What Is the Transmission Control Protocol?

Transmission Control Protocol (TCP, Transmission Control Protocol) is a connection-oriented, reliable, byte stream-based transport layer communication protocol, defined by IETF RFC 793 ^[1] .

Transmission Control Protocol (TCP) is a transmission protocol specifically designed to provide reliable end-to-end byte streams on unreliable internetwork. ^[2]

Formal definition of TCP by RFC793 of September 1981 ^[1]

When the application layer sends an 8-bit byte to the TCP layer for network transmission

TCP is a wide area network-oriented communication protocol. The purpose is to provide a communication method with the following characteristics between two communication endpoints when communicating across multiple networks: ^[1]

The header format of TCP is shown in Figure 1:

--- Source Port is the source port, 16 bits.

TCP is a connection-oriented transmission control protocol, while UDP provides a connectionless datagram service; TCP has high reliability to ensure the correctness of transmitted data without loss or out of order; UDP does not establish a connection before transmitting data. Datagrams are checked and modified without waiting for the other party's response, so packet loss, duplication, and out-of-order will occur. The application needs to be responsible for all tasks related to transmission reliability; UDP has better real-time performance and higher work efficiency than TCP ; UDP segment structure is simpler than TCP segment structure, so the network overhead is also small. The TCP protocol can ensure that the receiving end receives the byte stream sent by the sending end without error, and provides reliable communication services for applications. Communication systems with high reliability requirements often use TCP to transmit data. For example, HTTP uses TCP for data transmission. ^[11]