#include <TCP_NSC_Queues.h>

Inheritance diagram for TCP_NSC_SendQueue:

Public Member Functions
	TCP_NSC_SendQueue ()
virtual	~TCP_NSC_SendQueue ()
virtual void	setConnection (TCP_NSC_Connection *connP)
virtual void	enqueueAppData (cPacket *msgP)=0
virtual int	getNscMsg (void *bufferP, int bufferLengthP)=0
virtual void	dequeueNscMsg (int msgLengthP)=0
virtual ulong	getBytesAvailable ()=0
virtual TCPSegment *	createSegmentWithBytes (const void *tcpDataP, int tcpLengthP)=0
virtual void	discardUpTo (uint32 seqNumP)=0
Protected Attributes
TCP_NSC_Connection *	connM

Detailed Description

Abstract base class for TCP_NSC send queues. In fact a single object represents both the send queue and the retransmission queue (no need to separate them). The TCPConnection object knows which data in the queue have already been transmitted ("retransmission queue") and which not ("send queue"). This class is not interested in where's the boundary.

There is another particularity about this class: as a retransmission queue, it stores bytes and not segments. TCP is a bytestream oriented protocol (sequence numbers refer to bytes and not to TPDUs as e.g. in ISO TP4), and the protocol doesn't rely on retransmitted segments having the same segment boundaries as the original segments. Some implementations store segments on the retransmission queue, and others store only the data bytes; RFCs explicitly allow both. (See e.g. RFC1122 p90, section 4.2.2.15, "IMPLEMENTATION" note).

To simulate a TCP that retains segment boundaries in retransmissions, the appropriate TCPAlgorithm class should remember where the segment boundaries were at the original transmission, and it should form identical segments when retransmitting. The createSegmentWithBytes() send queue method makes this possible.

This class is polymorphic because depending on where and how you use the TCP model you might have different ideas about "sending data" on a simulated connection.

You might want to:

transmit a real bytes, especially if the application which uses TCP is a ported version of a real socket application.

simulate a "dummy" connection, that is, simulated TCP segments contain do not contain any real data, only the number of bytes they represent. You'll want to do this when the app is there solely as a traffic generator (e.g. simulated file transfer or telnet session), but actual data is unimportant.

transmit a sequence of cMessage objects, and you want exactly the same cMessage sequence to be reproduced on the receiver side. Here every cMessage maps to a sequence number range in the TCP stream, and the object is passed up to the application on the receiving side when its last byte has arrived on the simulated connection.

Different TCP_NSCSendQueue subclasses can be written to accomodate different needs.

This class goes hand-in-hand with TCP_NSCReceiveQueue.

See also:: TCP_NSCReceiveQueue

Definition at line 82 of file TCP_NSC_Queues.h.

Constructor & Destructor Documentation

TCP_NSC_SendQueue::TCP_NSC_SendQueue ( ) [inline]

Ctor.

Definition at line 88 of file TCP_NSC_Queues.h.

: connM(NULL) {}

virtual TCP_NSC_SendQueue::~TCP_NSC_SendQueue ( ) [inline, virtual]

Virtual dtor.

Definition at line 93 of file TCP_NSC_Queues.h.

{}

Member Function Documentation

virtual TCPSegment* TCP_NSC_SendQueue::createSegmentWithBytes	(	const void *	tcpDataP,
		int	tcpLengthP
	)			`[pure virtual]`

Called when the TCP wants to send or retransmit data, it constructs a TCP segment which contains the data from the requested sequence number range. The actually returned segment may contain less then maxNumBytes bytes if the subclass wants to reproduce the original segment boundaries when retransmitting.

called from inside of send_callback() called before called the send() to IP layer

Implemented in TCP_NSC_VirtualDataSendQueue.

virtual void TCP_NSC_SendQueue::dequeueNscMsg ( int msgLengthP ) [pure virtual]

The function should remove msgLengthP bytes from NSCqueue

But the NSC sometimes reread from this datapart (when data destroyed in IP Layer) inside of createSegmentWithBytes() function.

called with return value of socket->send_data() if larger than 0

Implemented in TCP_NSC_VirtualDataSendQueue.

virtual void TCP_NSC_SendQueue::discardUpTo ( uint32 seqNumP ) [pure virtual]

Tells the queue that bytes up to (but NOT including) seqNum have been transmitted and ACKed, so they can be removed from the queue.

Implemented in TCP_NSC_VirtualDataSendQueue.

virtual void TCP_NSC_SendQueue::enqueueAppData ( cPacket * msgP ) [pure virtual]

Called on SEND app command, it inserts in the queue the data the user wants to send. Implementations of this abstract class will decide what this means: copying actual bytes, just increasing the "last byte queued" variable, or storing cMessage object(s). The msg object should not be referenced after this point (sendQueue may delete it.)

Implemented in TCP_NSC_VirtualDataSendQueue.

virtual ulong TCP_NSC_SendQueue::getBytesAvailable ( ) [pure virtual]

Utility function: returns how many bytes are available in the queue.

Implemented in TCP_NSC_VirtualDataSendQueue.