(You may hear people say "HTTPS connection is slow" more or less. So what is the reason for "slow"?Through the study of the first two lectures, it can be seen that HTTPS connection can be roughly divided into two parts. The first is the asymmetric encryption handshake during connection establishment, and the second is the symmetric encryption message transmission after handshake.Due to the good performance of the popular AES and cha20 and hardware optimization, the performance loss of packet transmission can be said to be very small and almost negligible. Therefore, "HTTPS connection slow" usually refers to the time period when the connection is established for the first time.After the TCP connection is established and before the formal data transmission, HTTPS adds a TLS handshake step compared with HTTP. This step may require up to two message roundtrips, i.e. 2-rtt. In addition to the network time consumption of handshake messages, there are other "invisible" consumption, such as:)