TCP Segment

made up of a TCP header and a data section

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Destination Port - port of the service the traffic is intended for

Source Port - high-numbered port chosen from a special section of ports known as ephemeral ports

required to keep outgoing connections separate
necessary for when web server replies, the computer making the original request can send this data to the program that was actually requesting it

Sequence Number - 32-bit number used to keep track of where in a sequence of TCP segments this one is expected to be

Acknowledgment Number - number of the next expected segment

Data Offset Field - 4-bit number that communicates how long the TCP header for this segment is

this is so receiving network understands where the actual data payload begins

TCP Window or Checksum - specifies the range of sequence numbers that might be sent before an acknowledgement is required

Urgent Pointer Field - used in conjunction with one of the TCP control flags to point out particular segments that might be more important than others

Options Field - it is sometimes used for more complicated flow control protocols