Editing TCP/IP Stack (section)

== 4. Anatomy of a TCP Packet ==
Every TCP segment contains control fields in the header and a chunk of data. These fields help manage the flow and structure.

{| class="wikitable"
! Header Field !! What It Does
|-
| Source Port || Chosen by the sender to identify its own app
|-
| Destination Port || Tells the receiver which service should handle the data (e.g. port 80 for web)
|-
| Source IP || The sender’s IP address
|-
| Destination IP || The target machine’s IP address
|-
| Sequence Number || Tracks where this data fits in the overall stream
|-
| Acknowledgment Number || Confirms what data has been received so far
|-
| Flags || Signal events like start (SYN), end (FIN), or errors (RST)
|-
| Window Size || Controls how much data can be sent before pausing
|-
| Checksum || Used to detect if the packet was changed during transit
|-
| Payload || The actual content — like text, commands, files, etc.
|}