What is TCP and Where is TCP Applied?

The Transmission Control Protocol or TCP was developed to enable reliable end-to-end data delivery within applications and has become a dominant transport-layer protocol on the Internet. TCP implies accurate data delivery without errors, in the right order, and with minimal or zero duplication or loss. In addition, TCP manages congestion control to prevent network congestion. TCP is utilized in applications, such as web browsing (HTTP), email (SMTP), file transfer (FTP), and Internet of Things (IoT) protocols like MQTT.  


Both Transmission Control Protocol and User Datagram Protocol are transport layer protocols. While TCP focuses on reliability, UDP rolls around speed and simplicity. Unlike UDP, Transmission Control Protocol ensures the ordered delivery of data, enables congestion control to prevent network overloading, as well as detects failures and retransmits lost or corrupted packets.  

How Does TCP Work in Practice?  

1. Connection establishment

Transmission Control protocol (TCP) implies a three-way handshake process to set connection between the sender and the receiver: 

  • The client sends a SYN or synchronization packet to the server 

  • It responds with a SYN-ACK packet 

  • The client sends an acknowledgment packet to confirm the connection.  

2. Data transfer

After setting connection comes data segmentation. It is divided into smaller constituents - TCP segments, which all possess sequence numbers. TCP enables accurate data delivery – in the correct order and with any lost or corrupted segments being retransmitted. The recipient acknowledges the segments, while the sender adjusts its transmission based on the congestion control technology. 

3. Connection termination

After data is finally transmitted, the connection termination process starts: 

  • The client sends a FIN packet to initiate the termination. 

  • After that, the server responds with an ACK packet, and then the server sends its own FIN packet. 

  • Finally, the client acknowledges the server's FIN packet, and the connection is terminated.  

TCP Use Cases  

TCP is often utilized in various applications where the focus is on data integrity and reliability. Some of them comprise: 

  • Web browsing. TCP is used for HTTP communication, enabling reliable transmission of web pages, images, and other resources. 

  • Email. TCP is utilized in SMTP for sending and receiving emails, ensuring the accuracy of email delivery. 

  • File transfer. FTP relies on TCP to transfer files securely and reliably. 

  • Internet of Things (IoT). IoT protocols like MQTT utilize TCP to ensure the ordered and errorless transmission of data from IoT devices to servers. 

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