CodePudding user response:
A picture description
CodePudding user response:
20 bytes16 source port and the port number 16 purpose,
32-bit number: once a certain transmission direction during the process of TCP communications on the serial number of each byte stream of bytes, orderly, identified by the data such as serial number is 1000, now sent 1000, under a sequence number is 2000,
32-bit confirmation number: response to TCP segment, to receive TCP segment of serial number plus 1, third is to bring their own serial number,
Four head length: identify the TCP head how many 4 bytes, said the longest altogether 15 * 4=60 bytes, with IP header,
Six, six, URG (emergency pointer is valid) ACK (confirm whether effective) PSH (hint at the receiving end application should immediately from the TCP receive buffer read data) RST (said to each other to establish a connection) SYN request to establish a connection (said) FIN (inform the other party said the end to close the connection)
16 window size: a TCP flow control method, is used to tell TCP buffer can accommodate how many bytes to end,
16 the checksum: by sending end filling, the receiver of message segment perform CRC algorithm in order to test whether TCP segment in transit damage,
16 urgent pointer: a positive offset, it and the serial number of values in said the last emergency the next byte of data serial number