TCP & UDP (Quick Summary)

Both operate on L4 (Transport Layer) but have completely different purposes.

1. TCP (Transmission Control Protocol)

A Connection-Oriented protocol that prioritizes maximum data reliability.

• Features:
  • Guarantees that data reaches the destination completely and in the correct order.
  • Has Error Recovery (resends when lost) and Flow Control / Congestion Control (reduces speed when the network is congested).
• Three-way Handshake: Must establish a connection before sending data.
  1. SYN (Client requests connection)
  2. SYN-ACK (Server acknowledges)
  3. ACK (Client confirms)
• Use Cases: Web Browsing (HTTP/HTTPS), File Transfer (FTP), Email (SMTP), SSH

2. UDP (User Datagram Protocol)

A Connectionless protocol that focuses on speed and saving bandwidth.

• Features:
  • Sends data immediately without caring whether the destination is ready to receive.
  • No guarantee that data will arrive completely or in the correct order (No Acknowledgement).
• Use Cases: Video Streaming, Online Gaming, VoIP, DNS Resolution (because waiting for a TCP Handshake would be too slow)