Transmission Control Protocol

TCP CLOSE

Tcp

Transmission Control Protocol (TCP) is one of the core protocols of the Internet Protocol Suite. TCP provides reliable, ordered, and error-checked delivery of a stream of octets (bytes) between applications running on hosts communicating via an IP network. Major internet applications such as the World Wide Web, email, remote administration, and file transfer rely on TCP. It is part of the Transport Layer of the TCP/IP suite. TCP provides a communication service at an intermediate level between an application program and the Internet Protocol (IP). It provides host-to-host connectivity at the transport layer of the Internet model. TCP is used extensively by many of the Internet's most popular applications, including web browsers, email, and FTP.

Overview

TCP is a complex protocol due to its reliable transmission service. It manages data streams and guarantees that data will be delivered in the order it was sent and without duplication. This is achieved through a process known as the TCP handshake, which establishes a connection between the sender and receiver before data transmission begins. The protocol also implements flow control and congestion control to optimize data transfer rates and minimize network congestion.

Functionality

The primary functions of TCP include the division of a message into smaller packets, transmission of these packets, and the reassembly of the packets into the original message by the receiving host. Error checking is performed via checksums to ensure data integrity. TCP uses a set of rules called protocols for transmitting data from one network device to another. The sender and receiver establish a connection using a process known as a three-way handshake. After the connection is established, data transfer begins. Once the data is transmitted, the connection is terminated using a four-way handshake process.

TCP Header

The TCP header is an important part of the TCP packet, containing information necessary for controlling the transmission process, such as source and destination ports, sequence and acknowledgment numbers, and the checksum. The header also includes flags that manage the state of the connection, such as SYN (synchronize), ACK (acknowledge), and FIN (finish).

Reliability and Flow Control

TCP ensures reliability through the use of acknowledgments. When a TCP receiver gets a packet, it sends back an acknowledgment to the sender to confirm receipt. If the sender does not receive an acknowledgment within a certain amount of time, it will retransmit the packet. Flow control is managed through a sliding window mechanism, which controls the amount of data that can be in transit before an acknowledgment is received.

Congestion Control

Congestion control is a critical aspect of TCP that prevents network congestion by adjusting the rate of data transmission. TCP uses several algorithms for congestion control, such as slow start, congestion avoidance, fast retransmit, and fast recovery.

TCP/IP Model

The TCP/IP model, also known as the Internet Protocol Suite, is a set of communication protocols used on the Internet and similar networks. TCP and IP are the two foundational protocols in this suite. TCP is responsible for the data delivery once IP has handled the routing.

Development and Usage

Developed in the 1970s by Vinton Cerf and Bob Kahn, TCP has been instrumental in the expansion and success of the Internet. It has evolved over time to address the changing needs of the Internet, with significant improvements in speed, reliability, and security.

See Also

• Internet Protocol Suite
• User Datagram Protocol (UDP)
• IP address
• Port (computer networking)
• List of TCP and UDP port numbers

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