Network communication protocol-TCP protocol explained in detail!

TCP (Transmission Control Protocol) is a reliable transport layer protocol that ensures the orderly transmission and complete reception of data. TCP provides a connection-oriented communication method, using a three-way handshake to establish a connection, and manages data transmission through flow control and congestion control. The TCP protocol also supports two-way communication and data verification to ensure that data will not be lost or damaged during transmission. The TCP protocol plays an important role in Internet communications, providing the basis for reliable communication between applications.

1. Features of TCP:

   • Reliability: TCP uses acknowledgment and retransmission mechanisms to ensure reliable transmission of data. The receiver will send a confirmation message to the sender to inform the sender that the data has been received. If the sender does not receive the confirmation, the data will be retransmitted.
   • Orderliness: TCP maintains the order in which data is sent, and the receiver reorganizes it in the order sent by the sender to ensure the orderliness of the data.
   • Flow control: TCP uses a sliding window mechanism for flow control. It controls the rate at which the sender sends data by adjusting the window size to ensure that the receiver can process the received data.
   • Congestion control: TCP uses the congestion window mechanism to control the sending rate of data. When the network is congested, TCP will reduce the size of the sending window to reduce the network load.
   • Connection-oriented: TCP needs to establish a connection before communication and needs to disconnect after the data transmission is completed. The establishment and disconnection of a connection requires a three-way handshake and four waves.
2. TCP message format:
   
   TCP messages are composed of header and data parts. The header contains multiple fields used to control and manage various aspects of data transmission, such as source port, destination port, sequence number, confirmation number, window size, etc.

3. TCP connection establishment and disconnection process:

   • Connection establishment: The establishment of a TCP connection requires a three-way handshake, that is, the sender sends a SYN (synchronization) message, the receiver returns a SYN ACK message, and finally the sender returns an ACK message. This process is used to ensure that both parties are able to communicate properly.
   • Connection disconnection: The disconnection of the TCP connection requires four waves, that is, the sender sends a FIN message, the receiver returns an ACK message, then the receiver sends a FIN message, and finally the sender returns an ACK message. This process is used to gradually close the connection.

4. TCP application:

   • HTTP communication between web browser and server is based on TCP protocol.
   • Email transmission uses TCP protocol.
   • File Transfer Protocol (FTP) also uses the TCP protocol.
   • Remote login protocol (SSH) uses TCP protocol.

TCP is a reliable, connection-oriented transport layer protocol used to ensure the reliability of data transmission in the network. It provides ordered transmission, flow control, congestion control and other functions to ensure data integrity and reliability.

reliability. TCP is widely used in many applications and forms the basis for building reliable communications.

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