Bài giảng TCP/IP - Chapter 12: Transmission Control Protocol (TCP)

Chapter 12Transmission Control Protocol(TCP)CONTENTS PROCESS-TO-PROCESS COMMUNICATION TCP SERVICES NUMBERING BYTES FLOW CONTROL SILLY WINDOW SYNDROME ERROR CONTROL TCP TIMERSCONTENTS (continued) CONGESTION CONTROL SEGMENT OPTIONS CHECKSUM CONNECTION STATE TRANSITION DIAGRAM TCP OERATION TCP PACKAGEFigure 12-1Position of TCP in TCP/IP protocol suitePROCESS TO PROCESSCOMMUNICATION12.1Figure 12-2TCP versus IPFigure 12-3Port numbersTCPSERVICES12.2Figure 12-4Stream deliveryFigure 12-5Sending and receiving buffersFigure 12-6TCP segmentsNUMBERINGBYTES12.3The bytes of data being transferred in each connection are numbered by TCP. The numbering starts with a randomly generated number.Example 1Imagine a TCP connection is transferring a file of 6000 bytes. The first byte is numbered 10010. What are the sequencenumbers for each segment if data is sent in five segments with the first four segments carrying 1,000 bytes and the last segment carrying 2,000 bytes?SolutionThe following shows the sequence number for each segment:Segment 1  10,010 (10,010 to 11,009)Segment 2  11,010 (11,010 to 12,009)Segment 3  12,010 (12,010 to 13,009)Segment 4  13,010 (13,010 to 14,009)Segment 5  14,010 (14,010 to 16,009)The value of the sequence number field in a segment defines the number of the first data byte contained in that segment.The value of the acknowledgment field in a segment defines the number of the next byte a party expects to receives. The acknowledgment number is cumulative.FLOWCONTROL12.4A sliding window is used to make transmission more efficient as well as to control the flow of data so that the destination does not become overwhelmed with data. TCP’s sliding windows are byte oriented.Figure 12-7Sender bufferFigure 12-8Receiver windowFigure 12-9Sender buffer and sender windowFigure 12-10Sliding the sender windowFigure 12-11Expanding the sender windowFigure 12-12Shrinking the sender windowIn TCP, the sender window size is totally controlled by the receiver window value.However, the actual window size can be smaller if there is congestion in the network.Some Points about TCP’s Sliding Windows:1. The source does not have to send a  full window’s worth of data.2. The size of the window can be increased or decreased by the destination.3. The destination can send an  acknowledgment at any time.SILLYWINDOWSYNDROME12.5ERRORCONTROL12.6Figure 12-13Corrupted segmentFigure 12-14Lost segmentFigure 12-15Lost acknowledgmentTCPTIMERS12.7Figure 12-16TCP timersCONGESTIONCONTROL12.8TCP assumes that the cause of a lost segment is due to congestion in the network.If the cause of the lost segment is congestion, retransmission of the segment not only does not remove the cause, it aggravates it.Figure 12-17Multiplicative decreaseFigure 12-18Congestion avoidance strategiesSEGMENT12.9Figure 12-19TCP segment formatFigure 12-20Control fieldOPTIONS12.10Figure 12-21OptionsFigure 12-22End of option optionFigure 12-23No operation optionFigure 12-24Maximum segment size optionFigure 12-25Window scale factor optionFigure 12-26Timestamp option CHECKSUM12.11Figure 12-12Pseudoheader added to the TCP datagramCONNECTION12.12Figure 12-28Three-way handshakingFigure 12-29Four-way handshakingSTATETRANSITIONDIAGRAM12.13Figure 12-30State transition diagramFigure 12-31Client statesFigure 12-32Server statesTCPOPERATION12.14Figure 12-33Encapsulation and decapsulationFigure 12-34Multiplexing and demultiplexingTCP PACKAGE12.15Figure 12-35TCP packageFigure 12-36TCBsTransmission control blocks