What is TCP (Transmission Control Protocol)?

What is TCP?

TCP stands for Transmission Control Protocol. It’s a protocol that has been designed to handle reliable, real-time data exchange over the Internet.

The Transport layer of the OSI model is responsible for end-to-end connectivity and delivery of data packets. The significant difference between TCP and UDP is that TCP guarantees packet delivery while UDP does not.

This makes it suitable when you need to ensure reliability and accuracy in your application or distribution process (for example, sending financial information).

How Does TCP Work?

TCP is a connection-oriented protocol. This means that before two devices can transfer data, they need to connect with each other. TCP uses a three-way handshake to ensure both devices are ready and willing before communicating.

Once the connection has been established, TCP uses sequence numbers to keep track of all the bits in its stream of data.

Every byte of information sent is assigned an identifier that indicates where it belongs to other bytes that were sent earlier or later—and lets both parties know if there are any missing packets along the way.

TCP also uses acknowledgments from one device back out toward another device and timeouts for when no response is received within a certain amount of time (which helps prevent “deadlock” conditions).

A window size represents how many bytes can be sent at once; if this value gets too large due to network congestion or other problems with flow control between client and server machines, then packets may have difficulty getting through at all!

Finally, even though TCP was designed primarily for transmission over wired networks, several extensions are available that allow your PC software (such as Skype) to talk over wireless connections too!

These extensions include one called 802 11b/g Wi-Fi, which operates at 2 Mbps speeds, while newer 802 11n Wi-Fi operates at speeds up to 300 Mbps.

This means faster downloads and uploads than ever before possible through previous generations of wireless networking technologies like Bluetooth Low Energy technology which only offers a limited range but high-quality voice signals between two headsets connected by their respective smartphone apps.

Why TCP is Important?

TCP is used in many network protocols. It’s used to transfer data between systems on the Internet, which makes email work. TCP is significant because it provides reliability and flows control for data applications.

TCP provides these benefits:

  • Reliability — Data sent over the Internet can be received with no loss or error if TCP is used correctly by both sides of a communications link. Suppose you’re sending an email from your computer. You’ll receive an error message if something goes wrong instead of losing all of your message data when things go south (which would happen with UDP).
  • Flow Control — TCP ensures that both sides of a communication link exchange messages at roughly equal rates. Neither side gets overwhelmed with information or becomes idle, waiting for more data to arrive. Suppose one end sends too much data too quickly. Its counterpart reduces its rate until both sides are sending/receiving about equally fast against the ideal rate set by their TCP window size settings in advance.


TCP is a transport layer protocol used to transfer data between applications. It’s the protocol that provides reliable data transfer between two or more applications, and HTTP is one of those applications.

Useful Resource – HTTP vs TCP: Detailed Comparison

For example, when you click on a link and see a web page in your browser, the TCP protocol sends your request to the server hosting that website. The server then responds by sending back an HTTP response via Internet Protocol (IP).

TCP and IP

TCP/IP is a communication protocol suite used to connect hosts. It’s like a set of rules for how electronic devices should communicate. Without TCP/IP, the Internet and the web as we know them would not exist in their current forms.

TCP, UDP, and UDP-Lite

UDP-Lite is a simplified version of UDP. It was designed for error-prone networks and takes advantage of the fact that most data packets are received correctly to reduce the amount of overhead.

It does not perform checksums on all packets but only on those packet headers where errors are more likely to occur. This can result in substantial savings in bandwidth a network protocol stack uses if many packets are received correctly and some have header errors.

Since UDP-Lite is not widely used today, relatively little documentation is available on it. For example, Wikipedia has only one paragraph describing its characteristics (the rest covers TCP).


You now know how a TCP session works at the application level. A client sends an SYN packet to the server, responding with an ACK and an SYN-ACK packet.

The client then sends data in packets, which the server acknowledges in ACKs. Once all data has been sent, the client will send a FIN packet to close the session, followed by one more ACK from the server acknowledging the completion of both sessions.

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