Transmission Control Protocol (TCP) is a core protocol of the Internet protocol suite that provides reliable, connection-oriented communication between devices over IP networks. It ensures that data packets are delivered in order, without errors, duplication, or loss. TCP is a key component of many network applications and is widely used for transmitting data across the internet.
TCP operates at the transport layer of the TCP/IP model and is responsible for breaking data into packets, establishing a connection, managing flow control, handling congestion, and providing reliable delivery of data.
TCP has become the de facto standard for reliable data transmission on the internet due to its robustness, error recovery mechanisms, and ability to adapt to varying network conditions. It forms the foundation for numerous applications, including web browsing, email, file transfer, remote administration, and more.
Connection-oriented: TCP establishes a connection between a sender and a receiver before data transmission. This process is known as a TCP handshake. The handshake involves a three-way communication between the sender and receiver, where they exchange control information to synchronize sequence numbers and establish initial parameters.
Reliable delivery: TCP guarantees the reliable delivery of data packets. It achieves this through sequence numbers and acknowledgments. Each TCP segment is assigned a unique sequence number, allowing the receiver to reassemble the segments in the correct order. The receiver acknowledges the receipt of segments, and if a sender does not receive an acknowledgment within a certain time period, it retransmits the data.
Flow control: TCP implements flow control to ensure that the sender does not overwhelm the receiver with data. The receiver advertises a window size indicating the amount of data it can accept. The sender adjusts its transmission rate based on the receiver’s window size to avoid congestion and potential packet loss.
Congestion control: TCP employs congestion control mechanisms to prevent network congestion. It monitors network conditions, such as packet loss and delays, and adjusts the transmission rate accordingly. TCP uses various algorithms, such as Slow Start, Congestion Avoidance, and Fast Retransmit, to dynamically adapt to network congestion and maintain optimal performance.
Full-duplex communication: TCP supports full-duplex communication, allowing data to be transmitted in both directions simultaneously. Each TCP connection consists of two streams, one in each direction, enabling bi-directional data transfer.
Segmentation and reassembly: TCP breaks data into manageable segments for transmission over IP networks. It adds a TCP header to each segment containing control information, such as sequence numbers, acknowledgments, and window sizes. At the receiving end, TCP reassembles the segments into the original data.
Connection termination: TCP provides a reliable connection termination process. When both the sender and receiver have no more data to transmit, they exchange control messages to close the connection gracefully. This process involves a four-way handshake to ensure all data is delivered and both ends agree to terminate the connection.