Analysis of PPP protocol concepts and authentication methods

A Brief Analysis of the concept and authentication method of PPP (Point-to-Point Protocol) is a link layer Protocol designed for the transmission of data packets between equivalent units. This link provides full duplex operations and transmits data packets in sequence. The design is mainly used to establish a point-to-point connection to send data through dialing or leased lines, making it a common solution for simple connections between hosts, bridges, and routers. Www.2cto.com provides a complete set of solutions for link establishment, maintenance, removal, upper-layer protocol negotiation, and authentication. The PPP Protocol includes the Link Control Protocol (LCP), the Network Control Protocol (NCP), and the authentication Protocol, password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP) are commonly used ).
LCP is responsible for creating, maintaining or terminating a physical connection. NCP is a family of Protocols responsible for solving the network protocols running on physical connections and the problems arising from upper-layer network protocols. The following describes the process of establishing a PPP link: a typical process of establishing a link is divided into three stages: creation, authentication, and network negotiation. Phase 1: Create a PPP link LCP to create a link. At this stage, the basic communication mode will be selected. Devices at both ends of the link Send configuration Packets (Configure Packets) to each other through LCP ). Once a configuration packet (Configure-Ack packet) is sent and received, the switching is completed and the LCP is enabled. It should be noted that in the Link creation phase, only the authentication protocol is selected, and user authentication will be implemented in stage 2nd. Www.2cto.com Stage 2: in this phase, the client sends its identity to the remote access server. This phase uses a security authentication method to prevent a third party from stealing data or impersonating a remote client to take over the connection with the client. Before the authentication is completed, it is prohibited to move from the authentication phase to the network layer protocol phase. If the authentication fails, the authenticator should jump to the end of the link. In this phase, only the Link Control Protocol, authentication protocol, and packets of The Link Quality Monitoring Protocol are allowed. Other packages received in this phase must be quietly discarded. The most common authentication protocols are password authentication protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP ). The authentication method is described in the third part. Phase 3: After the network layer protocol authentication phase is completed, PPP will call various network control protocols (NCP) selected during the link creation phase (phase 1 ). The selected NCP solves the High-level protocol issues on the PPP link. For example, in this phase, IP Control Protocol (IPCP) can allocate dynamic addresses to the dial-in users. In this way, after three stages, a complete PPP link is established.