Transmission Control Protocol ensures reliable data delivery over the internet. It breaks data into packets. It numbers them. It sends them. It waits for acknowledgments. If a packet is lost, it retransmits. It reassembles packets in order. It delivers a reliable stream of data to the application.

TCP works with IP. IP routes packets. TCP ensures they arrive. IP is unreliable. TCP adds reliability. Together they are the foundation of the internet. TCP is connection-oriented. It establishes a connection before sending data. It closes the connection when done.

TCP features

• Connection-oriented: handshake first
• Reliable: acknowledgments and retransmissions
• Ordered: packets reassembled in sequence
• Flow control: prevents overwhelming the receiver
• Congestion control: adapts to network conditions

TCP is used for web browsing, email, file transfer, and streaming. It is not used for real-time applications like voice and video calls. Those use UDP, which is faster but less reliable. TCP is the reliable workhorse. UDP is the speedy alternative. The internet needs both.