SSF.OS.TCP
Class Rcv_WndManager

java.lang.Object
  |
  +--SSF.OS.TCP.Rcv_WndManager

public class Rcv_WndManager

extends java.lang.Object

Receive window manager keeps a record of the receive window parameters and change their value accordingly when it receives a new message and sends an ACK. It maintains the receive buffer and keeps all the messages in order before they are read by upper layer Application.

Field Summary

int	AdvertisedWnd Size of the advertised window
protected int	GapPosition Index of the first out-of-sequence packet in the Receive Buffer
protected long	LastRcvd Sequence number of the last received packet
protected long	LastRead Sequence number of the last packet read by application
int	MAX_RCV_WND Default maximum receive window size
long	maxAdvertised
int	MSS
protected long	NextExpected Sequence number of the next expected packet to receive ( = ACK number).
protected tcpSession	owner Reference to the owner of this receive window manager
protected TCP_Message[]	Rcv_Buffer Receive buffer for the received messages, including out of order messages.
static int	SIZE Maximum number of packets in receive buffer
protected TCP_Header	tcpHdr template of the reply message

Method Summary

void	Calc_AdvertisedWindow() Calculate the size of the advertised window which indicate the maximum number of bytes that can be received in the buffer.
void	push_Process() push all received and ordered virtual data to upper layer protocol session
void	Rcv_DataProcess(ProtocolMessage message) Process receives a data message, sorts messages in sequence number order, sends acknowledgment message with next expected sequence number and advertised window size, checks if the message contains flags indicating the end of data transmission.
void	Rcv_WndInit(TCP_Message data) Initialize the receive window according to message received.
void	ReassembleMessage() Sort the messages by sequence number, discard the message if it's duplicated, increase the next expected sequence number if needed.
void	Send_Ack_Process() Send ACK for the received in-sequence packet with the highest sequence number.
void	setACK(TCP_Message tcpMsg)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

owner

protected tcpSession owner

Reference to the owner of this receive window manager

NextExpected

protected long NextExpected

Sequence number of the next expected packet to receive ( = ACK number).

LastRead

protected long LastRead

Sequence number of the last packet read by application

LastRcvd

protected long LastRcvd

Sequence number of the last received packet

GapPosition

protected int GapPosition

Index of the first out-of-sequence packet in the Receive Buffer

AdvertisedWnd

public int AdvertisedWnd

Size of the advertised window

maxAdvertised

public long maxAdvertised

MAX_RCV_WND

public int MAX_RCV_WND

Default maximum receive window size

SIZE

public static final int SIZE

Maximum number of packets in receive buffer

See Also:

Constant Field Values

MSS

public int MSS

tcpHdr

protected TCP_Header tcpHdr

template of the reply message

Rcv_Buffer

protected TCP_Message[] Rcv_Buffer

Receive buffer for the received messages, including out of order messages.

Method Detail

Calc_AdvertisedWindow

public void Calc_AdvertisedWindow()

Calculate the size of the advertised window which indicate the maximum number of bytes that can be received in the buffer.

ReassembleMessage

public void ReassembleMessage()

Sort the messages by sequence number, discard the message if it's duplicated, increase the next expected sequence number if needed. Push in-order (virtual) data segments to the reading socket buffer.

Rcv_WndInit

public void Rcv_WndInit(TCP_Message data)

Initialize the receive window according to message received. Set the value of receive window variable and TCP header of the replying message, send acknowledgment message in reply to the connection request. Called by tcpSession.push() upon receiving SYN or SYN-ACK.

Rcv_DataProcess

public void Rcv_DataProcess(ProtocolMessage message)
                     throws TCPException

Process receives a data message, sorts messages in sequence number order, sends acknowledgment message with next expected sequence number and advertised window size, checks if the message contains flags indicating the end of data transmission. Note: dose not check if have a silly window syndrome.

Parameters:

message - received TCP message

TCPException

Send_Ack_Process

public void Send_Ack_Process()

Send ACK for the received in-sequence packet with the highest sequence number.

setACK

public void setACK(TCP_Message tcpMsg)

push_Process

public void push_Process()

push all received and ordered virtual data to upper layer protocol session