Link configuration Message: Negotiation link configuration parameter options, mainly including Config-Request, Config-Ack, Config-Nak and Config-Reject four kinds of messages. According to the function of each message, it is divided into the following three types: LCP protocol data message exchanged in the network protocol stage. In the information field of the frame, the NCP protocol data message is the LCP data packets are exchanged during the link establishment phase, and are encapsulated in PPP data as the PPP payload. Protocol multiplexing, link configuration, quality detection and error correction, and also supports negotiation of multiple configuration parameter options and CRC check.Ī PPP session mainly passes through the link establishment phase, the link verification phase, the network layer protocol phase and the network layer termination phase. The reason why the PPP protocol has a trend to replace the SLIP protocol is one of the reasons for the low line speed, but the main reason is that the SLIP protocol can only encapsulate IP datagrams, and the PPP protocol can encapsulate IP, IPX, AppleTalk, and support the network layer. Since it is through the RS232 serial port, it can be imagined that its line speed is very low, about 1200bps～19200bps. SLIP (Serial Line Internet Protocol) is a simple protocol for encapsulating IP datagrams on a point-to-point serial link. Before learning PPP protocol we need to understand its predecessor, SLIP protocol, 1980s home users are connected together for surfing the Internet via RS232 serial port and Modem PC's.

Tcp ip over serial ppp