The TCP segment includes 12 fields:
1. Source port 2.
Destination port. These first two fields
identify the upper layer source and destination ports processed by TCP
services. 3. Sequence number usually
specifies the number assigned to the first byte of data in the current message.
It can also be used to identify an initial sequence number for a future
transmission. 4. Acknowledgement number,
contains the sequence number of the next
byte of data the sender expects to receive.
5. Data offset indicates the
number of 32 bit words in the TCP header.
6. Reserved-for future use. 7. Flags- carries control information, including
syn-ack bits for connection establishment, and FIN for connection
termination. 8. Window-specifies the size of the sender’s
receive window (buffer space available for incoming data) 9. Checksum-indicating header transmission
damage if applicable. 10. Urgent pointer- points to the first urgent
byte in the packet 11. Options-various
tcp options, and 12. Data, contains upper layer information.
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