Why UDP Is the Wild West of Internet Protocols and How TCP Tames It

Preface

In the world of the Internet, UDP is like a reckless swordsman cutting through data streams without caring about packet loss, while TCP behaves like a courteous gentleman who establishes a three‑handshake connection and ensures reliable transmission, together forming the communication philosophy of the digital realm.

Wildman: UDP Protocol

UDP sends data directly to the known IP address without any prior handshake, acting as a pure data‑packet courier.

Connectionless

Connectionless (knowing the peer IP, send data directly)

Just a Data Courier

Just moves data packets without adding extra header (only 8 bytes overhead)

No Order or Reliability

No guarantee of packet order No guarantee of reliability (packet loss)

No Congestion Control

Because UDP lacks congestion control, its transmission rate stays constant regardless of network conditions, which can lead to packet loss.

Efficiency

Without congestion control, UDP can maintain a steady speed even on poor networks, making it efficient for certain use cases.

UDP Summary

Connectionless (send data once the IP is known) Data courier with minimal header (8 bytes overhead) No guarantee of packet order No guarantee of reliability (packet loss) No congestion control Efficient (the first five points contribute to efficiency)

Typical scenarios: live streaming, video, games, real‑time applications

Gentleman: TCP Protocol

TCP establishes a reliable connection through a three‑handshake process and ends it with a four‑way termination, ensuring ordered and dependable data delivery.

Header Contains More Information

TCP adds several fields to the packet header:

Sequence Number

Acknowledgment Number

Window Size (how many bytes the network can currently handle)

Flags

TCP Flags

URG – urgent packet

ACK – acknowledgment (packet is valid)

PSH – push data to the application layer immediately

SYN – establish connection

RST – reset / need reconnection

FIN – close connection

TCP Three‑Way Handshake

Client sends SYN, enters SYN‑SEND state. Server replies SYN+ACK, enters SYN‑RECEIVED state. Client replies ACK, both enter ESTABLISHED state.

Why Three Handshakes?

If the initial SYN is lost, the client retransmits it; the extra step prevents half‑open connections and resource waste.

TCP Four‑Way Termination

Client sends FIN, enters FIN‑WAIT‑1. Server replies ACK, enters CLOSE‑WAIT. Server sends its FIN, enters LAST‑ACK. Client replies ACK, enters TIME‑WAIT then CLOSED; server also moves to CLOSED.

TCP Summary

Reliable, connection‑oriented. Slow start and congestion control (adjusts sending rate based on network conditions). Ordered delivery via sequence numbers.