Transmission Control Protocol (TCP) is a foundational communication protocol used in computer networks, particularly the Internet. It operates at the transport layer of the Internet Protocol (IP) suite and is responsible for ensuring the reliable, ordered, and error-checked delivery of data between applications running on devices connected by a network.
TCP is connection-oriented, meaning a connection must be established between the communicating devices before any data is transferred. This is achieved through a process known as the three-way handshake, which synchronizes the sender and receiver and sets up parameters for the session.
Key Features and Functions of TCP
• Reliable Data Transmission: TCP guarantees that data sent from one device to another arrives intact and in the correct order. If any data is lost, duplicated, or arrives out of order, TCP detects these issues and retransmits the necessary data.
• Connection Establishment and Termination: TCP uses a three-way handshake to establish a connection and a four-way handshake to terminate it, ensuring both sides are synchronized and aware of the connection state.
• Flow Control: TCP manages the rate of data transmission so that the sender does not overwhelm the receiver. This is achieved using a sliding window mechanism, which specifies how much data can be sent before needing an acknowledgment.
• Error Detection and Correction: Each segment of data sent includes a checksum for error detection. If errors are found, the affected data is retransmitted.
• Congestion Control: TCP dynamically adjusts its data transmission rate based on network congestion, helping to prevent overload and maintain network performance.
How TCP Works
1. Handshake: The sender and receiver exchange control packets to establish a connection (SYN, SYN-ACK, ACK).
2. Data Transfer: Data is broken into segments, each with sequence numbers. Segments are sent to the receiver, which acknowledges receipt.
3. Acknowledgment and Retransmission: The sender waits for acknowledgments (ACKs). If an ACK is not received within a timeout, the data is retransmitted.
4. Flow and Congestion Control: The protocol manages the data flow and adapts to network conditions.
5. Connection Termination: A four-way handshake ensures both sides agree to end the communication session
TCP in the Protocol Stack
TCP works closely with IP, which handles addressing and routing of packets. While IP is responsible for delivering packets to the correct destination, TCP ensures that the data within those packets is reliable and correctly ordered.