Key Points of TCP

1. Sending is bidirectional, that is, the sender has a sending window, receiving window, congestion window, and the receiver also has its own sending window, receiving window, and congestion window. 2. There are three window concepts: sending window, receiving window, and congestion window. Only the receiving window is defined in the data packet format field. The values in the window indicate the size of the window that can be received, and the values in bytes indicate the size of the window that can be received. Www.2cto.com 3. Sending and receiving windows are not sliding windows. sliding windows are a protocol algorithm, which is used for sending and receiving windows. 4. The total size of the receiving window will change. the receiving end promises the latest window value based on its current receiving cache size, which is the traffic control from the receiving end. 5. The sending window and congestion window are not included in the packet format field, but are calculated and processed based on the received window value returned by the recipient. 6. In case of timeout retransmission, the congestion window will become smaller, and the value of the sending window will be the minimum value of the congestion window and the receiving window. 7. The sender maintains a pair of seq and ack numbers, and the receiver also maintains its own pair of seq and ack numbers. This is a full-duplex mode. Www.2cto.com 8. In a packet sent by the sender, seq indicates the first byte number sent by the packet, and ack indicates the number of the first byte of the next packet it wants to receive. 9. seq numbers increase by 1. 10. ack confirmation can be accumulated and confirmed. 11. Wireshark software can automatically diagnose retransmission packets, respond to lost packets, and receive window full. It is recommended for packet capture tools. Author wang7dao