DiscardUpTo(), TcpTxBufferTestCase::TestNewBlock(), TcpTxBufferTestCase::TestNextSeg(), and TcpTxBufferTestCase::TestUpdateScoreboardWithCraftedSACK().

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Ptr< const TcpOptionSack > ns3::TcpTxBuffer::CraftSackOption	(	const SequenceNumber32 &	seq,
		uint8_t	available
	)		const

Craft a SACK block.

Used in case the other end does not support SACK

Parameters

seq	Look to usable block starting from this sequence number (seq will not be included in the block)
available	Space left in the header for that SACK option

Returns: a SACK option that SACK the first un-SACKed segment in our sentList.

Definition at line 1053 of file tcp-tx-buffer.cc.

References ns3::Packet::GetSize(), m_firstByteSeq, m_highestSack, ns3::TcpTxItem::m_packet, ns3::TcpTxItem::m_sacked, m_sentList, NS_ASSERT, NS_LOG_DEBUG, NS_LOG_FUNCTION, and NS_LOG_INFO.

Referenced by TcpTxBufferTestCase::TestUpdateScoreboardWithCraftedSACK().

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void ns3::TcpTxBuffer::DiscardUpTo ( const SequenceNumber32 & seq )

Discard data up to but not including this sequence number.

Parameters

seq	The first sequence number to maintain after discarding all the previous sequences.

Definition at line 578 of file tcp-tx-buffer.cc.

References CopyFromSequence(), ns3::Packet::CreateFragment(), ns3::TracedValue< T >::Get(), ns3::Packet::GetSize(), m_firstByteSeq, m_highestSack, ns3::TcpTxItem::m_packet, ns3::TcpTxItem::m_sacked, m_sentList, m_sentSize, m_size, NS_ASSERT, NS_LOG_DEBUG, NS_LOG_FUNCTION, NS_LOG_INFO, and NS_LOG_LOGIC().

Referenced by TcpTxBufferTestCase::TestNewBlock(), TcpTxBufferTestCase::TestNextSeg(), and TcpTxBufferTestCase::TestUpdateScoreboardWithCraftedSACK().

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std::pair< TcpTxBuffer::PacketList::const_iterator, SequenceNumber32 > ns3::TcpTxBuffer::GetHighestSacked ( ) const

private

Find the highest SACK byte.

Returns: a pair with the highest byte and an iterator inside m_sentList

Definition at line 340 of file tcp-tx-buffer.cc.

References ns3::Packet::GetSize(), m_firstByteSeq, ns3::TcpTxItem::m_packet, ns3::TcpTxItem::m_sacked, m_sentList, and NS_LOG_FUNCTION.

Referenced by GetTransmittedSegment().

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TcpTxItem * ns3::TcpTxBuffer::GetNewSegment ( uint32_t numBytes )

private

Get a block of data not transmitted yet and move it into SentList.

If the block is not yet transmitted, hopefully, seq is exactly the sequence number of the first byte of the first packet inside AppList. We extract the block from AppList and move it into the SentList, before returning the block itself. We manage possible fragmentation (or merges) inside AppList through GetPacketFromList.

See also: GetPacketFromList

Parameters

numBytes number of bytes to copy

Returns: the item that contains the right packet

Definition at line 297 of file tcp-tx-buffer.cc.

References GetPacketFromList(), ns3::Packet::GetSize(), m_appList, m_firstByteSeq, ns3::TcpTxItem::m_packet, m_sentList, m_sentSize, NS_ASSERT, and NS_LOG_FUNCTION.

Referenced by CopyFromSequence().

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TcpTxItem * ns3::TcpTxBuffer::GetPacketFromList	(	PacketList &	list,
		const SequenceNumber32 &	startingSeq,
		uint32_t	numBytes,
		const SequenceNumber32 &	requestedSeq,
		bool *	listEdited
	)		const

private

Get a block (which is returned as Packet) from a list.

This function extract a block [requestedSeq,numBytes) from the list, which starts at startingSeq.

The cases we need to manage are two, and they are depicted in the following image:

                     |------|     |----|     |----|
              list = |      | --> |    | --> |    |
                     |------|     |----|     |----|

                     ^      ^
                     | ^ ^  |         (1)
                   seq | |  seq + numBytes
                       | |
                       | |
                    seq   seq + numBytes     (2)

The case 1 is easy to manage: the requested block is exactly a packet already stored. If one value (seq or seq + numBytes) does not align to a packet boundary, or when both values does not align (case 2), it is a bit more complex.

Basically, we have two possible operations:

fragment : split an existing packet in two
merge : merge two existing packets in one

and we reduce case (2) to case (1) through sequentially applying fragment or merge. For instance:

    |------|
    |      |
    |------|

    ^ ^  ^ ^
    | |  | |
start |  | |
      |  | end
     seq |
         seq + numBytes

To reduce to case (1), we need to perform two fragment operations:

fragment (start, seq)
fragment (seq + numBytes, end)

After these operations, the requested block is exactly the resulting packet. Merge operation is required when the requested block span over two (or more) existing packets.

