PPP (Point-to-Point Protocol)

PPP (Point-to-Point Protocol) encapsulates IP datagram on a serial link, it is a link control protocol for establishing, configuring, and testing data links and its network control protocol system for different network layer protocols. 1. PPP data frame form 2. Information segment feature ① if the transmitted character is 0x7e, two consecutive characters 0x7d and 0x5e must be transmitted to escape the escape character. ② If the character 0x7d is transmitted, two consecutive characters 0x7d and 0x5d are required to escape the escape character. ③ If the character value is less than 0x20, escape is generally required, that is, replace it with the special character 0x7d and the sixth bit of the transmitted character with its complement code (to prevent them from appearing in the serial interface driver or modem of both hosts, because sometimes they are interpreted as special meanings ). 3. PPP advantages ① each frame has a cyclic redundancy test. ② The communication parties can negotiate IP addresses dynamically (using the IP address control protocol ). ③ Multiple protocols can be run on a single serial line. ④ The Link Control Association can set multiple data link options. ⑤ Compresses the TCP and IP packet headers.