Transmission Control Protocol (TCP) is a fundamental communication protocol used in networking that enables reliable, ordered, and error-checked data transmission between devices over a network, particularly the internet
Key Characteristics of TCP
- Connection-oriented: TCP establishes a connection between the sender and receiver through a process called a three-way handshake before data transfer begins. This connection remains active until the communication is complete
- Reliable delivery: TCP ensures that data packets are delivered accurately and in the correct order. It achieves this by numbering packets, acknowledging received packets, and retransmitting any lost or corrupted packets
- Flow control: It manages the rate of data transmission to prevent overwhelming the receiver
- Error handling: TCP detects errors in transmitted data and retransmits corrupted segments to maintain data integrity
- Connection termination: Once data transfer is complete, TCP closes the connection using a four-way handshake
How TCP Works
- Handshake: Establishes connection parameters between sender and receiver.
- Data transfer: Breaks data into segments, assigns sequence numbers, and sends them.
- Acknowledgment: Receiver confirms receipt of packets; sender retransmits if no acknowledgment is received.
- Flow control and error handling: Ensures smooth and accurate data flow.
- Termination: Properly closes the connection after transfer
Usage and Importance
TCP is used by many high-level protocols and applications that require reliable data transmission, including:
- Web browsing (HTTP/HTTPS)
- Email protocols (SMTP, IMAP, POP)
- File transfers (FTP, SFTP)
- Remote access (SSH, Telnet)
- Messaging and chat applications
- Virtual private networks (VPNs)
TCP Ports
TCP uses 16-bit port numbers (0 to 65,535) to identify specific services or applications on devices, allowing multiple connections to different services on the same machine. Ports are categorized as:
- Well-known ports (0–1023): Reserved for common services like HTTP (80), HTTPS (443), FTP (21), SSH (22)
- Registered ports (1024–49151)
- Dynamic/private ports (49152–65535)
TCP ports help direct network traffic to the correct application or service on a device
. In summary, TCP is a core protocol in the internet protocol suite that ensures reliable, ordered, and error-free communication between networked devices, forming the backbone of many internet services and applications