While this could be extremely slow in the worst possible scenario (one big packet which is split in small packets for transmission, and merged for re-transmission) that scenario is unlikely during a TCP transmission (since MSS can change, but it is stable, and retransmissions do not happen for each segment).

Parameters

list	List to extract block from
startingSeq	Starting sequence of the list
numBytes	Bytes to extract, starting from requestedSeq
requestedSeq	Requested sequence
listEdited	output parameter which indicates if the list has been edited

Returns: the item that contains the right packet

Definition at line 379 of file tcp-tx-buffer.cc.

References ns3::Packet::GetSize(), ns3::TcpTxItem::m_packet, MergeItems(), NS_ASSERT, NS_FATAL_ERROR, NS_LOG_FUNCTION, NS_LOG_INFO, NS_LOG_WARN, and SplitItems().

Referenced by GetNewSegment(), and GetTransmittedSegment().

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uint32_t ns3::TcpTxBuffer::GetRetransmitsCount ( void ) const

Return the number of segments in the sent list that have been transmitted more than once, without acknowledgment.

This method is to support the retransmits count for determining PipeSize in NewReno-style TCP.

Returns: number of segments that have been transmitted more than once, without acknowledgment

Definition at line 911 of file tcp-tx-buffer.cc.

References ns3::TcpTxItem::m_retrans, m_sentList, and NS_LOG_FUNCTION.

TcpTxItem * ns3::TcpTxBuffer::GetTransmittedSegment	(	uint32_t	numBytes,
		const SequenceNumber32 &	seq
	)

private

Get a block of data previously transmitted.

This is clearly a retransmission, and if everything is going well, the block requested is matching perfectly with another one requested in the past. If not, fragmentation or merge are required. We manage both inside GetPacketFromList.

See also: GetPacketFromList

Parameters

numBytes	number of bytes to copy
seq	sequence requested

Returns: the item that contains the right packet

Definition at line 321 of file tcp-tx-buffer.cc.

References GetHighestSacked(), GetPacketFromList(), m_firstByteSeq, m_highestSack, m_sentList, m_sentSize, NS_ASSERT, and NS_LOG_FUNCTION.

Referenced by CopyFromSequence().

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TypeId ns3::TcpTxBuffer::GetTypeId ( void )

static

Get the type ID.

Returns: the object TypeId

Definition at line 93 of file tcp-tx-buffer.cc.

References m_firstByteSeq, ns3::MakeTraceSourceAccessor(), and ns3::TypeId::SetParent().

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SequenceNumber32 ns3::TcpTxBuffer::HeadSequence ( void ) const

Get the sequence number of the buffer head.

Returns: the first byte's sequence number

Definition at line 139 of file tcp-tx-buffer.cc.

References m_firstByteSeq.

bool ns3::TcpTxBuffer::IsHeadRetransmitted ( ) const

Check if the head is retransmitted.

Returns: true if the head is retransmitted, false in all other cases (including no segment sent)

Definition at line 1039 of file tcp-tx-buffer.cc.

References m_sentList, m_sentSize, NS_ASSERT, and NS_LOG_FUNCTION.

bool ns3::TcpTxBuffer::IsLost	(	const SequenceNumber32 &	seq,
		uint32_t	dupThresh,
		uint32_t	segmentSize
	)		const

Check if a segment is lost per RFC 6675.

Parameters

seq	sequence to check
dupThresh	dupAck threshold
segmentSize	segment size

Returns: true if the sequence is supposed to be lost, false otherwise

Definition at line 793 of file tcp-tx-buffer.cc.

References m_firstByteSeq, m_highestSack, m_sentList, and NS_LOG_FUNCTION.

Referenced by BytesInFlight(), NextSeg(), and TcpTxBufferTestCase::TestUpdateScoreboardWithCraftedSACK().

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bool ns3::TcpTxBuffer::IsLost	(	const SequenceNumber32 &	seq,
		const PacketList::const_iterator &	segment,
		uint32_t	dupThresh,
		uint32_t	segmentSize
	)		const

private

Check if a segment is lost per RFC 6675.

Parameters

seq	sequence to check
segment	Iterator pointing at seq
dupThresh	dupAck threshold
segmentSize	segment size

Returns: true if the sequence is supposed to be lost, false otherwise

Definition at line 731 of file tcp-tx-buffer.cc.

References ns3::Packet::GetSize(), m_highestSack, ns3::TcpTxItem::m_packet, ns3::TcpTxItem::m_sacked, NS_LOG_FUNCTION, and NS_LOG_INFO.

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uint32_t ns3::TcpTxBuffer::MaxBufferSize ( void ) const

Get the maximum buffer size.

