Chapter 3-2. Structure of the TCP Header
Recommended reading: 【Information and Communications Network Technology】 Chapter 3. Communication Protocol
1. Source Port Number
○ 16 bits
2. Destination Port Number
○ 16 bits
○ Mostly well-known port numbers
3. Sequence Number
○ 32 bits
○ Indicates which segment is the nth segment
4. Acknowledgement Number
○ 32 bits
○ Means acknowledgement response for the received segment
5. Header Length
○ Indicates the length of the TCP header
○ The TCP header length ranges from a minimum of 20 bytes to a maximum of 60 bytes
6. Reserved Bits
○ A field reserved for other purposes in the future
7. URG (Urgent)
○ If this bit is 1, urgent data specified by the urgent pointer field is processed with priority
8. ACK (Acknowledgement)
○ If this bit is 1, it means that all segments before the acknowledgement number have been received properly
9. PSH (Push)
○ A control bit that requests non-urgent data to be processed quickly
10. RST (Reset)
○ A control bit for controlling the TCP session
11. SYN (Synchronization)
○ A control bit for initializing a session between two hosts that want to start communication and synchronizing sequence numbers
12. FIN (Final)
○ A control bit used when terminating transmission of a TCP session
13. Window Size
○ 16 bits
○ A field that stores the amount of data that can be transmitted without receiving an acknowledgement number
14. TCP Checksum
○ 16 bits, a field for performing error checking on the header and the data transmitted by the segment
15. Urgent Pointer
○ 16 bits
○ A pointer indicating urgent data
16. Options
○ Up to 40 bytes
17. Data
Entered: 2018.10.23 23:27