PPP link Working Process

When a user connects to the ISP by dialing, the modem of the router responds to the dialing and establishes a physical connection. At this time, the PC sends a series of LCP groups to the router (encapsulated into multiple PPP frames ). These groups and their responses select some PPP parameters to be used, and then conduct network layer cultivation. NCP assigns a temporary IP address to the newly accessed PC, in this way, the PC becomes a host on the Internet.

When the user completes the communication, the NCP releases the network layer connection and revokes the original IP address. Then LCP releases the data link layer connection, and finally releases the physical layer connection. The preceding process can be described.

When the line is still, there is no physical layer connection. When the modem's carrier signal is detected and a physical layer connection is established, the line enters the established State. At this time, LCP starts to negotiate with some options. The authentication status is displayed after the negotiation. If the identity of both parties is successfully identified, the network status is displayed. NCP configures network failover, assigns an IP address, and then enters the enabling status for data communication. After the data transmission is completed, it is switched to the terminated state. After the carrier stops, it returns to the static state.