（精）TCP基础讲解.ppt

TCP Transmission Control Protocol Li, XiaoMeng 2007.6.20 TCP Overview TCP is the most widely used Internet protocol Web, Peer-to-peer, FTP, telnet, … A two way, reliable, byte stream oriented end-to-end protocol Includes flow and congestion control Closely tied to the Internet Protocol (IP) TCP Features End-to-End Transport Connection-oriented Full duplex Byte-stream Reliable data transfer Sequenced delivery Flow control Keep sender from overrunning receiver Congestion control keep sender from overrunning network Application process W rite bytes TCP Send buffer Segment Segment Segment T ransmit segments Application process Read bytes TCP Receive buffer … … … Segment Format Segment Format (cont) Each connection identified with 4-tuple: (SrcPort, SrcIPAddr, DsrPort, DstIPAddr) Sliding window + flow control acknowledgment, SequenceNum, AdvertisedWinow Sender Data (SequenceNum) Acknowledgment + AdvertisedWindow Receiver Segment Format (cont) Flags URG: signal the receiver to interrupt and receive the urgent data from the sequenced segment. ACK: indicate the segment contains an acknowledgement. PSH: request the receiver to deliver the data to the application upon arrival without being buffered. RST: indicate error occurs, host crash, invalid segment, etc…. SYN: Synchronize Sequence Numbers. FIN: release the connection (the sender has no more data to send). Checksum pseudo header + TCP header + data Sequence Numbers SYN 32 bit sequence numbers Wrap around supported TCP breaks byte stream from application into packets Limited by Max. Segment Size Each byte in the data stream is considered Each packet has a sequence number Initial number selected at connection time Subsequent numbers indicate first data byte number in packet ACK’s indicate next byte expected Connection Establishment Active participant (client) Passive participant (server) SYN (SeqNum = x) SYN + ACK (SeqNum = y, Ack = x+1) ACK (Ack = y+1) Connection Termination Active participant (server) Passive particip