Returns: the Tx window size (in bytes)

Definition at line 157 of file tcp-tx-buffer.cc.

References m_maxBuffer.

void ns3::TcpTxBuffer::MergeItems	(	TcpTxItem &	t1,
		TcpTxItem &	t2
	)		const

private

Merge two TcpTxItem.

Merge t2 in t1. It consists in copying the lastSent field if t2 is more recent than t1. Retransmitted field is copied only if it set in t2 but not in t1. Sacked is copied only if it is true in both items.

Parameters

t1	first item
t2	second item

Definition at line 549 of file tcp-tx-buffer.cc.

References ns3::Packet::AddAtEnd(), ns3::TcpTxItem::m_lastSent, ns3::TcpTxItem::m_lost, ns3::TcpTxItem::m_packet, ns3::TcpTxItem::m_retrans, ns3::TcpTxItem::m_sacked, and NS_LOG_FUNCTION.

Referenced by GetPacketFromList().

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bool ns3::TcpTxBuffer::NextSeg	(	SequenceNumber32 *	seq,
		uint32_t	dupThresh,
		uint32_t	segmentSize,
		bool	isRecovery
	)		const

Get the next sequence number to transmit, according to RFC 6675.

Parameters

seq	Next sequence number to transmit, based on the scoreboard information
dupThresh	dupAck threshold
segmentSize	segment size
isRecovery	true if the socket congestion state is in recovery mode

Returns: true is seq is updated, false otherwise

Definition at line 823 of file tcp-tx-buffer.cc.

References ns3::Packet::GetSize(), ns3::SequenceNumber< NUMERIC_TYPE, SIGNED_TYPE >::GetValue(), IsLost(), m_firstByteSeq, ns3::TcpTxItem::m_packet, ns3::TcpTxItem::m_retrans, ns3::TcpTxItem::m_sacked, m_sentList, m_sentSize, NS_LOG_FUNCTION, and SizeFromSequence().

Referenced by TcpTxBufferTestCase::TestNextSeg().

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void ns3::TcpTxBuffer::ResetLastSegmentSent ( )

Take the last segment sent and put it back into the un-sent list (at the beginning)

Definition at line 1012 of file tcp-tx-buffer.cc.

References ns3::Packet::GetSize(), m_appList, ns3::TcpTxItem::m_packet, m_sentList, m_sentSize, and NS_LOG_FUNCTION.

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void ns3::TcpTxBuffer::ResetScoreboard ( )

Reset the Scoreboard from all SACK informations.

Definition at line 964 of file tcp-tx-buffer.cc.

References m_firstByteSeq, m_highestSack, m_sentList, and NS_LOG_FUNCTION.

void ns3::TcpTxBuffer::ResetSentList ( uint32_t keepItems = 1 )

Reset the sent list.

Move all but the first 'keepItems' packets from the sent list to the appList. By default, the HEAD of hte sent list is kept and all others moved to the appList. All items kept on the sent list are then marked as un-sacked, un-retransmitted, and lost.

Parameters

keepItems Keep a number of items at the front of the sent list

Definition at line 981 of file tcp-tx-buffer.cc.

References ns3::Packet::GetSize(), m_appList, m_highestSack, ns3::TcpTxItem::m_lost, ns3::TcpTxItem::m_packet, ns3::TcpTxItem::m_retrans, ns3::TcpTxItem::m_sacked, m_sentList, m_sentSize, and NS_LOG_FUNCTION.

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void ns3::TcpTxBuffer::SetHeadSequence ( const SequenceNumber32 & seq )

Set the head sequence of the buffer.

Set the head (m_firstByteSeq) to seq. Supposed to be called only when the connection is just set up and we did not send any data out yet.

Parameters

seq	The sequence number of the head byte

Definition at line 175 of file tcp-tx-buffer.cc.

References m_firstByteSeq, m_highestSack, m_sentList, NS_ASSERT, and NS_LOG_FUNCTION.

Referenced by TcpTxBufferTestCase::TestNewBlock(), TcpTxBufferTestCase::TestNextSeg(), and TcpTxBufferTestCase::TestUpdateScoreboardWithCraftedSACK().

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void ns3::TcpTxBuffer::SetMaxBufferSize ( uint32_t n )

Set the maximum buffer size.

Parameters

n	Tx window size (in bytes)

Definition at line 163 of file tcp-tx-buffer.cc.

References m_maxBuffer.

void ns3::TcpTxBuffer::SetSentListLost ( )

Set the entire sent list as lost (typically after an RTO)

Used to set all the sent list as lost, so the bytes in flight is not counting them as in flight, but we will continue to use SACK informations for recovering the timeout.

Definition at line 1026 of file tcp-tx-buffer.cc.

References m_sentList, and NS_LOG_FUNCTION.

uint32_t ns3::TcpTxBuffer::Size ( void ) const

Returns total number of bytes in this buffer.