I built a detailed visual diagrams for the Transmission Control Protocol (TCP) — one of the core protocols powering the internet, that operates at the Transport Layer (Layer 4) of the OSI model.
I broke down:
🔹 TCP Segment Structure: -
Source & destination ports
Sequence number
Acknowledgment number
Flags (SYN, ACK, FIN, RST, PSH, URG)
Window size
Checksum
Options & payload
Here the full animated diagram svg link of TCP structure: - https://github.com/knkrn5/Programming-Concepts/blob/main/computer-networking/protocols/transmission-control-protocol/TCP-segment/tcps.svg
🔹 TCP 3-Way Handshake: -
SYN
SYN-ACK
ACK
Sequence & acknowledgment numbers
Window size negotiation
MSS negotiation
How a connection becomes ESTABLISHED
Here the full animated diagram svg link of TCP handshake: - https://github.com/knkrn5/Programming-Concepts/blob/main/computer-networking/protocols/transmission-control-protocol/tcp-handshake/tcph.svg
While studying networking, I realized many resources explain TCP theoretically but not visually.
So I created these diagrams to make the packet flow and header fields easier to understand step-by-step.
One thing I found especially interesting:
TCP reliability is achieved through sequence numbers, acknowledgments, retransmissions, and flow control — all working together behind the scenes every time we browse a website or send data online.
Understanding protocols at this level really changes how you see networking and distributed systems.
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